add GCP application default credentials detector (#2530)

* add GCP application default credentials detector

* add a comment

* update Keywords to better match the key

---------

Co-authored-by: Ahrav Dutta <ahrav.dutta@trufflesec.com>

pkg/detectors/gcpapplicationdefaultcredentials/gcpapplicationdefaultcredentials.go

@@ -0,0 +1,164 @@
+package gcpapplicationdefaultcredentials
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+
+	regexp "github.com/wasilibs/go-re2"
+
+	"github.com/trufflesecurity/trufflehog/v3/pkg/common"
+	"github.com/trufflesecurity/trufflehog/v3/pkg/detectors"
+	"github.com/trufflesecurity/trufflehog/v3/pkg/pb/detectorspb"
+	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/google"
+)
+
+type Scanner struct {
+	client *http.Client
+}
+
+// Ensure the Scanner satisfies the interface at compile time.
+var _ detectors.Detector = (*Scanner)(nil)
+
+var (
+	defaultClient = common.SaneHttpClient()
+
+	keyPat = regexp.MustCompile(`\{[^{]+client_secret[^}]+\}`)
+)
+
+type gcpApplicationDefaultCredentials struct {
+	ClientID     string `json:"client_id"`
+	ClientSecret string `json:"client_secret"`
+	RefreshToken string `json:"refresh_token"`
+	Type         string `json:"type"`
+}
+
+// Keywords are used for efficiently pre-filtering chunks.
+// Use identifiers in the secret preferably, or the provider name.
+func (s Scanner) Keywords() []string {
+	return []string{".apps.googleusercontent.com"}
+}
+
+// FromData will find and optionally verify Gcpapplicationdefaultcredentials secrets in a given set of bytes.
+func (s Scanner) FromData(ctx context.Context, verify bool, data []byte) (results []detectors.Result, err error) {
+	dataStr := string(data)
+
+	matches := keyPat.FindAllString(dataStr, -1)
+
+	for _, match := range matches {
+		key := match
+
+		// Detect keys by unmarshalling the data.
+		creds := gcpApplicationDefaultCredentials{}
+		err := json.Unmarshal([]byte(key), &creds)
+		if err != nil {
+			continue
+		}
+
+		// Trim prefix (".apps.googleusercontent.com") because it will be labeled as false positive
+		detectedClientID, _, _ := strings.Cut(creds.ClientID, ".")
+
+		s1 := detectors.Result{
+			DetectorType: detectorspb.DetectorType_GCPApplicationDefaultCredentials,
+			Raw:          []byte(detectedClientID),
+		}
+
+		if verify {
+			client := s.client
+			if client == nil {
+				client = defaultClient
+			}
+
+			// Use marshalled credential to verify if the found key is active
+			credBytes, _ := json.Marshal(creds)
+			isVerified, extraData, verificationErr := verifyMatch(ctx, client, string(credBytes))
+			s1.Verified = isVerified
+			s1.ExtraData = extraData
+			s1.SetVerificationError(verificationErr, match)
+		}
+
+		// This function will check false positives for common test words, but also it will make sure the key appears 'random' enough to be a real key.
+		if !s1.Verified && detectors.IsKnownFalsePositive(string(s1.Raw), detectors.DefaultFalsePositives, true) {
+			continue
+		}
+
+		results = append(results, s1)
+	}
+
+	return
+}
+
+func verifyMatch(ctx context.Context, client *http.Client, token string) (bool, map[string]string, error) {
+	// First load the credential from the found key
+	credentials, err := google.CredentialsFromJSON(ctx, []byte(token), "https://www.googleapis.com/auth/cloud-platform")
+	if err != nil {
+		return false, nil, err
+	}
+
+	// Credential not loaded. Not sure this can happend but it should be labeled unverified.
+	if credentials == nil {
+		return false, nil, nil
+	}
+
+	// Get token from the credentials
+	gcpToken, err := credentials.TokenSource.Token()
+
+	if err != nil {
+		// Return verification error if the error is temporary
+		// See https://pkg.go.dev/golang.org/x/oauth2/google#AuthenticationError.Temporary for details
+		var temporaryError *(google.AuthenticationError)
+		if errors.As(err, &temporaryError) {
+			if err.(*google.AuthenticationError).Temporary() {
+				return false, nil, err
+			}
+		}
+		return false, nil, nil
+	}
+
+	// Return verification error if the retrieved token is invalid
+	if !gcpToken.Valid() {
+		return false, nil, err
+	}
+
+	// Build request to call an IAM endpoint
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, "https://iam.googleapis.com/v1/roles", nil)
+	if err != nil {
+		return false, nil, nil
+	}
+
+	// If we are not using a faketransport, leave it as is because the test wants to modify the response. Otherwise, set the retrieved token to the client.
+	if _, ok := client.Transport.(common.FakeTransport); !ok {
+		client.Transport = &oauth2.Transport{
+			Source: credentials.TokenSource,
+		}
+	}
+
+	res, err := client.Do(req)
+	if err != nil {
+		return false, nil, err
+	}
+	defer func() {
+		_, _ = io.Copy(io.Discard, res.Body)
+		_ = res.Body.Close()
+	}()
+
+	if res.StatusCode >= 200 && res.StatusCode < 300 {
+		// If the endpoint returns useful information, we can return it as a map.
+		return true, nil, nil
+	} else if res.StatusCode == 401 {
+		// The secret is determinately not verified (nothing to do)
+		return false, nil, nil
+	} else {
+		err = fmt.Errorf("unexpected HTTP response status %d", res.StatusCode)
+		return false, nil, err
+	}
+}
+
+func (s Scanner) Type() detectorspb.DetectorType {
+	return detectorspb.DetectorType_GCPApplicationDefaultCredentials
+}

