获取证书的过期时间，格式为PEM

Question

我有一个要求通知客户，他们的证书将在几天后到期，因此在此时间之前续订TLS加密工作，如预期的那样工作。

如何获取PEM格式证书的过期时间？

Answer 1

 #if FROMFILE
 BIO* bio = BIO_new_file(filename, "rb");
 if (bio == null) goto err;
 #else
 BIO* bio = BIO_new(BIO_s_mem());
 BIO_write(bio, data, dataLen);
 #endif

 X509* x509 = PEM_read_bio_X509(bio, NULL, NULL, NULL);
 if (x509 == null) goto err;

 #if OPENSSL_11
 ASN1_TIME* notBefore = X509_get0_notBefore(x509);
 #else
 ASN1_TIME* notBefore = x509->validity->notBefore;
 #endif

 // Choose a time representation and convert the ASN1_TIME to it.

 goto cleanup;

 err:
 // Exercise left to the reader.

 cleanup:
 // Don't free notBefore, since it was obtained via a get0 or interior pointer.
 if (x509) X509_free(x509);
 if (bio) BIO_free(bio);

Answer 2

将PEM证书的内容复制到此站点，它将显示ssl证书详细信息，包括开始日期和过期日期

https://www.sslshopper.com/certificate-decoder.html