Rename Heuristics.Email.ExceedsMax alerts to start with
Heuristics.Limits.Exceeded.Email instead, so that all heuristic alerts
for exceeded scan limits have the same prefix.
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.
Adds an equivalent functionality to ClamScan's --gen-json option to
ClamD.
Behavior for GenerateMetadataJson is the same as with --gen-json.
If Debug is enabled, it will print out the JSON after each scan.
If LeaveTemporaryFiles is enabled, it will drop a metadat.json file
in the scan temp directory, which of course may be customized using
the TemporaryDirectory option.
The CURL_CA_BUNDLE environment variable used by freshclam & clamsubmit to
specify a custom path to a CA bundle is undocumented.
Feature was added here: https://bugzilla.clamav.net/show_bug.cgi?id=12504
Resolves: https://github.com/Cisco-Talos/clamav/issues/175
Also document:
- clamd/clamscan: using LD_LIBRARY_PATH to find libclamunrar_iface.so/dylib
- sigtool: using SIGNDUSER, SIGNDPASS for auth creds when building CVD
This info also needs to be added to the online documentation.
Disable the HTTPUserAgent config option if the DatabaseMirror uses
clamav.net. This will prevent users from being inadvertently blocked and
will ensure that we can keep better metrics on which clamav versions are
being used.
This change is needed because we observed some users being blocked by
the new CDN rules when they set custom user-agents.
Improvements to use modern block list and allow list verbiage.
blacklist -> block list
whitelist -> allow listed
blacklisted -> blocked
whitelisted -> allowed
In the case of certificate verification, use "trust" or "verify" when
something is allowed.
Also changed domainlist -> domain list (or DomainList) to match.
There are some merits of having the configs in `/etc/clamav` and the databases
in `/var/lib/clamav` to match the way the distros all package it and so these
directories can be mounted volumes if needed.
The DATABASE_DIRECTORY and APP_CONFIG_DIRECTORY variables don't support
absolute paths. This patch changes that.
Added special warning messages for 403 and 429 HTTP codes.
For 403, FreshClam will fail (non-zero exit code) if not in daemon-mode.
For 429, FreshClam will succeed (exit 0) if not in daemon-mode.
Adds If-Modified-Since header for CVD downloads (not just CVD-head)
which should reduce data usage if DNS is advertising a newer version
than is actually available, which seems to happen sometimes due to
caching issues, it should still fail out when this happens - it just
won't have to download the older CVD, and should detect the HTTP 304
(Not-Modified) response instead.
Also replaced "Freshclam" with "FreshClam" in a few places, for
consistency.
This commit resolves https://bugzilla.clamav.net/show_bug.cgi?id=12673
Changes in 0.103 to order of operations for creating fmaps and
performaing hashes of fmaps resulted errors when scanning files that are
4096M and a different (but related) error when scanning files > 4096M.
This is despite the fact that scanning is supposed to be limited to
--max-scansize (MaxScanSize) and was also apparently limited to
INT_MAX - 2 (aka ~1.999999G) back in 2014 to alleviate reported crashes
for a few large file formats.
(see https://bugzilla.clamav.net/show_bug.cgi?id=10960)
This last limitation was not documented, so I added it to the sample
clamd.conf.
Anyways, the main issue is that the fmap module was using "unsigned int"
and was then enforcing a limitation (verbose error messages) when that
a map length exceeded the capapacity of an unsigned int. This commit
switches the associated variables over to uint64_t, and while fmaps are
still limited to size_t in other places, the fmap module will at least
work with files > 4G on 64bit systems.
In testing this, I found that the time to hash a file, particularly when
hashing a file on an NTFS partition from Linux was really slow because
we were hashing in FILEBUFF chunks (about 8K) at a time. Increasing
this to 10MB chunks speeds up scanning of large files.
Finally, now that hashing is performed immediately when an fmap is
created for a file, hashing of files larger than max-scansize was
occuring. This commit adds checks to bail out early if the file size
exceeds the maximum before creating an fmap. It will alert with the
Heuristics.Limits.Exceeded name if the heuristic is enabled.
Also fixed CheckFmapFeatures.cmake module that detects if
sysconf(_SC_PAGESIZE) is available.