pkg/detectors/gcpapplicationdefaultcredentials/gcpapplicationdefaultcredentials_test.go

@@ -0,0 +1,230 @@
+//go:build detectors
+// +build detectors
+
+package gcpapplicationdefaultcredentials
+
+import (
+	"context"
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/google/go-cmp/cmp/cmpopts"
+
+	"github.com/trufflesecurity/trufflehog/v3/pkg/common"
+	"github.com/trufflesecurity/trufflehog/v3/pkg/detectors"
+	"github.com/trufflesecurity/trufflehog/v3/pkg/engine/ahocorasick"
+	"github.com/trufflesecurity/trufflehog/v3/pkg/pb/detectorspb"
+)
+
+var (
+	validTestString = `{'client_id': '191375729402-oiuj2498ry3497gjveoierj8294jfj41.apps.googleusercontent.com', 'client_secret': 'z-OIFJWEOIJGWER91834325R', 'refresh_token': '1//0_joijgor3i4ut98579862709342j3kjJOIE02834jijfewoifjowiejfhghyzznfoiwejfwnvuhewiufnwinciwu_-o2i3jjfcc', 'type': 'authorized_user'}`
+)
+
+func TestGcpapplicationdefaultcredentials_Pattern(t *testing.T) {
+	d := Scanner{}
+	ahoCorasickCore := ahocorasick.NewAhoCorasickCore([]detectors.Detector{d})
+	tests := []struct {
+		name  string
+		input string
+		want  []string
+	}{
+		{
+			name: "typical pattern",
+			input: `{
+					"client_id": "191375729402-oiuj2498ry3497gjveoierj8294jfj41.apps.googleusercontent.com",
+					"client_secret": "z-OIFJWEOIJGWER91834325R",
+					"refresh_token": "1//0_joijgor3i4ut98579862709342j3kjJOIE02834jijfewoifjowiejfhghyzznfoiwejfwnvuhewiufnwinciwu_-o2i3jjfcc",
+					"type": "authorized_user"
+				}`,
+			want: []string{"191375729402-oiuj2498ry3497gjveoierj8294jfj41"},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			chunkSpecificDetectors := make(map[ahocorasick.DetectorKey]detectors.Detector, 2)
+			ahoCorasickCore.PopulateMatchingDetectors(test.input, chunkSpecificDetectors)
+			if len(chunkSpecificDetectors) == 0 {
+				t.Errorf("keywords '%v' not matched by: %s", d.Keywords(), test.input)
+				return
+			}
+
+			results, err := d.FromData(context.Background(), false, []byte(test.input))
+			if err != nil {
+				t.Errorf("error = %v", err)
+				return
+			}
+
+			if len(results) != len(test.want) {
+				if len(results) == 0 {
+					t.Errorf("did not receive result")
+				} else {
+					t.Errorf("expected %d results, only received %d", len(test.want), len(results))
+				}
+				return
+			}
+
+			actual := make(map[string]struct{}, len(results))
+			for _, r := range results {
+				if len(r.RawV2) > 0 {
+					actual[string(r.RawV2)] = struct{}{}
+				} else {
+					actual[string(r.Raw)] = struct{}{}
+				}
+			}
+			expected := make(map[string]struct{}, len(test.want))
+			for _, v := range test.want {
+				expected[v] = struct{}{}
+			}
+
+			if diff := cmp.Diff(expected, actual); diff != "" {
+				t.Errorf("%s diff: (-want +got)\n%s", test.name, diff)
+			}
+		})
+	}
+}
+
+func TestGcpapplicationdefaultcredentials_FromChunk(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
+	defer cancel()
+	testSecrets, err := common.GetSecret(ctx, "trufflehog-testing", "detectors5")
+	if err != nil {
+		t.Fatalf("could not get test secrets from GCP: %s", err)
+	}
+	secret := testSecrets.MustGetField("GCPAPPLICATIONDEFAULTCREDENTIALS")
+	inactiveSecret := testSecrets.MustGetField("GCPAPPLICATIONDEFAULTCREDENTIALS_INACTIVE")
+
+	type args struct {
+		ctx    context.Context
+		data   []byte
+		verify bool
+	}
+	tests := []struct {
+		name                string
+		s                   Scanner
+		args                args
+		want                []detectors.Result
+		wantErr             bool
+		wantVerificationErr bool
+	}{
+		{
+			name: "found, verified",
