Hi bstraehl,

Thanks for attaching your test application.  We'll look into this and get back to you shortly.

Best Regards,
Chris

Hi Beat,

I had a chance to look over your examples and believe you may have just been mis-using the wc_PKCS7_VerifySignedData API for use with detached signatures.

wc_PKCS7_VerifySignedData() can verify detached signatures, but your application needs to explicitly set the content and content size using the "pkcs7.content" and "pkcs7.contentSz" structure members before doing the verification.

Internally in pkcs7.c we do some detection of empty content in the PKCS#7/CMS bundle and purposefully set our internal error state to ASN_PARSE_E.  But, we recover from that error state later on once we realize the user has set the pkcs7.content and pkcs7.contentSz correctly.

I have attached a modified version of your main.c (here as main_verifySignedData.c) where I explicitly set these two struct members before doing the verification.  Compiling this against the current version of wolfSSL, I am seeing a verification success.

I did also change wc_PKCS7_VerifySignedData_ex() to the normal wc_PKCS7_VerifySignedData() in your sample application.  wc_PKCS7_VerifySignedData_ex() requires as inputs the PKCS#7/CMS "head" and "foot" as inputs that would have been received as outputs from the corresponding call to wc_PKCS7_EncodeSignedData_ex().  My guess was that you did not have these available and meant to use wc_PKCS7_VerifySignedData() instead.  But, please correct me if I am wrong.  wc_PKCS7_VerifySignedData() also handles calculation of the message digest internally, so I removed that logic from your sample code.

Best Regards,
Chris

Hi Beat,

Thanks for the clarification.  I now see your desire/need to pass in only the pre-computed digest of the content rather than the content itself.

Let me revisit our wc_PKCS7_VerifySignedData_ex() code and I'll get back to you shortly.

Thanks,
Chris

After all this time I had a chance to test your solution. I clone the actual state of the repository, where master was at "8d70594". However function wc_PKCS7_VerifySignedData_ex didn't work from the beginning with our detached pre-calculated hash. I had to recompile wolfssl with PKCS7_STREAM disabled. The problem is a missing "ret = 0" here:

index 3bcbfec6f..f4c7d596e 100644
--- a/wolfcrypt/src/pkcs7.c
+++ b/wolfcrypt/src/pkcs7.c
@@ -4679,7 +4679,7 @@ static int PKCS7_VerifySignedData(PKCS7* pkcs7, const byte* hashBuf,
                 idx = localIdx;
             }
             else {
-
+               ret = 0;
                 /* If either pkcs7->content and pkcs7->contentSz are set
                  * (detached signature where user has set content explicitly
                  * into pkcs7->content/contentSz) OR pkcs7->hashBuf and

Because the following code section checks for the exitence of an embedded data length information, which doesn't exist in the detached case. So the GetLength_Ex will fail, which is okay. But the ret value will be checked again in the next code section, which is guarded with #ifndef NO_PKCS7_STREAM, without beeing updated by a regular function call in between. So, we have to set it by ourselfs.

            /* get length of content in case of single part */
            if (ret == 0 && !multiPart) {
                if (tag != ASN_OCTET_STRING)
                    ret = ASN_PARSE_E;

                if (ret == 0 && GetLength_ex(pkiMsg, &localIdx,
                            &length, pkiMsgSz, NO_USER_CHECK) < 0)
                    ret = ASN_PARSE_E;
            }

Do you agree?