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Fix ocsp reply validation - there were a few things that definitely were wrong.

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Now the right signer certificate for the reply is looked up (and no longer assumed that it is the first one) and a few compares are fixed. Plus - there are more test cases that partially send certificates in the ocsp message and partially do not - and it seems to work fine in all cases.

Addresses BIT-1212
This commit is contained in:
Johanna Amann 2014-09-04 11:15:16 -07:00
parent 2d8368fee9
commit 8f1cbb8b0a
6 changed files with 79 additions and 4 deletions
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57
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 )
{
@ -266,14 +300,30 @@ function x509_ocsp_verify%(certs: x509_opaque_vector, ocsp_reply: string, root_c
{
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 ( !signer )
// 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);
@ -292,7 +342,6 @@ 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
@ -333,7 +382,7 @@ 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...