go.crypto/ssh: introduce PublicKey interface type.

Public functions affected:
-AgentKey.Key
-AgentClient.SignRequest
-ClientKeyring.Key
-MarshalPublicKey
-ParsePublicKey

R=agl, jpsugar, jmpittman
CC=golang-dev
https://golang.org/cl/13642043

ssh/common_test.go

@@ -5,11 +5,6 @@
 package ssh
 
 import (
-	"crypto/dsa"
-	"crypto/ecdsa"
-	"crypto/elliptic"
-	"crypto/rsa"
-	"errors"
 	"testing"
 )
 
@@ -29,49 +24,3 @@ func TestSafeString(t *testing.T) {
 		}
 	}
 }
-
-func TestAlgoNameSupported(t *testing.T) {
-	supported := map[string]interface{}{
-		KeyAlgoRSA:          new(rsa.PublicKey),
-		KeyAlgoDSA:          new(dsa.PublicKey),
-		KeyAlgoECDSA256:     &ecdsa.PublicKey{Curve: elliptic.P256()},
-		KeyAlgoECDSA384:     &ecdsa.PublicKey{Curve: elliptic.P384()},
-		KeyAlgoECDSA521:     &ecdsa.PublicKey{Curve: elliptic.P521()},
-		CertAlgoRSAv01:      &OpenSSHCertV01{Key: new(rsa.PublicKey)},
-		CertAlgoDSAv01:      &OpenSSHCertV01{Key: new(dsa.PublicKey)},
-		CertAlgoECDSA256v01: &OpenSSHCertV01{Key: &ecdsa.PublicKey{Curve: elliptic.P256()}},
-		CertAlgoECDSA384v01: &OpenSSHCertV01{Key: &ecdsa.PublicKey{Curve: elliptic.P384()}},
-		CertAlgoECDSA521v01: &OpenSSHCertV01{Key: &ecdsa.PublicKey{Curve: elliptic.P521()}},
-	}
-
-	for expected, key := range supported {
-		actual := algoName(key)
-		if expected != actual {
-			t.Errorf("expected: %s, actual: %s", expected, actual)
-		}
-	}
-
-}
-
-func TestAlgoNameNotSupported(t *testing.T) {
-	notSupported := []interface{}{
-		&ecdsa.PublicKey{Curve: elliptic.P224()},
-		&OpenSSHCertV01{Key: &ecdsa.PublicKey{Curve: elliptic.P224()}},
-	}
-
-	panicTest := func(key interface{}) (algo string, err error) {
-		defer func() {
-			if r := recover(); r != nil {
-				err = errors.New(r.(string))
-			}
-		}()
-		algo = algoName(key)
-		return
-	}
-
-	for _, unsupportedKey := range notSupported {
-		if algo, err := panicTest(unsupportedKey); err == nil {
-			t.Errorf("Expected a panic, Got: %s (for type %T)", algo, unsupportedKey)
-		}
-	}
-}