+			s:    Scanner{},
+			args: args{
+				ctx:    context.Background(),
+				data:   []byte(fmt.Sprintf("You can find a gcpapplicationdefaultcredentials secret %s within", secret)),
+				verify: true,
+			},
+			want: []detectors.Result{
+				{
+					DetectorType: detectorspb.DetectorType_GCPApplicationDefaultCredentials,
+					Verified:     true,
+				},
+			},
+			wantErr:             false,
+			wantVerificationErr: false,
+		},
+		{
+			name: "found, unverified",
+			s:    Scanner{},
+			args: args{
+				ctx:    context.Background(),
+				data:   []byte(fmt.Sprintf("You can find a gcpapplicationdefaultcredentials secret %s within but not valid", inactiveSecret)), // the secret would satisfy the regex but not pass validation
+				verify: true,
+			},
+			want: []detectors.Result{
+				{
+					DetectorType: detectorspb.DetectorType_GCPApplicationDefaultCredentials,
+					Verified:     false,
+				},
+			},
+			wantErr:             false,
+			wantVerificationErr: false,
+		},
+		{
+			name: "not found",
+			s:    Scanner{},
+			args: args{
+				ctx:    context.Background(),
+				data:   []byte("You cannot find the secret within"),
+				verify: true,
+			},
+			want:                nil,
+			wantErr:             false,
+			wantVerificationErr: false,
+		},
+		{
+			name: "found, would be verified if not for timeout",
+			s:    Scanner{client: common.SaneHttpClientTimeOut(1 * time.Microsecond)},
+			args: args{
+				ctx:    context.Background(),
+				data:   []byte(fmt.Sprintf("You can find a gcpapplicationdefaultcredentials secret %s within", secret)),
+				verify: true,
+			},
+			want: []detectors.Result{
+				{
+					DetectorType: detectorspb.DetectorType_GCPApplicationDefaultCredentials,
+					Verified:     false,
+				},
+			},
+			wantErr:             false,
+			wantVerificationErr: true,
+		},
+		{
+			name: "found, verified but unexpected api surface",
+			s:    Scanner{client: common.ConstantResponseHttpClient(404, "")},
+			args: args{
+				ctx:    context.Background(),
+				data:   []byte(fmt.Sprintf("You can find a gcpapplicationdefaultcredentials secret %s within", secret)),
+				verify: true,
+			},
+			want: []detectors.Result{
+				{
+					DetectorType: detectorspb.DetectorType_GCPApplicationDefaultCredentials,
+					Verified:     false,
+				},
+			},
+			wantErr:             false,
+			wantVerificationErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := tt.s.FromData(tt.args.ctx, tt.args.verify, tt.args.data)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("Gcpapplicationdefaultcredentials.FromData() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			for i := range got {
+				if len(got[i].Raw) == 0 {
+					t.Fatalf("no raw secret present: \n %+v", got[i])
+				}
+				if (got[i].VerificationError() != nil) != tt.wantVerificationErr {
+					t.Fatalf("wantVerificationError = %v, verification error = %v", tt.wantVerificationErr, got[i].VerificationError())
+				}
+			}
+			ignoreOpts := cmpopts.IgnoreFields(detectors.Result{}, "Raw", "verificationError")
+			if diff := cmp.Diff(got, tt.want, ignoreOpts); diff != "" {
+				t.Errorf("Gcpapplicationdefaultcredentials.FromData() %s diff: (-got +want)\n%s", tt.name, diff)
+			}
+		})
+	}
+}
+
+func BenchmarkFromData(benchmark *testing.B) {
+	ctx := context.Background()
+	s := Scanner{}
+	for name, data := range detectors.MustGetBenchmarkData() {
+		benchmark.Run(name, func(b *testing.B) {
+			b.ResetTimer()
+			for n := 0; n < b.N; n++ {
+				_, err := s.FromData(ctx, false, data)
+				if err != nil {
+					b.Fatal(err)
+				}
+			}
+		})
+	}
+}