seaweedfs/weed/s3api/s3api_server.go

package s3api

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net"
	"net/http"
	"os"
	"slices"
	"strings"
	"sync"
	"time"

	"github.com/gorilla/mux"
	"google.golang.org/grpc"

	"github.com/seaweedfs/seaweedfs/weed/cluster"
	"github.com/seaweedfs/seaweedfs/weed/credential"
	"github.com/seaweedfs/seaweedfs/weed/filer"
	"github.com/seaweedfs/seaweedfs/weed/glog"
	"github.com/seaweedfs/seaweedfs/weed/iam/integration"
	"github.com/seaweedfs/seaweedfs/weed/iam/policy"
	"github.com/seaweedfs/seaweedfs/weed/iam/sts"
	"github.com/seaweedfs/seaweedfs/weed/pb"
	"github.com/seaweedfs/seaweedfs/weed/pb/s3_pb"
	"github.com/seaweedfs/seaweedfs/weed/s3api/policy_engine"
	. "github.com/seaweedfs/seaweedfs/weed/s3api/s3_constants"
	"github.com/seaweedfs/seaweedfs/weed/s3api/s3err"
	"github.com/seaweedfs/seaweedfs/weed/security"
	"github.com/seaweedfs/seaweedfs/weed/util"
	"github.com/seaweedfs/seaweedfs/weed/util/chunk_cache"
	"github.com/seaweedfs/seaweedfs/weed/util/grace"
	util_http "github.com/seaweedfs/seaweedfs/weed/util/http"
	util_http_client "github.com/seaweedfs/seaweedfs/weed/util/http/client"
	"github.com/seaweedfs/seaweedfs/weed/util/request_id"
	"github.com/seaweedfs/seaweedfs/weed/wdclient"
)

type S3ApiServerOption struct {
	Filers                    []pb.ServerAddress
	Masters                   []pb.ServerAddress // For filer discovery
	Port                      int
	Config                    string
	DomainName                string
	AllowedOrigins            []string
	BucketsPath               string
	GrpcDialOption            grpc.DialOption
	AllowDeleteBucketNotEmpty bool
	LocalFilerSocket          string
	DataCenter                string
	FilerGroup                string
	IamConfig                 string // Advanced IAM configuration file path
	ConcurrentUploadLimit     int64
	ConcurrentFileUploadLimit int64
	EnableIam                 bool // Enable embedded IAM API on the same port
	IamReadOnly               bool // Disable IAM write operations on this server
	Cipher                    bool // encrypt data on volume servers
	BindIp                    string
	GrpcPort                  int
	ExternalUrl               string // external URL clients use, for signature verification behind a reverse proxy
	DefaultFileMode           uint32 // default file permission mode for S3 uploads (e.g. 0660, 0644)
	CacheSizeMB               int64  // in-memory chunk cache capacity in MB for the shared ReaderCache; 0 disables
}

// s3ChunkCacheChunkSizeMB is the assumed chunk size (in MiB) used to convert
// CacheSizeMB into the entry count the in-memory cache accepts. This matches
// the default -filer.maxMB for all filer/webdav/mini flag sites. It is NOT a
// hard limit — larger chunks still get cached, this just means the byte budget
// is approximate when upload-side chunking is configured larger.
const s3ChunkCacheChunkSizeMB = 4

type S3ApiServer struct {
	s3_pb.UnimplementedSeaweedS3IamCacheServer
	option                *S3ApiServerOption
	iam                   *IdentityAccessManagement
	iamIntegration        *S3IAMIntegration // Advanced IAM integration for JWT authentication
	cb                    *CircuitBreaker
	randomClientId        int32
	filerGuard            *security.Guard
	filerClient           *wdclient.FilerClient
	client                util_http_client.HTTPClientInterface
	bucketRegistry        *BucketRegistry
	credentialManager     *credential.CredentialManager
	bucketConfigCache     *BucketConfigCache
	policyEngine          *BucketPolicyEngine // Engine for evaluating bucket policies
	inFlightDataSize      int64
	inFlightUploads       int64
	inFlightDataLimitCond *sync.Cond
	embeddedIam           *EmbeddedIamApi // Embedded IAM API server (when enabled)
	stsHandlers           *STSHandlers    // STS HTTP handlers for AssumeRoleWithWebIdentity
	cipher                bool            // encrypt data on volume servers
	newObjectWriteLock    func(bucket, object string) objectWriteLock
	// Shared ReaderCache used by the S3 GET streaming path. It lives for the
	// lifetime of the server so that concurrent and repeat reads share a
	// single in-flight download per chunk, and so that no per-request
	// teardown waits on context.Background() fetches. The chunkCache field
	// is nil in this commit; a follow-up wires in an in-memory chunk cache.
	readerCache *filer.ReaderCache
}

