add /auth for docker compatibility

This endpoint just validates credentials:
https://github.com/moby/moby/blob/v20.10.4/api/swagger.yaml#L7936-L7977

Fixes: #9564
Signed-off-by: troyready <troy@troyready.com>

pkg/api/handlers/compat/auth.go

@@ -0,0 +1,51 @@
+package compat
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strings"
+
+	DockerClient "github.com/containers/image/v5/docker"
+	"github.com/containers/image/v5/types"
+	"github.com/containers/podman/v3/pkg/api/handlers/utils"
+	"github.com/containers/podman/v3/pkg/domain/entities"
+	"github.com/containers/podman/v3/pkg/registries"
+	docker "github.com/docker/docker/api/types"
+	"github.com/pkg/errors"
+)
+
+func Auth(w http.ResponseWriter, r *http.Request) {
+	var authConfig docker.AuthConfig
+	err := json.NewDecoder(r.Body).Decode(&authConfig)
+	if err != nil {
+		utils.Error(w, "Something went wrong.", http.StatusInternalServerError, errors.Wrapf(err, "failed to parse request"))
+		return
+	}
+
+	skipTLS := types.NewOptionalBool(false)
+	if strings.HasPrefix(authConfig.ServerAddress, "http://localhost/") || strings.HasPrefix(authConfig.ServerAddress, "http://localhost:") {
+		// support for local testing
+		skipTLS = types.NewOptionalBool(true)
+	}
+
+	fmt.Println("Authenticating with existing credentials...")
+	sysCtx := types.SystemContext{
+		AuthFilePath:                "",
+		DockerCertPath:              "",
+		DockerInsecureSkipTLSVerify: skipTLS,
+		SystemRegistriesConfPath:    registries.SystemRegistriesConfPath(),
+	}
+	if err := DockerClient.CheckAuth(context.Background(), &sysCtx, authConfig.Username, authConfig.Password, authConfig.ServerAddress); err == nil {
+		utils.WriteResponse(w, http.StatusOK, entities.AuthReport{
+			IdentityToken: "",
+			Status:        "Login Succeeded",
+		})
+	} else {
+		utils.WriteResponse(w, http.StatusBadRequest, entities.AuthReport{
+			IdentityToken: "",
+			Status:        "login attempt to " + authConfig.ServerAddress + " failed with status: " + err.Error(),
+		})
+	}
+}

pkg/api/server/register_auth.go

@@ -1,13 +1,33 @@
 package server
 
 import (
+	"net/http"
+
 	"github.com/containers/podman/v3/pkg/api/handlers/compat"
 	"github.com/gorilla/mux"
 )
 
 func (s *APIServer) registerAuthHandlers(r *mux.Router) error {
-	r.Handle(VersionedPath("/auth"), s.APIHandler(compat.UnsupportedHandler))
+	// swagger:operation POST /auth compat auth
+	// ---
+	//   summary: Check auth configuration
+	//   tags:
+	//    - system (compat)
+	//   produces:
+	//   - application/json
+	//   parameters:
+	//    - in: body
+	//      name: authConfig
+	//      description: Authentication to check
+	//      schema:
+	//        $ref: "#/definitions/AuthConfig"
+	//   responses:
+	//     200:
+	//       $ref: "#/responses/SystemAuthResponse"
+	//     500:
+	//       $ref: "#/responses/InternalError"
+	r.Handle(VersionedPath("/auth"), s.APIHandler(compat.Auth)).Methods(http.MethodPost)
 	// Added non version path to URI to support docker non versioned paths
-	r.Handle("/auth", s.APIHandler(compat.UnsupportedHandler))
+	r.Handle("/auth", s.APIHandler(compat.Auth)).Methods(http.MethodPost)
 	return nil
 }

pkg/api/server/swagger.go

@@ -226,3 +226,12 @@ type swagSystemPruneReport struct {
 		entities.SystemPruneReport
 	}
 }
+
+// Auth response
+// swagger:response SystemAuthResponse
+type swagSystemAuthResponse struct {
+	// in:body
+	Body struct {
+		entities.AuthReport
+	}
+}

pkg/domain/entities/system.go

@@ -107,3 +107,14 @@ type ComponentVersion struct {
 type ListRegistriesReport struct {
 	Registries []string
 }
+
+// swagger:model AuthConfig
+type AuthConfig struct {
+	types.AuthConfig
+}
+
+// AuthReport describes the response for authentication check
+type AuthReport struct {
+	IdentityToken string
+	Status        string
+}

test/apiv2/rest_api/test_rest_v2_0_0.py

@@ -555,16 +555,17 @@ class TestApi(unittest.TestCase):
         self.assertIn(name, payload["VolumesDeleted"])
         self.assertGreater(payload["SpaceReclaimed"], 0)
 
-    def test_auth_compat(self):
-        r = requests.post(
-            PODMAN_URL + "/v1.40/auth",
-            json={
-                "username": "bozo",
-                "password": "wedontneednopasswords",
-                "serveraddress": "https://localhost/v1.40/",
-            },
-        )
-        self.assertEqual(r.status_code, 404, r.content)
+    # TBD: how to test auth endpoint (which in turn requires a docker registry to connect to)
+    # def test_auth_compat(self):
+    #     r = requests.post(
+    #         PODMAN_URL + "/v1.40/auth",
+    #         json={
+    #             "username": "bozo",
+    #             "password": "wedontneednopasswords",
+    #             "serveraddress": "https://localhost/v1.40/",
+    #         },
+    #     )
+    #     self.assertEqual(r.status_code, 404, r.content)
 
     def test_version(self):
         r = requests.get(PODMAN_URL + "/v1.40/version")