Loosen TLS 1.3 session/cipher matching in BoGo.

Draft 18 sadly loosens the requirements to only requiring the PRF hash
stay fixed.

BUG=117

Change-Id: Ic94d53fd9cabaee611fcf36b0071558075e10728
Reviewed-on: https://boringssl-review.googlesource.com/12310
Reviewed-by: Nick Harper <nharper@chromium.org>
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

ssl/test/runner/handshake_client.go

diff --git a/ssl/test/runner/handshake_client.go b/ssl/test/runner/handshake_client.go
index 208dcca..d074778 100644
--- a/ssl/test/runner/handshake_client.go
+++ b/ssl/test/runner/handshake_client.go
@@ -223,11 +223,17 @@
 			// Check that the ciphersuite/version used for the
 			// previous session are still valid.
 			cipherSuiteOk := false
-			for _, id := range hello.cipherSuites {
-				if id == candidateSession.cipherSuite {
-					cipherSuiteOk = true
-					break
+			if candidateSession.vers <= VersionTLS12 {
+				for _, id := range hello.cipherSuites {
+					if id == candidateSession.cipherSuite {
+						cipherSuiteOk = true
+						break
+					}
 				}
+			} else {
+				// TLS 1.3 allows the cipher to change on
+				// resumption.
+				cipherSuiteOk = true
 			}
 
 			versOk := candidateSession.vers >= minVersion &&
@@ -623,9 +629,10 @@
 			c.sendAlert(alertUnknownPSKIdentity)
 			return errors.New("tls: server sent unknown PSK identity")
 		}
-		if hs.session.cipherSuite != hs.suite.id {
+		sessionCipher := cipherSuiteFromID(hs.session.cipherSuite)
+		if sessionCipher == nil || sessionCipher.hash() != hs.suite.hash() {
 			c.sendAlert(alertHandshakeFailure)
-			return errors.New("tls: server sent invalid cipher suite")
+			return errors.New("tls: server resumed an invalid session for the cipher suite")
 		}
 		psk = hs.session.masterSecret
 		c.didResume = true

ssl/test/runner/handshake_server.go

diff --git a/ssl/test/runner/handshake_server.go b/ssl/test/runner/handshake_server.go
index c9a5b50..67950ba 100644
--- a/ssl/test/runner/handshake_server.go
+++ b/ssl/test/runner/handshake_server.go
@@ -462,7 +462,8 @@
 				if sessionState.ticketExpiration.Before(c.config.time()) {
 					continue
 				}
-				if sessionState.cipherSuite != hs.suite.id {
+				sessionCipher := cipherSuiteFromID(sessionState.cipherSuite)
+				if sessionCipher == nil || sessionCipher.hash() != hs.suite.hash() {
 					continue
 				}
 			}