type objectWriteLock interface {
	StopShortLivedLock() error
}

const (
	objectWriteLockTTL = 15 * time.Second
)

func NewS3ApiServer(router *mux.Router, option *S3ApiServerOption) (s3ApiServer *S3ApiServer, err error) {
	return NewS3ApiServerWithStore(router, option, "")
}

func NewS3ApiServerWithStore(router *mux.Router, option *S3ApiServerOption, explicitStore string) (s3ApiServer *S3ApiServer, err error) {
	if len(option.Filers) == 0 {
		return nil, fmt.Errorf("at least one filer address is required")
	}

	startTsNs := time.Now().UnixNano()

	v := util.GetViper()
	signingKey := v.GetString("jwt.filer_signing.key")
	v.SetDefault("jwt.filer_signing.expires_after_seconds", 10)
	expiresAfterSec := v.GetInt("jwt.filer_signing.expires_after_seconds")

	readSigningKey := v.GetString("jwt.filer_signing.read.key")
	v.SetDefault("jwt.filer_signing.read.expires_after_seconds", 60)
	readExpiresAfterSec := v.GetInt("jwt.filer_signing.read.expires_after_seconds")

	v.SetDefault("cors.allowed_origins.values", "*")

	if len(option.AllowedOrigins) == 0 {
		allowedOrigins := v.GetString("cors.allowed_origins.values")
		domains := strings.Split(allowedOrigins, ",")
		option.AllowedOrigins = domains
	}

	// Initialize basic/legacy IAM - filerClient not available yet, passed as nil
	iam := NewIdentityAccessManagementWithStore(option, nil, explicitStore)

	// Initialize bucket policy engine first
	policyEngine := NewBucketPolicyEngine()

	// Initialize FilerClient for volume location caching
	// Uses the battle-tested vidMap with filer-based lookups
	// Supports multiple filer addresses with automatic failover for high availability
	var filerClient *wdclient.FilerClient
	if len(option.Masters) > 0 {
		// Enable filer discovery via master
		masterMap := make(map[string]pb.ServerAddress)
		for i, addr := range option.Masters {
			masterMap[fmt.Sprintf("master%d", i)] = addr
		}
		clientHost := option.BindIp
		if clientHost == "0.0.0.0" || clientHost == "" {
			clientHost = util.DetectedHostAddress()
		}
		masterClient := wdclient.NewMasterClient(option.GrpcDialOption, option.FilerGroup, cluster.S3Type, pb.ServerAddress(util.JoinHostPort(clientHost, option.GrpcPort)), "", "", *pb.NewServiceDiscoveryFromMap(masterMap))
		// Start the master client connection loop - required for GetMaster() to work
		go masterClient.KeepConnectedToMaster(context.Background())

		filerClient = wdclient.NewFilerClient(option.Filers, option.GrpcDialOption, option.DataCenter, &wdclient.FilerClientOption{
			MasterClient:      masterClient,
			FilerGroup:        option.FilerGroup,
			DiscoveryInterval: 5 * time.Minute,
		})

		glog.V(1).Infof("S3 API initialized FilerClient with %d filer(s) and discovery enabled (group: %s, masters: %v)",
			len(option.Filers), option.FilerGroup, option.Masters)
	} else {
		filerClient = wdclient.NewFilerClient(option.Filers, option.GrpcDialOption, option.DataCenter)
		glog.V(1).Infof("S3 API initialized FilerClient with %d filer(s) (no discovery)", len(option.Filers))
	}

	// Initialize Global SSE-S3 Key Manager early so it's available for IAM fallback
	// This ensures we can access the KEK for STS signing key if needed
	if err := InitializeGlobalSSES3KeyManager(filerClient, option.GrpcDialOption); err != nil {
		glog.Errorf("Failed to initialize SSE-S3 Key Manager: %v", err)
		// We continue, as this might be a transient failure or non-critical for some setups,
		// but IAM fallback to KEK will fail if this didn't succeed.
	}

	// Update credential store to use FilerClient's current filer for HA
	iam.SetFilerClient(filerClient)

	// Keep attempting to load configuration from filer now that we have a client
	// The initial load in NewIdentityAccessManagementWithStore might have failed if client was nil
	go func() {
		if err := iam.loadS3ApiConfigurationFromFiler(option); err != nil {
			glog.Warningf("Failed to load IAM config from filer after client update: %v", err)
		}
	}()

