credentials: check and expose SPIFFE ID

credentials/credentials_test.go

@@ -21,7 +21,9 @@ package credentials
 import (
 	"context"
 	"crypto/tls"
+	"crypto/x509"
 	"net"
+	"net/url"
 	"reflect"
 	"strings"
 	"testing"
@@ -362,3 +364,124 @@ func (s) TestAppendH2ToNextProtos(t *testing.T) {
 		})
 	}
 }
+
+func (s) TestParseSpiffeID(t *testing.T) {
+	tests := []struct {
+		name string
+		urls []*url.URL
+		// If we expect ParseSpiffeID to return an error.
+		expectError bool
+		// If we expect TLSInfo.SpiffeID to be plumbed.
+		expectID bool
+	}{
+		{
+			name:        "empty URIs",
+			urls:        []*url.URL{},
+			expectError: false,
+			expectID:    false,
+		},
+		{
+			name: "good SPIFFE ID",
+			urls: []*url.URL{
+				{
+					Scheme:  "spiffe",
+					Host:    "foo.bar.com",
+					Path:    "workload/wl1",
+					RawPath: "workload/wl1",
+				},
+				{
+					Scheme:  "https",
+					Host:    "foo.bar.com",
+					Path:    "workload/wl1",
+					RawPath: "workload/wl1",
+				},
+			},
+			expectError: false,
+			expectID:    true,
+		},
+		{
+			name: "invalid host",
+			urls: []*url.URL{
+				{
+					Scheme:  "spiffe",
+					Host:    "",
+					Path:    "workload/wl1",
+					RawPath: "workload/wl1",
+				},
+			},
+			expectError: true,
+			expectID:    false,
+		},
+		{
+			name: "invalid path",
+			urls: []*url.URL{
+				{
+					Scheme:  "spiffe",
+					Host:    "foo.bar.com",
+					Path:    "",
+					RawPath: "",
+				},
+			},
+			expectError: true,
+			expectID:    false,
+		},
+		{
+			name: "large path",
+			urls: []*url.URL{
+				{
+					Scheme:  "spiffe",
+					Host:    "foo.bar.com",
+					Path:    string(make([]byte, 2050)),
+					RawPath: string(make([]byte, 2050)),
+				},
+			},
+			expectError: true,
+			expectID:    false,
+		},
+		{
+			name: "large host",
+			urls: []*url.URL{
+				{
+					Scheme:  "spiffe",
+					Host:    string(make([]byte, 256)),
+					Path:    "workload/wl1",
+					RawPath: "workload/wl1",
+				},
+			},
+			expectError: true,
+			expectID:    false,
+		},
+		{
+			name: "multiple SPIFFE IDs",
+			urls: []*url.URL{
+				{
+					Scheme:  "spiffe",
+					Host:    "foo.bar.com",
+					Path:    "workload/wl1",
+					RawPath: "workload/wl1",
+				},
+				{
+					Scheme:  "spiffe",
+					Host:    "bar.baz.com",
+					Path:    "workload/wl2",
+					RawPath: "workload/wl2",
+				},
+			},
+			expectError: false,
+			expectID:    false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			info := TLSInfo{
+				State: tls.ConnectionState{PeerCertificates: []*x509.Certificate{{URIs: tt.urls}}}}
+			err := info.ParseSpiffeID()
+			if got, want := err != nil, tt.expectError; got != want {
+				t.Errorf("want expectError = %v, but got expectError = %v, with error %v", want, got, err)
+			}
+			if got, want := info.SpiffeID != nil, tt.expectID; got != want {
+				t.Errorf("want expectID = %v, but spiffe ID is %v", want, info.SpiffeID)
+			}
+		})
+	}
+}

credentials/tls.go

@@ -25,14 +25,16 @@ import (
 	"fmt"
 	"io/ioutil"
 	"net"
+	"net/url"
 
 	"google.golang.org/grpc/credentials/internal"
 )
 
 // TLSInfo contains the auth information for a TLS authenticated connection.
 // It implements the AuthInfo interface.
 type TLSInfo struct {
-	State tls.ConnectionState
+	State    tls.ConnectionState
+	SpiffeID *url.URL
 	CommonAuthInfo
 }
 
