Don't panic on a nil credential value (Azure#21835)

Just skip the authorization step.

sdk/azcore/CHANGELOG.md

@@ -14,6 +14,7 @@
 * Include error text instead of error type in traces when the transport returns an error.
 * Fixed an issue that could cause an HTTP/2 request to hang when the TCP connection becomes unresponsive.
 * Block key and SAS authentication for non TLS protected endpoints.
+* Passing a `nil` credential value will no longer cause a panic. Instead, the authentication is skipped.
 
 ### Other Changes
 

sdk/azcore/runtime/policy_bearer_token.go

@@ -72,9 +72,17 @@ func (b *BearerTokenPolicy) authenticateAndAuthorize(req *policy.Request) func(p
 
 // Do authorizes a request with a bearer token
 func (b *BearerTokenPolicy) Do(req *policy.Request) (*http.Response, error) {
+	// skip adding the authorization header if no TokenCredential was provided.
+	// this prevents a panic that might be hard to diagnose and allows testing
+	// against http endpoints that don't require authentication.
+	if b.cred == nil {
+		return req.Next()
+	}
+
 	if err := checkHTTPSForAuth(req); err != nil {
 		return nil, err
 	}
+
 	var err error
 	if b.authzHandler.OnRequest != nil {
 		err = b.authzHandler.OnRequest(req, b.authenticateAndAuthorize(req))

sdk/azcore/runtime/policy_bearer_token_test.go

@@ -246,3 +246,15 @@ func TestCheckHTTPSForAuth(t *testing.T) {
 	require.NoError(t, err)
 	require.NoError(t, checkHTTPSForAuth(req))
 }
+
+func TestBearerTokenPolicy_NilCredential(t *testing.T) {
+	policy := NewBearerTokenPolicy(nil, nil, nil)
+	pl := exported.NewPipeline(shared.TransportFunc(func(req *http.Request) (*http.Response, error) {
+		require.Zero(t, req.Header.Get(shared.HeaderAuthorization))
+		return &http.Response{}, nil
+	}), policy)
+	req, err := NewRequest(context.Background(), "GET", "http://contoso.com")
+	require.NoError(t, err)
+	_, err = pl.Do(req)
+	require.NoError(t, err)
+}

sdk/azcore/runtime/policy_key_credential.go

@@ -40,13 +40,18 @@ func NewKeyCredentialPolicy(cred *exported.KeyCredential, header string, options
 
 // Do implementes the Do method on the [policy.Polilcy] interface.
 func (k *KeyCredentialPolicy) Do(req *policy.Request) (*http.Response, error) {
-	if err := checkHTTPSForAuth(req); err != nil {
-		return nil, err
+	// skip adding the authorization header if no KeyCredential was provided.
+	// this prevents a panic that might be hard to diagnose and allows testing
+	// against http endpoints that don't require authentication.
+	if k.cred != nil {
+		if err := checkHTTPSForAuth(req); err != nil {
+			return nil, err
+		}
+		val := exported.KeyCredentialGet(k.cred)
+		if k.prefix != "" {
+			val = k.prefix + val
+		}
+		req.Raw().Header.Add(k.header, val)
 	}
-	val := exported.KeyCredentialGet(k.cred)
-	if k.prefix != "" {
-		val = k.prefix + val
-	}
-	req.Raw().Header.Add(k.header, val)
 	return req.Next()
 }

sdk/azcore/runtime/policy_key_credential_test.go

@@ -65,3 +65,20 @@ func TestKeyCredentialPolicy_RequiresHTTPS(t *testing.T) {
 	_, err = pl.Do(req)
 	require.Error(t, err)
 }
+
+func TestKeyCredentialPolicy_NilCredential(t *testing.T) {
+	const headerName = "fake-auth"
+	policy := NewKeyCredentialPolicy(nil, headerName, nil)
+	require.NotNil(t, policy)
+
+	pl := exported.NewPipeline(shared.TransportFunc(func(req *http.Request) (*http.Response, error) {
+		require.Zero(t, req.Header.Get(headerName))
+		return &http.Response{}, nil
+	}), policy)
+
+	req, err := NewRequest(context.Background(), http.MethodGet, "http://contoso.com")
+	require.NoError(t, err)
+
+	_, err = pl.Do(req)
+	require.NoError(t, err)
+}

sdk/azcore/runtime/policy_sas_credential.go

@@ -34,9 +34,14 @@ func NewSASCredentialPolicy(cred *exported.SASCredential, header string, options
 
 // Do implementes the Do method on the [policy.Polilcy] interface.
 func (k *SASCredentialPolicy) Do(req *policy.Request) (*http.Response, error) {
-	if err := checkHTTPSForAuth(req); err != nil {
-		return nil, err
+	// skip adding the authorization header if no SASCredential was provided.
+	// this prevents a panic that might be hard to diagnose and allows testing
+	// against http endpoints that don't require authentication.
+	if k.cred != nil {
+		if err := checkHTTPSForAuth(req); err != nil {
+			return nil, err
+		}
+		req.Raw().Header.Add(k.header, exported.SASCredentialGet(k.cred))
 	}
-	req.Raw().Header.Add(k.header, exported.SASCredentialGet(k.cred))
 	return req.Next()
 }

sdk/azcore/runtime/policy_sas_credential_test.go

@@ -49,3 +49,20 @@ func TestSASCredentialPolicy_RequiresHTTPS(t *testing.T) {
 	_, err = pl.Do(req)
 	require.Error(t, err)
 }
+
+func TestSASCredentialPolicy_NilCredential(t *testing.T) {
+	const headerName = "fake-auth"
+	policy := NewSASCredentialPolicy(nil, headerName, nil)
+	require.NotNil(t, policy)
+
+	pl := exported.NewPipeline(shared.TransportFunc(func(req *http.Request) (*http.Response, error) {
+		require.Zero(t, req.Header.Get(headerName))
+		return &http.Response{}, nil
+	}), policy)
+
+	req, err := NewRequest(context.Background(), http.MethodGet, "http://contoso.com")
+	require.NoError(t, err)
+
+	_, err = pl.Do(req)
+	require.NoError(t, err)
+}