	// Shared ReaderCache for the S3 GET streaming path. Keeping this shared
	// (rather than per-request) avoids the per-request Close(), which would
	// otherwise wait for background chunk downloads that run on
	// context.Background() even after the client disconnects.
	//
	// The underlying ChunkCache is controlled by option.CacheSizeMB below:
	//   - CacheSizeMB == 0: a nil *chunk_cache.TieredChunkCache is used (its
	//     receiver methods are nil-safe). Completed chunks are not deposited
	//     into a cross-request cache — concurrent readers still share in-flight
	//     downloads through the ReaderCache's downloaders map, but repeat reads
	//     refetch from volume servers.
	//   - CacheSizeMB > 0: a chunk_cache.ChunkCacheInMemory is created and
	//     wrapped in the ReaderCache, so repeat and concurrent reads hit
	//     memory. maxEntries is approximated from the byte budget and the
	//     assumed chunk size (s3ChunkCacheChunkSizeMB), clamped to a small
	//     floor so tiny caches still function.
	//
	// Downloader slots: each slot holds one in-flight / recently-completed
	// chunk buffer (~4 MiB by default), so this caps both peak memory for
	// in-flight chunks (s3ReaderCacheDownloaderLimit × chunkSize) and the
	// global fetch concurrency across all S3 GET requests. WebDAV uses 32
	// because it typically has a handful of clients; S3 serves many
	// concurrent readers, so we pick a more generous default here.
	const s3ReaderCacheDownloaderLimit = 256

	// Negative CacheSizeMB is a misconfiguration; fail fast rather than
	// silently behaving like 0.
	if option.CacheSizeMB < 0 {
		return nil, fmt.Errorf("invalid -s3.cacheCapacityMB %d: must be >= 0", option.CacheSizeMB)
	}
	var chunkCache chunk_cache.ChunkCache
	if option.CacheSizeMB > 0 {
		// ccache sizes entries by count; convert the configured byte budget
		// via the assumed chunk size. Clamp to a floor so tiny caches still
		// function.
		maxEntries := option.CacheSizeMB / s3ChunkCacheChunkSizeMB
		if maxEntries < 8 {
			maxEntries = 8
		}
		chunkCache = chunk_cache.NewChunkCacheInMemory(maxEntries)
		// Log the effective capacity after the floor clamp, not the configured
		// value — a user passing `-s3.cacheCapacityMB=1` actually gets 8 entries
		// ≈ 32 MiB because of the floor.
		glog.V(0).Infof("s3 chunk cache enabled: in-memory, ~%dMB (%d chunks of ~%dMB)", maxEntries*s3ChunkCacheChunkSizeMB, maxEntries, s3ChunkCacheChunkSizeMB)
	} else {
		chunkCache = (*chunk_cache.TieredChunkCache)(nil)
	}
	readerCache := filer.NewReaderCache(s3ReaderCacheDownloaderLimit, chunkCache, filerClient.GetLookupFileIdFunction())

	s3ApiServer = &S3ApiServer{
		option:                option,
		iam:                   iam,
		randomClientId:        util.RandomInt32(),
		filerGuard:            security.NewGuard([]string{}, signingKey, expiresAfterSec, readSigningKey, readExpiresAfterSec),
		filerClient:           filerClient,
		cb:                    NewCircuitBreaker(option),
		credentialManager:     iam.credentialManager,
		bucketConfigCache:     NewBucketConfigCache(60 * time.Minute), // Increased TTL since cache is now event-driven
		policyEngine:          policyEngine,                           // Initialize bucket policy engine
		inFlightDataLimitCond: sync.NewCond(new(sync.Mutex)),
		cipher:                option.Cipher,
		readerCache:           readerCache,
	}

	if len(option.Filers) > 0 {
		objectWriteLockClient := cluster.NewLockClient(option.GrpcDialOption, option.Filers[0])
		s3ApiServer.newObjectWriteLock = func(bucket, object string) objectWriteLock {
			lockKey := fmt.Sprintf("s3.object.write:%s", s3ApiServer.toFilerPath(bucket, object))
			owner := fmt.Sprintf("s3api-%d", s3ApiServer.randomClientId)
			lock := objectWriteLockClient.NewShortLivedLock(lockKey, owner)
			if err := lock.AttemptToLock(objectWriteLockTTL); err != nil {
				// The initial acquisition already succeeded with the default short TTL.
				// Renewal to a longer TTL is opportunistic to cover slower metadata paths.
				glog.Warningf("objectWriteLock: failed to extend lock TTL for %s: %v", lockKey, err)
			}
			return lock
		}
	}

	// Set s3a reference in circuit breaker for upload limiting
	s3ApiServer.cb.s3a = s3ApiServer

	// Pass policy engine to IAM for bucket policy evaluation
	// This avoids circular dependency by not passing the entire S3ApiServer
	iam.policyEngine = policyEngine

