feat(detectors): docker auth detector (#2677)

Author: rgmz

pkg/detectors/docker/docker_auth_config.go

@@ -0,0 +1,316 @@
+package docker
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"github.com/go-logr/logr"
+	regexp "github.com/wasilibs/go-re2"
+
+	"github.com/trufflesecurity/trufflehog/v3/pkg/common"
+	logContext "github.com/trufflesecurity/trufflehog/v3/pkg/context"
+	"github.com/trufflesecurity/trufflehog/v3/pkg/detectors"
+	"github.com/trufflesecurity/trufflehog/v3/pkg/pb/detectorspb"
+)
+
+type Scanner struct {
+	client *http.Client
+}
+
+// Ensure the Scanner satisfies the interface at compile time.
+var _ interface {
+	detectors.Detector
+	detectors.MaxSecretSizeProvider
+} = (*Scanner)(nil)
+
+func (s Scanner) Type() detectorspb.DetectorType {
+	return detectorspb.DetectorType_Docker
+}
+
+func (s Scanner) Description() string {
+	return "Docker credentials can be used to pull images from private registries."
+}
+
+// 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{`"auths"`, `\"auths\`}
+}
+
+func (s Scanner) MaxSecretSize() int64 {
+	return 4096
+}
+
+var (
+	keyPat          = regexp.MustCompile(`{(?:\s|\\+[nrt])*\\*"auths\\*"(?:\s|\\+t)*:(?:\s|\\+t)*{(?:\s|\\+[nrt])*\\*"(?i:https?:\/\/)?[a-z0-9\-.:\/]+\\*"(?:\s|\\+t)*:(?:\s|\\+t)*{(?:(?:\s|\\+[nrt])*\\*"(?i:auth|email|username|password)\\*"\s*:\s*\\*".*\\*"\s*,?)+?(?:\s|\\+[nrt])*}(?:\s|\\+[nrt])*}(?:\s|\\+[nrt])*}`)
+	escapedReplacer = strings.NewReplacer(
+		`\n`, "",
+		`\r`, "",
+		`\t`, "",
+		`\\`, ``,
+		`\"`, `"`,
+	)
+
+	// Common false-positives used in examples.
+	exampleRegistries = map[string]struct{}{
+		"https://index.docker.io/v1/":       {}, // https://github.com/moby/moby/blob/34679e568a22b4f35ff8460f3b5b7bf7089df818/cliconfig/config_test.go#L259
+		"registry.hostname.com":             {}, // https://github.com/openshift/machine-config-operator/blob/82011335dbdd3d4c869b959d6048a3fba7742e47/pkg/controller/build/helpers_test.go#L47
+		"registry.example.com:5000":         {}, // https://github.com/openshift/cluster-baremetal-operator/blob/f908020b1d46667056f21cf1d79e032c535a41fc/provisioning/baremetal_secrets_test.go#L53
+		"registry2.example.com:5000":        {},
+		"your.private.registry.example.com": {}, // https://github.com/kubernetes/website/blob/d130f326758988553c42179c087bfeec5bf948a0/content/en/docs/tasks/configure-pod-container/pull-image-private-registry.md?plain=1#L167
+	}
+)
+
+// FromData will find and optionally verify Docker 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)
+	logCtx := logContext.AddLogger(ctx)
+	logger := logCtx.Logger().WithName("docker")
+
+	uniqueMatches := make(map[string]struct{})
+	for _, match := range keyPat.FindAllStringSubmatch(dataStr, -1) {
+		uniqueMatches[match[0]] = struct{}{}
+	}
+
+	for match := range uniqueMatches {
+		// Remove escaped quotes and literal whitespace characters, if present.
+		// It is common for auth to be escaped, however, the json package cannot unmarshal escaped JSON.
+		match := escapedReplacer.Replace(match)
+
+		// Unmarshal the config string.
+		// Doing byte->string->byte probably isn't the most efficient.
