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/*
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* Copyright ( C ) 2013 - 2022 Cisco Systems , Inc . and / or its affiliates . All rights reserved .
2019-01-25 10:15:50 -05:00
* Copyright ( C ) 2009 - 2013 Sourcefire , Inc .
2009-07-08 15:01:17 +02:00
*
* Authors : Tomasz Kojm < tkojm @ clamav . net >
*
* This program is free software ; you can redistribute it and / or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation .
*
* This program is distributed in the hope that it will be useful ,
* but WITHOUT ANY WARRANTY ; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE . See the
* GNU General Public License for more details .
*
* You should have received a copy of the GNU General Public License
* along with this program ; if not , write to the Free Software
* Foundation , Inc . , 51 Franklin Street , Fifth Floor , Boston ,
* MA 02110 - 1301 , USA .
*/
# include <stdio.h>
# include <string.h>
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# ifdef HAVE_UNISTD_H
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# include <unistd.h>
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# endif
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# include <stdlib.h>
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# include <sys/types.h>
# include <sys/stat.h>
# include <fcntl.h>
# include "clamav.h"
# include "others.h"
# include "macho.h"
# include "execs.h"
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# include "scanners.h"
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# define CLI_TMPUNLK() \
if ( ! ctx - > engine - > keeptmp ) { \
if ( cli_unlink ( tempfile ) ) { \
free ( tempfile ) ; \
return CL_EUNLINK ; \
} \
}
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# define EC32(v, conv) (conv ? cbswap32(v) : v)
# define EC64(v, conv) (conv ? cbswap64(v) : v)
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struct macho_hdr {
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uint32_t magic ;
uint32_t cpu_type ;
uint32_t cpu_subtype ;
uint32_t filetype ;
uint32_t ncmds ;
uint32_t sizeofcmds ;
uint32_t flags ;
} ;
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struct macho_load_cmd {
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uint32_t cmd ;
uint32_t cmdsize ;
} ;
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struct macho_segment_cmd {
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char segname [ 16 ] ;
uint32_t vmaddr ;
uint32_t vmsize ;
uint32_t fileoff ;
uint32_t filesize ;
uint32_t maxprot ;
uint32_t initprot ;
uint32_t nsects ;
uint32_t flags ;
} ;
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struct macho_segment_cmd64 {
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char segname [ 16 ] ;
uint64_t vmaddr ;
uint64_t vmsize ;
uint64_t fileoff ;
uint64_t filesize ;
uint32_t maxprot ;
uint32_t initprot ;
uint32_t nsects ;
uint32_t flags ;
} ;
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struct macho_section {
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char sectname [ 16 ] ;
char segname [ 16 ] ;
uint32_t addr ;
uint32_t size ;
uint32_t offset ;
uint32_t align ;
uint32_t reloff ;
uint32_t nreloc ;
uint32_t flags ;
uint32_t res1 ;
uint32_t res2 ;
} ;
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struct macho_section64 {
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char sectname [ 16 ] ;
char segname [ 16 ] ;
uint64_t addr ;
uint64_t size ;
uint32_t offset ;
uint32_t align ;
uint32_t reloff ;
uint32_t nreloc ;
uint32_t flags ;
uint32_t res1 ;
uint32_t res2 ;
} ;
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struct macho_thread_state_ppc {
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uint32_t srr0 ; /* PC */
uint32_t srr1 ;
uint32_t reg [ 32 ] ;
uint32_t cr ;
uint32_t xer ;
uint32_t lr ;
uint32_t ctr ;
uint32_t mq ;
uint32_t vrsave ;
} ;
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struct macho_thread_state_ppc64 {
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uint64_t srr0 ; /* PC */
uint64_t srr1 ;
uint64_t reg [ 32 ] ;
uint32_t cr ;
uint64_t xer ;
uint64_t lr ;
uint64_t ctr ;
uint32_t vrsave ;
} ;
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struct macho_thread_state_x86 {
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uint32_t eax ;
uint32_t ebx ;
uint32_t ecx ;
uint32_t edx ;
uint32_t edi ;
uint32_t esi ;
uint32_t ebp ;
uint32_t esp ;
uint32_t ss ;
uint32_t eflags ;
uint32_t eip ;
uint32_t cs ;
uint32_t ds ;
uint32_t es ;
uint32_t fs ;
uint32_t gs ;
} ;
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struct macho_fat_header {
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uint32_t magic ;
uint32_t nfats ;
} ;
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struct macho_fat_arch {
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uint32_t cputype ;
uint32_t cpusubtype ;
uint32_t offset ;
uint32_t size ;
uint32_t align ;
} ;
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# define RETURN_BROKEN \
if ( matcher ) \
return - 1 ; \
if ( SCAN_HEURISTIC_BROKEN ) { \
if ( CL_VIRUS = = cli_append_potentially_unwanted ( ctx , " Heuristics.Broken.Executable " ) ) \
return CL_VIRUS ; \
} \
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return CL_EFORMAT
static uint32_t cli_rawaddr ( uint32_t vaddr , struct cli_exe_section * sects , uint16_t nsects , unsigned int * err )
{
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unsigned int i , found = 0 ;
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for ( i = 0 ; i < nsects ; i + + ) {
if ( sects [ i ] . rva < = vaddr & & sects [ i ] . rva + sects [ i ] . vsz > vaddr ) {
found = 1 ;
break ;
}
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}
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if ( ! found ) {
* err = 1 ;
return 0 ;
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}
* err = 0 ;
return vaddr - sects [ i ] . rva + sects [ i ] . raw ;
}
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int cli_scanmacho ( cli_ctx * ctx , struct cli_exe_info * fileinfo )
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{
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struct macho_hdr hdr ;
struct macho_load_cmd load_cmd ;
struct macho_segment_cmd segment_cmd ;
struct macho_segment_cmd64 segment_cmd64 ;
struct macho_section section ;
struct macho_section64 section64 ;
unsigned int i , j , sect = 0 , conv , m64 , nsects , matcher = 0 ;
unsigned int arch = 0 , ep = 0 , err ;
struct cli_exe_section * sections = NULL ;
char name [ 16 ] ;
libclamav: Fix scan recursion tracking
Scan recursion is the process of identifying files embedded in other
files and then scanning them, recursively.
Internally this process is more complex than it may sound because a file
may have multiple layers of types before finding a new "file".
At present we treat the recursion count in the scanning context as an
index into both our fmap list AND our container list. These two lists
are conceptually a part of the same thing and should be unified.
But what's concerning is that the "recursion level" isn't actually
incremented or decremented at the same time that we add a layer to the
fmap or container lists but instead is more touchy-feely, increasing
when we find a new "file".
To account for this shadiness, the size of the fmap and container lists
has always been a little longer than our "max scan recursion" limit so
we don't accidentally overflow the fmap or container arrays (!).
I've implemented a single recursion-stack as an array, similar to before,
which includes a pointer to each fmap at each layer, along with the size
and type. Push and pop functions add and remove layers whenever a new
fmap is added. A boolean argument when pushing indicates if the new layer
represents a new buffer or new file (descriptor). A new buffer will reset
the "nested fmap level" (described below).
This commit also provides a solution for an issue where we detect
embedded files more than once during scan recursion.
For illustration, imagine a tarball named foo.tar.gz with this structure:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| └── foo.tar | TAR | 1 | 0 |
| ├── bar.zip | ZIP | 2 | 1 |
| │ └── hola.txt | ASCII | 3 | 0 |
| └── baz.exe | PE | 2 | 1 |
But suppose baz.exe embeds a ZIP archive and a 7Z archive, like this:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| baz.exe | PE | 0 | 0 |
| ├── sfx.zip | ZIP | 1 | 1 |
| │ └── hello.txt | ASCII | 2 | 0 |
| └── sfx.7z | 7Z | 1 | 1 |
| └── world.txt | ASCII | 2 | 0 |
(A) If we scan for embedded files at any layer, we may detect:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| ├── foo.tar | TAR | 1 | 0 |
| │ ├── bar.zip | ZIP | 2 | 1 |
| │ │ └── hola.txt | ASCII | 3 | 0 |
| │ ├── baz.exe | PE | 2 | 1 |
| │ │ ├── sfx.zip | ZIP | 3 | 1 |
| │ │ │ └── hello.txt | ASCII | 4 | 0 |
| │ │ └── sfx.7z | 7Z | 3 | 1 |
| │ │ └── world.txt | ASCII | 4 | 0 |
| │ ├── sfx.zip | ZIP | 2 | 1 |
| │ │ └── hello.txt | ASCII | 3 | 0 |
| │ └── sfx.7z | 7Z | 2 | 1 |
| │ └── world.txt | ASCII | 3 | 0 |
| ├── sfx.zip | ZIP | 1 | 1 |
| └── sfx.7z | 7Z | 1 | 1 |
(A) is bad because it scans content more than once.
Note that for the GZ layer, it may detect the ZIP and 7Z if the
signature hits on the compressed data, which it might, though
extracting the ZIP and 7Z will likely fail.
The reason the above doesn't happen now is that we restrict embedded
type scans for a bunch of archive formats to include GZ and TAR.
(B) If we scan for embedded files at the foo.tar layer, we may detect:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| └── foo.tar | TAR | 1 | 0 |
| ├── bar.zip | ZIP | 2 | 1 |
| │ └── hola.txt | ASCII | 3 | 0 |
| ├── baz.exe | PE | 2 | 1 |
| ├── sfx.zip | ZIP | 2 | 1 |
| │ └── hello.txt | ASCII | 3 | 0 |
| └── sfx.7z | 7Z | 2 | 1 |
| └── world.txt | ASCII | 3 | 0 |
(B) is almost right. But we can achieve it easily enough only scanning for
embedded content in the current fmap when the "nested fmap level" is 0.
