Go TLS Configuration

This is a summary of available algorithms in Go upstream TLS configuration, and the Chainguard Hardening changes to these.

Chainguard hardened TLS removes non-default, legacy, and deprecated algorithms to align with the Chainguard Hardened OpenSSL configuration. Everything it removes was already disabled by default in upstream Go, so default configurations don’t use any of it, and all of it has already been removed from Chainguard Hardened OpenSSL.

• Go 1.27: Chainguard builds offer hardened TLS as an opt-in. Without opting in, they behave like upstream Go 1.27.
• Go 1.28: Chainguard builds support only hardened TLS. Removed algorithms can’t be enabled.

Hardened TLS affects only applications that opt in to insecure settings:

• Applications that rely on the tlsrsakex, tls3des, tls10server, tlssha1, or x509sha1 GODEBUG settings. Upstream Go has already removed all of these except tlssha1.
• Applications that set Config.MaxVersion to TLS 1.1 or earlier.
• Applications that list only removed cipher suites in Config.CipherSuites, without any that are still available.

All of these settings are insecure.

In the tables below, Default means enabled by default, Available means supported but enabled only through configuration, and Removed means not supported.

The tables are presented in the format similar to the IANA TLS Parameters.

For more information about Transport Layer Security (TLS) please see the following references:

• NIST PQC
• RFC10024
• draft-ietf-tls-mldsa
• RFC10015
• BCP 195
• RFC 9846
• RFC 5246
• NIST SP 800-52 Rev. 2
• RFC 9151
• draft-becker-cnsa2-tls-profile

TLS Versions

In Go 1.27, TLS 1.0 and 1.1 are only enabled when Config.MinVersion is set below VersionTLS12. Go 1.27 Hardened removes TLS 1.0 and 1.1, and Go 1.28 won’t support them.

TLS Cipher Suites

TLS Supported Groups

TLS SignatureScheme

In Go 1.27, SHA-1 signatures in the TLS 1.2 handshake require GODEBUG=tlssha1=1. In TLS 1.3, rsa_pkcs1_* and SHA-1 schemes are accepted only for signatures in certificates.

Elliptic Curves

In Go 1.27, P-224 certificates can only be used with TLS 1.2 and earlier, because TLS 1.3 ECDSA signature schemes are bound to P-256, P-384 and P-521.