go.crypto/ssh: move interpretation of msgNewKeys into

transport.

Sending the msgNewKeys packet and setting up the key material
now happen under a lock, preventing races with concurrent
writers.

R=kardianos, agl, jpsugar, hanwenn
CC=golang-dev
https://golang.org/cl/14476043

ssh/common.go

@@ -90,49 +90,61 @@ func findCommonCipher(clientCiphers []string, serverCiphers []string) (commonCip
 	return
 }
 
-func findAgreedAlgorithms(transport *transport, clientKexInit, serverKexInit *kexInitMsg) (kexAlgo, hostKeyAlgo string, ok bool) {
-	kexAlgo, ok = findCommonAlgorithm(clientKexInit.KexAlgos, serverKexInit.KexAlgos)
+type algorithms struct {
+	kex          string
+	hostKey      string
+	wCipher      string
+	rCipher      string
+	rMAC         string
+	wMAC         string
+	rCompression string
+	wCompression string
+}
+
+func findAgreedAlgorithms(clientKexInit, serverKexInit *kexInitMsg) (algs *algorithms) {
+	var ok bool
+	result := &algorithms{}
+	result.kex, ok = findCommonAlgorithm(clientKexInit.KexAlgos, serverKexInit.KexAlgos)
 	if !ok {
 		return
 	}
 
-	hostKeyAlgo, ok = findCommonAlgorithm(clientKexInit.ServerHostKeyAlgos, serverKexInit.ServerHostKeyAlgos)
+	result.hostKey, ok = findCommonAlgorithm(clientKexInit.ServerHostKeyAlgos, serverKexInit.ServerHostKeyAlgos)
 	if !ok {
 		return
 	}
 
-	transport.writer.cipherAlgo, ok = findCommonCipher(clientKexInit.CiphersClientServer, serverKexInit.CiphersClientServer)
+	result.wCipher, ok = findCommonCipher(clientKexInit.CiphersClientServer, serverKexInit.CiphersClientServer)
 	if !ok {
 		return
 	}
 
-	transport.reader.cipherAlgo, ok = findCommonCipher(clientKexInit.CiphersServerClient, serverKexInit.CiphersServerClient)
+	result.rCipher, ok = findCommonCipher(clientKexInit.CiphersServerClient, serverKexInit.CiphersServerClient)
 	if !ok {
 		return
 	}
 
-	transport.writer.macAlgo, ok = findCommonAlgorithm(clientKexInit.MACsClientServer, serverKexInit.MACsClientServer)
+	result.wMAC, ok = findCommonAlgorithm(clientKexInit.MACsClientServer, serverKexInit.MACsClientServer)
 	if !ok {
 		return
 	}
 
-	transport.reader.macAlgo, ok = findCommonAlgorithm(clientKexInit.MACsServerClient, serverKexInit.MACsServerClient)
+	result.rMAC, ok = findCommonAlgorithm(clientKexInit.MACsServerClient, serverKexInit.MACsServerClient)
 	if !ok {
 		return
 	}
 
-	transport.writer.compressionAlgo, ok = findCommonAlgorithm(clientKexInit.CompressionClientServer, serverKexInit.CompressionClientServer)
+	result.wCompression, ok = findCommonAlgorithm(clientKexInit.CompressionClientServer, serverKexInit.CompressionClientServer)
 	if !ok {
 		return
 	}
 
-	transport.reader.compressionAlgo, ok = findCommonAlgorithm(clientKexInit.CompressionServerClient, serverKexInit.CompressionServerClient)
+	result.rCompression, ok = findCommonAlgorithm(clientKexInit.CompressionServerClient, serverKexInit.CompressionServerClient)
 	if !ok {
 		return
 	}
 
-	ok = true
-	return
+	return result
 }
 
 // Cryptographic configuration common to both ServerConfig and ClientConfig.