The upside is that it should safely detect all embedded content, even if
it may think the sfz.zip and sfx.7z are in foo.tar instead of in baz.exe.
The biggest risk I can think of affects ZIPs. SFXZIP detection
is identical to ZIP detection, which is why we don't allow SFXZIP to be
detected if insize of a ZIP. If we only allow embedded type scanning at
fmap-layer 0 in each buffer, this will fail to detect the embedded ZIP
if the bar.exe was not compressed in foo.zip and if non-compressed files
extracted from ZIPs aren't extracted as new buffers:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.zip | ZIP | 0 | 0 |
| └── bar.exe | PE | 1 | 1 |
| └── sfx.zip | ZIP | 2 | 2 |
Provided that we ensure all files extracted from zips are scanned in
new buffers, option (B) should be safe.
(C) If we scan for embedded files at the baz.exe layer, we may detect:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| └── foo.tar | TAR | 1 | 0 |
| ├── bar.zip | ZIP | 2 | 1 |
| │ └── hola.txt | ASCII | 3 | 0 |
| └── baz.exe | PE | 2 | 1 |
| ├── sfx.zip | ZIP | 3 | 1 |
| │ └── hello.txt | ASCII | 4 | 0 |
| └── sfx.7z | 7Z | 3 | 1 |
| └── world.txt | ASCII | 4 | 0 |
(C) is right. But it's harder to achieve. For this example we can get it by
restricting 7ZSFX and ZIPSFX detection only when scanning an executable.
But that may mean losing detection of archives embedded elsewhere.
And we'd have to identify allowable container types for each possible
embedded type, which would be very difficult.
So this commit aims to solve the issue the (B)-way.
Note that in all situations, we still have to scan with file typing
enabled to determine if we need to reassign the current file type, such
as re-identifying a Bzip2 archive as a DMG that happens to be Bzip2-
compressed. Detection of DMG and a handful of other types rely on
finding data partway through or near the ned of a file before
reassigning the entire file as the new type.
Other fixes and considerations in this commit:
- The utf16 HTML parser has weak error handling, particularly with respect
to creating a nested fmap for scanning the ascii decoded file.
This commit cleans up the error handling and wraps the nested scan with
the recursion-stack push()/pop() for correct recursion tracking.
Before this commit, each container layer had a flag to indicate if the
container layer is valid.
We need something similar so that the cli_recursion_stack_get_*()
functions ignore normalized layers. Details...
Imagine an LDB signature for HTML content that specifies a ZIP
container. If the signature actually alerts on the normalized HTML and
you don't ignore normalized layers for the container check, it will
appear as though the alert is in an HTML container rather than a ZIP
container.
This commit accomplishes this with a boolean you set in the scan context
before scanning a new layer. Then when the new fmap is created, it will
use that flag to set similar flag for the layer. The context flag is
reset those that anything after this doesn't have that flag.
The flag allows the new recursion_stack_get() function to ignore
normalized layers when iterating the stack to return a layer at a
requested index, negative or positive.
Scanning normalized extracted/normalized javascript and VBA should also
use the 'layer is normalized' flag.
- This commit also fixes Heuristic.Broken.Executable alert for ELF files
to make sure that:
A) these only alert if cli_append_virus() returns CL_VIRUS (aka it
respects the FP check).
B) all broken-executable alerts for ELF only happen if the
SCAN_HEURISTIC_BROKEN option is enabled.
- This commit also cleans up the error handling in cli_magic_scan_dir().
This was needed so we could correctly apply the layer-is-normalized-flag
to all VBA macros extracted to a directory when scanning the directory.
- Also fix an issue where exceeding scan maximums wouldn't cause embedded
file detection scans to abort. Granted we don't actually want to abort
if max filesize or max recursion depth are exceeded... only if max
scansize, max files, and max scantime are exceeded.
Add 'abort_scan' flag to scan context, to protect against depending on
correct error propagation for fatal conditions. Instead, setting this
flag in the scan context should guarantee that a fatal condition deep in
scan recursion isn't lost which result in more stuff being scanned
instead of aborting. This shouldn't be necessary, but some status codes
like CL_ETIMEOUT never used to be fatal and it's easier to do this than
to verify every parser only returns CL_ETIMEOUT and other "fatal
status codes" in fatal conditions.
- Remove duplicate is_tar() prototype from filestypes.c and include
is_tar.h instead.
- Presently we create the fmap hash when creating the fmap.
This wastes a bit of CPU if the hash is never needed.
Now that we're creating fmap's for all embedded files discovered with
file type recognition scans, this is a much more frequent occurence and
really slows things down.
This commit fixes the issue by only creating fmap hashes as needed.
This should not only resolve the perfomance impact of creating fmap's
for all embedded files, but also should improve performance in general.
- Add allmatch check to the zip parser after the central-header meta
match. That way we don't multiple alerts with the same match except in
allmatch mode. Clean up error handling in the zip parser a tiny bit.
- Fixes to ensure that the scan limits such as scansize, filesize,
recursion depth, # of embedded files, and scantime are always reported
if AlertExceedsMax (--alert-exceeds-max) is enabled.
- Fixed an issue where non-fatal alerts for exceeding scan maximums may
mask signature matches later on. I changed it so these alerts use the
"possibly unwanted" alert-type and thus only alert if no other alerts
were found or if all-match or heuristic-precedence are enabled.
- Added the "Heuristics.Limits.Exceeded.*" events to the JSON metadata
when the --gen-json feature is enabled. These will show up once under
"ParseErrors" the first time a limit is exceeded. In the present
implementation, only one limits-exceeded events will be added, so as to
prevent a malicious or malformed sample from filling the JSON buffer
with millions of events and using a tonne of RAM.
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fmap_t * map = ctx - > fmap ;
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ssize_t at ;
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if ( fileinfo ) {
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matcher = 1 ;
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// TODO This code assumes fileinfo->offset == 0, which might not always
// be the case. For now just print this debug message and continue on
if ( 0 ! = fileinfo - > offset ) {
cli_dbgmsg ( " cli_scanmacho: Assumption Violated: fileinfo->offset != 0 \n " ) ;
}
}
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if ( fmap_readn ( map , & hdr , 0 , sizeof ( hdr ) ) ! = sizeof ( hdr ) ) {
cli_dbgmsg ( " cli_scanmacho: Can't read header \n " ) ;
return matcher ? - 1 : CL_EFORMAT ;
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}
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at = sizeof ( hdr ) ;
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if ( hdr . magic = = 0xfeedface ) {
conv = 0 ;
m64 = 0 ;
} else if ( hdr . magic = = 0xcefaedfe ) {
conv = 1 ;
m64 = 0 ;
} else if ( hdr . magic = = 0xfeedfacf ) {
conv = 0 ;
m64 = 1 ;
} else if ( hdr . magic = = 0xcffaedfe ) {
conv = 1 ;
m64 = 1 ;
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} else {
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cli_dbgmsg ( " cli_scanmacho: Incorrect magic \n " ) ;
return matcher ? - 1 : CL_EFORMAT ;
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}
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switch ( EC32 ( hdr . cpu_type , conv ) ) {
case 7 :
if ( ! matcher )
cli_dbgmsg ( " MACHO: CPU Type: Intel 32-bit \n " ) ;
arch = 1 ;
break ;
case 7 | 0x1000000 :
if ( ! matcher )
cli_dbgmsg ( " MACHO: CPU Type: Intel 64-bit \n " ) ;
break ;
case 12 :
if ( ! matcher )
cli_dbgmsg ( " MACHO: CPU Type: ARM \n " ) ;
break ;
case 14 :
if ( ! matcher )
cli_dbgmsg ( " MACHO: CPU Type: SPARC \n " ) ;
break ;
case 18 :
if ( ! matcher )
cli_dbgmsg ( " MACHO: CPU Type: POWERPC 32-bit \n " ) ;
arch = 2 ;
break ;
case 18 | 0x1000000 :
if ( ! matcher )
cli_dbgmsg ( " MACHO: CPU Type: POWERPC 64-bit \n " ) ;
arch = 3 ;
break ;
default :
if ( ! matcher )
cli_dbgmsg ( " MACHO: CPU Type: ** UNKNOWN ** (%u) \n " , EC32 ( hdr . cpu_type , conv ) ) ;
break ;
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}
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if ( ! matcher ) switch ( EC32 ( hdr . filetype , conv ) ) {
case 0x1 : /* MH_OBJECT */
cli_dbgmsg ( " MACHO: Filetype: Relocatable object file \n " ) ;
break ;
case 0x2 : /* MH_EXECUTE */
cli_dbgmsg ( " MACHO: Filetype: Executable \n " ) ;
break ;
case 0x3 : /* MH_FVMLIB */
cli_dbgmsg ( " MACHO: Filetype: Fixed VM shared library file \n " ) ;
break ;
case 0x4 : /* MH_CORE */
cli_dbgmsg ( " MACHO: Filetype: Core file \n " ) ;
break ;
case 0x5 : /* MH_PRELOAD */
cli_dbgmsg ( " MACHO: Filetype: Preloaded executable file \n " ) ;
break ;
case 0x6 : /* MH_DYLIB */
cli_dbgmsg ( " MACHO: Filetype: Dynamically bound shared library \n " ) ;
break ;
case 0x7 : /* MH_DYLINKER */
cli_dbgmsg ( " MACHO: Filetype: Dynamic link editor \n " ) ;
break ;
case 0x8 : /* MH_BUNDLE */
cli_dbgmsg ( " MACHO: Filetype: Dynamically bound bundle file \n " ) ;
break ;
case 0x9 : /* MH_DYLIB_STUB */
cli_dbgmsg ( " MACHO: Filetype: Shared library stub for static \n " ) ;
break ;
default :
cli_dbgmsg ( " MACHO: Filetype: ** UNKNOWN ** (0x%x) \n " , EC32 ( hdr . filetype , conv ) ) ;
}
if ( ! matcher ) {
cli_dbgmsg ( " MACHO: Number of load commands: %u \n " , EC32 ( hdr . ncmds , conv ) ) ;
cli_dbgmsg ( " MACHO: Size of load commands: %u \n " , EC32 ( hdr . sizeofcmds , conv ) ) ;
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}
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if ( m64 )
at + = 4 ;
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hdr . ncmds = EC32 ( hdr . ncmds , conv ) ;
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if ( ! hdr . ncmds | | hdr . ncmds > 1024 ) {
cli_dbgmsg ( " cli_scanmacho: Invalid number of load commands (%u) \n " , hdr . ncmds ) ;
RETURN_BROKEN ;
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}
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for ( i = 0 ; i < hdr . ncmds ; i + + ) {
if ( fmap_readn ( map , & load_cmd , at , sizeof ( load_cmd ) ) ! = sizeof ( load_cmd ) ) {
cli_dbgmsg ( " cli_scanmacho: Can't read load command \n " ) ;
free ( sections ) ;
RETURN_BROKEN ;
}
at + = sizeof ( load_cmd ) ;
/*
libclamav: Fix scan recursion tracking
Scan recursion is the process of identifying files embedded in other
files and then scanning them, recursively.
