Merge pull request #504 from drone-plugins/ci-18951

feat: [CI-18951]: check for HARNESS prefixed proxy variables

.drone.yml

@@ -12,7 +12,7 @@ platform:
 
 steps:
   - name: vet
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - go vet ./...
     environment:
@@ -22,7 +22,7 @@ steps:
         path: /go
 
   - name: test
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - go test -cover ./...
     environment:
@@ -55,7 +55,7 @@ platform:
 
 steps:
   - name: go build
-    image: golang:1.23
+    image: golang:1.24.11
     environment:
       CGO_ENABLED: 0
     commands:
@@ -162,7 +162,7 @@ platform:
 
 steps:
   - name: go build
-    image: golang:1.23
+    image: golang:1.24.11
     environment:
       CGO_ENABLED: 0
     commands:
@@ -264,7 +264,7 @@ platform:
 
 steps:
   - name: build-push
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_COMMIT_SHA:0:8}" -a -tags netgo -o release/linux/amd64/drone-docker ./cmd/drone-docker'
     environment:
@@ -275,7 +275,7 @@ steps:
           - tag
 
   - name: build-tag
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_TAG##v}" -a -tags netgo -o release/linux/amd64/drone-docker ./cmd/drone-docker'
     environment:
@@ -285,7 +285,7 @@ steps:
         - tag
 
   - name: executable
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - ./release/linux/amd64/drone-docker --help
 
@@ -329,7 +329,7 @@ platform:
 
 steps:
   - name: build-push
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_COMMIT_SHA:0:8}" -a -tags netgo -o release/linux/arm64/drone-docker ./cmd/drone-docker'
     environment:
@@ -340,7 +340,7 @@ steps:
           - tag
 
   - name: build-tag
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_TAG##v}" -a -tags netgo -o release/linux/arm64/drone-docker ./cmd/drone-docker'
     environment:
@@ -350,7 +350,7 @@ steps:
         - tag
 
   - name: executable
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - ./release/linux/arm64/drone-docker --help
 
@@ -429,7 +429,7 @@ platform:
 
 steps:
   - name: build-push
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_COMMIT_SHA:0:8}" -a -tags netgo -o release/linux/amd64/drone-gcr ./cmd/drone-gcr'
     environment:
@@ -440,7 +440,7 @@ steps:
           - tag
 
   - name: build-tag
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_TAG##v}" -a -tags netgo -o release/linux/amd64/drone-gcr ./cmd/drone-gcr'
     environment:
@@ -488,7 +488,7 @@ platform:
 
 steps:
   - name: build-push
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_COMMIT_SHA:0:8}" -a -tags netgo -o release/linux/arm64/drone-gcr ./cmd/drone-gcr'
     environment:
@@ -499,7 +499,7 @@ steps:
           - tag
 
   - name: build-tag
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_TAG##v}" -a -tags netgo -o release/linux/arm64/drone-gcr ./cmd/drone-gcr'
     environment:
@@ -582,7 +582,7 @@ platform:
 
 steps:
   - name: build-push
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_COMMIT_SHA:0:8}" -a -tags netgo -o release/linux/amd64/drone-gar ./cmd/drone-gar'
     environment:
@@ -593,7 +593,7 @@ steps:
           - tag
 
   - name: build-tag
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_TAG##v}" -a -tags netgo -o release/linux/amd64/drone-gar ./cmd/drone-gar'
     environment:
@@ -641,7 +641,7 @@ platform:
 
 steps:
   - name: build-push
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_COMMIT_SHA:0:8}" -a -tags netgo -o release/linux/arm64/drone-gar ./cmd/drone-gar'
     environment:
@@ -652,7 +652,7 @@ steps:
           - tag
 
   - name: build-tag
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_TAG##v}" -a -tags netgo -o release/linux/arm64/drone-gar ./cmd/drone-gar'
     environment:
@@ -734,7 +734,7 @@ platform:
 
 steps:
   - name: build-push
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_COMMIT_SHA:0:8}" -a -tags netgo -o release/linux/amd64/drone-ecr ./cmd/drone-ecr'
     environment:
@@ -744,7 +744,7 @@ steps:
         exclude:
           - tag
   - name: build-tag
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_TAG##v}" -a -tags netgo -o release/linux/amd64/drone-ecr ./cmd/drone-ecr'
     environment:
@@ -792,7 +792,7 @@ platform:
 
 steps:
   - name: build-push
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_COMMIT_SHA:0:8}" -a -tags netgo -o release/linux/arm64/drone-ecr ./cmd/drone-ecr'
     environment:
@@ -802,7 +802,7 @@ steps:
         exclude:
           - tag
   - name: build-tag
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_TAG##v}" -a -tags netgo -o release/linux/arm64/drone-ecr ./cmd/drone-ecr'
     environment:
@@ -885,7 +885,7 @@ platform:
 
 steps:
   - name: build-push
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_COMMIT_SHA:0:8}" -a -tags netgo -o release/linux/amd64/drone-heroku ./cmd/drone-heroku'
     environment:
@@ -895,7 +895,7 @@ steps:
         exclude:
           - tag
   - name: build-tag
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_TAG##v}" -a -tags netgo -o release/linux/amd64/drone-heroku ./cmd/drone-heroku'
     environment:
@@ -944,7 +944,7 @@ platform:
 
 steps:
   - name: build-push
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_COMMIT_SHA:0:8}" -a -tags netgo -o release/linux/arm64/drone-heroku ./cmd/drone-heroku'
     environment:
@@ -954,7 +954,7 @@ steps:
         exclude:
           - tag
   - name: build-tag
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_TAG##v}" -a -tags netgo -o release/linux/arm64/drone-heroku ./cmd/drone-heroku'
     environment:
@@ -1035,7 +1035,7 @@ platform:
 
 steps:
   - name: build-push
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.build=${DRONE_BUILD_NUMBER}" -a -tags netgo -o release/linux/amd64/drone-acr ./cmd/drone-acr'
     environment:
@@ -1045,7 +1045,7 @@ steps:
         exclude:
           - tag
   - name: build-tag
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_TAG##v} -X main.build=${DRONE_BUILD_NUMBER}" -a -tags netgo -o release/linux/amd64/drone-acr ./cmd/drone-acr'
     environment:
@@ -1093,7 +1093,7 @@ platform:
 
 steps:
   - name: build-push
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.build=${DRONE_BUILD_NUMBER}" -a -tags netgo -o release/linux/arm64/drone-acr ./cmd/drone-acr'
     environment:
@@ -1104,7 +1104,7 @@ steps:
           - tag
 
   - name: build-tag
-    image: golang:1.23
+    image: golang:1.24.11
     commands:
       - 'go build -v -ldflags "-X main.version=${DRONE_TAG##v} -X main.build=${DRONE_BUILD_NUMBER}" -a -tags netgo -o release/linux/arm64/drone-acr ./cmd/drone-acr'
     environment:

