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fix(signature): fenrir 2626 enforce min hash strength

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This commit is contained in:
David Garske
2026-05-18 13:59:51 -07:00
parent 2fad30e394
commit 9a5bb8eb23
1 changed files with 42 additions and 0 deletions
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wolfcrypt/src/signature.c
+42
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@@ -51,6 +51,36 @@
#endif
#endif
/* Minimum hash strength accepted by the wc_SignatureVerify/Generate
* convenience APIs. Default is SHA-256 to keep MD5 and SHA-1 (both with
* known collision attacks) out of new code. Define WC_SIG_MIN_HASH_TYPE
* to a weaker wc_HashType (e.g. WC_HASH_TYPE_SHA) to opt back into legacy
* behavior. The lower-level wc_SignatureVerifyHash/wc_SignatureGenerateHash
* APIs are unaffected. */
#ifndef WC_SIG_MIN_HASH_TYPE
#define WC_SIG_MIN_HASH_TYPE WC_HASH_TYPE_SHA256
#endif
static int wc_SignatureCheckHashStrength(enum wc_HashType hash_type)
{
int min_sz, this_sz;
min_sz = wc_HashGetDigestSize(WC_SIG_MIN_HASH_TYPE);
if (min_sz < 0) {
/* configured floor not compiled in - skip enforcement */
return 0;
}
this_sz = wc_HashGetDigestSize(hash_type);
if (this_sz < 0) {
return this_sz;
}
if (this_sz < min_sz) {
WOLFSSL_MSG("wc_Signature*: hash weaker than WC_SIG_MIN_HASH_TYPE");
return BAD_FUNC_ARG;
}
return 0;
}
#if !defined(NO_RSA) && defined(WOLFSSL_CRYPTOCELL)
extern int cc310_RsaSSL_Verify(const byte* in, word32 inLen, byte* sig,
@@ -356,6 +386,12 @@ int wc_SignatureVerify(
}
hash_enc_len = hash_len = (word32)ret;
/* Reject hashes weaker than WC_SIG_MIN_HASH_TYPE (default SHA-256) */
ret = wc_SignatureCheckHashStrength(hash_type);
if (ret != 0) {
return ret;
}
#ifndef NO_RSA
if (sig_type == WC_SIGNATURE_TYPE_RSA_W_ENC) {
/* For RSA with ASN.1 encoding include room */
@@ -555,6 +591,12 @@ int wc_SignatureGenerate_ex(
}
hash_enc_len = hash_len = (word32)ret;
/* Reject hashes weaker than WC_SIG_MIN_HASH_TYPE (default SHA-256) */
ret = wc_SignatureCheckHashStrength(hash_type);
if (ret != 0) {
return ret;
}
#if !defined(NO_RSA) && !defined(WOLFSSL_RSA_PUBLIC_ONLY)
if (sig_type == WC_SIGNATURE_TYPE_RSA_W_ENC) {
/* For RSA with ASN.1 encoding include room */