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internally check PKCS7 content digest against messageDigest attribute

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This commit is contained in:
Chris Conlon 2019-08-23 16:40:12 -06:00
parent 2c97b040ff
commit 12687e5a2a
1 changed files with 125 additions and 1 deletions
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126
wolfcrypt/src/pkcs7.c
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@ -3399,6 +3399,118 @@ static int wc_PKCS7_BuildSignedDataDigest(PKCS7* pkcs7, byte* signedAttrib,
}
/* Verifies CMS/PKCS7 SignedData content digest matches that which is
* included in the messageDigest signed attribute. Only called when
* signed attributes are present, otherwise original signature verification
* is done over content.
*
* pkcs7 - pointer to initialized PKCS7 struct
* hashBuf - pointer to user-provided hash buffer, used with
* wc_PKCS7_VerifySignedData_ex()
* hashBufSz - size of hashBuf, octets
*
* return 0 on success, negative on error */
static int wc_PKCS7_VerifyContentMessageDigest(PKCS7* pkcs7,
const byte* hashBuf,
word32 hashSz)
{
int ret = 0, innerAttribSz = 0;
word32 digestSz = 0, idx = 0;
byte* digestBuf = NULL;
#ifdef WOLFSSL_SMALL_STACK
byte* digest;
#else
byte digest[MAX_PKCS7_DIGEST_SZ];
#endif
PKCS7DecodedAttrib* attrib;
enum wc_HashType hashType;
/* messageDigest OID (1.2.840.113549.1.9.4) */
const byte mdOid[] =
{ 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x09, 0x04 };
if (pkcs7 == NULL)
return BAD_FUNC_ARG;
if ((pkcs7->content == NULL || pkcs7->contentSz == 0) &&
(hashBuf == NULL || hashSz == 0)) {
WOLFSSL_MSG("SignedData bundle has no content or hash to verify");
return BAD_FUNC_ARG;
}
/* lookup messageDigest attribute */
attrib = findAttrib(pkcs7, mdOid, sizeof(mdOid));
if (attrib == NULL) {
WOLFSSL_MSG("messageDigest attribute not in bundle, must be when " +
"signed attribs are present");
return ASN_PARSE_E;
}
/* advance past attrib->value ASN.1 header and length */
if (attrib->value[idx++] != ASN_OCTET_STRING)
return ASN_PARSE_E;
if (GetLength(attrib->value, &idx, &innerAttribSz, attrib->valueSz) < 0)
return ASN_PARSE_E;
/* get hash type and size */
hashType = wc_OidGetHash(pkcs7->hashOID);
if (hashType == WC_HASH_TYPE_NONE) {
WOLFSSL_MSG("Error getting hash type for PKCS7 content verification");
return BAD_FUNC_ARG;
}
/* build content hash if needed, or use existing hash value */
if (hashBuf == NULL) {
#ifdef WOLFSSL_SMALL_STACK
digest = (byte*)XMALLOC(MAX_PKCS7_DIGEST_SZ, pkcs7->heap,
DYNAMIC_TYPE_TMP_BUFFER);
if (digest == NULL)
return MEMORY_E;
#endif
XMEMSET(digest, 0, MAX_PKCS7_DIGEST_SZ);
ret = wc_Hash(hashType, pkcs7->content, pkcs7->contentSz, digest,
MAX_PKCS7_DIGEST_SZ);
if (ret < 0) {
WOLFSSL_MSG("Error hashing PKCS7 content for verification");
#ifdef WOLFSSL_SMALL_STACK
XFREE(digest, pkcs7->heap, DYNAMIC_TYPE_TMP_BUFFER);
#endif
return ret;
}
digestBuf = digest;
digestSz = wc_HashGetDigestSize(hashType);
} else {
/* user passed in pre-computed hash */
digestBuf = (byte*)hashBuf;
digestSz = hashSz;
}
/* compare generated to hash in messageDigest attribute */
if ((innerAttribSz != (int)digestSz) ||
(XMEMCMP(attrib->value + idx, digestBuf, digestSz) != 0)) {
WOLFSSL_MSG("Content digest does not match messageDigest attrib value");
#ifdef WOLFSSL_SMALL_STACK
XFREE(digest, pkcs7->heap, DYNAMIC_TYPE_TMP_BUFFER);
#endif
return SIG_VERIFY_E;
}
if (hashBuf == NULL) {
#ifdef WOLFSSL_SMALL_STACK
XFREE(digest, pkcs7->heap, DYNAMIC_TYPE_TMP_BUFFER);
#endif
}
return 0;
}
/* verifies SignedData signature, over either PKCS#7 DigestInfo or
* content digest.
*
@ -3426,7 +3538,7 @@ static int wc_PKCS7_SignedDataVerifySignature(PKCS7* pkcs7, byte* sig,
if (pkcs7 == NULL)
return BAD_FUNC_ARG;
/* build hash to verify against */
/* allocate space to build hash */
pkcs7DigestSz = MAX_PKCS7_DIGEST_SZ;
#ifdef WOLFSSL_SMALL_STACK
pkcs7Digest = (byte*)XMALLOC(pkcs7DigestSz, pkcs7->heap,
@ -3437,6 +3549,18 @@ static int wc_PKCS7_SignedDataVerifySignature(PKCS7* pkcs7, byte* sig,
XMEMSET(pkcs7Digest, 0, pkcs7DigestSz);
/* verify signed attrib digest matches that of content */
if (signedAttrib != NULL) {
ret = wc_PKCS7_VerifyContentMessageDigest(pkcs7, hashBuf, hashSz);
if (ret != 0) {
#ifdef WOLFSSL_SMALL_STACK
XFREE(pkcs7Digest, pkcs7->heap, DYNAMIC_TYPE_TMP_BUFFER);
#endif
return ret;
}
}
/* build hash to verify against */
ret = wc_PKCS7_BuildSignedDataDigest(pkcs7, signedAttrib,
signedAttribSz, pkcs7Digest,
&pkcs7DigestSz, &plainDigest,