@@ -53,6 +55,42 @@ func (t TLSInfo) GetSecurityValue() ChannelzSecurityValue {
 	return v
 }
 
+// ParseSpiffeID parses the Spiffe ID from State and fill it into SpiffeID.
+// An error is returned only when we are sure Spiffe ID is used but the format
+// is wrong.
+func (t *TLSInfo) ParseSpiffeID() error {
+	if len(t.State.PeerCertificates) == 0 || len(t.State.PeerCertificates[0].URIs) == 0 {
+		return nil
+	}
+	spiffeIDCnt := 0
+	var spiffeID url.URL
+	for _, uri := range t.State.PeerCertificates[0].URIs {
+		if uri == nil || uri.Scheme != "spiffe" || uri.Opaque != "" || (uri.User != nil && uri.User.Username() != "") {
+			continue
+		}
+		// From this point, we assume the uri is intended for a Spiffe ID.
+		if len(uri.Host)+len(uri.Scheme)+len(uri.RawPath)+4 > 2048 ||
+			len(uri.Host)+len(uri.Scheme)+len(uri.Path)+4 > 2048 {
+			return fmt.Errorf("invalid SPIFFE ID: total ID length larger than 2048 bytes")
+		}
+		if len(uri.Host) == 0 || len(uri.RawPath) == 0 || len(uri.Path) == 0 {
+			return fmt.Errorf("invalid SPIFFE ID: domain or workload ID is empty")
+		}
+		if len(uri.Host) > 255 {
+			return fmt.Errorf("invalid SPIFFE ID: domain length larger than 255 characters")
+		}
+		// We use a default deep copy since we know the User field of a SPIFFE ID is empty.
+		spiffeID = *uri
+		spiffeIDCnt++
+	}
+	// A standard SPIFFE ID should be unique. If there are more, we don't raise
+	// any errors but simply not plumbing any of them.
+	if spiffeIDCnt == 1 {
+		t.SpiffeID = &spiffeID
+	}
+	return nil
+}
+
 // tlsCreds is the credentials required for authenticating a connection using TLS.
 type tlsCreds struct {
 	// TLS configuration
@@ -94,7 +132,16 @@ func (c *tlsCreds) ClientHandshake(ctx context.Context, authority string, rawCon
 		conn.Close()
 		return nil, nil, ctx.Err()
 	}
-	return internal.WrapSyscallConn(rawConn, conn), TLSInfo{conn.ConnectionState(), CommonAuthInfo{PrivacyAndIntegrity}}, nil
+	tlsInfo := TLSInfo{
+		State: conn.ConnectionState(),
+		CommonAuthInfo: CommonAuthInfo{
+			SecurityLevel: PrivacyAndIntegrity,
+		},
+	}
+	if err := tlsInfo.ParseSpiffeID(); err != nil {
+		return nil, nil, err
+	}
+	return internal.WrapSyscallConn(rawConn, conn), tlsInfo, nil
 }
 
 func (c *tlsCreds) ServerHandshake(rawConn net.Conn) (net.Conn, AuthInfo, error) {
@@ -103,7 +150,16 @@ func (c *tlsCreds) ServerHandshake(rawConn net.Conn) (net.Conn, AuthInfo, error)
 		conn.Close()
 		return nil, nil, err
 	}
-	return internal.WrapSyscallConn(rawConn, conn), TLSInfo{conn.ConnectionState(), CommonAuthInfo{PrivacyAndIntegrity}}, nil
+	tlsInfo := TLSInfo{
+		State: conn.ConnectionState(),
+		CommonAuthInfo: CommonAuthInfo{
+			SecurityLevel: PrivacyAndIntegrity,
+		},
+	}
+	if err := tlsInfo.ParseSpiffeID(); err != nil {
+		return nil, nil, err
+	}
+	return internal.WrapSyscallConn(rawConn, conn), tlsInfo, nil
 }
 
 func (c *tlsCreds) Clone() TransportCredentials {