Internally this process is more complex than it may sound because a file
may have multiple layers of types before finding a new "file".
At present we treat the recursion count in the scanning context as an
index into both our fmap list AND our container list. These two lists
are conceptually a part of the same thing and should be unified.
But what's concerning is that the "recursion level" isn't actually
incremented or decremented at the same time that we add a layer to the
fmap or container lists but instead is more touchy-feely, increasing
when we find a new "file".
To account for this shadiness, the size of the fmap and container lists
has always been a little longer than our "max scan recursion" limit so
we don't accidentally overflow the fmap or container arrays (!).
I've implemented a single recursion-stack as an array, similar to before,
which includes a pointer to each fmap at each layer, along with the size
and type. Push and pop functions add and remove layers whenever a new
fmap is added. A boolean argument when pushing indicates if the new layer
represents a new buffer or new file (descriptor). A new buffer will reset
the "nested fmap level" (described below).
This commit also provides a solution for an issue where we detect
embedded files more than once during scan recursion.
For illustration, imagine a tarball named foo.tar.gz with this structure:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| └── foo.tar | TAR | 1 | 0 |
| ├── bar.zip | ZIP | 2 | 1 |
| │ └── hola.txt | ASCII | 3 | 0 |
| └── baz.exe | PE | 2 | 1 |
But suppose baz.exe embeds a ZIP archive and a 7Z archive, like this:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| baz.exe | PE | 0 | 0 |
| ├── sfx.zip | ZIP | 1 | 1 |
| │ └── hello.txt | ASCII | 2 | 0 |
| └── sfx.7z | 7Z | 1 | 1 |
| └── world.txt | ASCII | 2 | 0 |
(A) If we scan for embedded files at any layer, we may detect:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| ├── foo.tar | TAR | 1 | 0 |
| │ ├── bar.zip | ZIP | 2 | 1 |
| │ │ └── hola.txt | ASCII | 3 | 0 |
| │ ├── baz.exe | PE | 2 | 1 |
| │ │ ├── sfx.zip | ZIP | 3 | 1 |
| │ │ │ └── hello.txt | ASCII | 4 | 0 |
| │ │ └── sfx.7z | 7Z | 3 | 1 |
| │ │ └── world.txt | ASCII | 4 | 0 |
| │ ├── sfx.zip | ZIP | 2 | 1 |
| │ │ └── hello.txt | ASCII | 3 | 0 |
| │ └── sfx.7z | 7Z | 2 | 1 |
| │ └── world.txt | ASCII | 3 | 0 |
| ├── sfx.zip | ZIP | 1 | 1 |
| └── sfx.7z | 7Z | 1 | 1 |
(A) is bad because it scans content more than once.
Note that for the GZ layer, it may detect the ZIP and 7Z if the
signature hits on the compressed data, which it might, though
extracting the ZIP and 7Z will likely fail.
The reason the above doesn't happen now is that we restrict embedded
type scans for a bunch of archive formats to include GZ and TAR.
(B) If we scan for embedded files at the foo.tar layer, we may detect:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| └── foo.tar | TAR | 1 | 0 |
| ├── bar.zip | ZIP | 2 | 1 |
| │ └── hola.txt | ASCII | 3 | 0 |
| ├── baz.exe | PE | 2 | 1 |
| ├── sfx.zip | ZIP | 2 | 1 |
| │ └── hello.txt | ASCII | 3 | 0 |
| └── sfx.7z | 7Z | 2 | 1 |
| └── world.txt | ASCII | 3 | 0 |
(B) is almost right. But we can achieve it easily enough only scanning for
embedded content in the current fmap when the "nested fmap level" is 0.
The upside is that it should safely detect all embedded content, even if
it may think the sfz.zip and sfx.7z are in foo.tar instead of in baz.exe.
The biggest risk I can think of affects ZIPs. SFXZIP detection
is identical to ZIP detection, which is why we don't allow SFXZIP to be
detected if insize of a ZIP. If we only allow embedded type scanning at
fmap-layer 0 in each buffer, this will fail to detect the embedded ZIP
if the bar.exe was not compressed in foo.zip and if non-compressed files
extracted from ZIPs aren't extracted as new buffers:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.zip | ZIP | 0 | 0 |
| └── bar.exe | PE | 1 | 1 |
| └── sfx.zip | ZIP | 2 | 2 |
Provided that we ensure all files extracted from zips are scanned in
new buffers, option (B) should be safe.
(C) If we scan for embedded files at the baz.exe layer, we may detect:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| └── foo.tar | TAR | 1 | 0 |
| ├── bar.zip | ZIP | 2 | 1 |
| │ └── hola.txt | ASCII | 3 | 0 |
| └── baz.exe | PE | 2 | 1 |
| ├── sfx.zip | ZIP | 3 | 1 |
| │ └── hello.txt | ASCII | 4 | 0 |
| └── sfx.7z | 7Z | 3 | 1 |
| └── world.txt | ASCII | 4 | 0 |
(C) is right. But it's harder to achieve. For this example we can get it by
restricting 7ZSFX and ZIPSFX detection only when scanning an executable.
But that may mean losing detection of archives embedded elsewhere.
And we'd have to identify allowable container types for each possible
embedded type, which would be very difficult.
So this commit aims to solve the issue the (B)-way.
Note that in all situations, we still have to scan with file typing
enabled to determine if we need to reassign the current file type, such
as re-identifying a Bzip2 archive as a DMG that happens to be Bzip2-
compressed. Detection of DMG and a handful of other types rely on
finding data partway through or near the ned of a file before
reassigning the entire file as the new type.
Other fixes and considerations in this commit:
- The utf16 HTML parser has weak error handling, particularly with respect
to creating a nested fmap for scanning the ascii decoded file.
This commit cleans up the error handling and wraps the nested scan with
the recursion-stack push()/pop() for correct recursion tracking.
Before this commit, each container layer had a flag to indicate if the
container layer is valid.
We need something similar so that the cli_recursion_stack_get_*()
functions ignore normalized layers. Details...
Imagine an LDB signature for HTML content that specifies a ZIP
container. If the signature actually alerts on the normalized HTML and
you don't ignore normalized layers for the container check, it will
appear as though the alert is in an HTML container rather than a ZIP
container.
This commit accomplishes this with a boolean you set in the scan context
before scanning a new layer. Then when the new fmap is created, it will
use that flag to set similar flag for the layer. The context flag is
reset those that anything after this doesn't have that flag.
The flag allows the new recursion_stack_get() function to ignore
normalized layers when iterating the stack to return a layer at a
requested index, negative or positive.
Scanning normalized extracted/normalized javascript and VBA should also
use the 'layer is normalized' flag.
- This commit also fixes Heuristic.Broken.Executable alert for ELF files
to make sure that:
A) these only alert if cli_append_virus() returns CL_VIRUS (aka it
respects the FP check).
B) all broken-executable alerts for ELF only happen if the
SCAN_HEURISTIC_BROKEN option is enabled.
- This commit also cleans up the error handling in cli_magic_scan_dir().
This was needed so we could correctly apply the layer-is-normalized-flag
to all VBA macros extracted to a directory when scanning the directory.
- Also fix an issue where exceeding scan maximums wouldn't cause embedded
file detection scans to abort. Granted we don't actually want to abort
if max filesize or max recursion depth are exceeded... only if max
scansize, max files, and max scantime are exceeded.
Add 'abort_scan' flag to scan context, to protect against depending on
correct error propagation for fatal conditions. Instead, setting this
flag in the scan context should guarantee that a fatal condition deep in
scan recursion isn't lost which result in more stuff being scanned
instead of aborting. This shouldn't be necessary, but some status codes
like CL_ETIMEOUT never used to be fatal and it's easier to do this than
to verify every parser only returns CL_ETIMEOUT and other "fatal
status codes" in fatal conditions.
- Remove duplicate is_tar() prototype from filestypes.c and include
is_tar.h instead.
- Presently we create the fmap hash when creating the fmap.