.harness/harness.yaml

@@ -33,7 +33,7 @@ pipeline:
                   identifier: Run_1
                   spec:
                     connectorRef: Plugins_Docker_Hub_Connector
-                    image: golang:1.23.0
+                    image: golang:1.24.11
                     shell: Sh
                     command: go vet ./...
               - step:
@@ -42,7 +42,7 @@ pipeline:
                   identifier: Run_2
                   spec:
                     connectorRef: Plugins_Docker_Hub_Connector
-                    image: golang:1.23.0
+                    image: golang:1.24.11
                     shell: Sh
                     command: go test -cover ./...
     - parallel:
@@ -70,7 +70,7 @@ pipeline:
                       identifier: Build_Push
                       spec:
                         connectorRef: Plugins_Docker_Hub_Connector
-                        image: golang:1.23.0
+                        image: golang:1.24.11
                         shell: Sh
                         command: go build -a -tags netgo -o release/linux/amd64/drone-<+matrix.repo> ./cmd/drone-<+matrix.repo>
                         envVariables:
@@ -157,7 +157,7 @@ pipeline:
                       identifier: buildpush
                       spec:
                         connectorRef: Plugins_Docker_Hub_Connector
-                        image: golang:1.23.0
+                        image: golang:1.24.11
                         shell: Sh
                         command: go build -a -tags netgo -o release/linux/arm64/drone-<+matrix.repo> ./cmd/drone-<+matrix.repo>
                         envVariables:

COSIGN_USAGE.md

@@ -0,0 +1,162 @@
+# Cosign Integration for Drone-Docker
+
+This document describes how to use the cosign container image signing feature in drone-docker.
+
+## Overview
+
+The drone-docker plugin now supports automatic container image signing using cosign after each successful push. This provides cryptographic verification that images haven't been tampered with.
+
+## Environment Variables
+
+The plugin accepts three cosign-related environment variables:
+
+### `PLUGIN_COSIGN_PRIVATE_KEY` (Required for signing)
+- **Description**: Private key for signing (PEM format content or file path)
+- **Format**: Either PEM content or file path to private key
+- **Usage**: Should be provided via secrets
+
+### `PLUGIN_COSIGN_PASSWORD` (Optional)
+- **Description**: Password for encrypted private keys
+- **Usage**: Only needed if your private key is password-protected
+
+### `PLUGIN_COSIGN_PARAMS` (Optional)
+- **Description**: Additional cosign parameters
+- **Examples**: 
+  - `-a build_id=123` (add annotations)
+  - `--tlog-upload=false` (disable transparency log)
+  - `--rekor-url=https://custom-rekor.example.com` (custom rekor instance)
+
+## Usage Examples
+
+### 1. Basic Signing (Drone)
+
+```yaml
+kind: pipeline
+type: docker
+name: default
+
+steps:
+- name: docker
+  image: plugins/docker
+  settings:
+    repo: myregistry/myapp
+    tags: latest
+    cosign_private_key:
+      from_secret: cosign_private_key
+    cosign_password:
+      from_secret: cosign_password
+```
+
+### 2. Advanced Signing with Annotations (Drone)
+
+```yaml
+steps:
+- name: docker
+  image: plugins/docker
+  settings:
+    repo: myregistry/myapp
+    tags: 
+      - latest
+      - ${DRONE_BUILD_NUMBER}
+    cosign_private_key:
+      from_secret: cosign_private_key
+    cosign_params: "-a build_id=${DRONE_BUILD_NUMBER} -a commit_sha=${DRONE_COMMIT_SHA} -a branch=${DRONE_BRANCH}"
+```
+
+### 3. Harness CI/CD Usage
+
+```yaml
+- step:
+    type: Plugin
+    name: Build and Sign
+    identifier: build_and_sign
+    spec:
+      connectorRef: account.harnessImage
+      image: plugins/docker
+      settings:
+        repo: myregistry/myapp
+        tags: <+pipeline.sequenceId>
+        cosign_private_key: <+secrets.getValue("cosign_private_key")>
+        cosign_password: <+secrets.getValue("cosign_password")>
+        cosign_params: "-a harness_build=<+pipeline.sequenceId> -a harness_project=<+project.name>"
+```
+
+## Key Management
+
+### Generating Cosign Keys
+
+```bash
+# Generate a new key pair
+cosign generate-key-pair
+
+# This creates:
+# - cosign.key (private key) 
+# - cosign.pub (public key)
+```
+
+### Storing Keys Securely
+**Harness Secrets:**
+1. Go to Project Settings → Secrets
+2. Create new secret with type "File" for private key
+3. Create new secret with type "Text" for password
+
+## Security Features
+
+### Automatic Validation
+- ✅ **Private key format validation**: Ensures PEM format is correct
+- ✅ **Password requirement detection**: Warns if encrypted key needs password
+- ✅ **Keyless signing prevention**: Warns that OIDC keyless signing isn't supported
+
+### Error Handling
+- **Invalid private key**: `❌ Invalid private key format. Expected PEM format`
+- **Missing password**: `🔐 Encrypted private key requires password. Set PLUGIN_COSIGN_PASSWORD`
+- **Keyless signing**: `⚠️ WARNING: Keyless signing (OIDC) isn't supported yet in this plugin`
+
+## Signing Behavior
+
+### When Signing Occurs
+- ✅ **After each successful push**: Images are signed immediately after push
+- ✅ **Multiple tags**: Each tag gets signed individually
+- ✅ **Push-only mode**: Works with existing images
+- ✅ **Dry-run respect**: Skips signing in dry-run mode
+
+### Image References
+- **Preferred**: Signs by digest (e.g., `image@sha256:abc123...`) for security
+- **Fallback**: Signs by tag if digest unavailable
+
+### Authentication
+- **Registry auth**: Automatically uses existing Docker registry credentials
+
+## Verification
+
+To verify a signed image:
+
+```bash
+# Verify with public key
+cosign verify --key cosign.pub myregistry/myapp:latest
+
+# Verify with annotations
+cosign verify --key cosign.pub \
+  -a build_id=123 \
+  myregistry/myapp:latest
+```
+
+## Troubleshooting
+
+### Common Issues
+
+1. **"cosign: command not found"**
+   - The container image includes cosign binary
+   - Use the latest plugin image: `plugins/docker:latest`
+
+2. **"keyless signing not supported"**
+   - This plugin only supports private key signing
+   - Don't use `--oidc` or `--identity-token` in `cosign_params`
+
+3. **"encrypted private key requires password"**
+   - Set `PLUGIN_COSIGN_PASSWORD` environment variable
+   - Or use an unencrypted private key
+
+4. **Registry authentication issues**
+   - Cosign uses the same Docker registry credentials
+   - Ensure Docker login is working first

card.go

@@ -17,8 +17,14 @@ import (
 	"github.com/inhies/go-bytesize"
 )
 
