c - 使用 openssl 以编程方式提取 pem 证书信息

Question

使用 openssl 命令行可以以人类可读的模式提取 .pem 证书中包含的所有信息；那是：

openssl x509 -noout -in <MyCertificate>.pem  -text

使用 openssl API 提取此信息的合适步骤是什么？

问候，

Answer 1

X509_print_ex函数族就是你的答案。

#include <openssl/x509.h>
#include <openssl/pem.h>
#include <openssl/bio.h>

int main(int argc, char **argv)
{
    X509 *x509;
    BIO *i = BIO_new(BIO_s_file());
    BIO *o = BIO_new_fp(stdout,BIO_NOCLOSE);

    if((argc < 2) ||
       (BIO_read_filename(i, argv[1]) <= 0) ||
       ((x509 = PEM_read_bio_X509_AUX(i, NULL, NULL, NULL)) == NULL)) {
        return -1;
    }

    X509_print_ex(o, x509, XN_FLAG_COMPAT, X509_FLAG_COMPAT);
}

Answer 2

作为与此问题相关的附加信息，如果拥有 DER 格式而不是 PEM 的证书；也可以使用以下代码以人类可读的模式提取信息：

//Assuming that the DER certificate binary information is stored in
//a byte array (unsigned char) called "pData" whose size is "lenData"
X509* x509;
BIO* input = BIO_new_mem_buf((void*)pData, lenData);
//d2i_X509_bio: Decodes the binary DER certificate
//and parses it to a X509 structure
x509 = d2i_X509_bio(input, NULL);
if (x509 == NULL)
{
   //Error in d2i_X509_bio
}
else
{
    //"certificateFile" is the full path file
    //where to store the certificate information
    //in a human readable mode (instead of stdout)
    FILE* fd = fopen(certificateFile, "w+");
    BIO* output = BIO_new_fp(fd, BIO_NOCLOSE);
    X509_print_ex(output, x509, XN_FLAG_COMPAT, X509_FLAG_COMPAT);
    fclose(fd);
    BIO_free_all(output);
}
BIO_free_all(input);