	// Give the policy engine a way to look up the SSE algorithm that was
	// stored at CreateMultipartUpload time, so that UploadPart/UploadPartCopy
	// policy conditions on s3:x-amz-server-side-encryption evaluate correctly.
	policyEngine.MultipartSSELookup = s3ApiServer.getMultipartSSEAlgorithm

	// Initialize advanced IAM system if config is provided or explicitly enabled
	if option.IamConfig != "" || option.EnableIam {
		configSource := "defaults"
		if option.IamConfig != "" {
			configSource = option.IamConfig
		}
		glog.V(1).Infof("Loading advanced IAM configuration from: %s", configSource)

		// Use FilerClient's GetCurrentFiler for HA-aware filer selection
		iamManager, err := loadIAMManagerFromConfig(option.IamConfig, func() string {
			return string(filerClient.GetCurrentFiler())
		}, func() string {
			return signingKey
		})
		if err != nil {
			glog.Errorf("Failed to load IAM configuration: %v", err)
		} else {
			if s3ApiServer.iam.credentialManager != nil {
				iamManager.SetUserStore(s3ApiServer.iam.credentialManager)
			}
			glog.V(1).Infof("IAM Manager loaded, creating integration")
			// Create S3 IAM integration with the loaded IAM manager
			// filerAddress not actually used, just for backward compatibility
			s3iam := NewS3IAMIntegration(iamManager, "")

			// Set IAM integration in server
			s3ApiServer.iamIntegration = s3iam

			// Set the integration in the traditional IAM for compatibility
			iam.SetIAMIntegration(s3iam)

			// Initialize STS HTTP handlers for AssumeRoleWithWebIdentity endpoint
			if stsService := iamManager.GetSTSService(); stsService != nil {
				s3ApiServer.stsHandlers = NewSTSHandlers(stsService, iam)
				glog.V(1).Infof("STS HTTP handlers initialized for AssumeRoleWithWebIdentity")
			}

			glog.V(1).Infof("Advanced IAM system initialized successfully with HA filer support")
		}
	}

	// Initialize embedded IAM API if enabled
	if option.EnableIam {
		s3ApiServer.embeddedIam = NewEmbeddedIamApi(s3ApiServer.credentialManager, iam, option.IamReadOnly)
		if option.IamReadOnly {
			glog.V(1).Infof("Embedded IAM API initialized in read-only mode (use -s3.iam.readOnly=false to enable write operations)")
		} else {
			glog.V(1).Infof("Embedded IAM API initialized in writable mode (WARNING: updates will not be propagated to other S3 servers)")
		}
	}

	if option.Config != "" {
		grace.OnReload(func() {
			if err := s3ApiServer.iam.loadS3ApiConfigurationFromFile(option.Config); err != nil {
				glog.Errorf("fail to load config file %s: %v", option.Config, err)
			} else {
				glog.V(1).Infof("Loaded %d identities from config file %s", len(s3ApiServer.iam.identities), option.Config)
				s3ApiServer.iam.updateCredentialManagerStaticIdentities()
			}
		})
	}
	s3ApiServer.bucketRegistry = NewBucketRegistry(s3ApiServer)

	// Update IAM with the final filer client (already handled by SetFilerClient above,
	// but this reinforces it if we ever change the flow)
	s3ApiServer.iam.SetFilerClient(s3ApiServer.filerClient)
	if option.LocalFilerSocket == "" {
		if s3ApiServer.client, err = util_http.NewGlobalHttpClient(); err != nil {
			return nil, err
		}
	} else {
		s3ApiServer.client = &http.Client{
			Transport: &http.Transport{
				DialContext: func(_ context.Context, _, _ string) (net.Conn, error) {
					return net.Dial("unix", option.LocalFilerSocket)
				},
			},
		}
	}

	s3ApiServer.registerRouter(router)

	go s3ApiServer.subscribeMetaEvents("s3", startTsNs, filer.DirectoryEtcRoot, []string{
		option.BucketsPath,
		filer.IamConfigDirectory,
		filer.IamConfigDirectory + "/identities",
		filer.IamConfigDirectory + "/policies",
		filer.IamConfigDirectory + "/service_accounts",
		filer.IamConfigDirectory + "/groups",
	})

	// Start bucket size metrics collection in background
	go s3ApiServer.startBucketSizeMetricsLoop(context.Background())

	return s3ApiServer, nil
}

func (s3a *S3ApiServer) Shutdown() {
	if s3a.iam != nil {
		s3a.iam.Shutdown()
	}
}

// getFilerAddress returns the current active filer address
// Uses FilerClient's tracked current filer which is updated on successful operations
// This provides better availability than always using the first filer
func (s3a *S3ApiServer) getFilerAddress() pb.ServerAddress {
	if s3a.filerClient != nil {
		return s3a.filerClient.GetCurrentFiler()
	}
	// Fallback to first filer if filerClient not initialized
	if len(s3a.option.Filers) > 0 {
		return s3a.option.Filers[0]
	}
	glog.Warningf("getFilerAddress: no filer addresses available")
	return ""
}