+// writeCard maintains backward compatibility by using TempTag
 func (p Plugin) writeCard() error {
-	cmd := exec.Command(dockerExe, "inspect", p.Build.TempTag)
+	return p.writeCardForImage(p.Build.TempTag)
+}
+
+// writeCardForImage generates card for any image reference
+func (p Plugin) writeCardForImage(imageRef string) error {
+	cmd := exec.Command(dockerExe, "inspect", imageRef)
 	data, err := cmd.CombinedOutput()
 	if err != nil {
 		return err
@@ -38,7 +44,11 @@ func (p Plugin) writeCard() error {
 	for _, tag := range inspect.RepoTags {
 		sliceTagStruct = append(sliceTagStruct, TagStruct{Tag: tag})
 	}
+	if len(sliceTagStruct) > 1 {
 		inspect.ParsedRepoTags = sliceTagStruct[1:] // remove the first tag which is always "hash:latest"
+	} else {
+		inspect.ParsedRepoTags = sliceTagStruct
+	}
 	// create the url from repo and registry
 	inspect.URL = mapRegistryToURL(p.Daemon.Registry, p.Build.Repo)
 	cardData, _ := json.Marshal(inspect)

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")
+		clientId       = getenv("CLIENT_ID", "AZURE_CLIENT_ID", "AZURE_APP_ID", "PLUGIN_CLIENT_ID")
-		clientSecret   = getenv("CLIENT_SECRET")
+		clientSecret   = getenv("CLIENT_SECRET", "PLUGIN_CLIENT_SECRET")
-		clientCert     = getenv("CLIENT_CERTIFICATE")
+		clientCert     = getenv("CLIENT_CERTIFICATE", "PLUGIN_CLIENT_CERTIFICATE")
-		tenantId       = getenv("TENANT_ID")
+		tenantId       = getenv("TENANT_ID", "AZURE_TENANT_ID", "PLUGIN_TENANT_ID")
-		subscriptionId = getenv("SUBSCRIPTION_ID")
+		subscriptionId = getenv("SUBSCRIPTION_ID", "PLUGIN_SUBSCRIPTION_ID")
-		publicUrl      = getenv("DAEMON_REGISTRY")
+		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
@@ -80,11 +83,31 @@ func main() {
 		// docker login credentials are not provided
 		var err error
 		username = defaultUsername
+		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)
 			}
 		}
+	}
 
 	// must use the fully qualified repo name. If the
 	// repo name does not have the registry prefix we

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)
+    }
+}
+

cmd/drone-docker/main.go

@@ -33,7 +33,7 @@ func main() {
 		cli.BoolFlag{
 			Name:   "dry-run",
 			Usage:  "dry run disables docker push",
-			EnvVar: "PLUGIN_DRY_RUN",
+			EnvVar: "PLUGIN_DRY_RUN, PLUGIN_NO_PUSH",
 		},
 		cli.StringFlag{
 			Name:   "remote.url",
@@ -112,6 +112,12 @@ func main() {
 			Usage:  "don't start the docker daemon",
 			EnvVar: "PLUGIN_DAEMON_OFF",
 		},
+		cli.IntFlag{
+			Name:   "daemon.retry-count",
+			Usage:  "number of retry attempts to reach docker daemon",
+			Value:  15,
+			EnvVar: "PLUGIN_DAEMON_RETRY_COUNT",
+		},
 		cli.StringFlag{
 			Name:   "dockerfile",
 			Usage:  "build dockerfile",
@@ -323,6 +329,32 @@ func main() {
 			Usage:  "access token",
 			EnvVar: "ACCESS_TOKEN",
 		},
+		// Cosign signing configuration
+		cli.StringFlag{
+			Name:   "cosign.private-key",
+			Usage:  "cosign private key content or file path for signing",
+			EnvVar: "PLUGIN_COSIGN_PRIVATE_KEY",
+		},
+		cli.StringFlag{
+			Name:   "cosign.password",
+			Usage:  "password for encrypted cosign private key",
+			EnvVar: "PLUGIN_COSIGN_PASSWORD",
+		},
+		cli.StringFlag{
+			Name:   "cosign.params",
+			Usage:  "additional cosign parameters (e.g., annotations, flags)",
+			EnvVar: "PLUGIN_COSIGN_PARAMS",
+		},
+		cli.BoolFlag{
+			Name:   "push-only",
+			Usage:  "skip build and only push images",
+			EnvVar: "PLUGIN_PUSH_ONLY",
+		},
+		cli.StringFlag{
+			Name:   "source-image",
+			Usage:  "source image to tag and push (format: repo:tag)",
+			EnvVar: "PLUGIN_SOURCE_IMAGE",
+		},
 	}
 
 	if err := app.Run(os.Args); err != nil {
@@ -393,11 +425,19 @@ func run(c *cli.Context) error {
 			DNSSearch:     c.StringSlice("daemon.dns-search"),
 			MTU:           c.String("daemon.mtu"),
 			Experimental:  c.Bool("daemon.experimental"),
+			RetryCount:    c.Int("daemon.retry-count"),
 			RegistryType:  registryType,
 		},
 		BaseImageRegistry: c.String("docker.baseimageregistry"),
 		BaseImageUsername: c.String("docker.baseimageusername"),
 		BaseImagePassword: c.String("docker.baseimagepassword"),
+		Cosign: docker.CosignConfig{
+			PrivateKey: c.String("cosign.private-key"),
+			Password:   c.String("cosign.password"),
+			Params:     c.String("cosign.params"),
+		},
+		PushOnly:    c.Bool("push-only"),
+		SourceImage: c.String("source-image"),
 	}
 
 	if c.Bool("tags.auto") {

daemon.go

@@ -11,6 +11,7 @@ import (
 const dockerExe = "/usr/local/bin/docker"
 const dockerdExe = "/usr/local/bin/dockerd"
 const dockerHome = "/root/.docker/"
+const cosignExe = "/usr/local/bin/cosign"
 
 func (p Plugin) startDaemon() {
 	cmd := commandDaemon(p.Daemon)

daemon_win.go

@@ -1,3 +1,4 @@
+//go:build windows
 // +build windows
 
 package docker
@@ -5,6 +6,7 @@ package docker
 const dockerExe = "C:\\bin\\docker.exe"
 const dockerdExe = ""
 const dockerHome = "C:\\ProgramData\\docker\\"
+const cosignExe = "C:\\bin\\cosign.exe"
 
 func (p Plugin) startDaemon() {
 	// this is a no-op on windows

docker.go

@@ -30,6 +30,7 @@ type (
 		MTU           string             // Docker daemon mtu setting
 		IPv6          bool               // Docker daemon IPv6 networking
 		Experimental  bool               // Docker daemon enable experimental mode
+		RetryCount    int                // Number of retry attempts to reach Docker daemon
 		RegistryType  drone.RegistryType // Docker registry type
 	}
 
@@ -76,11 +77,19 @@ type (
 		SSHKeyPath          string   // Docker build ssh key path
 	}
 
