使用OpenSSL获取SCTs的方法及返回0个SCTs的问题求助
Hey Brian, let's break down why you're stuck getting 0 SCTs with OpenSSL—this is a tricky but fixable issue, and I’ve helped folks work through it before. Here are the most likely culprits and how to check them:
1. Did you enable SCT support in your SSL context?
Older versions of OpenSSL don’t enable SCT extensions by default, and even newer ones might require explicit configuration. Before you initiate the connection, make sure you’ve set the right flag:
// Add this to your SSL_CTX setup code SSL_CTX_set_options(your_ctx, SSL_OP_ENABLE_SCT);
Also, double-check your OpenSSL version—anything below 1.1.0 has limited or broken SCT support. If you’re on an older release, upgrading is your first step.
2. Are you using the correct APIs to fetch SCTs?
There are two places SCTs can live: embedded in the certificate itself, or sent via a TLS extension during handshake. You need to check both with the right functions:
- For certificate-embedded SCTs: Use
X509_get_sct_list(your_cert)which returns aSTACK_OF(SCT) - For TLS extension SCTs: Use
SSL_get_server_scts(your_ssl)right after handshake completes
If you’re only checking one of these, you’re missing half the picture—some servers/CAs use one method over the other.
3. Verify the server actually provides SCTs
Don’t assume every domain sends SCTs! Use OpenSSL’s command line to test first—it’ll tell you definitively:
openssl s_client -connect yourdomain.com:443 -status
Scan the output for lines starting with SignedCertificateTimestamp. If the command line shows nothing, the server isn’t sending SCTs (maybe the CA didn’t embed them, or the server is misconfigured). If the command line shows SCTs but your code doesn’t, the issue is in your implementation.
4. Are you fetching SCTs at the right time?
SCTs are only available immediately after the TLS handshake finishes. If you wait to call the SCT functions until after you’ve sent/received application data, OpenSSL might have already cleaned up the handshake-related data. Make sure you call SSL_get_server_scts() right after SSL_connect() returns successfully.
5. Check OpenSSL’s error stack!
Never ignore error codes—even if the connection succeeds, there might be hidden failures in parsing SCTs. Add this line after trying to fetch SCTs to see what’s going wrong:
ERR_print_errors_fp(stderr);
This will print out any low-level errors (like parsing failures or memory issues) that might be preventing SCTs from being stored correctly.
内容的提问来源于stack exchange，提问作者Brian Hogan
