crypto/tls: expand ClientHelloInfo

Fixes #17430

Change-Id: Ia1c25363d64e3091455ce00644438715aff30a0d
Reviewed-on: https://go-review.googlesource.com/31391
Run-TryBot: Adam Langley <agl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Filippo Valsorda <hi@filippo.io>

src/crypto/tls/common.go

@@ -14,6 +14,7 @@ import (
 	"fmt"
 	"io"
 	"math/big"
+	"net"
 	"strings"
 	"sync"
 	"time"
@@ -238,6 +239,32 @@ type ClientHelloInfo struct {
 	// is being used (see
 	// http://tools.ietf.org/html/rfc4492#section-5.1.2).
 	SupportedPoints []uint8
+
+	// SignatureSchemes lists the signature and hash schemes that the client
+	// is willing to verify. SignatureSchemes is set only if the Signature
+	// Algorithms Extension is being used (see
+	// https://tools.ietf.org/html/rfc5246#section-7.4.1.4.1).
+	SignatureSchemes []uint16
+
+	// SupportedProtos lists the application protocols supported by the client.
+	// SupportedProtos is set only if the Application-Layer Protocol
+	// Negotiation Extension is being used (see
+	// https://tools.ietf.org/html/rfc7301#section-3.1).
+	//
+	// Servers can select a protocol by setting Config.NextProtos in a
+	// GetConfigForClient return value.
+	SupportedProtos []string
+
+	// SupportedVersions lists the TLS versions supported by the client.
+	// For TLS versions less than 1.3, this is extrapolated from the max
+	// version advertised by the client, so values other than the greatest
+	// might be rejected if used.
+	SupportedVersions []uint16
+
+	// Conn is the underlying net.Conn for the connection. Do not read
+	// from, or write to, this connection; that will cause the TLS
+	// connection to fail.
+	Conn net.Conn
 }
 
 // RenegotiationSupport enumerates the different levels of support for TLS

src/crypto/tls/handshake_server.go

@@ -32,6 +32,7 @@ type serverHandshakeState struct {
 	masterSecret          []byte
 	certsFromClient       [][]byte
 	cert                  *Certificate
+	cachedClientHelloInfo *ClientHelloInfo
 }
 
 // serverHandshake performs a TLS handshake as a server.
@@ -123,15 +124,8 @@ func (hs *serverHandshakeState) readClientHello() (isResume bool, err error) {
 		return false, unexpectedMessageError(hs.clientHello, msg)
 	}
 
-	clientHelloInfo := &ClientHelloInfo{
-		CipherSuites:    hs.clientHello.cipherSuites,
-		ServerName:      hs.clientHello.serverName,
-		SupportedCurves: hs.clientHello.supportedCurves,
-		SupportedPoints: hs.clientHello.supportedPoints,
-	}
-
 	if c.config.GetConfigForClient != nil {
-		if newConfig, err := c.config.GetConfigForClient(clientHelloInfo); err != nil {
+		if newConfig, err := c.config.GetConfigForClient(hs.clientHelloInfo()); err != nil {
 			c.sendAlert(alertInternalError)
 			return false, err
 		} else if newConfig != nil {
@@ -223,7 +217,7 @@ Curves:
 		}
 	}
 
-	hs.cert, err = c.config.getCertificate(clientHelloInfo)
+	hs.cert, err = c.config.getCertificate(hs.clientHelloInfo())
 	if err != nil {
 		c.sendAlert(alertInternalError)
 		return false, err
@@ -812,3 +806,37 @@ func (hs *serverHandshakeState) setCipherSuite(id uint16, supportedCipherSuites
 	}
 	return false
 }
+
+// suppVersArray is the backing array of ClientHelloInfo.SupportedVersions
+var suppVersArray = [...]uint16{VersionTLS12, VersionTLS11, VersionTLS10, VersionSSL30}
+
+func (hs *serverHandshakeState) clientHelloInfo() *ClientHelloInfo {
+	if hs.cachedClientHelloInfo != nil {
+		return hs.cachedClientHelloInfo
+	}
+
+	var supportedVersions []uint16
+	if hs.clientHello.vers > VersionTLS12 {
+		supportedVersions = suppVersArray[:]
+	} else if hs.clientHello.vers >= VersionSSL30 {
+		supportedVersions = suppVersArray[VersionTLS12-hs.clientHello.vers:]
+	}
+
+	signatureSchemes := make([]uint16, 0, len(hs.clientHello.signatureAndHashes))
+	for _, sah := range hs.clientHello.signatureAndHashes {
+		signatureSchemes = append(signatureSchemes, uint16(sah.hash)<<8+uint16(sah.signature))
+	}
+
+	hs.cachedClientHelloInfo = &ClientHelloInfo{
+		CipherSuites:      hs.clientHello.cipherSuites,
+		ServerName:        hs.clientHello.serverName,
+		SupportedCurves:   hs.clientHello.supportedCurves,
+		SupportedPoints:   hs.clientHello.supportedPoints,
+		SignatureSchemes:  signatureSchemes,
+		SupportedProtos:   hs.clientHello.alpnProtocols,
+		SupportedVersions: supportedVersions,
+		Conn:              hs.c.conn,
+	}
+
+	return hs.cachedClientHelloInfo
+}