+	// CosignConfig defines Cosign signing parameters.
+	CosignConfig struct {
+		PrivateKey string // Private key content (PEM format) or file path
+		Password   string // Password for encrypted private keys
+		Params     string // Additional cosign parameters
+	}
+
 	// Plugin defines the Docker plugin parameters.
 	Plugin struct {
 		Login             Login        // Docker login configuration
 		Build             Build        // Docker build configuration
 		Daemon            Daemon       // Docker daemon configuration
+		Cosign            CosignConfig // Cosign signing configuration
 		Dryrun            bool         // Docker push is skipped
 		Cleanup           bool         // Docker purge is enabled
 		CardPath          string       // Card path to write file to
@@ -88,6 +97,8 @@ type (
 		BaseImageRegistry string       // Docker registry to pull base image
 		BaseImageUsername string       // Docker registry username to pull base image
 		BaseImagePassword string       // Docker registry password to pull base image
+		PushOnly          bool         // Push only mode, skips build process
+		SourceImage       string       // Source image to push (optional)
 	}
 
 	Card []struct {
@@ -127,14 +138,18 @@ func (p Plugin) Exec() error {
 
 	// poll the docker daemon until it is started. This ensures the daemon is
 	// ready to accept connections before we proceed.
+	maxRetries := p.Daemon.RetryCount
+	if maxRetries <= 0 {
+		maxRetries = 15 // default value
+	}
 	for i := 0; ; i++ {
 		cmd := commandInfo()
 		err := cmd.Run()
 		if err == nil {
 			break
 		}
-		if i == 15 {
+		if i == maxRetries {
-			fmt.Println("Unable to reach Docker Daemon after 15 attempts.")
+			fmt.Printf("Unable to reach Docker Daemon after %d attempts.\n", maxRetries)
 			break
 		}
 		time.Sleep(time.Second * 1)
@@ -193,7 +208,8 @@ func (p Plugin) Exec() error {
 			fmt.Println(out)
 			return fmt.Errorf("Error authenticating base connector: exit status 1")
 		}
-	} else {
+	} else if !p.PushOnly {
+		// Skip base image connector warning in push-only mode (not pulling anything)
 		fmt.Println("\033[33mTo ensure consistent and reliable pipeline execution, we recommend setting up a Base Image Connector.\033[0m\n" +
 			"\033[33mWhile optional at this time, configuring it helps prevent failures caused by Docker Hub's rate limits.\033[0m")
 	}
@@ -221,6 +237,16 @@ func (p Plugin) Exec() error {
 		}
 	}
 
+	// Enforce mutual exclusivity: push-only and dry-run cannot be used together
+	if p.PushOnly && p.Dryrun {
+		return fmt.Errorf("conflict: push-only and dry-run cannot be used together")
+	}
+
+	// Handle push-only mode if requested
+	if p.PushOnly {
+		return p.pushOnly()
+	}
+
 	if p.Build.Squash && !p.Daemon.Experimental {
 		fmt.Println("Squash build flag is only available when Docker deamon is started with experimental flag. Ignoring...")
 		p.Build.Squash = false
@@ -249,6 +275,14 @@ func (p Plugin) Exec() error {
 
 	cmds = append(cmds, commandBuild(p.Build)) // docker build
 
+	// Validate cosign configuration if present
+	if p.shouldSignWithCosign() {
+		if err := validateCosignConfig(p.Cosign); err != nil {
+			return fmt.Errorf("cosign validation failed: %w", err)
+		}
+		fmt.Println("🔐 Cosign signing enabled - images will be signed after push")
+	}
+
 	for _, tag := range p.Build.Tags {
 		cmds = append(cmds, commandTag(p.Build, tag)) // docker tag
 
@@ -290,6 +324,31 @@ func (p Plugin) Exec() error {
 		}
 	}
 
+	// Handle cosign signing after all commands complete (like artifact generation)
+	if p.shouldSignWithCosign() && !p.Dryrun {
+		// Set up environment variables for cosign
+		os.Setenv("COSIGN_YES", "true")
+
+		if digest, err := getDigest(p.Build.TempTag); err == nil {
+			fmt.Printf("🔐 Found image digest: %s\n", digest)
+			
+			// Sign with digest reference
+			imageRef := fmt.Sprintf("%s@%s", p.Build.Repo, digest)
+			cosignCmd := createCosignCommand(imageRef, p.Cosign)
+			executeCosignCommand(cosignCmd)
+		} else {
+			fmt.Printf("⚠️  WARNING: Could not get image digest for cosign signing: %s\n", err)
+			fmt.Printf("   Falling back to tag-based signing\n")
+			
+			// Fall back to tag-based signing for each tag
+			for _, tag := range p.Build.Tags {
+				imageRef := fmt.Sprintf("%s:%s", p.Build.Repo, tag)
+				cosignCmd := createCosignCommand(imageRef, p.Cosign)
+				executeCosignCommand(cosignCmd)
+			}
+		}
+	}
+
 	// execute cleanup routines in batch mode
 	if p.Cleanup {
 		// clear the slice
@@ -538,7 +597,8 @@ func addProxyValue(build *Build, key string) {
 
 // helper function to get a proxy value from the environment.
 //
-// assumes that the upper and lower case versions of are the same.
+// Checks in order: lowercase key, uppercase key, then HARNESS_<UPPERCASE_KEY>.
+// Assumes that the upper and lower case versions are the same value.
 func getProxyValue(key string) string {
 	value := os.Getenv(key)
 
@@ -546,15 +606,26 @@ func getProxyValue(key string) string {
 		return value
 	}
 
-	return os.Getenv(strings.ToUpper(key))
+	value = os.Getenv(strings.ToUpper(key))
+
+	if len(value) > 0 {
+		return value
+	}
+
+	harnessValue := os.Getenv("HARNESS_" + strings.ToUpper(key))
+	if len(harnessValue) > 0 {
+		fmt.Printf("Using HARNESS_%s as proxy value for %s\n", strings.ToUpper(key), key)
+	}
+	return harnessValue
 }
 
 // helper function that looks to see if a proxy value was set in the build args.
 func hasProxyBuildArg(build *Build, key string) bool {
 	keyUpper := strings.ToUpper(key)
+	harnessKey := "HARNESS_" + keyUpper
 
 	for _, s := range build.Args {
-		if strings.HasPrefix(s, key) || strings.HasPrefix(s, keyUpper) {
+		if strings.HasPrefix(s, key) || strings.HasPrefix(s, keyUpper) || strings.HasPrefix(s, harnessKey) {
 			return true
 		}
 	}
@@ -563,9 +634,10 @@ func hasProxyBuildArg(build *Build, key string) bool {
 }
 func hasProxyBuildArgNew(build *Build, key string) bool {
 	keyUpper := strings.ToUpper(key)
+	harnessKey := "HARNESS_" + keyUpper
 
 	for _, s := range build.ArgsNew {
-		if strings.HasPrefix(s, key) || strings.HasPrefix(s, keyUpper) {
+		if strings.HasPrefix(s, key) || strings.HasPrefix(s, keyUpper) || strings.HasPrefix(s, harnessKey) {
 			return true
 		}
 	}
@@ -645,6 +717,11 @@ func isCommandRmi(args []string) bool {
 	return len(args) > 2 && args[1] == "rmi"
 }
 
