agent/azure: adds ability to use specific user-assigned managed identities for auto auth

changelog/14214.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+agent: Adds ability to configure specific user-assigned managed identities for Azure auto-auth.
+```

command/agent/auth/azure/azure.go

@@ -30,6 +30,8 @@ type azureMethod struct {
 
 	role     string
 	resource string
+	objectID string
+	clientID string
 }
 
 func NewAzureAuthMethod(conf *auth.AuthConfig) (auth.AuthMethod, error) {
@@ -63,11 +65,29 @@ func NewAzureAuthMethod(conf *auth.AuthConfig) (auth.AuthMethod, error) {
 		return nil, errors.New("could not convert 'resource' config value to string")
 	}
 
+	objectIDRaw, ok := conf.Config["object_id"]
+	if ok {
+		a.objectID, ok = objectIDRaw.(string)
+		if !ok {
+			return nil, errors.New("could not convert 'object_id' config value to string")
+		}
+	}
+
+	clientIDRaw, ok := conf.Config["client_id"]
+	if ok {
+		a.clientID, ok = clientIDRaw.(string)
+		if !ok {
+			return nil, errors.New("could not convert 'client_id' config value to string")
+		}
+	}
+
 	switch {
 	case a.role == "":
 		return nil, errors.New("'role' value is empty")
 	case a.resource == "":
 		return nil, errors.New("'resource' value is empty")
+	case a.objectID != "" && a.clientID != "":
+		return nil, errors.New("only one of 'object_id' or 'client_id' may be provided")
 	}
 
 	return a, nil
@@ -86,7 +106,7 @@ func (a *azureMethod) Authenticate(ctx context.Context, client *api.Client) (ret
 		}
 	}
 
-	body, err := getMetadataInfo(ctx, instanceEndpoint, "")
+	body, err := getMetadataInfo(ctx, instanceEndpoint, "", "", "")
 	if err != nil {
 		retErr = err
 		return
@@ -103,7 +123,7 @@ func (a *azureMethod) Authenticate(ctx context.Context, client *api.Client) (ret
 		AccessToken string `json:"access_token"`
 	}
 
-	body, err = getMetadataInfo(ctx, identityEndpoint, a.resource)
+	body, err = getMetadataInfo(ctx, identityEndpoint, a.resource, a.objectID, a.clientID)
 	if err != nil {
 		retErr = err
 		return
@@ -138,7 +158,7 @@ func (a *azureMethod) CredSuccess() {
 func (a *azureMethod) Shutdown() {
 }
 
-func getMetadataInfo(ctx context.Context, endpoint, resource string) ([]byte, error) {
+func getMetadataInfo(ctx context.Context, endpoint, resource, objectID, clientID string) ([]byte, error) {
 	req, err := http.NewRequest("GET", endpoint, nil)
 	if err != nil {
 		return nil, err
@@ -149,6 +169,12 @@ func getMetadataInfo(ctx context.Context, endpoint, resource string) ([]byte, er
 	if resource != "" {
 		q.Add("resource", resource)
 	}
+	if objectID != "" {
+		q.Add("object_id", objectID)
+	}
+	if clientID != "" {
+		q.Add("client_id", clientID)
+	}
 	req.URL.RawQuery = q.Encode()
 	req.Header.Set("Metadata", "true")
 	req.Header.Set("User-Agent", useragent.String())

website/content/docs/agent/autoauth/methods/azure.mdx

@@ -17,3 +17,11 @@ on the value of the `resource` parameter.
 - `role` `(string: required)` - The role to authenticate against on Vault
 
 - `resource` `(string: required)` - The resource name to use when getting instance information
+
+- `object_id` `(string: optional)` - The object ID of the user-assigned managed identity to use
+  when acquiring an [access token](https://docs.microsoft.com/en-us/azure/active-directory/managed-identities-azure-resources/how-to-use-vm-token#get-a-token-using-http).
+  This parameter is interchangeable with `client_id`. Only one of `object_id` or `client_id` may be provided.
+
+- `client_id` `(string: optional)` - The client ID of the user-assigned managed identity to use
+  when acquiring an [access token](https://docs.microsoft.com/en-us/azure/active-directory/managed-identities-azure-resources/how-to-use-vm-token#get-a-token-using-http).
+  This parameter is interchangeable with `object_id`. Only one of `object_id` or `client_id` may be provided.