What is Mercurial TLS Configuration?

**What is Mercurial TLS Configuration?**
Mercurial uses Transport Layer Security to encrypt connections between clients and servers. It protects repository data during clone, pull, and push operations. Proper TLS configuration ensures strong encryption, verified certificates, and defense against protocol downgrade attacks.

Core TLS Settings in Mercurial
You control TLS with the hgrc file and system-wide OpenSSL or GnuTLS settings. In [web] and [hostfingerprint] sections, you pin known server fingerprints. This prevents man-in-the-middle attacks. Use certificatefile to point to trusted CA bundles. Avoid expired or self-signed certs unless policy dictates and you control both ends.

Cipher Suites
Set only modern cipher suites: TLS 1.2 and TLS 1.3 with AES-GCM or ChaCha20-Poly1305. Disable weak algorithms like RC4, 3DES, and MD5. In OpenSSL config, define CipherString tightly—Mercurial inherits that setting.

Protocol Versions
Force TLS 1.2 minimum. Many clients already speak TLS 1.3, which is faster and safer. Block SSLv3 and TLS 1.0/1.1 to prevent known attacks like POODLE and BEAST.

Certificate Verification
Enable strict certificate validation. In Mercurial, this is controlled by your CA list and hostfingerprint. When working in automated environments, keep certificates updated and automate renewal with tools like Let’s Encrypt.

Performance Considerations
Strong TLS can be fast. Use session resumption and HTTP/2 where possible. Tune your server for larger buffers and avoid unnecessary renegotiation.

Security Audits
Regularly inspect TLS configs with openssl s_client or nmap --script ssl-enum-ciphers. Keep dependencies patched. Audit both Mercurial and server libraries after updates.

Misconfiguring TLS in Mercurial is easy. Fixing it is harder if trust is already broken. Lock it down. Test every handshake. Make sure every byte is encrypted with the best your stack can offer.

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