feat: [CI-19349]: Added oidc support for azure connector (#496)

* feat: [CI-19349]: Added oidc support for azure connector

* feat: [CI-19349]: Added env variables

* feat: [CI-19349]: Added tests

* Update cmd/drone-acr/main.go

* Update cmd/drone-acr/main.go

* feat: [CI-19349]: Added Debug statements

---------

Co-authored-by: OP (oppenheimer) <[email protected]>

Author: tapankarangiya

cmd/drone-acr/main.go

@@ -20,6 +20,7 @@ import (
 	"github.com/sirupsen/logrus"
 
 	docker "github.com/drone-plugins/drone-docker"
+	azureutil "github.com/drone-plugins/drone-docker/internal/azure"
 )
 
 type subscriptionUrlResponse struct {
@@ -62,12 +63,14 @@ func main() {
 		password = getenv("SERVICE_PRINCIPAL_CLIENT_SECRET")
 
 		// Service principal credentials
-		clientId       = getenv("CLIENT_ID")
-		clientSecret   = getenv("CLIENT_SECRET")
-		clientCert     = getenv("CLIENT_CERTIFICATE")
-		tenantId       = getenv("TENANT_ID")
-		subscriptionId = getenv("SUBSCRIPTION_ID")
-		publicUrl      = getenv("DAEMON_REGISTRY")
+		clientId       = getenv("CLIENT_ID", "AZURE_CLIENT_ID", "AZURE_APP_ID", "PLUGIN_CLIENT_ID")
+		clientSecret   = getenv("CLIENT_SECRET", "PLUGIN_CLIENT_SECRET")
+		clientCert     = getenv("CLIENT_CERTIFICATE", "PLUGIN_CLIENT_CERTIFICATE")
+		tenantId       = getenv("TENANT_ID", "AZURE_TENANT_ID", "PLUGIN_TENANT_ID")
+		subscriptionId = getenv("SUBSCRIPTION_ID", "PLUGIN_SUBSCRIPTION_ID")
+		publicUrl      = getenv("DAEMON_REGISTRY", "PLUGIN_DAEMON_REGISTRY")
+		authorityHost  = getenv("AZURE_AUTHORITY_HOST", "PLUGIN_AZURE_AUTHORITY_HOST")
+		idToken        = getenv("PLUGIN_OIDC_TOKEN_ID")
 	)
 
 	// default registry value
@@ -80,9 +83,29 @@ func main() {
 		// docker login credentials are not provided
 		var err error
 		username = defaultUsername
-		password, publicUrl, err = getAuth(clientId, clientSecret, clientCert, tenantId, subscriptionId, registry)
-		if err != nil {
-			logrus.Fatal(err)
+		if idToken != "" && clientId != "" && tenantId != "" {
+			logrus.Debug("Using OIDC authentication flow")
+			var aadToken string
+			aadToken, err = azureutil.GetAADAccessTokenViaClientAssertion(context.Background(), tenantId, clientId, idToken, authorityHost)
+			if err != nil {
+				logrus.Fatal(err)
+			}
+			var p string
+			p, err = getPublicUrl(aadToken, registry, subscriptionId)
+			if err == nil {
+				publicUrl = p
+			} else {
+				fmt.Fprintf(os.Stderr, "failed to get public url with error: %s\n", err)
+			}
+			password, err = fetchACRToken(tenantId, aadToken, registry)
+			if err != nil {
+				logrus.Fatal(err)
+			}
+		} else {
+			password, publicUrl, err = getAuth(clientId, clientSecret, clientCert, tenantId, subscriptionId, registry)
+			if err != nil {
+				logrus.Fatal(err)
+			}
 		}
 	}
 

cmd/drone-acr/main_test.go

@@ -0,0 +1,32 @@
+package main
+
+import (
+    "os"
+    "testing"
+)
+
+func TestGetAuthInputValidation(t *testing.T) {
+    // missing tenant
+    if _, _, err := getAuth("client", "secret", "", "", "sub", "registry.azurecr.io"); err == nil {
+        t.Fatalf("expected error for missing tenantId")
+    }
+    // missing clientId
+    if _, _, err := getAuth("", "secret", "", "tenant", "sub", "registry.azurecr.io"); err == nil {
+        t.Fatalf("expected error for missing clientId")
+    }
+    // missing both secret and cert
+    if _, _, err := getAuth("client", "", "", "tenant", "sub", "registry.azurecr.io"); err == nil {
+        t.Fatalf("expected error for missing credentials")
+    }
+}
+
+func TestGetenvAuthorityHost(t *testing.T) {
+    os.Setenv("AZURE_AUTHORITY_HOST", "https://login.microsoftonline.us")
+    defer os.Unsetenv("AZURE_AUTHORITY_HOST")
+
+    got := getenv("AZURE_AUTHORITY_HOST")
+    if got != "https://login.microsoftonline.us" {
+        t.Fatalf("expected AZURE_AUTHORITY_HOST to be returned, got %q", got)
+    }
+}
+