This wastes a bit of CPU if the hash is never needed.
Now that we're creating fmap's for all embedded files discovered with
file type recognition scans, this is a much more frequent occurence and
really slows things down.
This commit fixes the issue by only creating fmap hashes as needed.
This should not only resolve the perfomance impact of creating fmap's
for all embedded files, but also should improve performance in general.
- Add allmatch check to the zip parser after the central-header meta
match. That way we don't multiple alerts with the same match except in
allmatch mode. Clean up error handling in the zip parser a tiny bit.
- Fixes to ensure that the scan limits such as scansize, filesize,
recursion depth, # of embedded files, and scantime are always reported
if AlertExceedsMax (--alert-exceeds-max) is enabled.
- Fixed an issue where non-fatal alerts for exceeding scan maximums may
mask signature matches later on. I changed it so these alerts use the
"possibly unwanted" alert-type and thus only alert if no other alerts
were found or if all-match or heuristic-precedence are enabled.
- Added the "Heuristics.Limits.Exceeded.*" events to the JSON metadata
when the --gen-json feature is enabled. These will show up once under
"ParseErrors" the first time a limit is exceeded. In the present
implementation, only one limits-exceeded events will be added, so as to
prevent a malicious or malformed sample from filling the JSON buffer
with millions of events and using a tonne of RAM.
2021-09-11 14:15:21 -07:00
if ( ( m64 & & EC32 ( load_cmd . cmdsize , conv ) % 8 ) | | ( ! m64 & & EC32 ( load_cmd . cmdsize , conv ) % 4 ) ) {
cli_dbgmsg ( " cli_scanmacho: Invalid command size (%u) \n " , EC32 ( load_cmd . cmdsize , conv ) ) ;
free ( sections ) ;
RETURN_BROKEN ;
}
*/
2018-12-03 12:40:13 -05:00
load_cmd . cmd = EC32 ( load_cmd . cmd , conv ) ;
if ( ( m64 & & load_cmd . cmd = = 0x19 ) | | ( ! m64 & & load_cmd . cmd = = 0x01 ) ) { /* LC_SEGMENT */
if ( m64 ) {
if ( fmap_readn ( map , & segment_cmd64 , at , sizeof ( segment_cmd64 ) ) ! = sizeof ( segment_cmd64 ) ) {
cli_dbgmsg ( " cli_scanmacho: Can't read segment command \n " ) ;
free ( sections ) ;
RETURN_BROKEN ;
}
at + = sizeof ( segment_cmd64 ) ;
nsects = EC32 ( segment_cmd64 . nsects , conv ) ;
strncpy ( name , segment_cmd64 . segname , sizeof ( name ) ) ;
name [ sizeof ( name ) - 1 ] = ' \0 ' ;
} else {
if ( fmap_readn ( map , & segment_cmd , at , sizeof ( segment_cmd ) ) ! = sizeof ( segment_cmd ) ) {
cli_dbgmsg ( " cli_scanmacho: Can't read segment command \n " ) ;
free ( sections ) ;
RETURN_BROKEN ;
}
at + = sizeof ( segment_cmd ) ;
nsects = EC32 ( segment_cmd . nsects , conv ) ;
strncpy ( name , segment_cmd . segname , sizeof ( name ) ) ;
name [ sizeof ( name ) - 1 ] = ' \0 ' ;
}
if ( ! matcher ) {
cli_dbgmsg ( " MACHO: Segment name: %s \n " , name ) ;
cli_dbgmsg ( " MACHO: Number of sections: %u \n " , nsects ) ;
}
if ( nsects > 255 ) {
cli_dbgmsg ( " cli_scanmacho: Invalid number of sections \n " ) ;
free ( sections ) ;
RETURN_BROKEN ;
}
if ( ! nsects ) {
if ( ! matcher )
cli_dbgmsg ( " MACHO: ------------------ \n " ) ;
continue ;
}
sections = ( struct cli_exe_section * ) cli_realloc2 ( sections , ( sect + nsects ) * sizeof ( struct cli_exe_section ) ) ;
if ( ! sections ) {
cli_errmsg ( " cli_scanmacho: Can't allocate memory for 'sections' \n " ) ;
return matcher ? - 1 : CL_EMEM ;
}
for ( j = 0 ; j < nsects ; j + + ) {
if ( m64 ) {
if ( fmap_readn ( map , & section64 , at , sizeof ( section64 ) ) ! = sizeof ( section64 ) ) {
cli_dbgmsg ( " cli_scanmacho: Can't read section \n " ) ;
free ( sections ) ;
RETURN_BROKEN ;
}
at + = sizeof ( section64 ) ;
sections [ sect ] . rva = EC64 ( section64 . addr , conv ) ;
sections [ sect ] . vsz = EC64 ( section64 . size , conv ) ;
sections [ sect ] . raw = EC32 ( section64 . offset , conv ) ;
section64 . align = 1 < < EC32 ( section64 . align , conv ) ;
sections [ sect ] . rsz = sections [ sect ] . vsz + ( section64 . align - ( sections [ sect ] . vsz % section64 . align ) ) % section64 . align ; /* most likely we can assume it's the same as .vsz */
strncpy ( name , section64 . sectname , sizeof ( name ) ) ;
name [ sizeof ( name ) - 1 ] = ' \0 ' ;
} else {
if ( fmap_readn ( map , & section , at , sizeof ( section ) ) ! = sizeof ( section ) ) {
cli_dbgmsg ( " cli_scanmacho: Can't read section \n " ) ;
free ( sections ) ;
RETURN_BROKEN ;
}
at + = sizeof ( section ) ;
sections [ sect ] . rva = EC32 ( section . addr , conv ) ;
sections [ sect ] . vsz = EC32 ( section . size , conv ) ;
sections [ sect ] . raw = EC32 ( section . offset , conv ) ;
2021-06-04 16:48:37 -07:00
if ( EC32 ( section . align , conv ) > = 32 ) {
2019-07-01 12:42:47 -04:00
cli_dbgmsg ( " cli_scanmacho: Section aligned is malformed \n " ) ;
free ( sections ) ;
2019-03-12 14:20:17 -04:00
RETURN_BROKEN ;
}
2018-12-03 12:40:13 -05:00
section . align = 1 < < EC32 ( section . align , conv ) ;
sections [ sect ] . rsz = sections [ sect ] . vsz + ( section . align - ( sections [ sect ] . vsz % section . align ) ) % section . align ;
strncpy ( name , section . sectname , sizeof ( name ) ) ;
name [ sizeof ( name ) - 1 ] = ' \0 ' ;
}
if ( ! matcher ) {
cli_dbgmsg ( " MACHO: --- Section %u --- \n " , sect ) ;
cli_dbgmsg ( " MACHO: Name: %s \n " , name ) ;
cli_dbgmsg ( " MACHO: Virtual address: 0x%x \n " , ( unsigned int ) sections [ sect ] . rva ) ;
cli_dbgmsg ( " MACHO: Virtual size: %u \n " , ( unsigned int ) sections [ sect ] . vsz ) ;
cli_dbgmsg ( " MACHO: Raw size: %u \n " , ( unsigned int ) sections [ sect ] . rsz ) ;
if ( sections [ sect ] . raw )
cli_dbgmsg ( " MACHO: File offset: %u \n " , ( unsigned int ) sections [ sect ] . raw ) ;
}
sect + + ;
}
if ( ! matcher )
cli_dbgmsg ( " MACHO: ------------------ \n " ) ;
} else if ( arch & & ( load_cmd . cmd = = 0x4 | | load_cmd . cmd = = 0x5 ) ) { /* LC_(UNIX)THREAD */
at + = 8 ;
switch ( arch ) {
case 1 : /* x86 */
{
struct macho_thread_state_x86 thread_state_x86 ;
if ( fmap_readn ( map , & thread_state_x86 , at , sizeof ( thread_state_x86 ) ) ! = sizeof ( thread_state_x86 ) ) {
cli_dbgmsg ( " cli_scanmacho: Can't read thread_state_x86 \n " ) ;
free ( sections ) ;
RETURN_BROKEN ;
}
at + = sizeof ( thread_state_x86 ) ;
break ;
}
case 2 : /* PPC */
{
struct macho_thread_state_ppc thread_state_ppc ;
if ( fmap_readn ( map , & thread_state_ppc , at , sizeof ( thread_state_ppc ) ) ! = sizeof ( thread_state_ppc ) ) {
cli_dbgmsg ( " cli_scanmacho: Can't read thread_state_ppc \n " ) ;
free ( sections ) ;
RETURN_BROKEN ;
}
at + = sizeof ( thread_state_ppc ) ;
ep = EC32 ( thread_state_ppc . srr0 , conv ) ;
break ;
}
case 3 : /* PPC64 */
{
struct macho_thread_state_ppc64 thread_state_ppc64 ;
if ( fmap_readn ( map , & thread_state_ppc64 , at , sizeof ( thread_state_ppc64 ) ) ! = sizeof ( thread_state_ppc64 ) ) {
cli_dbgmsg ( " cli_scanmacho: Can't read thread_state_ppc64 \n " ) ;
free ( sections ) ;
RETURN_BROKEN ;
}
at + = sizeof ( thread_state_ppc64 ) ;
ep = EC64 ( thread_state_ppc64 . srr0 , conv ) ;
break ;
}
default :
cli_errmsg ( " cli_scanmacho: Invalid arch setting! \n " ) ;
free ( sections ) ;
return matcher ? - 1 : CL_EARG ;
}
} else {
if ( EC32 ( load_cmd . cmdsize , conv ) > sizeof ( load_cmd ) )
at + = EC32 ( load_cmd . cmdsize , conv ) - sizeof ( load_cmd ) ;
}
2009-07-08 15:01:17 +02:00
}
2018-12-03 12:40:13 -05:00
if ( ep ) {
if ( ! matcher )
cli_dbgmsg ( " Entry Point: 0x%x \n " , ep ) ;
if ( sections ) {
ep = cli_rawaddr ( ep , sections , sect , & err ) ;
if ( err ) {
cli_dbgmsg ( " cli_scanmacho: Can't calculate EP offset \n " ) ;
free ( sections ) ;
return matcher ? - 1 : CL_EFORMAT ;
}
if ( ! matcher )
cli_dbgmsg ( " Entry Point file offset: %u \n " , ep ) ;
}
2009-07-13 16:07:08 +02:00
}
2018-12-03 12:40:13 -05:00
if ( matcher ) {
fileinfo - > ep = ep ;
fileinfo - > nsections = sect ;
PE parsing code improvements, db loading bug fixes
Consolidate the PE parsing code into one function. I tried to preserve all existing functionality from the previous, distinct implementations to a large extent (with the exceptions mentioned below). If I noticed potential bugs/improvements, I added a TODO statement about those so that they can be fixed in a smaller commit later. Also, there are more TODOs in places where I'm not entirely sure why certain actions are performed - more research is needed for these.
