Parsing counter signatures - HELP - (UPDATED)

[Massimiliano Ziccardi]

Hi all.

I've been able to parse the first counter signature of each signature.
At the end of this e-mail, you'll find the code I use to parse the file (no
error handling, it's just a working snippet).

Attached you'll find my test P7M. The signature/countersignature tree is as
follows:

SIGNATURE 1
    COUNTER SIGNATURE 1
    COUNTER SIGNATURE 2
SIGNATURE 2
    COUNTER SIGNATURE 1

Can someone please give me an advice about the changes I've to make to the
following code to parse the COUNTER SIGNATURE 2 too?

Many thanks.

#include <openssl/pkcs7.h>
#include <openssl/bio.h>
#include <openssl/err.h>
#include <openssl/x509.h>

void parse(char *pszFileName)
{
    // Parsing PKCS#7 file
    BIO *foo = BIO_new_file(pszFileName, "rb");

    PKCS7* pP7 = d2i_PKCS7_bio(foo,NULL);

    STACK_OF(X509) *pSigners = PKCS7_get0_signers(pP7, NULL, 0);

    STACK_OF(PKCS7_SIGNER_INFO) *pSignerInfos = PKCS7_get_signer_info(pP7);

    // Looping through the signatures
    for (int i = 0; i < sk_PKCS7_SIGNER_INFO_num(pSignerInfos); i++)
    {
        PKCS7_SIGNER_INFO *si = sk_PKCS7_SIGNER_INFO_value(pSignerInfos, i);
        X509* pSignerCert = sk_X509_value(pSigners, i);

        printf ("FOUND SIGNATURE : %p\n", si);
        // Parsing counter signatures
        ASN1_TYPE *pCounterSignatureAttribute = PKCS7_get_attribute(si,
NID_pkcs9_countersignature);

        ASN1_STRING *pSequence = pCounterSignatureAttribute->value.sequence;

        if (pSequence != NULL)
        {
            unsigned char *ps = NULL;
            ps = pSequence->data;

            PKCS7_SIGNER_INFO *cs = d2i_PKCS7_SIGNER_INFO(NULL, (const
unsigned char**)&ps, pSequence->length);
            printf ("FOUND COUNTER SIGNATURE: %p\n", si);
        }
    }
}

Regards,
Massimiliano Ziccardi

test.txt.p7m
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