// syncBucketPolicyToEngine syncs a bucket policy to the policy engine
// This helper method centralizes the logic for loading bucket policies into the engine
// to avoid duplication and ensure consistent error handling
func (s3a *S3ApiServer) syncBucketPolicyToEngine(bucket string, policyDoc *policy_engine.PolicyDocument) {
	if s3a.policyEngine == nil {
		return
	}

	if policyDoc != nil {
		if err := s3a.policyEngine.LoadBucketPolicyFromCache(bucket, policyDoc); err != nil {
			glog.Errorf("Failed to sync bucket policy for %s to policy engine: %v", bucket, err)
		}
	} else {
		// No policy - ensure it's removed from engine if it was there
		s3a.policyEngine.DeleteBucketPolicy(bucket)
	}
}

// checkPolicyWithEntry re-evaluates bucket policy with the object entry metadata.
// This is used by handlers after fetching the entry to enforce tag-based conditions
// like s3:ExistingObjectTag/<key>.
//
// Returns:
//   - s3err.ErrCode: ErrNone if allowed, ErrAccessDenied if denied
//   - bool: true if policy was evaluated (has policy for bucket), false if no policy
func (s3a *S3ApiServer) checkPolicyWithEntry(r *http.Request, bucket, object, action, principal string, objectEntry map[string][]byte) (s3err.ErrorCode, bool) {
	if s3a.policyEngine == nil {
		return s3err.ErrNone, false
	}

	// Skip if no policy for this bucket
	hasPolicy := s3a.policyEngine.HasPolicyForBucket(bucket)
	// glog.V(4).Infof("checkPolicyWithEntry: bucket=%s hasPolicy=%v", bucket, hasPolicy)
	if !hasPolicy {
		return s3err.ErrNone, false
	}

	identityRaw := GetIdentityFromContext(r)
	var identity *Identity
	if identityRaw != nil {
		if id, ok := identityRaw.(*Identity); ok {
			identity = id
		}
	}

	var claims map[string]interface{}
	if identity != nil {
		claims = identity.Claims
	}

	if principal == "" {
		principal = buildPrincipalARN(identity, r)
	}

	allowed, evaluated, err := s3a.policyEngine.EvaluatePolicy(bucket, object, action, principal, r, claims, objectEntry)
	if err != nil {
		glog.Errorf("checkPolicyWithEntry: error evaluating policy for %s/%s: %v", bucket, object, err)
		return s3err.ErrInternalError, true
	}

	if !evaluated {
		return s3err.ErrNone, false
	}

	if !allowed {
		glog.V(3).Infof("checkPolicyWithEntry: policy denied access to %s/%s for principal %s", bucket, object, principal)
		return s3err.ErrAccessDenied, true
	}

	return s3err.ErrNone, true
}

// recheckPolicyWithObjectEntry performs the second phase of policy evaluation after
// an object's entry is fetched. It extracts identity from context and checks for
// tag-based conditions like s3:ExistingObjectTag/<key>.
//
// Returns s3err.ErrNone if allowed, or an error code if denied or on error.
func (s3a *S3ApiServer) recheckPolicyWithObjectEntry(r *http.Request, bucket, object, action string, objectEntry map[string][]byte, handlerName string) s3err.ErrorCode {
	identityRaw := GetIdentityFromContext(r)
	var identity *Identity
	if identityRaw != nil {
		var ok bool
		identity, ok = identityRaw.(*Identity)
		if !ok {
			glog.Errorf("%s: unexpected identity type in context for %s/%s", handlerName, bucket, object)
			return s3err.ErrInternalError
		}
	}
	principal := buildPrincipalARN(identity, r)
	errCode, _ := s3a.checkPolicyWithEntry(r, bucket, object, action, principal, objectEntry)
	return errCode
}

// classifyDomainNames classifies domains into path-style and virtual-host style domains.
// A domain is considered path-style if:
//  1. It contains a dot (has subdomains)
//  2. Its parent domain is also in the list of configured domains
//
// For example, if domains are ["s3.example.com", "develop.s3.example.com"],
// then "develop.s3.example.com" is path-style (parent "s3.example.com" is in the list),
// while "s3.example.com" is virtual-host style.
func classifyDomainNames(domainNames []string) (pathStyleDomains, virtualHostDomains []string) {
	for _, domainName := range domainNames {
		parts := strings.SplitN(domainName, ".", 2)
		if len(parts) == 2 && slices.Contains(domainNames, parts[1]) {
			// This is a subdomain and its parent is also in the list
			// Register as path-style: domain.com/bucket/object
			pathStyleDomains = append(pathStyleDomains, domainName)
		} else {
			// This is a top-level domain or its parent is not in the list
			// Register as virtual-host style: bucket.domain.com/object
			virtualHostDomains = append(virtualHostDomains, domainName)
		}
	}
	return pathStyleDomains, virtualHostDomains
}

