authorize: add support for passing access or id token upstream (#3047)

* authorize: add support for passing access or id token upstream

* use an enum

authorize/evaluator/headers_evaluator.go

@@ -12,6 +12,7 @@ import (
 	"github.com/pomerium/pomerium/config"
 	"github.com/pomerium/pomerium/internal/telemetry/trace"
 	"github.com/pomerium/pomerium/internal/urlutil"
+	configpb "github.com/pomerium/pomerium/pkg/grpc/config"
 )
 
 // HeadersRequest is the input to the headers.rego script.
@@ -22,6 +23,8 @@ type HeadersRequest struct {
 	KubernetesServiceAccountToken             string         `json:"kubernetes_service_account_token"`
 	ToAudience                                string         `json:"to_audience"`
 	Session                                   RequestSession `json:"session"`
+	PassAccessToken                           bool           `json:"pass_access_token"`
+	PassIDToken                               bool           `json:"pass_id_token"`
 }
 
 // NewHeadersRequestFromPolicy creates a new HeadersRequest from a policy.
@@ -37,6 +40,8 @@ func NewHeadersRequestFromPolicy(policy *config.Policy) *HeadersRequest {
 	for _, wu := range policy.To {
 		input.ToAudience = "https://" + wu.URL.Hostname()
 	}
+	input.PassAccessToken = policy.GetSetAuthorizationHeader() == configpb.Route_ACCESS_TOKEN
+	input.PassIDToken = policy.GetSetAuthorizationHeader() == configpb.Route_ID_TOKEN
 	return input
 }
 

authorize/evaluator/headers_evaluator_test.go

@@ -106,4 +106,40 @@ func TestHeadersEvaluator(t *testing.T) {
 		assert.Equal(t, "u2", claims["sub"], "should set subject to user id")
 		assert.Equal(t, "u2", claims["user"], "should set user to user id")
 	})
+
+	t.Run("access token", func(t *testing.T) {
+		output, err := eval(t,
+			[]proto.Message{
+				&session.Session{Id: "s1", OauthToken: &session.OAuthToken{
+					AccessToken: "ACCESS_TOKEN",
+				}},
+			},
+			&HeadersRequest{
+				FromAudience:    "from.example.com",
+				ToAudience:      "to.example.com",
+				Session:         RequestSession{ID: "s1"},
+				PassAccessToken: true,
+			})
+		require.NoError(t, err)
+
+		assert.Equal(t, "Bearer ACCESS_TOKEN", output.Headers.Get("Authorization"))
+	})
+
+	t.Run("id token", func(t *testing.T) {
+		output, err := eval(t,
+			[]proto.Message{
+				&session.Session{Id: "s1", IdToken: &session.IDToken{
+					Raw: "ID_TOKEN",
+				}},
+			},
+			&HeadersRequest{
+				FromAudience: "from.example.com",
+				ToAudience:   "to.example.com",
+				Session:      RequestSession{ID: "s1"},
+				PassIDToken:  true,
+			})
+		require.NoError(t, err)
+
+		assert.Equal(t, "Bearer ID_TOKEN", output.Headers.Get("Authorization"))
+	})
 }

authorize/evaluator/opa/policy/headers.rego

@@ -8,6 +8,8 @@ package pomerium.headers
 #   session:
 #     id: string
 #   to_audience: string
+#   pass_access_token: boolean
+#   pass_id_token: boolean
 #
 # data:
 #   issuer: string
@@ -153,7 +155,7 @@ base_jwt_claims := [
 	["user", jwt_payload_user],
 	["email", jwt_payload_email],
 	["groups", jwt_payload_groups],
-	["sid", jwt_payload_sid]
+	["sid", jwt_payload_sid],
 ]
 
 additional_jwt_claims := [[k, v] |
@@ -209,9 +211,21 @@ google_cloud_serverless_headers = h {
 
