Ssl 以PEM格式检索证书的到期时间

我有一个要求，通知客户，他们的证书将在几天内到期，所以在此之前更新工作TLS加密，以正常工作

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如何检索PEM格式证书的到期时间？

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

 #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);

可能存在的副本