// handleCORSOriginValidation handles the common CORS origin validation logic
func (s3a *S3ApiServer) handleCORSOriginValidation(w http.ResponseWriter, r *http.Request) bool {
	origin := r.Header.Get("Origin")
	if origin != "" {
		if len(s3a.option.AllowedOrigins) == 0 || s3a.option.AllowedOrigins[0] == "*" {
			origin = "*"
		} else {
			originFound := false
			for _, allowedOrigin := range s3a.option.AllowedOrigins {
				if origin == allowedOrigin {
					originFound = true
					break
				}
			}
			if !originFound {
				writeFailureResponse(w, r, http.StatusForbidden)
				return false
			}
		}
	}

	w.Header().Set("Access-Control-Allow-Origin", origin)
	w.Header().Set("Access-Control-Expose-Headers", "*")
	w.Header().Set("Access-Control-Allow-Methods", "*")
	w.Header().Set("Access-Control-Allow-Headers", "*")
	w.Header().Set("Access-Control-Allow-Credentials", "true")
	return true
}

// UnifiedPostHandler handles authenticated POST requests to the root path
// It inspects the Action parameter to dispatch to either STS or IAM handlers
func (s3a *S3ApiServer) UnifiedPostHandler(w http.ResponseWriter, r *http.Request) {
	// 1. Authenticate (preserves body)
	identity, errCode := s3a.iam.AuthSignatureOnly(r)
	if errCode != s3err.ErrNone {
		s3err.WriteErrorResponse(w, r, errCode)
		return
	}

	// 2. Parse Form to get Action
	// Save the body first so we can restore it for STS handler signature verification
	var bodyBytes []byte
	if r.Body != nil {
		// Limit body size to prevent DoS attacks
		r.Body = http.MaxBytesReader(w, r.Body, iamRequestBodyLimit)
		var err error
		bodyBytes, err = io.ReadAll(r.Body)
		if err != nil {
			glog.Errorf("failed to read request body: %v", err)
			s3err.WriteErrorResponse(w, r, s3err.ErrInvalidRequest)
			return
		}
		r.Body.Close()
		// Restore body for ParseForm
		r.Body = io.NopCloser(bytes.NewBuffer(bodyBytes))
	}

	if err := r.ParseForm(); err != nil {
		s3err.WriteErrorResponse(w, r, s3err.ErrInvalidRequest)
		return
	}

	// Restore body again for downstream handlers (STS needs it for signature verification)
	if bodyBytes != nil {
		r.Body = io.NopCloser(bytes.NewBuffer(bodyBytes))
	}

	// 3. Dispatch
	action := r.Form.Get("Action")
	if strings.HasPrefix(action, "AssumeRole") || action == "GetCallerIdentity" || action == "GetFederationToken" {
		// STS
		if s3a.stsHandlers == nil {
			s3err.WriteErrorResponse(w, r, s3err.ErrServiceUnavailable)
			return
		}
		s3a.stsHandlers.HandleSTSRequest(w, r)
	} else {
		// IAM
		// IAM API requests must be authenticated - reject nil identity
		if identity == nil {
			s3err.WriteErrorResponse(w, r, s3err.ErrAccessDenied)
			return
		}

		// Store identity in context
		// Always set identity in context when non-nil to ensure downstream handlers have access
		ctx := r.Context()
		if identity.Name != "" {
			ctx = SetIdentityNameInContext(ctx, identity.Name)
		}
		ctx = SetIdentityInContext(ctx, identity)
		r = r.WithContext(ctx)

		targetUserName := r.Form.Get("UserName")

		// Check permissions based on action type
		isSelfServiceAction := iamRequiresAdminForOthers(action)
		isActingOnSelf := targetUserName == "" || targetUserName == identity.Name

		// Permission check is required for all actions except for self-service actions
		// performed on the user's own identity.
		if !(isSelfServiceAction && isActingOnSelf) {
			if !identity.isAdmin() {
				if s3a.iam.VerifyActionPermission(r, identity, Action("iam:"+action), "arn:aws:iam:::*", "") != s3err.ErrNone {
					s3err.WriteErrorResponse(w, r, s3err.ErrAccessDenied)
					return
				}
			}
		}

