From 8202c7db4b3bc4b01bb1c5b7a40c7e03918b221e Mon Sep 17 00:00:00 2001
From: Robert <17119716+robmonte@users.noreply.github.com>
Date: Fri, 6 Oct 2023 14:29:28 -0500
Subject: [PATCH] auth/aws: fix panic in IAM-based login when client config
 doesn't exist (#23555)

Co-authored-by: Austin Gebauer <34121980+austingebauer@users.noreply.github.com>
---
 builtin/credential/aws/backend_test.go    |  2 +-
 builtin/credential/aws/path_login.go      | 32 +++++++--------
 builtin/credential/aws/path_login_test.go | 50 +++++++++++++++++++++++
 changelog/23555.txt                       |  3 ++
 4 files changed, 70 insertions(+), 17 deletions(-)
 create mode 100644 changelog/23555.txt

diff --git a/builtin/credential/aws/backend_test.go b/builtin/credential/aws/backend_test.go
index d737492391..d56478266d 100644
--- a/builtin/credential/aws/backend_test.go
+++ b/builtin/credential/aws/backend_test.go
@@ -1504,7 +1504,7 @@ func buildCallerIdentityLoginData(request *http.Request, roleName string) (map[s
 		"iam_request_url":         base64.StdEncoding.EncodeToString([]byte(request.URL.String())),
 		"iam_request_headers":     base64.StdEncoding.EncodeToString(headersJson),
 		"iam_request_body":        base64.StdEncoding.EncodeToString(requestBody),
-		"request_role":            roleName,
+		"role":                    roleName,
 	}, nil
 }
 
diff --git a/builtin/credential/aws/path_login.go b/builtin/credential/aws/path_login.go
index 68a1708ee9..ca74344172 100644
--- a/builtin/credential/aws/path_login.go
+++ b/builtin/credential/aws/path_login.go
@@ -292,7 +292,7 @@ func (b *backend) pathLoginIamGetRoleNameCallerIdAndEntity(ctx context.Context,
 
 	config, err := b.lockedClientConfigEntry(ctx, req.Storage)
 	if err != nil {
-		return "", nil, nil, logical.ErrorResponse("error getting configuration"), nil
+		return "", nil, nil, nil, fmt.Errorf("error getting configuration: %w", err)
 	}
 
 	endpoint := "https://sts.amazonaws.com"
@@ -319,23 +319,23 @@ func (b *backend) pathLoginIamGetRoleNameCallerIdAndEntity(ctx context.Context,
 		if config.MaxRetries >= 0 {
 			maxRetries = config.MaxRetries
 		}
-	}
 
-	// Extract and use a regional STS endpoint
-	// based on the region set in the Authorization header.
-	if config.UseSTSRegionFromClient {
-		clientSpecifiedRegion, err := awsRegionFromHeader(headers.Get("Authorization"))
-		if err != nil {
-			return "", nil, nil, logical.ErrorResponse("region missing from Authorization header"), nil
+		// Extract and use a regional STS endpoint
+		// based on the region set in the Authorization header.
+		if config.UseSTSRegionFromClient {
+			clientSpecifiedRegion, err := awsRegionFromHeader(headers.Get("Authorization"))
+			if err != nil {
+				return "", nil, nil, logical.ErrorResponse("region missing from Authorization header"), nil
+			}
+
+			url, err := stsRegionalEndpoint(clientSpecifiedRegion)
+			if err != nil {
+				return "", nil, nil, logical.ErrorResponse(err.Error()), nil
+			}
+
+			b.Logger().Debug("use_sts_region_from_client set; using region specified from header", "region", clientSpecifiedRegion)
+			endpoint = url
 		}
-
-		url, err := stsRegionalEndpoint(clientSpecifiedRegion)
-		if err != nil {
-			return "", nil, nil, logical.ErrorResponse(err.Error()), nil
-		}
-
-		b.Logger().Debug("use_sts_region_from_client set; using region specified from header", "region", clientSpecifiedRegion)
-		endpoint = url
 	}
 
 	b.Logger().Debug("submitting caller identity request", "endpoint", endpoint)
diff --git a/builtin/credential/aws/path_login_test.go b/builtin/credential/aws/path_login_test.go
index 26d9b194ad..b3a9c63913 100644
--- a/builtin/credential/aws/path_login_test.go
+++ b/builtin/credential/aws/path_login_test.go
@@ -308,6 +308,56 @@ func TestBackend_validateVaultPostRequestValues(t *testing.T) {
 	}
 }
 
+// TestBackend_pathLogin_NoClientConfig covers logging in via IAM auth when the
+// client config does not exist. This is a regression test to cover potential
+// panics when referencing the potentially-nil config in the login handler. For
+// details see https://github.com/hashicorp/vault/issues/23361.
+func TestBackend_pathLogin_NoClientConfig(t *testing.T) {
+	storage := new(logical.InmemStorage)
+	config := logical.TestBackendConfig()
+	config.StorageView = storage
+	b, err := Backend(config)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = b.Setup(context.Background(), config)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Intentionally left out the client configuration
+
+	roleEntry := &awsRoleEntry{
+		RoleID:   "foo",
+		Version:  currentRoleStorageVersion,
+		AuthType: iamAuthType,
+	}
+	err = b.setRole(context.Background(), storage, testValidRoleName, roleEntry)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	loginData, err := defaultLoginData()
+	if err != nil {
+		t.Fatal(err)
+	}
+	loginRequest := &logical.Request{
+		Operation:  logical.UpdateOperation,
+		Path:       "login",
+		Storage:    storage,
+		Data:       loginData,
+		Connection: &logical.Connection{},
+	}
+	resp, err := b.HandleRequest(context.Background(), loginRequest)
+	if err != nil {
+		t.Fatalf("expected nil error, got: %v", err)
+	}
+	if !resp.IsError() {
+		t.Fatalf("expected error response, got: %+v", resp)
+	}
+}
+
 // TestBackend_pathLogin_IAMHeaders tests login with iam_request_headers,
 // supporting both base64 encoded string and JSON headers
 func TestBackend_pathLogin_IAMHeaders(t *testing.T) {
diff --git a/changelog/23555.txt b/changelog/23555.txt
new file mode 100644
index 0000000000..32405057f5
--- /dev/null
+++ b/changelog/23555.txt
@@ -0,0 +1,3 @@
+```release-note:bug
+auth/aws: Fixes a panic that can occur in IAM-based login when a [client config](https://developer.hashicorp.com/vault/api-docs/auth/aws#configure-client) does not exist.
+```
\ No newline at end of file