 routing_key_headers = h {
 	input.enable_routing_key
-    h := [
-        ["x-pomerium-routing-key", crypto.sha256(input.session.id)]
-    ]
+	h := [["x-pomerium-routing-key", crypto.sha256(input.session.id)]]
+} else = [] {
+	true
+}
+
+pass_access_token_headers = h {
+	input.pass_access_token
+	h := [["Authorization", concat(" ", ["Bearer", session.oauth_token.access_token])]]
+} else = [] {
+	true
+}
+
+pass_id_token_headers = h {
+	input.pass_id_token
+	h := [["Authorization", concat(" ", ["Bearer", session.id_token.raw])]]
 } else = [] {
 	true
 }
@@ -226,16 +240,19 @@ identity_headers := {key: values |
 				[ck, cv] := jwt_claims[_]
 				ck == k
 			],
-			[""]
+			[""],
 		)[0]
+
 		header_value := get_header_string_value(raw_header_value)
 	]
 
 	h3 := kubernetes_headers
 	h4 := [[k, v] | v := google_cloud_serverless_headers[k]]
 	h5 := routing_key_headers
+	h6 := pass_access_token_headers
+	h7 := pass_id_token_headers
 
-	h := array.concat(array.concat(array.concat(array.concat(h1, h2), h3), h4), h5)
+	h := array.concat(array.concat(array.concat(array.concat(array.concat(array.concat(h1, h2), h3), h4), h5), h6), h7)
 
 	some i
 	[key, v1] := h[i]

config/policy.go

@@ -117,6 +117,10 @@ type Policy struct {
 	TLSDownstreamClientCA     string `mapstructure:"tls_downstream_client_ca" yaml:"tls_downstream_client_ca,omitempty"`
 	TLSDownstreamClientCAFile string `mapstructure:"tls_downstream_client_ca_file" yaml:"tls_downstream_client_ca_file,omitempty"`
 
+	// SetAuthorizationHeader sets the authorization request header based on the user's identity. Supported modes are
+	// `pass_through`, `access_token` and `id_token`.
+	SetAuthorizationHeader string `mapstructure:"set_authorization_header" yaml:"set_authorization_header,omitempty"`
+
 	// SetRequestHeaders adds a collection of headers to the upstream request
 	// in the form of key value pairs. Note bene, this will overwrite the
 	// value of any existing value of a given header key.
@@ -242,6 +246,7 @@ func NewPolicyFromProto(pb *configpb.Route) (*Policy, error) {
 		TLSClientKeyFile:                 pb.GetTlsClientKeyFile(),
 		TLSDownstreamClientCA:            pb.GetTlsDownstreamClientCa(),
 		TLSDownstreamClientCAFile:        pb.GetTlsDownstreamClientCaFile(),
+		SetAuthorizationHeader:           pb.GetSetAuthorizationHeader().String(),
 		SetRequestHeaders:                pb.GetSetRequestHeaders(),
 		RemoveRequestHeaders:             pb.GetRemoveRequestHeaders(),
 		PreserveHostHeader:               pb.GetPreserveHostHeader(),
@@ -364,6 +369,7 @@ func (p *Policy) ToProto() (*configpb.Route, error) {
 		RemoveRequestHeaders:             p.RemoveRequestHeaders,
 		PreserveHostHeader:               p.PreserveHostHeader,
 		PassIdentityHeaders:              p.PassIdentityHeaders,
+		SetAuthorizationHeader:           p.GetSetAuthorizationHeader(),
 		KubernetesServiceAccountToken:    p.KubernetesServiceAccountToken,
 		Policies:                         sps,
 		SetResponseHeaders:               p.SetResponseHeaders,
@@ -513,6 +519,10 @@ func (p *Policy) Validate() error {
 		p.compiledRegex, _ = regexp.Compile(rawRE)
 	}
 
+	if _, ok := configpb.Route_AuthorizationHeaderModeFromString(p.SetAuthorizationHeader); !ok && p.SetAuthorizationHeader != "" {
+		return fmt.Errorf("config: invalid policy set_authorization_header: %v", p.SetAuthorizationHeader)
+	}
+
 	return nil
 }
 
@@ -639,6 +649,12 @@ func (p *Policy) AllAllowedUsers() []string {
 	return aus
 }
 
+// GetSetAuthorizationHeader gets the set authorization header mode.
+func (p *Policy) GetSetAuthorizationHeader() configpb.Route_AuthorizationHeaderMode {
+	mode, _ := configpb.Route_AuthorizationHeaderModeFromString(p.SetAuthorizationHeader)
+	return mode
+}
+
 // StringURL stores a URL as a string in json.
 type StringURL struct {
 	*url.URL

docs/reference/readme.md

@@ -1476,6 +1476,18 @@ explicitly set, then `timeout` would be unlimited (`0s`). You still may specify
 of the connection using `timeout` value (i.e. to 1 day).
 
