SMIME digital signature

This is a discussion on SMIME digital signature within the C Programming forums, part of the General Programming Boards category; Hello, I'm trying to write an app which digitally signs emails. The problem I have is that SMIME_write_PKCS7() won't output ...

  1. #1
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    SMIME digital signature

    Hello,
    I'm trying to write an app which digitally signs emails. The problem I have is that SMIME_write_PKCS7() won't output any MIME headers the email previously had. I tested it with mails from my client so the headers should be ok.

    Here is the code:
    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <openssl/bio.h>
    #include <openssl/pkcs7.h>
    #include <openssl/pkcs12.h>
    #include <openssl/x509.h>
    
    / * Arguments: to be signed email, PKCS#12 certificate with private key
     */
    int main(int argc, char** argv) {
    
        if (argc < 3) exit(1);
        OpenSSL_add_all_algorithms();
    
        BIO *data = BIO_new_file(argv[1], "rb");
        if (!data) exit(1);
    
        BIO *p12file = BIO_new_file(argv[2], "rb");
        if (!p12file) exit(1);
        PKCS12 *p12 = d2i_PKCS12_bio(p12file, NULL);
        if (!p12) exit(1);
    
        X509 *signcert;
        EVP_PKEY *pkey;
        STACK_OF(X509) *ca;
        int ret = PKCS12_parse(p12, "", &pkey, &signcert, &ca);
        if (!ret) exit(1);
    
        PKCS7 *p7 = PKCS7_sign(signcert, pkey, ca, data, 0);
        if (!p7) exit(1);
    
        BIO *out = BIO_new_file("email.eml", "wb");
        if (!out) exit(1);
    
        ret = SMIME_write_PKCS7(out, p7, data, 0);
        if (!ret) exit(1);
    
        BIO_free(data);
        BIO_free(p12file);
        PKCS12_free(p12);
        PKCS7_free(p7);
    
        return (EXIT_SUCCESS);
    }
    Thank you for any advice I can get.
    Last edited by Yawney; 11-23-2010 at 04:53 AM. Reason: Added the return value of SMIME_write_PKCS7().

  2. #2
    and the hat of wrongness Salem's Avatar
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    OpenSSL: Documents, SMIME_write_PKCS7(3)
    Why is flags zero?
    Why are you ignoring the return result?
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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  3. #3
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    Ignoring the return is my fault but it doesn't change anything. The program actually produces signed email but it completely ignores the MIME headers. The flags are 0 because I figured I don't need any.

    I think it could have something to do with parsing the original mail and CRLF/LF endings of lines.

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