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crypto/internal/fips140/rsa: check hash length in PKCS#1 v1.5 signatures

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This was already checked by crypto/rsa, so there should be no observable
change.

Change-Id: I2dfbfc7fd710a5782ab1d2eea8be8f5f6a6a6964
Reviewed-on: https://go-review.googlesource.com/c/go/+/765642
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Daniel McCarney <daniel@binaryparadox.net>
Reviewed-by: Roland Shoemaker <roland@golang.org>
This commit is contained in:
Filippo Valsorda 2026-04-11 14:48:19 +02:00
parent 47cc60743b
commit e01f29f918
1 changed files with 27 additions and 0 deletions
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27
src/crypto/internal/fips140/rsa/pkcs1v15.go
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@ -22,6 +22,9 @@ import (
// For performance, we don't use the generic ASN1 encoder. Rather, we
// precompute a prefix of the digest value that makes a valid ASN1 DER string
// with the correct contents.
//
// For any new entry, also add the size to [hashSize], and if applicable, add
// the hash name to [checkApprovedHashName].
var hashPrefixes = map[string][]byte{
"MD5": {0x30, 0x20, 0x30, 0x0c, 0x06, 0x08, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x02, 0x05, 0x05, 0x00, 0x04, 0x10},
"SHA-1": {0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00, 0x04, 0x14},
@ -69,6 +72,9 @@ func pkcs1v15ConstructEM(pub *PublicKey, hash string, hashed []byte) ([]byte, er
if !ok {
return nil, errors.New("crypto/rsa: unsupported hash function")
}
if len(hashed) != hashSize(hash) {
return nil, errors.New("crypto/rsa: hashed message length does not match hash function")
}
}
// EM = 0x00 || 0x01 || PS || 0x00 || T
@ -128,6 +134,27 @@ func verifyPKCS1v15(pub *PublicKey, hash string, hashed []byte, sig []byte) erro
return nil
}
func hashSize(hash string) int {
switch hash {
case "MD5":
return 16
case "SHA-1", "RIPEMD-160":
return 20
case "SHA-224", "SHA-512/224", "SHA3-224":
return 28
case "SHA-256", "SHA-512/256", "SHA3-256":
return 32
case "SHA-384", "SHA3-384":
return 48
case "SHA-512", "SHA3-512":
return 64
case "MD5+SHA1":
return 36
default:
return -1
}
}
func checkApprovedHashName(hash string) {
switch hash {
case "SHA-224", "SHA-256", "SHA-384", "SHA-512", "SHA-512/224", "SHA-512/256",