Is there any OpenSSL function to convert PKCS7 file to PEM

问题

Is there any openssl api function to convert PKCS7 file to PEM. I am able to convert a PKCS12 file to PEM using PKCS12_parse() function which returns key and certificate given the password. There is no similar function for pkcs7.

My pkcs7 input has just the certificate in binary format. I am able to do the conversion using command

openssl pkcs7 -inform DER -in input.p7b -printcerts -text

How do I do this in a C program? I am able to read it to a PKCS7 structure like this

 FILE* fp;
 if (!(fp = fopen("ca.p7b", "rb"))) { 
  fprintf(stderr, "Error reading input pkcs7 file\n" ); 
  exit(1); 
 } 
 PKCS7 *p7; 
 p7 = d2i_PKCS7_fp(cafp, NULL);

回答1:

After some googling I am able to do that.

if(p7->d.sign->cert != NULL){
    PEM_write_X509(fp, sk_X509_value(p7->d.sign->cert, 0)); 
}

where p7 is a pointer to pkcs7 struct and fp is the file pointer to PEM file

来源：https://stackoverflow.com/questions/2023046/is-there-any-openssl-function-to-convert-pkcs7-file-to-pem