		// Call Limit middleware + DoActions
		handler, _ := s3a.cb.Limit(s3a.embeddedIam.DoActions, ACTION_WRITE)
		handler.ServeHTTP(w, r)
	}
}

func (s3a *S3ApiServer) registerRouter(router *mux.Router) {
	// API Router
	apiRouter := router.PathPrefix("/").Subrouter()
	apiRouter.Use(request_id.Middleware)

	// S3 Tables API endpoint
	// POST / with X-Amz-Target: S3Tables.<OperationName>
	// plus REST-style endpoints for AWS CLI
	s3a.registerS3TablesRoutes(apiRouter)

	// Readiness Probe
	apiRouter.Methods(http.MethodGet, http.MethodHead).Path("/status").HandlerFunc(s3a.StatusHandler)
	apiRouter.Methods(http.MethodGet, http.MethodHead).Path("/healthz").HandlerFunc(s3a.StatusHandler)

	// Object path pattern with (?s) flag to match newlines in object keys
	const objectPath = "/{object:(?s).+}"

	var routers []*mux.Router
	if s3a.option.DomainName != "" {
		domainNames := strings.Split(s3a.option.DomainName, ",")
		pathStyleDomains, virtualHostDomains := classifyDomainNames(domainNames)

		// Register path-style domains
		for _, domain := range pathStyleDomains {
			routers = append(routers, apiRouter.Host(domain).PathPrefix("/{bucket}").Subrouter())
		}

		// Register virtual-host style domains
		for _, virtualHost := range virtualHostDomains {
			routers = append(routers, apiRouter.Host(
				fmt.Sprintf("%s.%s", "{bucket:.+}", virtualHost)).Subrouter())
		}
	}
	routers = append(routers, apiRouter.PathPrefix("/{bucket}").Subrouter())

	// Get CORS middleware instance with caching
	corsMiddleware := s3a.getCORSMiddleware()

	for _, bucket := range routers {
		// Apply CORS middleware to bucket routers for automatic CORS header handling
		bucket.Use(corsMiddleware.Handler)

		// Bucket-specific OPTIONS handler for CORS preflight requests
		// Use PathPrefix to catch all bucket-level preflight routes including /bucket/object
		bucket.PathPrefix("/").Methods(http.MethodOptions).HandlerFunc(corsMiddleware.HandleOptionsRequest)

		// each case should follow the next rule:
		// - requesting object with query must precede any other methods
		// - requesting object must precede any methods with buckets
		// - requesting bucket with query must precede raw methods with buckets
		// - requesting bucket must be processed in the end

		// objects with query

		// CopyObjectPart
		bucket.Methods(http.MethodPut).Path(objectPath).HeadersRegexp("X-Amz-Copy-Source", `(?i).*?(\/|%2F).*?`).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.CopyObjectPartHandler, ACTION_WRITE)), "PUT")).Queries("partNumber", "{partNumber:[0-9]+}", "uploadId", "{uploadId:.*}")
		// PutObjectPart
		bucket.Methods(http.MethodPut).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutObjectPartHandler, ACTION_WRITE)), "PUT")).Queries("partNumber", "{partNumber:[0-9]+}", "uploadId", "{uploadId:.*}")
		// CompleteMultipartUpload
		bucket.Methods(http.MethodPost).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.CompleteMultipartUploadHandler, ACTION_WRITE)), "POST")).Queries("uploadId", "{uploadId:.*}")
		// NewMultipartUpload
		bucket.Methods(http.MethodPost).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.NewMultipartUploadHandler, ACTION_WRITE)), "POST")).Queries("uploads", "")
		// AbortMultipartUpload
		bucket.Methods(http.MethodDelete).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.AbortMultipartUploadHandler, ACTION_WRITE)), "DELETE")).Queries("uploadId", "{uploadId:.*}")
		// ListObjectParts
		bucket.Methods(http.MethodGet).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.ListObjectPartsHandler, ACTION_READ)), "GET")).Queries("uploadId", "{uploadId:.*}")
		// ListMultipartUploads
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.ListMultipartUploadsHandler, ACTION_READ)), "GET")).Queries("uploads", "")

		// GetObjectAttributes
		bucket.Methods(http.MethodGet).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetObjectAttributesHandler, ACTION_READ)), "GET")).Queries("attributes", "")
		// GetObjectTagging
		bucket.Methods(http.MethodGet).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetObjectTaggingHandler, ACTION_READ)), "GET")).Queries("tagging", "")
		// PutObjectTagging
		bucket.Methods(http.MethodPut).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutObjectTaggingHandler, ACTION_TAGGING)), "PUT")).Queries("tagging", "")
		// DeleteObjectTagging
		bucket.Methods(http.MethodDelete).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.DeleteObjectTaggingHandler, ACTION_TAGGING)), "DELETE")).Queries("tagging", "")