I'm submitting a pull request now so that regression testing can be done, and because merging what I have thus far now will likely have fewer conflicts than if I try to merge later
PE parsing code improvements:
- PEs without all 16 data directories are parsed more appropriately now
- Added lots more debug statements
Also:
- Allow MAX_BC and MAX_TRACKED_PCRE to be specified via CFLAGS
When doing performance testing with the latest CVD, MAX_BC and
MAX_TRACKED_PCRE need to be raised to track all the events.
Allow these to be specified via CFLAGS by not redefining them
if they are already defined
- Fix an issue preventing wildcard sizes in .MDB/.MSB rules
I'm not sure what the original intent of the check I removed was,
but it prevents using wildcard sizes in .MDB/.MSB rules. AFAICT
these wildcard sizes should be handled appropriately by the MD5
section hash computation code, so I don't think a check on that
is needed.
- Fix several issues related to db loading
- .imp files will now get loaded if they exist in a directory passed
via clamscan's '-d' flag
- .pwdb files will now get loaded if they exist in a directory passed
via clamscan's '-d' flag even when compiling without yara support
- Changes to .imp, .ign, and .ign2 files will now be reflected in calls
to cl_statinidir and cl_statchkdir (and also .pwdb files, even when
compiling without yara support)
- The contents of .sfp files won't be included in some of the signature
counts, and the contents of .cud files will be
- Any local.gdb files will no longer be loaded twice
- For .imp files, you are no longer required to specify a minimum flevel for wildcard rules, since this isn't needed
2019-01-08 00:09:08 -05:00
fileinfo - > sections = sections ;
2018-12-03 12:40:13 -05:00
return 0 ;
2009-07-13 21:29:46 +02:00
} else {
2018-12-03 12:40:13 -05:00
free ( sections ) ;
return CL_SUCCESS ;
2009-07-13 21:29:46 +02:00
}
}
libclamav: Fix scan recursion tracking
Scan recursion is the process of identifying files embedded in other
files and then scanning them, recursively.
Internally this process is more complex than it may sound because a file
may have multiple layers of types before finding a new "file".
At present we treat the recursion count in the scanning context as an
index into both our fmap list AND our container list. These two lists
are conceptually a part of the same thing and should be unified.
But what's concerning is that the "recursion level" isn't actually
incremented or decremented at the same time that we add a layer to the
fmap or container lists but instead is more touchy-feely, increasing
when we find a new "file".
To account for this shadiness, the size of the fmap and container lists
has always been a little longer than our "max scan recursion" limit so
we don't accidentally overflow the fmap or container arrays (!).
I've implemented a single recursion-stack as an array, similar to before,
which includes a pointer to each fmap at each layer, along with the size
and type. Push and pop functions add and remove layers whenever a new
fmap is added. A boolean argument when pushing indicates if the new layer
represents a new buffer or new file (descriptor). A new buffer will reset
the "nested fmap level" (described below).
This commit also provides a solution for an issue where we detect
embedded files more than once during scan recursion.
For illustration, imagine a tarball named foo.tar.gz with this structure:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| └── foo.tar | TAR | 1 | 0 |
| ├── bar.zip | ZIP | 2 | 1 |
| │ └── hola.txt | ASCII | 3 | 0 |
| └── baz.exe | PE | 2 | 1 |
But suppose baz.exe embeds a ZIP archive and a 7Z archive, like this:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| baz.exe | PE | 0 | 0 |
| ├── sfx.zip | ZIP | 1 | 1 |
| │ └── hello.txt | ASCII | 2 | 0 |
| └── sfx.7z | 7Z | 1 | 1 |
| └── world.txt | ASCII | 2 | 0 |
(A) If we scan for embedded files at any layer, we may detect:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| ├── foo.tar | TAR | 1 | 0 |
| │ ├── bar.zip | ZIP | 2 | 1 |
| │ │ └── hola.txt | ASCII | 3 | 0 |
| │ ├── baz.exe | PE | 2 | 1 |
| │ │ ├── sfx.zip | ZIP | 3 | 1 |
| │ │ │ └── hello.txt | ASCII | 4 | 0 |
| │ │ └── sfx.7z | 7Z | 3 | 1 |
| │ │ └── world.txt | ASCII | 4 | 0 |
| │ ├── sfx.zip | ZIP | 2 | 1 |
| │ │ └── hello.txt | ASCII | 3 | 0 |
| │ └── sfx.7z | 7Z | 2 | 1 |
| │ └── world.txt | ASCII | 3 | 0 |
| ├── sfx.zip | ZIP | 1 | 1 |
| └── sfx.7z | 7Z | 1 | 1 |
(A) is bad because it scans content more than once.
Note that for the GZ layer, it may detect the ZIP and 7Z if the
signature hits on the compressed data, which it might, though
extracting the ZIP and 7Z will likely fail.
The reason the above doesn't happen now is that we restrict embedded
type scans for a bunch of archive formats to include GZ and TAR.
(B) If we scan for embedded files at the foo.tar layer, we may detect:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| └── foo.tar | TAR | 1 | 0 |
| ├── bar.zip | ZIP | 2 | 1 |
| │ └── hola.txt | ASCII | 3 | 0 |
| ├── baz.exe | PE | 2 | 1 |
| ├── sfx.zip | ZIP | 2 | 1 |
| │ └── hello.txt | ASCII | 3 | 0 |
| └── sfx.7z | 7Z | 2 | 1 |
| └── world.txt | ASCII | 3 | 0 |
(B) is almost right. But we can achieve it easily enough only scanning for
embedded content in the current fmap when the "nested fmap level" is 0.
The upside is that it should safely detect all embedded content, even if
it may think the sfz.zip and sfx.7z are in foo.tar instead of in baz.exe.
The biggest risk I can think of affects ZIPs. SFXZIP detection
is identical to ZIP detection, which is why we don't allow SFXZIP to be
detected if insize of a ZIP. If we only allow embedded type scanning at
fmap-layer 0 in each buffer, this will fail to detect the embedded ZIP
if the bar.exe was not compressed in foo.zip and if non-compressed files
extracted from ZIPs aren't extracted as new buffers:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.zip | ZIP | 0 | 0 |
| └── bar.exe | PE | 1 | 1 |
| └── sfx.zip | ZIP | 2 | 2 |
Provided that we ensure all files extracted from zips are scanned in
new buffers, option (B) should be safe.
(C) If we scan for embedded files at the baz.exe layer, we may detect:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| └── foo.tar | TAR | 1 | 0 |
| ├── bar.zip | ZIP | 2 | 1 |
| │ └── hola.txt | ASCII | 3 | 0 |
| └── baz.exe | PE | 2 | 1 |
| ├── sfx.zip | ZIP | 3 | 1 |
| │ └── hello.txt | ASCII | 4 | 0 |
| └── sfx.7z | 7Z | 3 | 1 |
| └── world.txt | ASCII | 4 | 0 |
(C) is right. But it's harder to achieve. For this example we can get it by
restricting 7ZSFX and ZIPSFX detection only when scanning an executable.
But that may mean losing detection of archives embedded elsewhere.
And we'd have to identify allowable container types for each possible
embedded type, which would be very difficult.
So this commit aims to solve the issue the (B)-way.
Note that in all situations, we still have to scan with file typing
enabled to determine if we need to reassign the current file type, such
as re-identifying a Bzip2 archive as a DMG that happens to be Bzip2-
compressed. Detection of DMG and a handful of other types rely on
finding data partway through or near the ned of a file before
reassigning the entire file as the new type.
Other fixes and considerations in this commit:
- The utf16 HTML parser has weak error handling, particularly with respect
to creating a nested fmap for scanning the ascii decoded file.
This commit cleans up the error handling and wraps the nested scan with
the recursion-stack push()/pop() for correct recursion tracking.
Before this commit, each container layer had a flag to indicate if the
container layer is valid.
We need something similar so that the cli_recursion_stack_get_*()
functions ignore normalized layers. Details...
Imagine an LDB signature for HTML content that specifies a ZIP
container. If the signature actually alerts on the normalized HTML and
you don't ignore normalized layers for the container check, it will
appear as though the alert is in an HTML container rather than a ZIP
container.
This commit accomplishes this with a boolean you set in the scan context
before scanning a new layer. Then when the new fmap is created, it will
use that flag to set similar flag for the layer. The context flag is
reset those that anything after this doesn't have that flag.