+// helper to check if args match "cosign sign"
+func isCommandCosign(args []string) bool {
+	return len(args) > 1 && args[0] == cosignExe
+}
+
 func commandRmi(tag string) *exec.Cmd {
 	return exec.Command(dockerExe, "rmi", tag)
 }
@@ -681,7 +758,7 @@ func GetDroneDockerExecCmd() string {
 }
 
 func getDigest(buildName string) (string, error) {
-	cmd := exec.Command("docker", "inspect", "--format='{{index .RepoDigests 0}}'", buildName)
+	cmd := exec.Command(dockerExe, "inspect", "--format='{{index .RepoDigests 0}}'", buildName)
 	output, err := cmd.Output()
 	if err != nil {
 		return "", err
@@ -695,3 +772,284 @@ func getDigest(buildName string) (string, error) {
 	}
 	return "", errors.New("unable to fetch digest")
 }
+
+// imageExists checks if an image exists in local daemon
+func imageExists(tag string) bool {
+	cmd := exec.Command(dockerExe, "image", "inspect", tag)
+	return cmd.Run() == nil
+}
+
+// getDigestAfterPush gets digest from a pushed image
+func getDigestAfterPush(tag string) (string, error) {
+	cmd := exec.Command(dockerExe, "inspect", "--format", "{{ index (split (index .RepoDigests 0) \"@\") 1 }}", tag)
+	output, err := cmd.Output()
+	if err != nil {
+		return "", fmt.Errorf("failed to get digest for %s: %w", tag, err)
+	}
+	return strings.TrimSpace(string(output)), nil
+}
+
+// shouldSignWithCosign determines if cosign signing should be performed
+func (p Plugin) shouldSignWithCosign() bool {
+	return p.Cosign.PrivateKey != ""
+}
+
+// validateCosignConfig validates the cosign configuration
+func validateCosignConfig(config CosignConfig) error {
+	if config.PrivateKey == "" {
+		return nil // No cosign config, skip silently
+	}
+
+	// Check if cosign binary is available
+	if _, err := exec.LookPath(cosignExe); err != nil {
+		fmt.Printf("❌ ERROR: cosign binary not found at %s\n", cosignExe)
+		fmt.Println("   Ensure you're using a plugin image that includes cosign")
+		return fmt.Errorf("cosign binary not available: %w", err)
+	}
+
+	// Check if it's trying to use keyless signing
+	if strings.Contains(config.Params, "--oidc") ||
+		strings.Contains(config.Params, "--identity-token") {
+		fmt.Println("⚠️  WARNING: Keyless signing (OIDC) isn't supported yet in this plugin. Use private key signing instead.")
+		return errors.New("keyless signing not supported")
+	}
+
+	// Validate private key format if it's PEM content
+	if strings.HasPrefix(config.PrivateKey, "-----BEGIN") {
+		if !isValidPEMKey(config.PrivateKey) {
+			return errors.New("❌ Invalid private key format. Expected PEM format")
+		}
+
+		// Check encrypted key password requirement
+		if isEncryptedPEMKey(config.PrivateKey) && config.Password == "" {
+			return errors.New("🔐 Encrypted private key requires password. Set PLUGIN_COSIGN_PASSWORD")
+		}
+
+	} else {
+		// File-based key - check if it's accessible (basic check)
+		if _, err := os.Stat(config.PrivateKey); err != nil {
+			fmt.Printf("⚠️  WARNING: Private key file may not be accessible: %s\n", config.PrivateKey)
+			fmt.Println("   This will be verified during signing")
+		}
+	}
+
+	return nil
+}
+
+// isEncryptedPEMKey checks if a PEM key is encrypted
+func isEncryptedPEMKey(pemContent string) bool {
+	return strings.Contains(pemContent, "ENCRYPTED")
+}
+
+// isValidPEMKey performs basic PEM format validation
+func isValidPEMKey(pemContent string) bool {
+	return strings.Contains(pemContent, "-----BEGIN") &&
+		strings.Contains(pemContent, "-----END") &&
+		(strings.Contains(pemContent, "PRIVATE KEY") ||
+			strings.Contains(pemContent, "RSA PRIVATE KEY") ||
+			strings.Contains(pemContent, "EC PRIVATE KEY"))
+}
+
+// createCosignCommand creates a cosign sign command with the given image reference
+func createCosignCommand(imageRef string, cosign CosignConfig) *exec.Cmd {
+	args := []string{"sign", "--yes"}
+	
+	// Handle private key (content vs file path)
+	if strings.HasPrefix(cosign.PrivateKey, "-----BEGIN") {
+		args = append(args, "--key", "env://COSIGN_PRIVATE_KEY")
+		os.Setenv("COSIGN_PRIVATE_KEY", cosign.PrivateKey)
+	} else {
+		args = append(args, "--key", cosign.PrivateKey)
+	}
+	
+	// Set password if provided
+	if cosign.Password != "" {
+		os.Setenv("COSIGN_PASSWORD", cosign.Password)
+	}
+	
+	// Add any extra parameters
+	if cosign.Params != "" {
+		extraArgs := strings.Fields(cosign.Params)
+		args = append(args, extraArgs...)
+	}
+	
+	// Add the image reference to sign
+	args = append(args, imageRef)
+	
+	return exec.Command(cosignExe, args...)
+}
+
+// executeCosignCommand executes the given cosign command and handles errors
+func executeCosignCommand(cmd *exec.Cmd) {
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	fmt.Printf("🚀 Executing: %s %s\n", cmd.Path, strings.Join(cmd.Args[1:], " "))
+
+	if err := cmd.Run(); err != nil {
+		fmt.Printf("⚠️  WARNING: Image signing failed: %s\n", err)
+		fmt.Printf("   Image was pushed successfully but could not be signed\n")
+		fmt.Printf("   This is not fatal - continuing with the build\n")
+	}
+}
+
+// pushOnly handles pushing images without building them
+func (p Plugin) pushOnly() error {
+	// Check if source image is specified
+	sourceImageName := p.SourceImage
+	var sourceTags []string
+
+	if sourceImageName == "" {
+		// If no source image specified, use the repo and first tag
+		fmt.Println("source_image not provided, using repo and tag value")
+		sourceImageName = p.Build.Repo
+		sourceTags = p.Build.Tags
+	} else {
+		// If source image is specified, check if it has a tag
+		lastColonIndex := strings.LastIndex(sourceImageName, ":")
+		if lastColonIndex > 0 && lastColonIndex < len(sourceImageName) {
+			// Check if there's a slash after the last colon (indicating it's a port, not a tag)
+			// For example: registry:5000/image (has slash after colon - port not tag)
+			// vs image:tag (no slash after colon - it's a tag)
+			if strings.LastIndex(sourceImageName, "/") > lastColonIndex {
+				// The last colon is part of the registry:port, not a tag separator
+				sourceTags = []string{"latest"}
+			} else {
+				// The last colon separates the tag
+				tag := sourceImageName[lastColonIndex+1:]
+				sourceImageName = sourceImageName[:lastColonIndex]
+
+				if tag == "" {
+					fmt.Printf("No tag specified in source image (or empty tag). Using 'latest' as the default tag.\n")
+					tag = "latest"
+				}
+				sourceTags = []string{tag}
+			}
+		} else {
+			// Default to "latest" if no tag specified
+			sourceTags = []string{"latest"}
+		}
+		fmt.Printf("Using source image: %s with tag(s): %s\n", sourceImageName, strings.Join(sourceTags, ", "))
+	}
+
+	// For each source tag and target tag combination
+	var digest string
+	var firstPushedImage string
+
+	for _, sourceTag := range sourceTags {
+		sourceFullImageName := fmt.Sprintf("%s:%s", sourceImageName, sourceTag)
+
+		// Check if the source image exists in local daemon
+		if !imageExists(sourceFullImageName) {
+			fmt.Printf("Warning: Source image %s not found\n", sourceFullImageName)
+			// Continue to the next source tag if available, otherwise return error
+			if len(sourceTags) > 1 {
+				continue
+			}
+			return fmt.Errorf("source image %s not found, cannot push", sourceFullImageName)
+		}
+
+		// For each target tag, tag and push
+		for _, targetTag := range p.Build.Tags {
+			targetFullImageName := fmt.Sprintf("%s:%s", p.Build.Repo, targetTag)
+
+			// Skip if source and target are identical
+			if sourceFullImageName == targetFullImageName {
+				fmt.Printf("Source and target image names are identical: %s\n", sourceFullImageName)
+			} else {
+				// Tag the source image with the target name
+				fmt.Printf("Tagging %s as %s\n", sourceFullImageName, targetFullImageName)
+				tagCmd := exec.Command(dockerExe, "tag", sourceFullImageName, targetFullImageName)
+				tagCmd.Stdout = os.Stdout
+				tagCmd.Stderr = os.Stderr
+				trace(tagCmd)
+				if err := tagCmd.Run(); err != nil {
+					return fmt.Errorf("failed to tag image %s as %s: %w", sourceFullImageName, targetFullImageName, err)
+				}
+			}
+		}
+	}
+
+	// Push all target images
+	for _, tag := range p.Build.Tags {
+		fullImageName := fmt.Sprintf("%s:%s", p.Build.Repo, tag)
+
+		// Check if image exists in local daemon
+		if !imageExists(fullImageName) {
+			return fmt.Errorf("image %s not found, cannot push", fullImageName)
+		}
+
+		// Push image
+		fmt.Println("Pushing image:", fullImageName)
+		pushCmd := commandPush(p.Build, tag)
+		pushCmd.Stdout = os.Stdout
+		pushCmd.Stderr = os.Stderr
+		trace(pushCmd)
+		if err := pushCmd.Run(); err != nil {
+			return fmt.Errorf("failed to push image %s: %w", fullImageName, err)
+		}
+
+		// Track the first pushed image for card generation
+		if firstPushedImage == "" {
+			firstPushedImage = fullImageName
+		}
+
+		// Get the digest after push (we only need one)
+		if digest == "" {
+			d, err := getDigestAfterPush(fullImageName)
+			if err == nil {
+				digest = d
+			} else {
+				fmt.Printf("Warning: Could not get digest for %s: %v\n", fullImageName, err)
+			}
+		}
+	}
+
+	// Output the adaptive card
+	if firstPushedImage != "" {
+		if err := p.writeCardForImage(firstPushedImage); err != nil {
+			fmt.Printf("Could not create adaptive card. %s\n", err)
+		}
+	}
+
+	// Write to artifact file
+	if p.ArtifactFile != "" && digest != "" {
+		if err := drone.WritePluginArtifactFile(
+			p.Daemon.RegistryType,
+			p.ArtifactFile,
+			p.Daemon.Registry,
+			p.Build.Repo,
+			digest,
+			p.Build.Tags,
+		); err != nil {
+			fmt.Printf("Failed to write plugin artifact file at path: %s with error: %s\n",
+				p.ArtifactFile, err)
+		}
+	}
+
+	// Handle cosign signing after push
+	if p.shouldSignWithCosign() {
+		// Set up environment variables for cosign
+		os.Setenv("COSIGN_YES", "true")
+
+		if digest != "" {
+			fmt.Printf("🔐 Found image digest: %s\n", digest)
+
+			// Sign with digest reference
+			imageRef := fmt.Sprintf("%s@%s", p.Build.Repo, digest)
+			cosignCmd := createCosignCommand(imageRef, p.Cosign)
+			executeCosignCommand(cosignCmd)
+		} else {
+			fmt.Printf("⚠️  WARNING: Could not get image digest for cosign signing\n")
+			fmt.Printf("   Falling back to tag-based signing\n")
+
+			// Fall back to tag-based signing for each tag
+			for _, tag := range p.Build.Tags {
+				imageRef := fmt.Sprintf("%s:%s", p.Build.Repo, tag)
+				cosignCmd := createCosignCommand(imageRef, p.Cosign)
+				executeCosignCommand(cosignCmd)
+			}
+		}
+	}
+
+	return nil
+}