VirusEvent commands may use %v to get the signature name (virus name)
for the alert but do not have a format option to get the file name.
This commit adds %f to get the file name.
The VirusEvent feature does provide two environment variables,
$CLAM_VIRUSEVENT_FILENAME and $CLAM_VIRUSEVENT_VIRUSNAME which provide
file and virus names, but they weren't documented in the sample configs.
This commit also adds these environment variables to the sample configs.
Added a new scan option to alert on broken media (graphics) file
formats. This feature mitigates the risk of malformed media files
intended to exploit vulnerabilities in other software. At present
media validation exists for JPEG, TIFF, PNG, and GIF files.
To enable this feature, set `AlertBrokenMedia yes` in clamd.conf, or
use the `--alert-broken-media` option when using `clamscan`.
These options are disabled by default for now.
Application developers may enable this scan option by enabling
`CL_SCAN_HEURISTIC_BROKEN_MEDIA` for the `heuristic` scan option bit
field.
Fixed PNG parser logic bugs that caused an excess of parsing errors
and fixed a stack exhaustion issue affecting some systems when
scanning PNG files. PNG file type detection was disabled via
signature database update for 0.103.0 to mitigate effects from these
bugs.
Fixed an issue where PNG and GIF files no longer work with Target:5
(graphics) signatures if detected as CL_TYPE_PNG/GIF rather than as
CL_TYPE_GRAPHICS. Target types now support up to 10 possible file
types to make way for additional graphics types in future releases.
Scanning JPEG, TIFF, PNG, and GIF files will no longer return "parse"
errors when file format validation fails. Instead, the scan will alert
with the "Heuristics.Broken.Media" signature prefix and a descriptive
suffix to indicate the issue, provided that the "alert broken media"
feature is enabled.
GIF format validation will no longer fail if the GIF image is missing
the trailer byte, as this appears to be a relatively common issue in
otherwise functional GIF files.
Added a TIFF dynamic configuration (DCONF) option, which was missing.
This will allow us to disable TIFF format validation via signature
database update in the event that it proves to be problematic.
This feature already exists for many other file types.
Added CL_TYPE_JPEG and CL_TYPE_TIFF types.
Default --wait timeout adjusted from 29 to 30 seconds.
--ping and --wait should exit with CL_ETIMEOUT (21) on timeout.
--ping should only return exit code 0 if clamd responds.
Silenced a couple switch fall-through warnings.
Added proc_fd_fname stack buffer to use with readlink, because the
pointers are restricted and using the same buffer with readlink could
result in undefined behavior.
Relocated clamonacc log verbosity initialization so early verbose log
messages will be printed.
Added a new status code for clamonacc startup checks so the --ping
feature can exit the process early with exit code 0.
Update the NEWS to add and correct content prior to the release
candidate.
Changed the version string to have the -rc suffix.
Also fixed a couple of --help and manpage issues.
This patch adds experimental-quality CMake build tooling.
The libmspack build required a modification to use "" instead of <> for
header #includes. This will hopefully be included in the libmspack
upstream project when adding CMake build tooling to libmspack.
Removed use of libltdl when using CMake.
Flex & Bison are now required to build.
If -DMAINTAINER_MODE, then GPERF is also required, though it currently
doesn't actually do anything. TODO!
I found that the autotools build system was generating the lexer output
but not actually compiling it, instead using previously generated (and
manually renamed) lexer c source. As a consequence, changes to the .l
and .y files weren't making it into the build. To resolve this, I
removed generated flex/bison files and fixed the tooling to use the
freshly generated files. Flex and bison are now required build tools.
On Windows, this adds a dependency on the winflexbison package,
which can be obtained using Chocolatey or may be manually installed.
CMake tooling only has partial support for building with external LLVM
library, and no support for the internal LLVM (to be removed in the
future). I.e. The CMake build currently only supports the bytecode
interpreter.
Many files used include paths relative to the top source directory or
relative to the current project, rather than relative to each build
target. Modern CMake support requires including internal dependency
headers the same way you would external dependency headers (albeit
with "" instead of <>). This meant correcting all header includes to
be relative to the build targets and not relative to the workspace.
For example, ...