The flag allows the new recursion_stack_get() function to ignore
normalized layers when iterating the stack to return a layer at a
requested index, negative or positive.
Scanning normalized extracted/normalized javascript and VBA should also
use the 'layer is normalized' flag.
- This commit also fixes Heuristic.Broken.Executable alert for ELF files
to make sure that:
A) these only alert if cli_append_virus() returns CL_VIRUS (aka it
respects the FP check).
B) all broken-executable alerts for ELF only happen if the
SCAN_HEURISTIC_BROKEN option is enabled.
- This commit also cleans up the error handling in cli_magic_scan_dir().
This was needed so we could correctly apply the layer-is-normalized-flag
to all VBA macros extracted to a directory when scanning the directory.
- Also fix an issue where exceeding scan maximums wouldn't cause embedded
file detection scans to abort. Granted we don't actually want to abort
if max filesize or max recursion depth are exceeded... only if max
scansize, max files, and max scantime are exceeded.
Add 'abort_scan' flag to scan context, to protect against depending on
correct error propagation for fatal conditions. Instead, setting this
flag in the scan context should guarantee that a fatal condition deep in
scan recursion isn't lost which result in more stuff being scanned
instead of aborting. This shouldn't be necessary, but some status codes
like CL_ETIMEOUT never used to be fatal and it's easier to do this than
to verify every parser only returns CL_ETIMEOUT and other "fatal
status codes" in fatal conditions.
- Remove duplicate is_tar() prototype from filestypes.c and include
is_tar.h instead.
- Presently we create the fmap hash when creating the fmap.
This wastes a bit of CPU if the hash is never needed.
Now that we're creating fmap's for all embedded files discovered with
file type recognition scans, this is a much more frequent occurence and
really slows things down.
This commit fixes the issue by only creating fmap hashes as needed.
This should not only resolve the perfomance impact of creating fmap's
for all embedded files, but also should improve performance in general.
- Add allmatch check to the zip parser after the central-header meta
match. That way we don't multiple alerts with the same match except in
allmatch mode. Clean up error handling in the zip parser a tiny bit.
- Fixes to ensure that the scan limits such as scansize, filesize,
recursion depth, # of embedded files, and scantime are always reported
if AlertExceedsMax (--alert-exceeds-max) is enabled.
- Fixed an issue where non-fatal alerts for exceeding scan maximums may
mask signature matches later on. I changed it so these alerts use the
"possibly unwanted" alert-type and thus only alert if no other alerts
were found or if all-match or heuristic-precedence are enabled.
- Added the "Heuristics.Limits.Exceeded.*" events to the JSON metadata
when the --gen-json feature is enabled. These will show up once under
"ParseErrors" the first time a limit is exceeded. In the present
implementation, only one limits-exceeded events will be added, so as to
prevent a malicious or malformed sample from filling the JSON buffer
with millions of events and using a tonne of RAM.
2021-09-11 14:15:21 -07:00
int cli_machoheader ( cli_ctx * ctx , struct cli_exe_info * fileinfo )
2009-07-13 21:29:46 +02:00
{
libclamav: Fix scan recursion tracking
Scan recursion is the process of identifying files embedded in other
files and then scanning them, recursively.
Internally this process is more complex than it may sound because a file
may have multiple layers of types before finding a new "file".
At present we treat the recursion count in the scanning context as an
index into both our fmap list AND our container list. These two lists
are conceptually a part of the same thing and should be unified.
But what's concerning is that the "recursion level" isn't actually
incremented or decremented at the same time that we add a layer to the
fmap or container lists but instead is more touchy-feely, increasing
when we find a new "file".
To account for this shadiness, the size of the fmap and container lists
has always been a little longer than our "max scan recursion" limit so
we don't accidentally overflow the fmap or container arrays (!).
I've implemented a single recursion-stack as an array, similar to before,
which includes a pointer to each fmap at each layer, along with the size
and type. Push and pop functions add and remove layers whenever a new
fmap is added. A boolean argument when pushing indicates if the new layer
represents a new buffer or new file (descriptor). A new buffer will reset
the "nested fmap level" (described below).
This commit also provides a solution for an issue where we detect
embedded files more than once during scan recursion.
For illustration, imagine a tarball named foo.tar.gz with this structure:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| └── foo.tar | TAR | 1 | 0 |
| ├── bar.zip | ZIP | 2 | 1 |
| │ └── hola.txt | ASCII | 3 | 0 |
| └── baz.exe | PE | 2 | 1 |
But suppose baz.exe embeds a ZIP archive and a 7Z archive, like this:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| baz.exe | PE | 0 | 0 |
| ├── sfx.zip | ZIP | 1 | 1 |
| │ └── hello.txt | ASCII | 2 | 0 |
| └── sfx.7z | 7Z | 1 | 1 |
| └── world.txt | ASCII | 2 | 0 |
(A) If we scan for embedded files at any layer, we may detect:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| ├── foo.tar | TAR | 1 | 0 |
| │ ├── bar.zip | ZIP | 2 | 1 |
| │ │ └── hola.txt | ASCII | 3 | 0 |
| │ ├── baz.exe | PE | 2 | 1 |
| │ │ ├── sfx.zip | ZIP | 3 | 1 |
| │ │ │ └── hello.txt | ASCII | 4 | 0 |
| │ │ └── sfx.7z | 7Z | 3 | 1 |
| │ │ └── world.txt | ASCII | 4 | 0 |
| │ ├── sfx.zip | ZIP | 2 | 1 |
| │ │ └── hello.txt | ASCII | 3 | 0 |
| │ └── sfx.7z | 7Z | 2 | 1 |
| │ └── world.txt | ASCII | 3 | 0 |
| ├── sfx.zip | ZIP | 1 | 1 |
| └── sfx.7z | 7Z | 1 | 1 |
(A) is bad because it scans content more than once.
Note that for the GZ layer, it may detect the ZIP and 7Z if the
signature hits on the compressed data, which it might, though
extracting the ZIP and 7Z will likely fail.
The reason the above doesn't happen now is that we restrict embedded
type scans for a bunch of archive formats to include GZ and TAR.
(B) If we scan for embedded files at the foo.tar layer, we may detect:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| └── foo.tar | TAR | 1 | 0 |
| ├── bar.zip | ZIP | 2 | 1 |
| │ └── hola.txt | ASCII | 3 | 0 |
| ├── baz.exe | PE | 2 | 1 |
| ├── sfx.zip | ZIP | 2 | 1 |
| │ └── hello.txt | ASCII | 3 | 0 |
| └── sfx.7z | 7Z | 2 | 1 |
| └── world.txt | ASCII | 3 | 0 |
(B) is almost right. But we can achieve it easily enough only scanning for
embedded content in the current fmap when the "nested fmap level" is 0.
The upside is that it should safely detect all embedded content, even if
it may think the sfz.zip and sfx.7z are in foo.tar instead of in baz.exe.
The biggest risk I can think of affects ZIPs. SFXZIP detection
is identical to ZIP detection, which is why we don't allow SFXZIP to be
detected if insize of a ZIP. If we only allow embedded type scanning at
fmap-layer 0 in each buffer, this will fail to detect the embedded ZIP
if the bar.exe was not compressed in foo.zip and if non-compressed files
extracted from ZIPs aren't extracted as new buffers:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.zip | ZIP | 0 | 0 |
| └── bar.exe | PE | 1 | 1 |
| └── sfx.zip | ZIP | 2 | 2 |
Provided that we ensure all files extracted from zips are scanned in
new buffers, option (B) should be safe.
(C) If we scan for embedded files at the baz.exe layer, we may detect:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| └── foo.tar | TAR | 1 | 0 |
| ├── bar.zip | ZIP | 2 | 1 |
| │ └── hola.txt | ASCII | 3 | 0 |
| └── baz.exe | PE | 2 | 1 |
| ├── sfx.zip | ZIP | 3 | 1 |
| │ └── hello.txt | ASCII | 4 | 0 |
| └── sfx.7z | 7Z | 3 | 1 |
| └── world.txt | ASCII | 4 | 0 |
(C) is right. But it's harder to achieve. For this example we can get it by
restricting 7ZSFX and ZIPSFX detection only when scanning an executable.
But that may mean losing detection of archives embedded elsewhere.
And we'd have to identify allowable container types for each possible
embedded type, which would be very difficult.
So this commit aims to solve the issue the (B)-way.
Note that in all situations, we still have to scan with file typing
enabled to determine if we need to reassign the current file type, such
as re-identifying a Bzip2 archive as a DMG that happens to be Bzip2-
compressed. Detection of DMG and a handful of other types rely on
finding data partway through or near the ned of a file before
reassigning the entire file as the new type.
Other fixes and considerations in this commit:
- The utf16 HTML parser has weak error handling, particularly with respect
to creating a nested fmap for scanning the ascii decoded file.
This commit cleans up the error handling and wraps the nested scan with
the recursion-stack push()/pop() for correct recursion tracking.
Before this commit, each container layer had a flag to indicate if the
container layer is valid.
We need something similar so that the cli_recursion_stack_get_*()
functions ignore normalized layers. Details...
Imagine an LDB signature for HTML content that specifies a ZIP
container. If the signature actually alerts on the normalized HTML and
you don't ignore normalized layers for the container check, it will
appear as though the alert is in an HTML container rather than a ZIP
container.
This commit accomplishes this with a boolean you set in the scan context
before scanning a new layer. Then when the new fmap is created, it will
use that flag to set similar flag for the layer. The context flag is
reset those that anything after this doesn't have that flag.