 
+### Set Authorization Header
+- `yaml`/`json` setting: `set_authorization_header`
+- Type: `string` (`pass_through`, `access_token` or `id_token`)
+- Optional
+- Default: `pass_through`
+
+Set Authorization Header allows you to send a user's identity token through as a Bearer token in the Authorization header.
+
+Use `access_token` to send the OAuth access token, `id_token` to send the OIDC id token, or `pass_through` (the default) to leave the Authorization header unchanged
+when it's not used for Pomerium authentication.
+
+
 ### Set Request Headers
 - Config File Key: `set_request_headers`
 - Type: map of `strings` key value pairs

docs/reference/settings.yaml

@@ -1622,6 +1622,19 @@ settings:
           or set it to unlimited (`0s`). If `idle_timeout` is specified, and `timeout` is not
           explicitly set, then `timeout` would be unlimited (`0s`). You still may specify maximum lifetime
           of the connection using `timeout` value (i.e. to 1 day).
+
+      - name: "Set Authorization Header"
+        keys: ["set_authorization_header"]
+        attributes: |
+          - `yaml`/`json` setting: `set_authorization_header`
+          - Type: `string` (`pass_through`, `access_token` or `id_token`)
+          - Optional
+          - Default: `pass_through`
+        doc: |
+          Set Authorization Header allows you to send a user's identity token through as a Bearer token in the Authorization header.
+
+          Use `access_token` to send the OAuth access token, `id_token` to send the OIDC id token, or `pass_through` (the default) to leave the Authorization header unchanged
+          when it's not used for Pomerium authentication.
       - name: "Set Request Headers"
         keys: ["set_request_headers"]
         attributes: |

pkg/grpc/config/config.go

@@ -1,6 +1,8 @@
 // Package config contains protobuf definitions for config.
 package config
 
+import "strings"
+
 // IsSet returns true if one of the route redirect options has been chosen.
 func (rr *RouteRedirect) IsSet() bool {
 	if rr == nil {
@@ -16,3 +18,9 @@ func (rr *RouteRedirect) IsSet() bool {
 		rr.SchemeRedirect != nil ||
 		rr.HttpsRedirect != nil
 }
+
+// Route_AuthorizationHeaderModeFromString returns the Route_AuthorizationHeaderMode from a string.
+func Route_AuthorizationHeaderModeFromString(raw string) (Route_AuthorizationHeaderMode, bool) { //nolint
+	mode, ok := Route_AuthorizationHeaderMode_value[strings.ToUpper(raw)]
+	return Route_AuthorizationHeaderMode(mode), ok
+}

pkg/grpc/config/config.proto

@@ -34,6 +34,12 @@ message RouteRedirect {
 }
 
 message Route {
+  enum AuthorizationHeaderMode {
+    PASS_THROUGH = 0;
+    ACCESS_TOKEN = 1;
+    ID_TOKEN = 2;
+  }
+
   string name = 1;
 
   string from = 2;
@@ -86,6 +92,7 @@ message Route {
   repeated string remove_request_headers = 23;
   map<string, string> set_response_headers = 41;
   repeated RouteRewriteHeader rewrite_response_headers = 40;
+  AuthorizationHeaderMode set_authorization_header = 54;
 
   bool preserve_host_header = 24;
   bool pass_identity_headers = 25;
@@ -102,6 +109,7 @@ message Route {
   optional string host_rewrite_header = 51;
   optional string host_path_regex_rewrite_pattern = 52;
   optional string host_path_regex_rewrite_substitution = 53;
+
 }
 
 message Policy {