Get the S/MIME Signer's Certificate

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Demonstrates the Chilkat Mime.LastSignerCert method, which loads the signer certificate at a zero-based index from the most recent successful verification (or security-unwrapping) into a Cert. The first argument is the signer index and the second is the receiving Cert.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: Verifying tells you the signature is mathematically valid, but you usually also need to know who signed — the subject, the issuer, the validity dates — to decide whether to trust it. This retrieves each signer's certificate after verification so your code can inspect and apply its own trust rules. A message can have multiple signers, so iterate from 0 to NumSignerCerts - 1.

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#include <C_CkMime.h>
#include <C_CkCert.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkMime mime;
    int n;
    HCkCert cert;
    int i;

    success = FALSE;

    mime = CkMime_Create();
    success = CkMime_LoadMimeFile(mime,"qa_data/signed.eml");
    if (success == FALSE) {
        printf("%s\n",CkMime_lastErrorText(mime));
        CkMime_Dispose(mime);
        return;
    }

    //  After a successful verification, load each signer's certificate to inspect it.  The 1st argument
    //  is the zero-based signer index and the 2nd is a Cert object that receives the certificate.
    success = CkMime_Verify(mime);
    if (success != TRUE) {
        printf("%s\n",CkMime_lastErrorText(mime));
        CkMime_Dispose(mime);
        return;
    }

    n = CkMime_getNumSignerCerts(mime);
    cert = CkCert_Create();

    for (i = 0; i <= n - 1; i++) {
        success = CkMime_LastSignerCert(mime,i,cert);
        if (success == FALSE) {
            printf("%s\n",CkMime_lastErrorText(mime));
            CkMime_Dispose(mime);
            CkCert_Dispose(cert);
            return;
        }

        printf("Signer %d: %s (issued by %s)\n",i,CkCert_subjectCN(cert),CkCert_issuerCN(cert));
    }



    CkMime_Dispose(mime);
    CkCert_Dispose(cert);

    }