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crypto/tls: de-prioritize AES-GCM ciphers when lacking hardware support

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When either the server or client are lacking hardware support for
AES-GCM ciphers, indicated by the server lacking the relevant
instructions and by the client not putting AES-GCM ciphers at the top
of its preference list, reorder the preference list to de-prioritize
AES-GCM based ciphers when they are adjacent to other AEAD ciphers.

Also updates a number of recorded openssl TLS tests which previously
only specified TLS 1.2 cipher preferences (using -cipher), but not
TLS 1.3 cipher preferences (using -ciphersuites), to specify both
preferences, making these tests more predictable.

Fixes #41181.

Change-Id: Ied896c96c095481e755aaff9ff0746fb4cb9568e
Reviewed-on: https://go-review.googlesource.com/c/go/+/262857
Run-TryBot: Roland Shoemaker <roland@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Trust: Roland Shoemaker <roland@golang.org>
Trust: Katie Hockman <katie@golang.org>
This commit is contained in:
Roland Shoemaker 2020-10-15 18:32:20 -07:00 • committed by Roland Shoemaker
parent 3e0f07eb2d
commit 18d259497e
37 changed files with 2879 additions and 2549 deletions
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13
handshake_server_tls13.go
View file

@ -153,9 +153,22 @@ func (hs *serverHandshakeStateTLS13) processClientHello() error {
if c.config.PreferServerCipherSuites {
preferenceList = defaultCipherSuitesTLS13()
supportedList = hs.clientHello.cipherSuites
// If the client does not seem to have hardware support for AES-GCM,
// prefer other AEAD ciphers even if we prioritized AES-GCM ciphers
// by default.
if !aesgcmPreferred(hs.clientHello.cipherSuites) {
preferenceList = deprioritizeAES(preferenceList)
}
} else {
preferenceList = hs.clientHello.cipherSuites
supportedList = defaultCipherSuitesTLS13()
// If we don't have hardware support for AES-GCM, prefer other AEAD
// ciphers even if the client prioritized AES-GCM.
if !hasAESGCMHardwareSupport {
preferenceList = deprioritizeAES(preferenceList)
}
}
for _, suiteID := range preferenceList {
hs.suite = mutualCipherSuiteTLS13(supportedList, suiteID)