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crypto/tls: remove RSA KEX ciphers from the default list

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Removes the RSA KEX based ciphers from the default list. This can be
reverted using the tlsrsakex GODEBUG.

Fixes #63413

Change-Id: Id221be3eb2f6c24b91039d380313f0c87d339f98
Reviewed-on: https://go-review.googlesource.com/c/go/+/541517
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>
This commit is contained in:
Roland Shoemaker 2023-11-10 10:42:42 -08:00
parent 3dc2410818
commit ae820c6a3c
3 changed files with 36 additions and 4 deletions
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30
cipher_suites.go
View file

@ -17,6 +17,7 @@ import (
"fmt"
"hash"
"internal/cpu"
"internal/godebug"
"runtime"
"golang.org/x/crypto/chacha20poly1305"
@ -335,10 +336,35 @@ var disabledCipherSuites = []uint16{
}
var (
defaultCipherSuitesLen = len(cipherSuitesPreferenceOrder) - len(disabledCipherSuites)
defaultCipherSuites = cipherSuitesPreferenceOrder[:defaultCipherSuitesLen]
defaultCipherSuitesLen int
defaultCipherSuites []uint16
)
// rsaKexCiphers contains the ciphers which use RSA based key exchange,
// which we disable by default.
var rsaKexCiphers = map[uint16]bool{
TLS_RSA_WITH_RC4_128_SHA: true,
TLS_RSA_WITH_3DES_EDE_CBC_SHA: true,
TLS_RSA_WITH_AES_128_CBC_SHA: true,
TLS_RSA_WITH_AES_256_CBC_SHA: true,
TLS_RSA_WITH_AES_128_CBC_SHA256: true,
TLS_RSA_WITH_AES_128_GCM_SHA256: true,
TLS_RSA_WITH_AES_256_GCM_SHA384: true,
}
var rsaKEXgodebug = godebug.New("tlsrsakex")
func init() {
rsaKexEnabled := rsaKEXgodebug.Value() == "1"
for _, c := range cipherSuitesPreferenceOrder[:len(cipherSuitesPreferenceOrder)-len(disabledCipherSuites)] {
if !rsaKexEnabled && rsaKexCiphers[c] {
continue
}
defaultCipherSuites = append(defaultCipherSuites, c)
}
defaultCipherSuitesLen = len(defaultCipherSuites)
}
// defaultCipherSuitesTLS13 is also the preference order, since there are no
// disabled by default TLS 1.3 cipher suites. The same AES vs ChaCha20 logic as
// cipherSuitesPreferenceOrder applies.

4
common.go
View file

@ -670,7 +670,9 @@ type Config struct {
// the list is ignored. Note that TLS 1.3 ciphersuites are not configurable.
//
// If CipherSuites is nil, a safe default list is used. The default cipher
// suites might change over time.
// suites might change over time. In Go 1.22 RSA key exchange based cipher
// suites were removed from the default list, but can be re-added with the
// GODEBUG setting tlsrsakex=1.
CipherSuites []uint16
// PreferServerCipherSuites is a legacy field and has no effect.

6
tls_test.go
View file

@ -1288,7 +1288,8 @@ func TestClientHelloInfo_SupportsCertificate(t *testing.T) {
SignatureSchemes: []SignatureScheme{PKCS1WithSHA1},
SupportedVersions: []uint16{VersionTLS13, VersionTLS12},
config: &Config{
MaxVersion: VersionTLS12,
CipherSuites: []uint16{TLS_RSA_WITH_AES_128_GCM_SHA256},
MaxVersion: VersionTLS12,
},
}, ""}, // Check that mutual version selection works.
@ -1385,6 +1386,9 @@ func TestClientHelloInfo_SupportsCertificate(t *testing.T) {
{rsaCert, &ClientHelloInfo{
CipherSuites: []uint16{TLS_RSA_WITH_AES_128_GCM_SHA256},
SupportedVersions: []uint16{VersionTLS12},
config: &Config{
CipherSuites: []uint16{TLS_RSA_WITH_AES_128_GCM_SHA256},
},
}, ""}, // static RSA fallback
}
for i, tt := range tests {