Add AuthInfoFromContext utility API (#2062)

credentials/alts/utils.go

@@ -30,6 +30,9 @@ import (
 	"runtime"
 	"strings"
 	"time"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/peer"
 )
 
 const (
@@ -115,3 +118,19 @@ func readManufacturer() ([]byte, error) {
 	}
 	return manufacturer, nil
 }
+
+// AuthInfoFromContext extracts the alts.AuthInfo object from the given context,
+// if it exists. This API should be used by gRPC server RPC handlers to get
+// information about the communicating peer. For client-side, use grpc.Peer()
+// CallOption.
+func AuthInfoFromContext(ctx context.Context) (AuthInfo, error) {
+	peer, ok := peer.FromContext(ctx)
+	if !ok {
+		return nil, errors.New("no Peer found in Context")
+	}
+	altsAuthInfo, ok := peer.AuthInfo.(AuthInfo)
+	if !ok {
+		return nil, errors.New("no alts.AuthInfo found in Context")
+	}
+	return altsAuthInfo, nil
+}

credentials/alts/utils_test.go

@@ -22,6 +22,10 @@ import (
 	"io"
 	"strings"
 	"testing"
+
+	"golang.org/x/net/context"
+	altspb "google.golang.org/grpc/credentials/alts/core/proto/grpc_gcp"
+	"google.golang.org/grpc/peer"
 )
 
 func TestIsRunningOnGCP(t *testing.T) {
@@ -64,3 +68,44 @@ func setup(testOS string, testReader io.Reader) func() {
 		manufacturerReader = tmpReader
 	}
 }
+
+func TestAuthInfoFromContext(t *testing.T) {
+	ctx := context.Background()
+	altsAuthInfo := &fakeALTSAuthInfo{}
+	p := &peer.Peer{
+		AuthInfo: altsAuthInfo,
+	}
+	for _, tc := range []struct {
+		desc    string
+		ctx     context.Context
+		success bool
+		out     AuthInfo
+	}{
+		{
+			"working case",
+			peer.NewContext(ctx, p),
+			true,
+			altsAuthInfo,
+		},
+	} {
+		authInfo, err := AuthInfoFromContext(tc.ctx)
+		if got, want := (err == nil), tc.success; got != want {
+			t.Errorf("%v: AuthInfoFromContext(_)=(err=nil)=%v, want %v", tc.desc, got, want)
+		}
+		if got, want := authInfo, tc.out; got != want {
+			t.Errorf("%v:, AuthInfoFromContext(_)=(%v, _), want (%v, _)", tc.desc, got, want)
+		}
+	}
+}
+
+type fakeALTSAuthInfo struct{}
+
+func (*fakeALTSAuthInfo) AuthType() string            { return "" }
+func (*fakeALTSAuthInfo) ApplicationProtocol() string { return "" }
+func (*fakeALTSAuthInfo) RecordProtocol() string      { return "" }
+func (*fakeALTSAuthInfo) SecurityLevel() altspb.SecurityLevel {
+	return altspb.SecurityLevel_SECURITY_NONE
+}
+func (*fakeALTSAuthInfo) PeerServiceAccount() string                   { return "" }
+func (*fakeALTSAuthInfo) LocalServiceAccount() string                  { return "" }
+func (*fakeALTSAuthInfo) PeerRPCVersions() *altspb.RpcProtocolVersions { return nil }