The flag allows the new recursion_stack_get() function to ignore
normalized layers when iterating the stack to return a layer at a
requested index, negative or positive.
Scanning normalized extracted/normalized javascript and VBA should also
use the 'layer is normalized' flag.
- This commit also fixes Heuristic.Broken.Executable alert for ELF files
to make sure that:
A) these only alert if cli_append_virus() returns CL_VIRUS (aka it
respects the FP check).
B) all broken-executable alerts for ELF only happen if the
SCAN_HEURISTIC_BROKEN option is enabled.
- This commit also cleans up the error handling in cli_magic_scan_dir().
This was needed so we could correctly apply the layer-is-normalized-flag
to all VBA macros extracted to a directory when scanning the directory.
- Also fix an issue where exceeding scan maximums wouldn't cause embedded
file detection scans to abort. Granted we don't actually want to abort
if max filesize or max recursion depth are exceeded... only if max
scansize, max files, and max scantime are exceeded.
Add 'abort_scan' flag to scan context, to protect against depending on
correct error propagation for fatal conditions. Instead, setting this
flag in the scan context should guarantee that a fatal condition deep in
scan recursion isn't lost which result in more stuff being scanned
instead of aborting. This shouldn't be necessary, but some status codes
like CL_ETIMEOUT never used to be fatal and it's easier to do this than
to verify every parser only returns CL_ETIMEOUT and other "fatal
status codes" in fatal conditions.
- Remove duplicate is_tar() prototype from filestypes.c and include
is_tar.h instead.
- Presently we create the fmap hash when creating the fmap.
This wastes a bit of CPU if the hash is never needed.
Now that we're creating fmap's for all embedded files discovered with
file type recognition scans, this is a much more frequent occurence and
really slows things down.
This commit fixes the issue by only creating fmap hashes as needed.
This should not only resolve the perfomance impact of creating fmap's
for all embedded files, but also should improve performance in general.
- Add allmatch check to the zip parser after the central-header meta
match. That way we don't multiple alerts with the same match except in
allmatch mode. Clean up error handling in the zip parser a tiny bit.
- Fixes to ensure that the scan limits such as scansize, filesize,
recursion depth, # of embedded files, and scantime are always reported
if AlertExceedsMax (--alert-exceeds-max) is enabled.
- Fixed an issue where non-fatal alerts for exceeding scan maximums may
mask signature matches later on. I changed it so these alerts use the
"possibly unwanted" alert-type and thus only alert if no other alerts
were found or if all-match or heuristic-precedence are enabled.
- Added the "Heuristics.Limits.Exceeded.*" events to the JSON metadata
when the --gen-json feature is enabled. These will show up once under
"ParseErrors" the first time a limit is exceeded. In the present
implementation, only one limits-exceeded events will be added, so as to
prevent a malicious or malformed sample from filling the JSON buffer
with millions of events and using a tonne of RAM.
2021-09-11 14:15:21 -07:00
return cli_scanmacho ( ctx , fileinfo ) ;
2009-07-08 15:01:17 +02:00
}
2009-07-14 18:19:54 +02:00
2022-08-27 09:28:38 -07:00
cl_error_t cli_scanmacho_unibin ( cli_ctx * ctx )
2009-07-14 18:19:54 +02:00
{
2018-12-03 12:40:13 -05:00
struct macho_fat_header fat_header ;
struct macho_fat_arch fat_arch ;
unsigned int conv , i , matcher = 0 ;
2022-08-27 09:28:38 -07:00
cl_error_t ret = CL_SUCCESS ;
fmap_t * map = ctx - > fmap ;
2018-12-03 12:40:13 -05:00
ssize_t at ;
if ( fmap_readn ( map , & fat_header , 0 , sizeof ( fat_header ) ) ! = sizeof ( fat_header ) ) {
cli_dbgmsg ( " cli_scanmacho_unibin: Can't read fat_header \n " ) ;
return CL_EFORMAT ;
2009-07-14 18:19:54 +02:00
}
2009-10-01 17:56:35 +02:00
at = sizeof ( fat_header ) ;
2009-07-14 18:19:54 +02:00
2018-12-03 12:40:13 -05:00
if ( fat_header . magic = = 0xcafebabe ) {
conv = 0 ;
} else if ( fat_header . magic = = 0xbebafeca ) {
conv = 1 ;
2009-07-14 18:19:54 +02:00
} else {
2018-12-03 12:40:13 -05:00
cli_dbgmsg ( " cli_scanmacho_unibin: Incorrect magic \n " ) ;
return CL_EFORMAT ;
2009-07-14 18:19:54 +02:00
}
fat_header . nfats = EC32 ( fat_header . nfats , conv ) ;
2018-12-03 12:40:13 -05:00
if ( ( fat_header . nfats & 0xffff ) > = 39 ) /* Java Bytecode */
return CL_CLEAN ;
2009-07-27 13:54:20 +02:00
2018-12-03 12:40:13 -05:00
if ( fat_header . nfats > 32 ) {
cli_dbgmsg ( " cli_scanmacho_unibin: Invalid number of architectures \n " ) ;
return CL_EFORMAT ;
2009-07-14 18:19:54 +02:00
}
2018-12-03 12:40:13 -05:00
cli_dbgmsg ( " UNIBIN: Number of architectures: %u \n " , ( unsigned int ) fat_header . nfats ) ;
for ( i = 0 ; i < fat_header . nfats ; i + + ) {
if ( fmap_readn ( map , & fat_arch , at , sizeof ( fat_arch ) ) ! = sizeof ( fat_arch ) ) {
cli_dbgmsg ( " cli_scanmacho_unibin: Can't read fat_arch \n " ) ;
RETURN_BROKEN ;
}
at + = sizeof ( fat_arch ) ;
fat_arch . offset = EC32 ( fat_arch . offset , conv ) ;
fat_arch . size = EC32 ( fat_arch . size , conv ) ;
cli_dbgmsg ( " UNIBIN: Binary %u of %u \n " , i + 1 , fat_header . nfats ) ;
cli_dbgmsg ( " UNIBIN: File offset: %u \n " , fat_arch . offset ) ;
cli_dbgmsg ( " UNIBIN: File size: %u \n " , fat_arch . size ) ;
2021-06-17 11:30:23 -07:00
/* The offset must be greater than the location of the header or we risk
re - scanning the same data over and over again . The scan recursion max
will save us , but it will still cause other problems and waste CPU . */
if ( fat_arch . offset < at ) {
cli_dbgmsg ( " Invalid fat offset: %d \n " , fat_arch . offset ) ;
RETURN_BROKEN ;
}
2022-08-27 09:28:38 -07:00
ret = cli_magic_scan_nested_fmap_type ( map , fat_arch . offset , fat_arch . size , ctx , CL_TYPE_ANY , NULL , LAYER_ATTRIBUTES_NONE ) ;
if ( ret ! = CL_SUCCESS ) {
2018-12-03 12:40:13 -05:00
break ;
2022-08-27 09:28:38 -07:00
}
2009-07-14 18:19:54 +02:00
}
return ret ; /* result from the last binary */
}
2019-04-17 20:30:21 +02:00
2022-08-27 09:28:38 -07:00
cl_error_t cli_unpackmacho ( cli_ctx * ctx )
2019-04-17 20:30:21 +02:00
{
2022-08-27 09:28:38 -07:00
cl_error_t ret = CL_SUCCESS ;
char * tempfile = NULL ;
int ndesc = - 1 ;
2019-04-17 20:30:21 +02:00
struct cli_bc_ctx * bc_ctx ;
2022-08-27 09:28:38 -07:00
bool bc_ctx_set = false ;
2019-04-17 20:30:21 +02:00
/* Bytecode BC_MACHO_UNPACKER hook */
bc_ctx = cli_bytecode_context_alloc ( ) ;
if ( ! bc_ctx ) {
2022-08-27 09:28:38 -07:00
cli_errmsg ( " cli_unpackmacho: can't allocate memory for bc_ctx \n " ) ;
ret = CL_EMEM ;
goto done ;
2019-04-17 20:30:21 +02:00
}
cli_bytecode_context_setctx ( bc_ctx , ctx ) ;
2022-08-27 09:28:38 -07:00
bc_ctx_set = true ;
2019-04-17 20:30:21 +02:00
2022-08-27 09:28:38 -07:00
cli_dbgmsg ( " Running bytecode hook \n " ) ;
libclamav: Fix scan recursion tracking
Scan recursion is the process of identifying files embedded in other
files and then scanning them, recursively.
Internally this process is more complex than it may sound because a file
may have multiple layers of types before finding a new "file".
At present we treat the recursion count in the scanning context as an
index into both our fmap list AND our container list. These two lists
are conceptually a part of the same thing and should be unified.
But what's concerning is that the "recursion level" isn't actually
incremented or decremented at the same time that we add a layer to the
fmap or container lists but instead is more touchy-feely, increasing
when we find a new "file".
To account for this shadiness, the size of the fmap and container lists
has always been a little longer than our "max scan recursion" limit so
we don't accidentally overflow the fmap or container arrays (!).
I've implemented a single recursion-stack as an array, similar to before,
which includes a pointer to each fmap at each layer, along with the size
and type. Push and pop functions add and remove layers whenever a new
fmap is added. A boolean argument when pushing indicates if the new layer
represents a new buffer or new file (descriptor). A new buffer will reset
the "nested fmap level" (described below).
This commit also provides a solution for an issue where we detect
embedded files more than once during scan recursion.
