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Support RSA-PSS certificates in x509_utils_get_signature_alg

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RSA-PSS in X.509 is truly horrible, and OpenSSL does not expose very good APIs
to extract this, even though the library does handle it internally. Instead, we
must tediously unwrap RFC 4055's unnecessarily complicated encoding of
RFC 8017's unnecessarily flexible RSA-PSS definition.
This commit is contained in:
David Benjamin
2024-02-05 23:09:14 -05:00
committed by akallabeth
parent f987e304ee
commit 7548be62c3
2 changed files with 103 additions and 11 deletions
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2
libfreerdp/crypto/test/Test_x509_utils.c
View File

@@ -172,7 +172,6 @@ static const signature_alg_test_t signature_alg_tests[] = {
{ "ecdsa_sha384_cert.pem", WINPR_MD_SHA384 },
{ "ecdsa_sha512_cert.pem", WINPR_MD_SHA512 },
#if 0
{ "rsa_pss_sha1_cert.pem", WINPR_MD_SHA1 },
{ "rsa_pss_sha256_cert.pem", WINPR_MD_SHA256 },
{ "rsa_pss_sha384_cert.pem", WINPR_MD_SHA384 },
@@ -182,7 +181,6 @@ static const signature_alg_test_t signature_alg_tests[] = {
leaves the tls-server-end-point hash unspecified, so it should return WINPR_MD_NONE.
*/
{ "rsa_pss_sha256_mgf1_sha384_cert.pem", WINPR_MD_NONE },
#endif
};
static int TestSignatureAlgorithm(const signature_alg_test_t* test)

112
libfreerdp/crypto/x509_utils.c
View File

@@ -716,16 +716,8 @@ X509* x509_utils_from_pem(const char* data, size_t len, BOOL fromFile)
return x509;
}
WINPR_MD_TYPE x509_utils_get_signature_alg(const X509* xcert)
static WINPR_MD_TYPE hash_nid_to_winpr(int hash_nid)
{
WINPR_ASSERT(xcert);
const int nid = X509_get_signature_nid(xcert);
int hash_nid = 0;
if (OBJ_find_sigid_algs(nid, &hash_nid, NULL) != 1)
return WINPR_MD_NONE;
switch (hash_nid)
{
case NID_md2:
@@ -766,6 +758,108 @@ WINPR_MD_TYPE x509_utils_get_signature_alg(const X509* xcert)
}
}
static WINPR_MD_TYPE get_rsa_pss_digest(const X509_ALGOR* alg)
{
WINPR_MD_TYPE ret = WINPR_MD_NONE;
WINPR_MD_TYPE message_digest, mgf1_digest;
int param_type;
const void* param_value;
const ASN1_STRING* sequence;
const unsigned char* inp;
RSA_PSS_PARAMS* params = NULL;
X509_ALGOR* mgf1_digest_alg = NULL;
/* The RSA-PSS digest is encoded in a complex structure, defined in
https://www.rfc-editor.org/rfc/rfc4055.html. */
X509_ALGOR_get0(NULL, &param_type, &param_value, alg);
/* param_type and param_value the parameter in ASN1_TYPE form, but split into two parameters. A
SEQUENCE is has type V_ASN1_SEQUENCE, and the value is an ASN1_STRING with the encoded
structure. */
if (param_type != V_ASN1_SEQUENCE)
goto end;
sequence = param_value;
/* Decode the structure. */
inp = ASN1_STRING_get0_data(sequence);
params = d2i_RSA_PSS_PARAMS(NULL, &inp, ASN1_STRING_length(sequence));
if (params == NULL)
goto end;
/* RSA-PSS uses two hash algorithms, a message digest and also an MGF function which is, itself,
parameterized by a hash function. Both fields default to SHA-1, so we must also check for the
value being NULL. */
message_digest = WINPR_MD_SHA1;
if (params->hashAlgorithm != NULL)
{
const ASN1_OBJECT* obj;
X509_ALGOR_get0(&obj, NULL, NULL, params->hashAlgorithm);
message_digest = hash_nid_to_winpr(OBJ_obj2nid(obj));
if (message_digest == WINPR_MD_NONE)
goto end;
}
mgf1_digest = WINPR_MD_SHA1;
if (params->maskGenAlgorithm != NULL)
{
const ASN1_OBJECT* obj;
int mgf_param_type;
const void* mgf_param_value;
const ASN1_STRING* mgf_param_sequence;
/* First, check this is MGF-1, the only one ever defined. */
X509_ALGOR_get0(&obj, &mgf_param_type, &mgf_param_value, params->maskGenAlgorithm);
if (OBJ_obj2nid(obj) != NID_mgf1)
goto end;
/* MGF-1 is, itself, parameterized by a hash function, encoded as an AlgorithmIdentifier. */
if (mgf_param_type != V_ASN1_SEQUENCE)
goto end;
mgf_param_sequence = mgf_param_value;
inp = ASN1_STRING_get0_data(mgf_param_sequence);
mgf1_digest_alg = d2i_X509_ALGOR(NULL, &inp, ASN1_STRING_length(mgf_param_sequence));
if (mgf1_digest_alg == NULL)
goto end;
/* Finally, extract the digest. */
X509_ALGOR_get0(&obj, NULL, NULL, mgf1_digest_alg);
mgf1_digest = hash_nid_to_winpr(OBJ_obj2nid(obj));
if (mgf1_digest == WINPR_MD_NONE)
goto end;
}
/* If the two digests do not match, it is ambiguous which to return. tls-server-end-point leaves
it undefined, so return none.
https://www.rfc-editor.org/rfc/rfc5929.html#section-4.1 */
if (message_digest != mgf1_digest)
goto end;
ret = message_digest;
end:
RSA_PSS_PARAMS_free(params);
X509_ALGOR_free(mgf1_digest_alg);
return ret;
}
WINPR_MD_TYPE x509_utils_get_signature_alg(const X509* xcert)
{
WINPR_ASSERT(xcert);
const int nid = X509_get_signature_nid(xcert);
if (nid == NID_rsassaPss)
{
const X509_ALGOR* alg;
X509_get0_signature(NULL, &alg, xcert);
return get_rsa_pss_digest(alg);
}
int hash_nid = 0;
if (OBJ_find_sigid_algs(nid, &hash_nid, NULL) != 1)
return WINPR_MD_NONE;
return hash_nid_to_winpr(hash_nid);
}
char* x509_utils_get_common_name(const X509* xcert, size_t* plength)
{
X509_NAME* subject_name = X509_get_subject_name(xcert);