docker/docker/Dockerfile.linux.amd64

@@ -2,5 +2,9 @@ FROM docker:28.1.1-dind
 
 ENV DOCKER_HOST=unix:///var/run/docker.sock
 
+# Install cosign for container image signing
+RUN wget -O /usr/local/bin/cosign https://github.com/sigstore/cosign/releases/download/v2.5.3/cosign-linux-amd64 \
+    && chmod +x /usr/local/bin/cosign
+
 ADD release/linux/amd64/drone-docker /bin/
 ENTRYPOINT ["/usr/local/bin/dockerd-entrypoint.sh", "/bin/drone-docker"]

docker/docker/Dockerfile.linux.arm64

@@ -2,5 +2,9 @@ FROM arm64v8/docker:28.1.1-dind
 
 ENV DOCKER_HOST=unix:///var/run/docker.sock
 
+# Install cosign for container image signing
+RUN wget -O /usr/local/bin/cosign https://github.com/sigstore/cosign/releases/download/v2.5.3/cosign-linux-arm64 \
+    && chmod +x /usr/local/bin/cosign
+
 ADD release/linux/arm64/drone-docker /bin/
 ENTRYPOINT ["/usr/local/bin/dockerd-entrypoint.sh", "/bin/drone-docker"]

docker/docker/Dockerfile.windows.amd64.1809

@@ -24,6 +24,10 @@ LABEL maintainer="Drone.IO Community <drone-dev@googlegroups.com>" `
   org.label-schema.schema-version="1.0"
 
 RUN mkdir C:\bin
+
+# Install cosign for container image signing
+ADD https://github.com/sigstore/cosign/releases/download/v2.5.3/cosign-windows-amd64.exe C:/bin/cosign.exe
+
 COPY --from=download /windows/system32/netapi32.dll /windows/system32/netapi32.dll
 COPY --from=download /app/docker.exe C:/bin/docker.exe
 ADD release/windows/amd64/drone-docker.exe C:/bin/drone-docker.exe

docker/docker/Dockerfile.windows.amd64.ltsc2022

@@ -22,6 +22,10 @@ LABEL maintainer="Drone.IO Community <drone-dev@googlegroups.com>" `
   org.label-schema.schema-version="1.0"
 