+		var auths dockerAuths
+		if err := json.NewDecoder(strings.NewReader(match)).Decode(&auths); err != nil {
+			logger.Error(err, "Could not parse Docker auth JSON")
+			return results, err
+		} else if len(auths.Auths) == 0 {
+			continue
+		}
+
+		for registry, auth := range auths.Auths {
+			// `docker.io` is a special case, Docker is hard-coded to rewrite it as `index.docker.io`.
+			// https://github.com/moby/moby/blob/145a73a36c171b34c196ad780e699b154ddf47b5/registry/config_test.go#L329
+			if strings.EqualFold(registry, "docker.io") {
+				registry = "index.docker.io"
+			}
+
+			// Skip known invalid registries.
+			if _, ok := exampleRegistries[registry]; ok {
+				continue
+			}
+
+			// Skip configs with no credentials.
+			// TODO: Should this be an error? What if it's a logic issue?
+			username, password, b64encoded := parseBasicAuth(logger, auth)
+			if username == "" && password == "" {
+				logger.V(2).Info("Skipping empty credentials", "auth", auth, "username", username, "password", password)
+				continue
+			}
+
+			r := detectors.Result{
+				DetectorType: detectorspb.DetectorType_Docker,
+				Raw:          []byte(b64encoded),
+				RawV2:        []byte(`{"registry":"` + registry + `","auth":"` + b64encoded + `"}`),
+				ExtraData:    map[string]string{"Username": username},
+			}
+
+			if verify {
+				client := s.client
+				if client == nil {
+					client = common.SaneHttpClient()
+				}
+
+				isVerified, verificationErr := verifyMatch(logCtx, client, registry, username, b64encoded)
+				r.Verified = isVerified
+				r.SetVerificationError(verificationErr, match)
+			}
+
+			results = append(results, r)
+		}
+	}
+	return
+}
+
+func verifyMatch(ctx logContext.Context, client *http.Client, registry string, username string, basicAuth string) (bool, error) {
+	// Build the registry URL path.
+	var registryUrl string
+	registry, _ = strings.CutSuffix(registry, "/")
+	if strings.HasPrefix(registry, "http://") || strings.HasPrefix(registry, "https://") {
+		registryUrl = registry + "/v2/"
+	} else {
+		registryUrl = "https://" + registry + "/v2/"
+	}
+
+	// Build the request.
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, registryUrl, nil)
+	if err != nil {
+		return false, nil
+	}
+
+	req.Header.Set("Authorization", "Basic "+basicAuth)
+	req.Header.Set("Accept", "application/json")
+	req.Header.Set("Content-Type", "application/json")
+
+	// Send the initial request.
+	res, err := client.Do(req)
+	if err != nil {
+		return false, err
+	}
+	defer func() {
+		_, _ = io.Copy(io.Discard, res.Body)
+		_ = res.Body.Close()
+	}()
+
+	// Handle the initial response.
+	switch res.StatusCode {
+	case http.StatusOK:
+		body, err := io.ReadAll(res.Body)
+		if err != nil {
+			return false, err
+		}
+
+		return json.Valid(body), nil
+	case http.StatusUnauthorized:
+		// Some registries do not support basic auth, so we must follow the `Www-Authenticate` header, if present.
