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Merge remote-tracking branch 'origin/topic/johanna/ticket-1212'

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* origin/topic/johanna/ticket-1212:
  Fix ocsp reply validation - there were a few things that definitely were wrong.
  fix null pointer dereference in ocsp verification code in case no certificate is sent as part as the ocsp reply.
This commit is contained in:
Robin Sommer 2014-09-04 16:16:36 -07:00
commit daae28c72e
8 changed files with 101 additions and 5 deletions
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69
src/file_analysis/analyzer/x509/functions.bif
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@ -104,6 +104,39 @@ STACK_OF(X509)* x509_get_untrusted_stack(VectorVal* certs_vec)
return untrusted_certs;
}
// We need this function to be able to identify the signer certificate of an
// OCSP request out of a list of possible certificates.
X509* x509_get_ocsp_signer(STACK_OF(X509) *certs, OCSP_RESPID *rid)
{
// We support two lookup types - either by response id or by key.
if ( rid->type == V_OCSP_RESPID_NAME )
return X509_find_by_subject(certs, rid->value.byName);
// There only should be name and type - but let's be sure...
if ( rid->type != V_OCSP_RESPID_KEY )
return 0;
// Just like OpenSSL, we just support SHA-1 lookups and bail out otherwhise.
if ( rid->value.byKey->length != SHA_DIGEST_LENGTH )
return 0;
unsigned char* key_hash = rid->value.byKey->data;
for ( int i = 0; i < sk_X509_num(certs); ++i )
{
unsigned char digest[SHA_DIGEST_LENGTH];
X509* cert = sk_X509_value(certs, i);
if ( ! X509_pubkey_digest(cert, EVP_sha1(), digest, NULL) )
// digest failed for this certificate, try with next
continue;
if ( memcmp(digest, key_hash, SHA_DIGEST_LENGTH) == 0 )
// keys match, return certificate
return cert;
}
return 0;
}
%%}
## Parses a certificate into an X509::Certificate structure.
@ -221,6 +254,7 @@ function x509_ocsp_verify%(certs: x509_opaque_vector, ocsp_reply: string, root_c
int out = -1;
int result = -1;
X509* issuer_certificate = 0;
X509* signer = 0;
OCSP_RESPONSE *resp = d2i_OCSP_RESPONSE(NULL, &start, ocsp_reply->Len());
if ( ! resp )
{
@ -250,19 +284,47 @@ function x509_ocsp_verify%(certs: x509_opaque_vector, ocsp_reply: string, root_c
// inject the certificates in the certificate list of the OCSP reply, they actually are used during
// the lookup.
// Yay.
if ( ! basic->certs )
{
basic->certs = sk_X509_new_null();
if ( ! basic->certs )
{
rval = x509_result_record(-1, "Could not allocate basic x509 stack");
goto x509_ocsp_cleanup;
}
}
issuer_certificate = 0;
for ( int i = 0; i < sk_X509_num(untrusted_certs); i++)
{
sk_X509_push(basic->certs, X509_dup(sk_X509_value(untrusted_certs, i)));
if ( X509_NAME_cmp(X509_get_issuer_name(cert), X509_get_subject_name(sk_X509_value(untrusted_certs, i))) )
if ( X509_NAME_cmp(X509_get_issuer_name(cert), X509_get_subject_name(sk_X509_value(untrusted_certs, i))) == 0 )
issuer_certificate = sk_X509_value(untrusted_certs, i);
}
// Because we actually want to be able to give nice error messages that show why we were
// not able to verify the OCSP response - do our own verification logic first.
signer = x509_get_ocsp_signer(basic->certs, basic->tbsResponseData->responderId);
/*
Do this perhaps - OpenSSL also cannot do it, so I do not really feel bad about it.
Needs a different lookup because the root store is no stack of X509 certs
if ( !s igner )
// if we did not find it in the certificates that were sent, search in the root store
signer = x509_get_ocsp_signer(basic->certs, basic->tbsResponseData->responderId);
*/
if ( ! signer )
{
rval = x509_result_record(-1, "Could not find OCSP responder certificate");
goto x509_ocsp_cleanup;
}
csc = X509_STORE_CTX_new();
X509_STORE_CTX_init(csc, ctx, sk_X509_value(basic->certs, 0), basic->certs);
X509_STORE_CTX_init(csc, ctx, signer, basic->certs);
X509_STORE_CTX_set_time(csc, 0, (time_t) verify_time);
X509_STORE_CTX_set_purpose(csc, X509_PURPOSE_OCSP_HELPER);
@ -281,7 +343,6 @@ function x509_ocsp_verify%(certs: x509_opaque_vector, ocsp_reply: string, root_c
goto x509_ocsp_cleanup;
}
// ok, now we verified the OCSP response. This means that we have a valid chain tying it
// to a root that we trust and that the signature also hopefully is valid. This does not yet
// mean that the ocsp response actually matches the certificate the server send us or that
@ -322,7 +383,7 @@ function x509_ocsp_verify%(certs: x509_opaque_vector, ocsp_reply: string, root_c
goto x509_ocsp_cleanup;
}
if ( ! OCSP_id_cmp(certid, single->certId) )
if ( OCSP_id_cmp(certid, single->certId) != 0 )
return x509_result_record(-1, "OCSP reply is not for host certificate");
// next - check freshness of proof...