From 992d1547178fe0d18c2827e34d62fbc545ace64c Mon Sep 17 00:00:00 2001
From: Daniel McCarney <daniel@binaryparadox.net>
Date: Tue, 29 Apr 2025 15:10:10 -0400
Subject: [PATCH] crypto/tls: update TLS 1.3 client compression validation
Unlike in earlier TLS versions, in TLS 1.3 when processing a server
hello the legacy_compression_method MUST have the value 0. It is no
longer a parameter that offers a choice of compression method.
With this in mind, it seems more appropriate to return a decode error
when we encounter a non-zero compression method in a server hello
message. We haven't found a parameter value we reject, we've found
a message that doesn't decode according to its specification.
Making this change also aligns with BoringSSL and allows enabling the
TLS13-HRR-InvalidCompressionMethod bogo test.
Updates #72006
Change-Id: I27a2cd231e4b8762b0d9e2dbd3d8ddd5b87fd5c4
Reviewed-on: https://go-review.googlesource.com/c/go/+/669156
Reviewed-by: Roland Shoemaker <roland@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
---
src/crypto/tls/bogo_config.json | 1 -
src/crypto/tls/handshake_client_tls13.go | 4 ++--
2 files changed, 2 insertions(+), 3 deletions(-)
diff --git a/src/crypto/tls/bogo_config.json b/src/crypto/tls/bogo_config.json
index 7184f56b058..81601d22c04 100644
--- a/src/crypto/tls/bogo_config.json
+++ b/src/crypto/tls/bogo_config.json
@@ -64,7 +64,6 @@
"SupportTicketsWithSessionID": "TODO: first pass, this should be fixed",
"NoNullCompression-TLS12": "TODO: first pass, this should be fixed",
"KeyUpdate-RequestACK": "TODO: first pass, this should be fixed",
- "TLS13-HRR-InvalidCompressionMethod": "TODO: first pass, this should be fixed",
"TLS-TLS12-RSA_WITH_AES_128_GCM_SHA256-LargeRecord": "TODO: first pass, this should be fixed",
"TLS-TLS1-RSA_WITH_AES_128_CBC_SHA-LargeRecord": "TODO: first pass, this should be fixed",
"TLS-TLS11-RSA_WITH_AES_128_CBC_SHA-LargeRecord": "TODO: first pass, this should be fixed",
diff --git a/src/crypto/tls/handshake_client_tls13.go b/src/crypto/tls/handshake_client_tls13.go
index 66dc76f72d6..444c6f311ce 100644
--- a/src/crypto/tls/handshake_client_tls13.go
+++ b/src/crypto/tls/handshake_client_tls13.go
@@ -197,8 +197,8 @@ func (hs *clientHandshakeStateTLS13) checkServerHelloOrHRR() error {
}
if hs.serverHello.compressionMethod != compressionNone {
- c.sendAlert(alertIllegalParameter)
- return errors.New("tls: server selected unsupported compression format")
+ c.sendAlert(alertDecodeError)
+ return errors.New("tls: server sent non-zero legacy TLS compression method")
}
selectedSuite := mutualCipherSuiteTLS13(hs.hello.cipherSuites, hs.serverHello.cipherSuite)
--
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