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crypt32: Check key usage during chain validation.

This commit is contained in:
Juan Lang 2009-10-20 18:25:06 -07:00 committed by Alexandre Julliard
parent f2057592bf
commit 7fa618aa8e
2 changed files with 114 additions and 17 deletions
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125
dlls/crypt32/chain.c
View File

@ -815,6 +815,106 @@ static void dump_element(PCCERT_CONTEXT cert)
dump_extension(&cert->pCertInfo->rgExtension[i]);
}
static void trace_usage(const CRYPT_BIT_BLOB *usage)
{
#define trace_usage_bit(bits, bit) \
if ((bits) & (bit)) TRACE_(chain)("%s\n", #bit)
if (usage->cbData)
{
trace_usage_bit(usage->pbData[0], CERT_DIGITAL_SIGNATURE_KEY_USAGE);
trace_usage_bit(usage->pbData[0], CERT_NON_REPUDIATION_KEY_USAGE);
trace_usage_bit(usage->pbData[0], CERT_KEY_ENCIPHERMENT_KEY_USAGE);
trace_usage_bit(usage->pbData[0], CERT_DATA_ENCIPHERMENT_KEY_USAGE);
trace_usage_bit(usage->pbData[0], CERT_KEY_AGREEMENT_KEY_USAGE);
trace_usage_bit(usage->pbData[0], CERT_KEY_CERT_SIGN_KEY_USAGE);
trace_usage_bit(usage->pbData[0], CERT_CRL_SIGN_KEY_USAGE);
trace_usage_bit(usage->pbData[0], CERT_ENCIPHER_ONLY_KEY_USAGE);
}
#undef trace_usage_bit
if (usage->cbData > 1 && usage->pbData[1] & CERT_DECIPHER_ONLY_KEY_USAGE)
TRACE_(chain)("CERT_DECIPHER_ONLY_KEY_USAGE\n");
}
static BOOL CRYPT_KeyUsageValid(PCCERT_CONTEXT cert, BOOL isRoot, BOOL isCA,
DWORD index)
{
PCERT_EXTENSION ext;
BOOL ret;
BYTE usageBits = 0;
ext = CertFindExtension(szOID_KEY_USAGE, cert->pCertInfo->cExtension,
cert->pCertInfo->rgExtension);
if (ext)
{
CRYPT_BIT_BLOB usage;
DWORD size = sizeof(usage);
ret = CryptDecodeObjectEx(cert->dwCertEncodingType, X509_BITS,
ext->Value.pbData, ext->Value.cbData, CRYPT_DECODE_NOCOPY_FLAG, NULL,
&usage, &size);
if (!ret)
return FALSE;
else if (usage.cbData > 2)
{
/* The key usage extension only defines 9 bits => no more than 2
* bytes are needed to encode all known usages.
*/
return FALSE;
}
else
{
/* The only bit relevant to chain validation is the keyCertSign
* bit, which is always in the least significant byte of the
* key usage bits.
*/
usageBits = usage.pbData[usage.cbData - 1];
if (TRACE_ON(chain))
trace_usage(&usage);
}
}
if (isCA)
{
if (!ext)
{
/* MS appears to violate RFC 3280, section 4.2.1.3 (Key Usage)
* here. Quoting the RFC:
* "This [key usage] extension MUST appear in certificates that
* contain public keys that are used to validate digital signatures
* on other public key certificates or CRLs."
* Most of the test chains' certs do not contain key usage
* extensions, yet are allowed to be CA certs. This appears to
* be common usage too: the root CA in a chain often does not have
* the key usage extension. We are a little more restrictive:
* root certs, which commonly do not have any extensions, are
* allowed to sign certificates without the key usage extension.
*/
WARN_(chain)("no key usage extension on a CA cert\n");
ret = isRoot;
}
else
{
if (!(usageBits & CERT_KEY_CERT_SIGN_KEY_USAGE))
{
WARN_(chain)("keyCertSign not asserted on a CA cert\n");
ret = FALSE;
}
else
ret = TRUE;
}
}
else
{
if (ext && (usageBits & CERT_KEY_CERT_SIGN_KEY_USAGE))
{
WARN_(chain)("keyCertSign asserted on a non-CA cert\n");
ret = FALSE;
}
else
ret = TRUE;
}
return ret;
}
static BOOL CRYPT_CriticalExtensionsSupported(PCCERT_CONTEXT cert)
{
BOOL ret = TRUE;
@ -833,13 +933,7 @@ static BOOL CRYPT_CriticalExtensionsSupported(PCCERT_CONTEXT cert)
else if (!strcmp(oid, szOID_NAME_CONSTRAINTS))
ret = TRUE;
else if (!strcmp(oid, szOID_KEY_USAGE))
{
static int warned;
if (!warned++)
FIXME("key usage extension unsupported, ignoring\n");
ret = TRUE;
}
else if (!strcmp(oid, szOID_SUBJECT_ALT_NAME))
ret = TRUE;
else
@ -865,21 +959,21 @@ static void CRYPT_CheckSimpleChain(PCertificateChainEngine engine,
chain->cElement, debugstr_w(filetime_to_str(time)));
for (i = chain->cElement - 1; i >= 0; i--)
{
BOOL isRoot;
if (TRACE_ON(chain))
dump_element(chain->rgpElement[i]->pCertContext);
if (CertVerifyTimeValidity(time,
chain->rgpElement[i]->pCertContext->pCertInfo) != 0)
chain->rgpElement[i]->TrustStatus.dwErrorStatus |=
CERT_TRUST_IS_NOT_TIME_VALID;
if (i == chain->cElement - 1)
isRoot = CRYPT_IsCertificateSelfSigned(
chain->rgpElement[i]->pCertContext);
else
isRoot = FALSE;
if (i != 0)
{
BOOL isRoot;
if (i == chain->cElement - 1)
isRoot = CRYPT_IsCertificateSelfSigned(
chain->rgpElement[i]->pCertContext);
else
isRoot = FALSE;
/* Check the signature of the cert this issued */
if (!CryptVerifyCertificateSignatureEx(0, X509_ASN_ENCODING,
CRYPT_VERIFY_CERT_SIGN_SUBJECT_CERT,
@ -914,6 +1008,10 @@ static void CRYPT_CheckSimpleChain(PCertificateChainEngine engine,
chain->rgpElement[i]->TrustStatus.dwErrorStatus |=
CERT_TRUST_INVALID_BASIC_CONSTRAINTS;
}
if (!CRYPT_KeyUsageValid(chain->rgpElement[i]->pCertContext, isRoot,
constraints.fCA, i))
chain->rgpElement[i]->TrustStatus.dwErrorStatus |=
CERT_TRUST_IS_NOT_VALID_FOR_USAGE;
if (CRYPT_IsSimpleChainCyclic(chain))
{
/* If the chain is cyclic, then the path length constraints
@ -924,7 +1022,6 @@ static void CRYPT_CheckSimpleChain(PCertificateChainEngine engine,
CERT_TRUST_IS_PARTIAL_CHAIN |
CERT_TRUST_INVALID_BASIC_CONSTRAINTS;
}
/* FIXME: check valid usages */
/* Check whether every critical extension is supported */
if (!CRYPT_CriticalExtensionsSupported(
chain->rgpElement[i]->pCertContext))