 RUN mkdir C:\bin
+
+# Install cosign for container image signing
+ADD https://github.com/sigstore/cosign/releases/download/v2.5.3/cosign-windows-amd64.exe C:/bin/cosign.exe
+
 COPY --from=download /windows/system32/netapi32.dll /windows/system32/netapi32.dll
 COPY --from=download /app/docker.exe C:/bin/docker.exe
 ADD release/windows/amd64/drone-docker.exe C:/bin/drone-docker.exe

docker_test.go

@@ -1,6 +1,7 @@
 package docker
 
 import (
+	"os"
 	"os/exec"
 	"reflect"
 	"strings"
@@ -179,3 +180,90 @@ func TestCommandBuild(t *testing.T) {
 		})
 	}
 }
+
+func TestGetProxyValue(t *testing.T) {
+	tests := []struct {
+		name     string
+		key      string
+		envVars  map[string]string
+		expected string
+	}{
+		{
+			name:     "lowercase env var set",
+			key:      "http_proxy",
+			envVars:  map[string]string{"http_proxy": "http://proxy:8080"},
+			expected: "http://proxy:8080",
+		},
+		{
+			name:     "uppercase env var set",
+			key:      "http_proxy",
+			envVars:  map[string]string{"HTTP_PROXY": "http://proxy:8080"},
+			expected: "http://proxy:8080",
+		},
+		{
+			name:     "HARNESS prefixed env var set",
+			key:      "http_proxy",
+			envVars:  map[string]string{"HARNESS_HTTP_PROXY": "http://harness-proxy:8080"},
+			expected: "http://harness-proxy:8080",
+		},
+		{
+			name: "standard takes precedence over HARNESS",
+			key:  "http_proxy",
+			envVars: map[string]string{
+				"HTTP_PROXY":         "http://standard:8080",
+				"HARNESS_HTTP_PROXY": "http://harness:8080",
+			},
+			expected: "http://standard:8080",
+		},
+		{
+			name: "lowercase takes precedence over uppercase",
+			key:  "no_proxy",
+			envVars: map[string]string{
+				"no_proxy":        "localhost,127.0.0.1",
+				"NO_PROXY":         "*.example.com",
+				"HARNESS_NO_PROXY": "*.local",
+			},
+			expected: "localhost,127.0.0.1",
+		},
+		{
+			name: "lowercase takes precedence over HARNESS",
+			key:  "https_proxy",
+			envVars: map[string]string{
+				"https_proxy":        "https://standard:8080",
+				"HARNESS_HTTPS_PROXY": "https://harness:8080",
+			},
+			expected: "https://standard:8080",
+		},
+		{
+			name:     "no env var set",
+			key:      "http_proxy",
+			envVars:  map[string]string{},
+			expected: "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Clean env
+			lowercaseKey := tt.key
+			uppercaseKey := strings.ToUpper(tt.key)
+			harnessKey := "HARNESS_" + strings.ToUpper(tt.key)
+
+			os.Unsetenv(lowercaseKey)
+			os.Unsetenv(uppercaseKey)
+			os.Unsetenv(harnessKey)
+
+			// Set test environment variables
+			for k, v := range tt.envVars {
+				os.Setenv(k, v)
+				defer os.Unsetenv(k)
+			}
+
+			// Execute and verify
+			result := getProxyValue(tt.key)
+			if result != tt.expected {
+				t.Errorf("getProxyValue(%q) = %q, want %q", tt.key, result, tt.expected)
+			}
+		})
+	}
+}

go.mod

@@ -11,16 +11,15 @@ require (
 	github.com/inhies/go-bytesize v0.0.0-20210819104631-275770b98743
 	github.com/joho/godotenv v1.3.0
 	github.com/pkg/errors v0.9.1
-	github.com/sirupsen/logrus v1.9.0
+	github.com/sirupsen/logrus v1.9.3
 	github.com/stretchr/testify v1.10.0
 	github.com/urfave/cli v1.22.2
-	golang.org/x/oauth2 v0.13.0
+	golang.org/x/oauth2 v0.27.0
 	google.golang.org/api v0.146.0
 )
 
 require (
-	cloud.google.com/go/compute v1.23.1 // indirect
+	cloud.google.com/go/compute/metadata v0.3.0 // indirect
-	cloud.google.com/go/compute/metadata v0.2.3 // indirect
 	github.com/Azure/azure-sdk-for-go/sdk/internal v1.10.0 // indirect
 	github.com/AzureAD/microsoft-authentication-library-for-go v1.3.3 // indirect
 	github.com/cpuguy83/go-md2man/v2 v2.0.2 // indirect
@@ -42,7 +41,6 @@ require (
 	golang.org/x/net v0.37.0 // indirect
 	golang.org/x/sys v0.31.0 // indirect
 	golang.org/x/text v0.23.0 // indirect
-	google.golang.org/appengine v1.6.8 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20231016165738-49dd2c1f3d0b // indirect
 	google.golang.org/grpc v1.59.0 // indirect
 	google.golang.org/protobuf v1.31.0 // indirect
@@ -50,6 +48,6 @@ require (
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
 