For illustration, imagine a tarball named foo.tar.gz with this structure:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| └── foo.tar | TAR | 1 | 0 |
| ├── bar.zip | ZIP | 2 | 1 |
| │ └── hola.txt | ASCII | 3 | 0 |
| └── baz.exe | PE | 2 | 1 |
But suppose baz.exe embeds a ZIP archive and a 7Z archive, like this:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| baz.exe | PE | 0 | 0 |
| ├── sfx.zip | ZIP | 1 | 1 |
| │ └── hello.txt | ASCII | 2 | 0 |
| └── sfx.7z | 7Z | 1 | 1 |
| └── world.txt | ASCII | 2 | 0 |
(A) If we scan for embedded files at any layer, we may detect:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| ├── foo.tar | TAR | 1 | 0 |
| │ ├── bar.zip | ZIP | 2 | 1 |
| │ │ └── hola.txt | ASCII | 3 | 0 |
| │ ├── baz.exe | PE | 2 | 1 |
| │ │ ├── sfx.zip | ZIP | 3 | 1 |
| │ │ │ └── hello.txt | ASCII | 4 | 0 |
| │ │ └── sfx.7z | 7Z | 3 | 1 |
| │ │ └── world.txt | ASCII | 4 | 0 |
| │ ├── sfx.zip | ZIP | 2 | 1 |
| │ │ └── hello.txt | ASCII | 3 | 0 |
| │ └── sfx.7z | 7Z | 2 | 1 |
| │ └── world.txt | ASCII | 3 | 0 |
| ├── sfx.zip | ZIP | 1 | 1 |
| └── sfx.7z | 7Z | 1 | 1 |
(A) is bad because it scans content more than once.
Note that for the GZ layer, it may detect the ZIP and 7Z if the
signature hits on the compressed data, which it might, though
extracting the ZIP and 7Z will likely fail.
The reason the above doesn't happen now is that we restrict embedded
type scans for a bunch of archive formats to include GZ and TAR.
(B) If we scan for embedded files at the foo.tar layer, we may detect:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| └── foo.tar | TAR | 1 | 0 |
| ├── bar.zip | ZIP | 2 | 1 |
| │ └── hola.txt | ASCII | 3 | 0 |
| ├── baz.exe | PE | 2 | 1 |
| ├── sfx.zip | ZIP | 2 | 1 |
| │ └── hello.txt | ASCII | 3 | 0 |
| └── sfx.7z | 7Z | 2 | 1 |
| └── world.txt | ASCII | 3 | 0 |
(B) is almost right. But we can achieve it easily enough only scanning for
embedded content in the current fmap when the "nested fmap level" is 0.
The upside is that it should safely detect all embedded content, even if
it may think the sfz.zip and sfx.7z are in foo.tar instead of in baz.exe.
The biggest risk I can think of affects ZIPs. SFXZIP detection
is identical to ZIP detection, which is why we don't allow SFXZIP to be
detected if insize of a ZIP. If we only allow embedded type scanning at
fmap-layer 0 in each buffer, this will fail to detect the embedded ZIP
if the bar.exe was not compressed in foo.zip and if non-compressed files
extracted from ZIPs aren't extracted as new buffers:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.zip | ZIP | 0 | 0 |
| └── bar.exe | PE | 1 | 1 |
| └── sfx.zip | ZIP | 2 | 2 |
Provided that we ensure all files extracted from zips are scanned in
new buffers, option (B) should be safe.
(C) If we scan for embedded files at the baz.exe layer, we may detect:
| description | type | rec level | nested fmap level |
| ------------------------- | ----- | --------- | ----------------- |
| foo.tar.gz | GZ | 0 | 0 |
| └── foo.tar | TAR | 1 | 0 |
| ├── bar.zip | ZIP | 2 | 1 |
| │ └── hola.txt | ASCII | 3 | 0 |
| └── baz.exe | PE | 2 | 1 |
| ├── sfx.zip | ZIP | 3 | 1 |
| │ └── hello.txt | ASCII | 4 | 0 |
| └── sfx.7z | 7Z | 3 | 1 |
| └── world.txt | ASCII | 4 | 0 |
(C) is right. But it's harder to achieve. For this example we can get it by
restricting 7ZSFX and ZIPSFX detection only when scanning an executable.
But that may mean losing detection of archives embedded elsewhere.
And we'd have to identify allowable container types for each possible
embedded type, which would be very difficult.
So this commit aims to solve the issue the (B)-way.
Note that in all situations, we still have to scan with file typing
enabled to determine if we need to reassign the current file type, such
as re-identifying a Bzip2 archive as a DMG that happens to be Bzip2-
compressed. Detection of DMG and a handful of other types rely on
finding data partway through or near the ned of a file before
reassigning the entire file as the new type.
Other fixes and considerations in this commit:
- The utf16 HTML parser has weak error handling, particularly with respect
to creating a nested fmap for scanning the ascii decoded file.
This commit cleans up the error handling and wraps the nested scan with
the recursion-stack push()/pop() for correct recursion tracking.
Before this commit, each container layer had a flag to indicate if the
container layer is valid.
We need something similar so that the cli_recursion_stack_get_*()
functions ignore normalized layers. Details...
Imagine an LDB signature for HTML content that specifies a ZIP
container. If the signature actually alerts on the normalized HTML and
you don't ignore normalized layers for the container check, it will
appear as though the alert is in an HTML container rather than a ZIP
container.
This commit accomplishes this with a boolean you set in the scan context
before scanning a new layer. Then when the new fmap is created, it will
use that flag to set similar flag for the layer. The context flag is
reset those that anything after this doesn't have that flag.
The flag allows the new recursion_stack_get() function to ignore
normalized layers when iterating the stack to return a layer at a
requested index, negative or positive.
Scanning normalized extracted/normalized javascript and VBA should also
use the 'layer is normalized' flag.
- This commit also fixes Heuristic.Broken.Executable alert for ELF files
to make sure that:
A) these only alert if cli_append_virus() returns CL_VIRUS (aka it
respects the FP check).
B) all broken-executable alerts for ELF only happen if the
SCAN_HEURISTIC_BROKEN option is enabled.
- This commit also cleans up the error handling in cli_magic_scan_dir().
This was needed so we could correctly apply the layer-is-normalized-flag
to all VBA macros extracted to a directory when scanning the directory.
- Also fix an issue where exceeding scan maximums wouldn't cause embedded
file detection scans to abort. Granted we don't actually want to abort
if max filesize or max recursion depth are exceeded... only if max
scansize, max files, and max scantime are exceeded.
Add 'abort_scan' flag to scan context, to protect against depending on
correct error propagation for fatal conditions. Instead, setting this
flag in the scan context should guarantee that a fatal condition deep in
scan recursion isn't lost which result in more stuff being scanned
instead of aborting. This shouldn't be necessary, but some status codes
like CL_ETIMEOUT never used to be fatal and it's easier to do this than
to verify every parser only returns CL_ETIMEOUT and other "fatal
status codes" in fatal conditions.
- Remove duplicate is_tar() prototype from filestypes.c and include
is_tar.h instead.
- Presently we create the fmap hash when creating the fmap.
This wastes a bit of CPU if the hash is never needed.
Now that we're creating fmap's for all embedded files discovered with
file type recognition scans, this is a much more frequent occurence and
really slows things down.
This commit fixes the issue by only creating fmap hashes as needed.
This should not only resolve the perfomance impact of creating fmap's
for all embedded files, but also should improve performance in general.
- Add allmatch check to the zip parser after the central-header meta
match. That way we don't multiple alerts with the same match except in
allmatch mode. Clean up error handling in the zip parser a tiny bit.
- Fixes to ensure that the scan limits such as scansize, filesize,
recursion depth, # of embedded files, and scantime are always reported
if AlertExceedsMax (--alert-exceeds-max) is enabled.
- Fixed an issue where non-fatal alerts for exceeding scan maximums may
mask signature matches later on. I changed it so these alerts use the
"possibly unwanted" alert-type and thus only alert if no other alerts
were found or if all-match or heuristic-precedence are enabled.
- Added the "Heuristics.Limits.Exceeded.*" events to the JSON metadata
when the --gen-json feature is enabled. These will show up once under
"ParseErrors" the first time a limit is exceeded. In the present
implementation, only one limits-exceeded events will be added, so as to
prevent a malicious or malformed sample from filling the JSON buffer
with millions of events and using a tonne of RAM.
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ret = cli_bytecode_runhook ( ctx , ctx - > engine , bc_ctx , BC_MACHO_UNPACKER , ctx - > fmap ) ;
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cli_dbgmsg ( " Finished running bytecode hook \n " ) ;
if ( CL_SUCCESS = = ret ) {
// check for unpacked/rebuilt executable
ndesc = cli_bytecode_context_getresult_file ( bc_ctx , & tempfile ) ;
if ( ndesc ! = - 1 & & tempfile ) {
cli_dbgmsg ( " cli_unpackmacho: Unpacked and rebuilt Mach-O executable saved in %s \n " , tempfile ) ;
lseek ( ndesc , 0 , SEEK_SET ) ;
cli_dbgmsg ( " ***** Scanning rebuilt Mach-O file ***** \n " ) ;
ret = cli_magic_scan_desc ( ndesc , tempfile , ctx , NULL , LAYER_ATTRIBUTES_NONE ) ;
}
}
done :
// cli_bytecode_context_getresult_file() gives up ownership of temp file, so we must clean it up.
if ( - 1 ! = ndesc ) {
close ( ndesc ) ;
}
if ( NULL ! = tempfile ) {
if ( ! ctx - > engine - > keeptmp ) {
( void ) cli_unlink ( tempfile ) ;
}
free ( tempfile ) ;
}
if ( bc_ctx_set ) {
cli_bytecode_context_destroy ( bc_ctx ) ;
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}
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return ret ;
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}