+		// https://distribution.github.io/distribution/spec/auth/token/
+		h := res.Header.Get("Www-Authenticate")
+		if h == "" {
+			return false, nil
+		}
+
+		if !strings.HasPrefix(h, "Bearer") {
+			return false, fmt.Errorf("unsupported WWW-Authenticate auth scheme: %s", h)
+		}
+
+		authParams, err := parseAuthenticateHeader(h)
+		if err != nil {
+			return false, fmt.Errorf("failed to parse registry auth header: %w", err)
+		}
+		realm := authParams["realm"]
+		if realm == "" {
+			return false, fmt.Errorf("unexpected empty realm for WWW-Authenticate header: %s", h)
+		}
+
+		authReq, err := http.NewRequestWithContext(ctx, http.MethodGet, realm, nil)
+		if err != nil {
+			return false, nil
+		}
+
+		authReq.Header.Set("Authorization", "Basic "+basicAuth)
+		authReq.Header.Set("Accept", "application/json")
+		authReq.Header.Set("Content-Type", "application/json")
+
+		params := url.Values{}
+		params.Add("account", username)
+		params.Add("service", authParams["service"])
+		authReq.URL.RawQuery = params.Encode()
+
+		authRes, err := client.Do(authReq)
+		if err != nil {
+			return false, err
+		}
+		defer func() {
+			_, _ = io.Copy(io.Discard, authRes.Body)
+			_ = authRes.Body.Close()
+		}()
+
+		switch authRes.StatusCode {
+		case http.StatusOK:
+			return true, nil
+		case http.StatusUnauthorized, http.StatusForbidden:
+			// Auth was rejected.
+			return false, nil
+		default:
+			return false, fmt.Errorf("unexpected HTTP response status %d for '%s'", authRes.StatusCode, authReq.URL.String())
+		}
+	default:
+		err = fmt.Errorf("unexpected HTTP response status %d for '%s'", res.StatusCode, req.URL.String())
+		return false, err
+	}
+}
+
+type dockerAuths struct {
+	Auths map[string]dockerAuth `json:"auths"`
+}
+
+type dockerAuth struct {
+	Auth     string `json:"auth"`
+	Username string `json:"username"`
+	Password string `json:"password"`
+	Email    string `json:"email"`
+}
+
+// parseBasicAuth handles cases where configs can have `username` and `password` but no `auth`,
+// or vice-versa.
+func parseBasicAuth(logger logr.Logger, auth dockerAuth) (string, string, string) {
+	var (
+		username string
+		password string
+	)
+
+	if auth.Username != "" && auth.Password != "" {
+		username = auth.Username
+		password = auth.Password
+	}
+
+	if auth.Auth != "" {
+		data, err := base64.StdEncoding.DecodeString(auth.Auth)
+		if err != nil {
+			goto end
+		}
+
+		parts := strings.SplitN(string(data), ":", 2)
+		if len(parts) != 2 {
+			logger.V(2).Info("Skipping invalid parts", "length", len(parts), "parts", parts)
+			goto end
+		}
+
+		if (username != "" && parts[0] != username) || (password != "" && parts[1] != password) {
+			logger.V(2).Info("WARNING: Creds have more than two usernames or passwords")
+		}
+
+		username = parts[0]
+		password = parts[1]
+	}
+
+end:
+	if username == "" && password == "" {
+		return "", "", ""
+	}
+
+	basicAuth := base64.StdEncoding.EncodeToString([]byte(username + ":" + password))
+	if auth.Auth != "" && basicAuth != auth.Auth {
+		logger.Error(fmt.Errorf("base64-encoded auth does not match source"), "failed to parse auths JSON")
+	}
+	return username, password, basicAuth
+}
+
+// This is an ad-hoc implementation and not RFC compliant.
+// See https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/WWW-Authenticate
+func parseAuthenticateHeader(headerValue string) (map[string]string, error) {
+	authParams := make(map[string]string)
+
+	parts := strings.Split(headerValue, " ")
+	if len(parts) < 2 {
+		return nil, fmt.Errorf("invalid WWW-Authenticate header format")
+	}
+	authParams["scheme"] = parts[0]
+
+	parts = strings.Split(parts[1], ",")
+	for _, part := range parts {
+		keyVal := strings.SplitN(strings.TrimSpace(part), "=", 2)
+		if len(keyVal) == 2 {
+			key := strings.TrimSpace(keyVal[0])
+			value := strings.Trim(strings.TrimSpace(keyVal[1]), `"`)
+			authParams[key] = value
+		}
+	}
+
+	return authParams, nil
+}