-go 1.23.0
+go 1.24
 
-toolchain go1.23.7
+toolchain go1.24.11

go.sum

@@ -1,8 +1,6 @@
 cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
-cloud.google.com/go/compute v1.23.1 h1:V97tBoDaZHb6leicZ1G6DLK2BAaZLJ/7+9BB/En3hR0=
+cloud.google.com/go/compute/metadata v0.3.0 h1:Tz+eQXMEqDIKRsmY3cHTL6FVaynIjX2QxYC4trgAKZc=
-cloud.google.com/go/compute v1.23.1/go.mod h1:CqB3xpmPKKt3OJpW2ndFIXnA9A4xAy/F3Xp1ixncW78=
+cloud.google.com/go/compute/metadata v0.3.0/go.mod h1:zFmK7XCadkQkj6TtorcaGlCW1hT1fIilQDwofLpJ20k=
-cloud.google.com/go/compute/metadata v0.2.3 h1:mg4jlk7mCAj6xXp9UJ4fjI9VUI5rubuGBW5aJ7UnBMY=
-cloud.google.com/go/compute/metadata v0.2.3/go.mod h1:VAV5nSsACxMJvgaAuX6Pk2AawlZn8kiOGuCv6gTkwuA=
 github.com/99designs/httpsignatures-go v0.0.0-20170731043157-88528bf4ca7e/go.mod h1:Xa6lInWHNQnuWoF0YPSsx+INFA9qk7/7pTjwb3PInkY=
 github.com/Azure/azure-sdk-for-go/sdk/azcore v1.17.1 h1:DSDNVxqkoXJiko6x8a90zidoYqnYYa6c1MTzDKzKkTo=
 github.com/Azure/azure-sdk-for-go/sdk/azcore v1.17.1/go.mod h1:zGqV2R4Cr/k8Uye5w+dgQ06WJtEcbQG/8J7BB6hnCr4=
@@ -61,7 +59,6 @@ github.com/golang/protobuf v1.4.0/go.mod h1:jodUvKwWbYaEsadDk5Fwe5c77LiNKVO9IDvq
 github.com/golang/protobuf v1.4.1/go.mod h1:U8fpvMrcmy5pZrNK1lt4xCsGvpyWQ/VVv6QDs8UjoX8=
 github.com/golang/protobuf v1.4.3/go.mod h1:oDoupMAO8OvCJWAcko0GGGIgR6R6ocIYbsSw735rRwI=
 github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
-github.com/golang/protobuf v1.5.2/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
 github.com/golang/protobuf v1.5.3 h1:KhyjKVUg7Usr/dYsdSqoFveMYd5ko72D+zANwlG1mmg=
 github.com/golang/protobuf v1.5.3/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
 github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
@@ -111,8 +108,8 @@ github.com/russross/blackfriday/v2 v2.0.1/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQD
 github.com/russross/blackfriday/v2 v2.1.0 h1:JIOH55/0cWyOuilr9/qlrm0BSXldqnqwMsf35Ld67mk=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
 github.com/shurcooL/sanitized_anchor_name v1.0.0/go.mod h1:1NzhyTcUVG4SuEtjjoZeVRXNmyL/1OwPU0+IJeTBvfc=
-github.com/sirupsen/logrus v1.9.0 h1:trlNQbNUG3OdDrDil03MCb1H2o9nJ1x4/5LYw7byDE0=
+github.com/sirupsen/logrus v1.9.3 h1:dueUQJ1C2q9oE3F7wvmSGAaVtTmUizReu6fjN8uqzbQ=
-github.com/sirupsen/logrus v1.9.0/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
+github.com/sirupsen/logrus v1.9.3/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
 github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
@@ -124,57 +121,42 @@ github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOf
 github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 github.com/urfave/cli v1.22.2 h1:gsqYFH8bb9ekPA12kRo0hfjngWQjkJPlN9R0N78BoUo=
 github.com/urfave/cli v1.22.2/go.mod h1:Gos4lmkARVdJ6EkW0WaNv/tZAAMe9V7XWyB60NtXRu0=
-github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
 go.opencensus.io v0.24.0 h1:y73uSU6J157QMP2kn2r30vwW1A2W2WFwSCGnAVxeaD0=
 go.opencensus.io v0.24.0/go.mod h1:vNK8G9p7aAivkbmorf4v+7Hgx+Zs0yY+0fOtgBfjQKo=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
-golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
 golang.org/x/crypto v0.36.0 h1:AnAEvhDddvBdpY+uR+MyHmuZzzNqXSe/GvuDeob5L34=
 golang.org/x/crypto v0.36.0/go.mod h1:Y4J0ReaxCR1IMaabaSMugxJES1EpwhBHhv2bDHklZvc=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/lint v0.0.0-20181026193005-c67002cb31c3/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
 golang.org/x/lint v0.0.0-20190227174305-5b3e6a55c961/go.mod h1:wehouNa3lNwaWXcvxsM5YxQ5yQlVC4a0KAMCusXpPoU=
 golang.org/x/lint v0.0.0-20190313153728-d0100b6bd8b3/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
-golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
 golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180826012351-8a410e7b638d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20190213061140-3a22650c66bd/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20201110031124-69a78807bb2b/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
-golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
-golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
 golang.org/x/net v0.37.0 h1:1zLorHbz+LYj7MQlSf1+2tPIIgibq2eL5xkrGk6f+2c=
 golang.org/x/net v0.37.0/go.mod h1:ivrbrMbzFq5J41QOQh0siUuly180yBYtLp+CKbEaFx8=
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
-golang.org/x/oauth2 v0.13.0 h1:jDDenyj+WgFtmV3zYVoi8aE2BwtXFLWOA67ZfNWftiY=
+golang.org/x/oauth2 v0.27.0 h1:da9Vo7/tDv5RH/7nZDz1eMGS/q1Vv1N/7FCrBhI9I3M=
-golang.org/x/oauth2 v0.13.0/go.mod h1:/JMhi4ZRXAf4HG9LiNmxvk+45+96RUlVThiH8FzNBn0=
+golang.org/x/oauth2 v0.27.0/go.mod h1:onh5ek6nERTohokkhCD/y2cV4Do3fxFHFuAejCkRWT8=
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.12.0 h1:MHc5BpPuC30uJk597Ri8TV3CNZcTLu6B6z4lJy+g6Jw=
 golang.org/x/sync v0.12.0/go.mod h1:1dzgHSNfp02xaA81J2MS99Qcpr2w7fw1gpm99rleRqA=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.1.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.31.0 h1:ioabZlmFYtWhL+TRYpcnNlLwhyxaM9kWTDEmfnprqik=
 golang.org/x/sys v0.31.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
-golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
-golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
-golang.org/x/text v0.3.8/go.mod h1:E6s5w1FMmriuDzIBO73fBruAKo1PCIq6d2Q6DHfQ8WQ=
 golang.org/x/text v0.23.0 h1:D71I7dUrlY+VX0gQShAThNGHFxZ13dGLBHQLVl1mJlY=
 golang.org/x/text v0.23.0/go.mod h1:/BLNzu4aZCJ1+kcD0DNRotWKage4q2rGVAg4o22unh4=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
@@ -182,16 +164,11 @@ golang.org/x/tools v0.0.0-20190114222345-bf090417da8b/go.mod h1:n7NCudcB/nEzxVGm
 golang.org/x/tools v0.0.0-20190226205152-f727befe758c/go.mod h1:9Yl7xja0Znq3iFh3HoIrodX9oNMXvdceNzlUR8zjMvY=
 golang.org/x/tools v0.0.0-20190311212946-11955173bddd/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
 golang.org/x/tools v0.0.0-20190524140312-2c0ae7006135/go.mod h1:RgjU9mgBXZiqYHBnxXauZ1Gv1EHHAz9KjViQ78xBX0Q=
-golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
-golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
-golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/api v0.146.0 h1:9aBYT4vQXt9dhCuLNfwfd3zpwu8atg0yPkjBymwSrOM=
 google.golang.org/api v0.146.0/go.mod h1:OARJqIfoYjXJj4C1AiBSXYZt03qsoz8FQYU6fBEfrHM=
 google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
 google.golang.org/appengine v1.4.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
-google.golang.org/appengine v1.6.8 h1:IhEN5q69dyKagZPYMSdIjS2HqprW324FRQZJcGqPAsM=
-google.golang.org/appengine v1.6.8/go.mod h1:1jJ3jBArFh5pcgW8gCtRJnepW8FzD1V44FJffLiz/Ds=
 google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8/go.mod h1:JiN7NxoALGmiZfu7CAH4rXhgtRTLTxftemlI0sWmxmc=
 google.golang.org/genproto v0.0.0-20190819201941-24fa4b261c55/go.mod h1:DMBHOl98Agz4BDEuKkezgsaosCRResVns1a3J2ZsMNc=
 google.golang.org/genproto v0.0.0-20200526211855-cb27e3aa2013/go.mod h1:NbSheEEYHJ7i3ixzK3sjbqSGDJWnxyFXZblF3eUsNvo=

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)
+	}
+}
+