6
dlls/crypt32/tests/chain.c
View File

@ -1782,7 +1782,7 @@ static ChainCheck chainCheck[] = {
{ { CERT_TRUST_IS_NOT_TIME_NESTED, CERT_TRUST_HAS_PREFERRED_ISSUER },
{ CERT_TRUST_IS_UNTRUSTED_ROOT | CERT_TRUST_IS_NOT_VALID_FOR_USAGE, 0 },
1, simpleStatus15 },
TODO_ERROR },
0 },
/* Windows XP incorrectly does not complain that the end cert's key usage is
* invalid, so ignore that error.
*/
@ -1791,7 +1791,7 @@ static ChainCheck chainCheck[] = {
CERT_TRUST_HAS_PREFERRED_ISSUER },
{ CERT_TRUST_IS_UNTRUSTED_ROOT | CERT_TRUST_IS_NOT_VALID_FOR_USAGE, 0 },
1, simpleStatus16 },
TODO_ERROR },
0 },
{ { sizeof(chain17) / sizeof(chain17[0]), chain17 },
{ { CERT_TRUST_IS_NOT_TIME_NESTED, CERT_TRUST_HAS_PREFERRED_ISSUER },
{ CERT_TRUST_IS_UNTRUSTED_ROOT, 0 }, 1, simpleStatus17 },
@ -1800,7 +1800,7 @@ static ChainCheck chainCheck[] = {
{ { CERT_TRUST_IS_NOT_TIME_NESTED, CERT_TRUST_HAS_PREFERRED_ISSUER },
{ CERT_TRUST_IS_UNTRUSTED_ROOT | CERT_TRUST_IS_NOT_VALID_FOR_USAGE, 0 },
1, simpleStatus18 },
TODO_ERROR },
0 },
{ { sizeof(selfSignedChain) / sizeof(selfSignedChain[0]), selfSignedChain },
{ { 0, CERT_TRUST_HAS_PREFERRED_ISSUER },
{ CERT_TRUST_IS_NOT_TIME_VALID | CERT_TRUST_IS_UNTRUSTED_ROOT, 0 },