internal/azure/tokenutil.go

@@ -0,0 +1,75 @@
+package azure
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+const DefaultResource = "https://management.azure.com/"
+const defaultAuthorityHost = "https://login.microsoftonline.com"
+const defaultHTTPTimeout = 30 * time.Second
+
+// GetAADAccessTokenViaClientAssertion exchanges an external OIDC ID token for an Azure AD access token
+
+func GetAADAccessTokenViaClientAssertion(ctx context.Context, tenantID, clientID, oidcToken, authorityHost string) (string, error) {
+    resource := DefaultResource
+
+	form := url.Values{
+		"client_id":             {clientID},
+		"scope":                 {resource + ".default"},
+		"grant_type":            {"client_credentials"},
+		"client_assertion_type": {"urn:ietf:params:oauth:client-assertion-type:jwt-bearer"},
+		"client_assertion":      {oidcToken},
+	}
+
+	base := authorityHost
+	if strings.TrimSpace(base) == "" {
+		base = defaultAuthorityHost
+	}
+	base = strings.TrimRight(base, "/")
+	endpoint := fmt.Sprintf("%s/%s/oauth2/v2.0/token", base, tenantID)
+
+	client := &http.Client{Timeout: defaultHTTPTimeout}
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, strings.NewReader(form.Encode()))
+	if err != nil {
+		return "", err
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	req.Header.Set("Accept", "application/json")
+
+	resp, err := client.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		var aadErr struct {
+			Error            string `json:"error"`
+			ErrorDescription string `json:"error_description"`
+		}
+		limited := io.LimitedReader{R: resp.Body, N: 4096}
+		_ = json.NewDecoder(&limited).Decode(&aadErr)
+		if aadErr.Error != "" {
+			return "", fmt.Errorf("AAD token request failed: status=%d, error=%s", resp.StatusCode, aadErr.Error)
+		}
+		return "", fmt.Errorf("AAD token request failed: status=%d", resp.StatusCode)
+	}
+	var payload struct {
+		AccessToken string `json:"access_token"`
+		TokenType   string `json:"token_type"`
+		ExpiresIn   int    `json:"expires_in"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&payload); err != nil {
+		return "", err
+	}
+	if payload.AccessToken == "" {
+		return "", fmt.Errorf("AAD token response missing access_token")
+	}
+	return payload.AccessToken, nil
+}

internal/azure/tokenutil_test.go

@@ -0,0 +1,104 @@
+package azure
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+func TestGetAADAccessTokenViaClientAssertion_Success(t *testing.T) {
+
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPost {
+			t.Fatalf("expected POST, got %s", r.Method)
+		}
+		if ct := r.Header.Get("Content-Type"); !strings.Contains(ct, "application/x-www-form-urlencoded") {
+			t.Fatalf("expected form content-type, got %s", ct)
+		}
+		if err := r.ParseForm(); err != nil {
+			t.Fatalf("failed parsing form: %v", err)
+		}
+		assertEq(t, r.Form.Get("client_id"), "client")
+		assertEq(t, r.Form.Get("grant_type"), "client_credentials")
+		assertEq(t, r.Form.Get("client_assertion_type"), "urn:ietf:params:oauth:client-assertion-type:jwt-bearer")
+		assertEq(t, r.Form.Get("client_assertion"), "idtoken")
+		assertEq(t, r.Form.Get("scope"), DefaultResource+".default")
+
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte(`{"access_token":"AT","token_type":"Bearer","expires_in":3600}`))
+	}))
+	defer ts.Close()
+
+	tok, err := GetAADAccessTokenViaClientAssertion(context.Background(), "tenant", "client", "idtoken", ts.URL)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if tok != "AT" {
+		t.Fatalf("expected access token AT, got %q", tok)
+	}
+}
+
+func TestGetAADAccessTokenViaClientAssertion_400WithErrorField(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusBadRequest)
+		_, _ = w.Write([]byte(`{"error":"invalid_client","error_description":"bad"}`))
+	}))
+	defer ts.Close()
+
+	_, err := GetAADAccessTokenViaClientAssertion(context.Background(), "tenant", "client", "idtoken", ts.URL)
+	if err == nil || !strings.Contains(err.Error(), "status=400") || !strings.Contains(err.Error(), "invalid_client") {
+		t.Fatalf("expected 400 with invalid_client error, got %v", err)
+	}
+}
+
+func TestGetAADAccessTokenViaClientAssertion_400WithoutErrorField(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusBadRequest)
+		_, _ = w.Write([]byte("{}"))
+	}))
+	defer ts.Close()
+
+	_, err := GetAADAccessTokenViaClientAssertion(context.Background(), "tenant", "client", "idtoken", ts.URL)
+	if err == nil || !strings.Contains(err.Error(), "status=400") {
+		t.Fatalf("expected 400 error, got %v", err)
+	}
+}
+
+func TestGetAADAccessTokenViaClientAssertion_MalformedJSON(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte("not-json"))
+	}))
+	defer ts.Close()
+
+	_, err := GetAADAccessTokenViaClientAssertion(context.Background(), "tenant", "client", "idtoken", ts.URL)
+	if err == nil {
+		t.Fatalf("expected JSON decode error, got nil")
+	}
+}
+
+func TestGetAADAccessTokenViaClientAssertion_MissingAccessToken(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte(`{"token_type":"Bearer","expires_in":3600}`))
+	}))
+	defer ts.Close()
+
+	_, err := GetAADAccessTokenViaClientAssertion(context.Background(), "tenant", "client", "idtoken", ts.URL)
+	if err == nil || !strings.Contains(err.Error(), "missing access_token") {
+		t.Fatalf("expected missing access_token error, got %v", err)
+	}
+}
+
+func assertEq(t *testing.T, got, want string) {
+	t.Helper()
+	if got != want {
+		t.Fatalf("mismatch: got=%q want=%q", got, want)
+	}
+}
+