```c
include "../libclamav/clamav.h"
include "clamd/clamd_others.h"
```
... becomes:
```c
// libclamav
include "clamav.h"
// clamd
include "clamd_others.h"
```
Fixes header name conflicts by renaming a few of the files.
Converted the "shared" code into a static library, which depends on
libclamav. The ironically named "shared" static library provides
features common to the ClamAV apps which are not required in
libclamav itself and are not intended for use by downstream projects.
This change was required for correct modern CMake practices but was
also required to use the automake "subdir-objects" option.
This eliminates warnings when running autoreconf which, in the next
version of autoconf & automake are likely to break the build.
libclamav used to build in multiple stages where an earlier stage is
a static library containing utils required by the "shared" code.
Linking clamdscan and clamdtop with this libclamav utils static lib
allowed these two apps to function without libclamav. While this is
nice in theory, the practical gains are minimal and it complicates
the build system. As such, the autotools and CMake tooling was
simplified for improved maintainability and this feature was thrown
out. clamdtop and clamdscan now require libclamav to function.
Removed the nopthreads version of the autotools
libclamav_internal_utils static library and added pthread linking to
a couple apps that may have issues building on some platforms without
it, with the intention of removing needless complexity from the
source. Kept the regular version of libclamav_internal_utils.la
though it is no longer used anywhere but in libclamav.
Added an experimental doxygen build option which attempts to build
clamav.h and libfreshclam doxygen html docs.
The CMake build tooling also may build the example program(s), which
isn't a feature in the Autotools build system.
Changed C standard to C90+ due to inline linking issues with socket.h
when linking libfreshclam.so on Linux.
Generate common.rc for win32.
Fix tabs/spaces in shared Makefile.am, and remove vestigial ifndef
from misc.c.
Add CMake files to the automake dist, so users can try the new
CMake tooling w/out having to build from a git clone.
clamonacc changes:
- Renamed FANOTIFY macro to HAVE_SYS_FANOTIFY_H to better match other
similar macros.
- Added a new clamav-clamonacc.service systemd unit file, based on
the work of ChadDevOps & Aaron Brighton.
- Added missing clamonacc man page.
Updates to clamdscan man page, add missing options.
Remove vestigial CL_NOLIBCLAMAV definitions (all apps now use
libclamav).
Rename Windows mspack.dll to libmspack.dll so all ClamAV-built
libraries have the lib-prefix with Visual Studio as with CMake.
Removed all autotools generates files. Autotools (autoconf, automake,
libtool, pkg-config, m4) will be required from now on for builds from
git clones.
Added autogen.sh to be run before ./configure.
Significant update to main .gitignore file.
Removed extraneous .gitignore files. A Git repository only needs one
.gitignore file.
Add notices to man pages and help strings cautioning against running
bytecode signatures from untrusted sources.
Also adds missing BytecodeUnsigned option to clamd.conf.sample files.
Add clamd config option to force blocking clamd database reload to
conserve RAM. Users may set `ConcurrentDatabaseReload no` in their
clamd.conf config file to force a blocking reload.
The blocking mode will still perform the reload in a new thread, but
will first free the current database, wait for scans targeting that
database to complete, and then load the new database in the new thread
and wait (`pthread_join()`) on that thread. Once loaded, any pending
scans will continue. This is effectively the same behavior as how
clamd reloads worked before the multi-threaded database reload feature
was added.
Add Data-Loss-Prevention option to detect credit cards only, excluding
debit and private label cards where possible.
You can select the credit card-only DLP mode for clamscan with the
`--structured-cc-mode` command-line option.
You can select the credit card-only DLP mode for clamd with the
`StructuredCCOnly` clamd.conf config option.
This patch also adds credit card matching for additional vendors:
- Mastercard 2016
- China Union Pay
- Discover 2009
This fixes issues in cvd download when network speed is slow.
Setting is passed to libcurl CURLOPT_TIMEOUT. Original default of 60s
was not enough if network speed is limited. Curl handles this as
total time for http(s) transfer.
https://curl.haxx.se/libcurl/c/CURLOPT_TIMEOUT.html
Also change commented out setting of ReceiveTimeout on example configs
to somewhat sensible value (1800s).
Signed-off-by: Tuomo Soini <tis@foobar.fi>
