1 files changed, 144 insertions, 0 deletions
diff --git a/vendor/google.golang.org/api/internal/dca.go b/vendor/google.golang.org/api/internal/dca.go
new file mode 100644
index 0000000..204a3fd
--- /dev/null
+++ b/vendor/google.golang.org/api/internal/dca.go
@@ -0,0 +1,144 @@
+// Copyright 2020 Google LLC.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package dca contains utils for implementing Device Certificate
+// Authentication according to https://google.aip.dev/auth/4114
+//
+// The overall logic for DCA is as follows:
+//  1. If both endpoint override and client certificate are specified, use them as is.
+//  2. If user does not specify client certificate, we will attempt to use default
+//     client certificate.
+//  3. If user does not specify endpoint override, we will use defaultMtlsEndpoint if
+//     client certificate is available and defaultEndpoint otherwise.
+//
+// Implications of the above logic:
+//  1. If the user specifies a non-mTLS endpoint override but client certificate is
+//     available, we will pass along the cert anyway and let the server decide what to do.
+//  2. If the user specifies an mTLS endpoint override but client certificate is not
+//     available, we will not fail-fast, but let backend throw error when connecting.
+//
+// We would like to avoid introducing client-side logic that parses whether the
+// endpoint override is an mTLS url, since the url pattern may change at anytime.
+//
+// This package is not intended for use by end developers. Use the
+// google.golang.org/api/option package to configure API clients.
+
+// Package internal supports the options and transport packages.
+package internal
+
+import (
+	"net/url"
+	"os"
+	"strings"
+
+	"google.golang.org/api/internal/cert"
+)
+
+const (
+	mTLSModeAlways = "always"
+	mTLSModeNever  = "never"
+	mTLSModeAuto   = "auto"
+)
+
+// GetClientCertificateSourceAndEndpoint is a convenience function that invokes
+// getClientCertificateSource and getEndpoint sequentially and returns the client
+// cert source and endpoint as a tuple.
+func GetClientCertificateSourceAndEndpoint(settings *DialSettings) (cert.Source, string, error) {
+	clientCertSource, err := getClientCertificateSource(settings)
+	if err != nil {
+		return nil, "", err
+	}
+	endpoint, err := getEndpoint(settings, clientCertSource)
+	if err != nil {
+		return nil, "", err
+	}
+	return clientCertSource, endpoint, nil
+}
+
+// getClientCertificateSource returns a default client certificate source, if
+// not provided by the user.
+//
+// A nil default source can be returned if the source does not exist. Any exceptions
+// encountered while initializing the default source will be reported as client
+// error (ex. corrupt metadata file).
+//
+// Important Note: For now, the environment variable GOOGLE_API_USE_CLIENT_CERTIFICATE
+// must be set to "true" to allow certificate to be used (including user provided
+// certificates). For details, see AIP-4114.
+func getClientCertificateSource(settings *DialSettings) (cert.Source, error) {
+	if !isClientCertificateEnabled() {
+		return nil, nil
+	} else if settings.ClientCertSource != nil {
+		return settings.ClientCertSource, nil
+	} else {
+		return cert.DefaultSource()
+	}
+}
+
+func isClientCertificateEnabled() bool {
+	useClientCert := os.Getenv("GOOGLE_API_USE_CLIENT_CERTIFICATE")
+	// TODO(andyrzhao): Update default to return "true" after DCA feature is fully released.
+	return strings.ToLower(useClientCert) == "true"
+}
+
+// getEndpoint returns the endpoint for the service, taking into account the
+// user-provided endpoint override "settings.Endpoint".
+//
+// If no endpoint override is specified, we will either return the default endpoint or
+// the default mTLS endpoint if a client certificate is available.
+//
+// You can override the default endpoint choice (mtls vs. regular) by setting the
+// GOOGLE_API_USE_MTLS_ENDPOINT environment variable.
+//
+// If the endpoint override is an address (host:port) rather than full base
+// URL (ex. https://...), then the user-provided address will be merged into
+// the default endpoint. For example, WithEndpoint("myhost:8000") and
+// WithDefaultEndpoint("https://foo.com/bar/baz") will return "https://myhost:8080/bar/baz"
+func getEndpoint(settings *DialSettings, clientCertSource cert.Source) (string, error) {
+	if settings.Endpoint == "" {
+		mtlsMode := getMTLSMode()
+		if mtlsMode == mTLSModeAlways || (clientCertSource != nil && mtlsMode == mTLSModeAuto) {
+			return settings.DefaultMTLSEndpoint, nil
+		}
+		return settings.DefaultEndpoint, nil
+	}
+	if strings.Contains(settings.Endpoint, "://") {
+		// User passed in a full URL path, use it verbatim.
+		return settings.Endpoint, nil
+	}
+	if settings.DefaultEndpoint == "" {
+		// If DefaultEndpoint is not configured, use the user provided endpoint verbatim.
+		// This allows a naked "host[:port]" URL to be used with GRPC Direct Path.
+		return settings.Endpoint, nil
+	}
+
+	// Assume user-provided endpoint is host[:port], merge it with the default endpoint.
+	return mergeEndpoints(settings.DefaultEndpoint, settings.Endpoint)
+}
+
+func getMTLSMode() string {
+	mode := os.Getenv("GOOGLE_API_USE_MTLS_ENDPOINT")
+	if mode == "" {
+		mode = os.Getenv("GOOGLE_API_USE_MTLS") // Deprecated.
+	}
+	if mode == "" {
+		return mTLSModeAuto
+	}
+	return strings.ToLower(mode)
+}
+
+func mergeEndpoints(baseURL, newHost string) (string, error) {
+	u, err := url.Parse(fixScheme(baseURL))
+	if err != nil {
+		return "", err
+	}
+	return strings.Replace(baseURL, u.Host, newHost, 1), nil
+}
+
+func fixScheme(baseURL string) string {
+	if !strings.Contains(baseURL, "://") {
+		return "https://" + baseURL
+	}
+	return baseURL
+}