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crypto/tls: ensure the server picked an advertised ALPN protocol

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This is a SHALL in RFC 7301, Section 3.2.

Also some more cleanup after NPN, which worked the other way around
(with the possibility that the client could pick a protocol the server
did not suggest).

Change-Id: I83cc43ca1b3c686dfece8315436441c077065d82
Reviewed-on: https://go-review.googlesource.com/c/go/+/239748
Run-TryBot: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Filippo Valsorda <filippo@golang.org>
Trust: Roland Shoemaker <roland@golang.org>
Reviewed-by: Roland Shoemaker <roland@golang.org>
This commit is contained in:
Filippo Valsorda 2020-06-24 17:01:00 -04:00
parent a2d01473ae
commit d7fff1f2cf
7 changed files with 38 additions and 30 deletions
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14
src/crypto/tls/handshake_client_tls13.go
View file

@ -396,11 +396,17 @@ func (hs *clientHandshakeStateTLS13) readServerParameters() error {
}
hs.transcript.Write(encryptedExtensions.marshal())
if len(encryptedExtensions.alpnProtocol) != 0 && len(hs.hello.alpnProtocols) == 0 {
c.sendAlert(alertUnsupportedExtension)
return errors.New("tls: server advertised unrequested ALPN extension")
if encryptedExtensions.alpnProtocol != "" {
if len(hs.hello.alpnProtocols) == 0 {
c.sendAlert(alertUnsupportedExtension)
return errors.New("tls: server advertised unrequested ALPN extension")
}
if mutualProtocol([]string{encryptedExtensions.alpnProtocol}, hs.hello.alpnProtocols) == "" {
c.sendAlert(alertUnsupportedExtension)
return errors.New("tls: server selected unadvertised ALPN protocol")
}
c.clientProtocol = encryptedExtensions.alpnProtocol
}
c.clientProtocol = encryptedExtensions.alpnProtocol
return nil
}