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crypto/tls: Never resume sessions across different versions.

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Instead, decline the session and do a full handshake. The semantics of
cross-version resume are unclear, and all major client implementations
treat this as a fatal error. (This doesn't come up very much, mostly if
the client does the browser version fallback without sharding the
session cache.)

See BoringSSL's bdf5e72f50e25f0e45e825c156168766d8442dde and OpenSSL's
9e189b9dc10786c755919e6792e923c584c918a1.

Change-Id: I51ca95ac1691870dd0c148fd967739e2d4f58824
Reviewed-on: https://go-review.googlesource.com/21152
Reviewed-by: Adam Langley <agl@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
David Benjamin 2016-02-15 11:41:40 -05:00 committed by Brad Fitzpatrick
parent 6885da92a7
commit 6781899784
2 changed files with 60 additions and 4 deletions
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6
handshake_server.go
View File

@ -284,10 +284,8 @@ func (hs *serverHandshakeState) checkForResumption() bool {
return false return false
} }
if hs.sessionState.vers > hs.clientHello.vers { // Never resume a session for a different TLS version.
return false if c.vers != hs.sessionState.vers {
}
if vers, ok := c.config.mutualVersion(hs.sessionState.vers); !ok || vers != hs.sessionState.vers {
return false return false
} }

58
handshake_server_test.go
View File

@ -399,6 +399,64 @@ func TestSCTHandshake(t *testing.T) {
} }
} }
func TestCrossVersionResume(t *testing.T) {
serverConfig := &Config{
CipherSuites: []uint16{TLS_RSA_WITH_AES_128_CBC_SHA},
Certificates: testConfig.Certificates,
}
clientConfig := &Config{
CipherSuites: []uint16{TLS_RSA_WITH_AES_128_CBC_SHA},
InsecureSkipVerify: true,
ClientSessionCache: NewLRUClientSessionCache(1),
ServerName: "servername",
}
// Establish a session at TLS 1.1.
clientConfig.MaxVersion = VersionTLS11
_, _, err := testHandshake(clientConfig, serverConfig)
if err != nil {
t.Fatalf("handshake failed: %s", err)
}
// The client session cache now contains a TLS 1.1 session.
state, _, err := testHandshake(clientConfig, serverConfig)
if err != nil {
t.Fatalf("handshake failed: %s", err)
}
if !state.DidResume {
t.Fatalf("handshake did not resume at the same version")
}
// Test that the server will decline to resume at a lower version.
clientConfig.MaxVersion = VersionTLS10
state, _, err = testHandshake(clientConfig, serverConfig)
if err != nil {
t.Fatalf("handshake failed: %s", err)
}
if state.DidResume {
t.Fatalf("handshake resumed at a lower version")
}
// The client session cache now contains a TLS 1.0 session.
state, _, err = testHandshake(clientConfig, serverConfig)
if err != nil {
t.Fatalf("handshake failed: %s", err)
}
if !state.DidResume {
t.Fatalf("handshake did not resume at the same version")
}
// Test that the server will decline to resume at a higher version.
clientConfig.MaxVersion = VersionTLS11
state, _, err = testHandshake(clientConfig, serverConfig)
if err != nil {
t.Fatalf("handshake failed: %s", err)
}
if state.DidResume {
t.Fatalf("handshake resumed at a higher version")
}
}
// Note: see comment in handshake_test.go for details of how the reference // Note: see comment in handshake_test.go for details of how the reference
// tests work. // tests work.