[openssl-dev] PKCS7_verify() behavior - possible bug ?

[Massimiliano Pala]

Hi all,

I was looking at the behavior of PKCS7_verify(). It seems that, if the 
flags are set to 0, then the function will assume that the "smime_sign" 
purpose is to be used when verifying the certificate, however, if the 
PKCS7_NOCHAIN is actually used, it seems that the purpose is not 
checked. From the code (crypto/pkcs7/pk7_smime.c - line ~320 - function 
PKCS7_verify() ):

             if (!(flags & PKCS7_NOVERIFY)) for (k = 0; k < sk_X509_num(signers); k++) {
                     signer = sk_X509_value (signers, k);
                     if (!(flags & PKCS7_NOCHAIN)) {
                             if(!X509_STORE_CTX_init(&cert_ctx, store, signer,
                                                             p7->d.sign->cert))
                                     {
                                     PKCS7err(PKCS7_F_PKCS7_VERIFY,ERR_R_X509_LIB);
                                     sk_X509_free(signers);
                                     return 0;
                                     }
                             X509_STORE_CTX_set_default(&cert_ctx, "smime_sign");
                     } else if(!X509_STORE_CTX_init (&cert_ctx, store, signer, NULL)) {
                             PKCS7err(PKCS7_F_PKCS7_VERIFY,ERR_R_X509_LIB);
                             sk_X509_free(signers);
                             return 0;
                     }
                     if (!(flags & PKCS7_NOCRL))
                             X509_STORE_CTX_set0_crls(&cert_ctx, p7->d.sign->crl);
                     i = X509_verify_cert(&cert_ctx);
                     if (i <= 0) j = X509_STORE_CTX_get_error(&cert_ctx);
                     X509_STORE_CTX_cleanup(&cert_ctx);
                     if (i <= 0) {
                             PKCS7err(PKCS7_F_PKCS7_VERIFY,PKCS7_R_CERTIFICATE_VERIFY_ERROR);
                             ERR_add_error_data(2, "Verify error:",
                                              X509_verify_cert_error_string(j));
                             sk_X509_free(signers);
                             return 0;
                     }
                     /* Check for revocation status here */
             }

Is this the desired behavior or if this is an error ? In other words, 
shouldn't the "smime_sign" purpose be checked in both cases ? I am 
asking because I am trying to understand if this behavior is going to be 
fixed / changed in the future or not (i.e., can we rely on the fact that 
by using the PKCS7_NOCHAIN flag the "smime_sign" purpose will not be 
checked) ?.

Thanks,
Max


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