		// PutObjectACL
		bucket.Methods(http.MethodPut).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutObjectAclHandler, ACTION_WRITE_ACP)), "PUT")).Queries("acl", "")
		// PutObjectRetention
		bucket.Methods(http.MethodPut).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutObjectRetentionHandler, ACTION_WRITE)), "PUT")).Queries("retention", "")
		// PutObjectLegalHold
		bucket.Methods(http.MethodPut).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutObjectLegalHoldHandler, ACTION_WRITE)), "PUT")).Queries("legal-hold", "")

		// GetObjectACL
		bucket.Methods(http.MethodGet).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetObjectAclHandler, ACTION_READ_ACP)), "GET")).Queries("acl", "")
		// GetObjectRetention
		bucket.Methods(http.MethodGet).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetObjectRetentionHandler, ACTION_READ)), "GET")).Queries("retention", "")
		// GetObjectLegalHold
		bucket.Methods(http.MethodGet).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetObjectLegalHoldHandler, ACTION_READ)), "GET")).Queries("legal-hold", "")

		// objects with query

		// raw objects

		// HeadObject
		bucket.Methods(http.MethodHead).Path(objectPath).HandlerFunc(track(s3a.AuthWithPublicRead(func(w http.ResponseWriter, r *http.Request) {
			limitedHandler, _ := s3a.cb.Limit(s3a.HeadObjectHandler, ACTION_READ)
			limitedHandler(w, r)
		}, ACTION_READ), "GET"))

		// GetObject, but directory listing is not supported
		bucket.Methods(http.MethodGet).Path(objectPath).HandlerFunc(track(s3a.AuthWithPublicRead(func(w http.ResponseWriter, r *http.Request) {
			limitedHandler, _ := s3a.cb.Limit(s3a.GetObjectHandler, ACTION_READ)
			limitedHandler(w, r)
		}, ACTION_READ), "GET"))

		// CopyObject
		bucket.Methods(http.MethodPut).Path(objectPath).HeadersRegexp("X-Amz-Copy-Source", `(?i).*?(\/|%2F).*?`).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.CopyObjectHandler, ACTION_WRITE)), "COPY"))
		// PutObject
		bucket.Methods(http.MethodPut).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutObjectHandler, ACTION_WRITE)), "PUT"))
		// DeleteObject
		bucket.Methods(http.MethodDelete).Path(objectPath).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.DeleteObjectHandler, ACTION_WRITE)), "DELETE"))

		// raw objects

		// buckets with query

		// DeleteMultipleObjects
		bucket.Methods(http.MethodPost).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.DeleteMultipleObjectsHandler, ACTION_WRITE)), "DELETE")).Queries("delete", "")

		// GetBucketACL
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetBucketAclHandler, ACTION_READ_ACP)), "GET")).Queries("acl", "")
		// PutBucketACL
		bucket.Methods(http.MethodPut).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutBucketAclHandler, ACTION_WRITE_ACP)), "PUT")).Queries("acl", "")

		// GetBucketPolicy
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetBucketPolicyHandler, ACTION_READ)), "GET")).Queries("policy", "")
		// PutBucketPolicy
		bucket.Methods(http.MethodPut).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutBucketPolicyHandler, ACTION_WRITE)), "PUT")).Queries("policy", "")
		// DeleteBucketPolicy
		bucket.Methods(http.MethodDelete).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.DeleteBucketPolicyHandler, ACTION_WRITE)), "DELETE")).Queries("policy", "")

		// GetBucketCors
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetBucketCorsHandler, ACTION_READ)), "GET")).Queries("cors", "")
		// PutBucketCors
		bucket.Methods(http.MethodPut).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutBucketCorsHandler, ACTION_WRITE)), "PUT")).Queries("cors", "")
		// DeleteBucketCors
		bucket.Methods(http.MethodDelete).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.DeleteBucketCorsHandler, ACTION_WRITE)), "DELETE")).Queries("cors", "")

		// GetBucketLifecycleConfiguration
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetBucketLifecycleConfigurationHandler, ACTION_READ)), "GET")).Queries("lifecycle", "")
		// PutBucketLifecycleConfiguration
		bucket.Methods(http.MethodPut).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutBucketLifecycleConfigurationHandler, ACTION_WRITE)), "PUT")).Queries("lifecycle", "")
		// DeleteBucketLifecycleConfiguration
		bucket.Methods(http.MethodDelete).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.DeleteBucketLifecycleHandler, ACTION_WRITE)), "DELETE")).Queries("lifecycle", "")

		// GetBucketLocation
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetBucketLocationHandler, ACTION_READ)), "GET")).Queries("location", "")

		// GetBucketRequestPayment
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetBucketRequestPaymentHandler, ACTION_READ)), "GET")).Queries("requestPayment", "")

		// GetBucketVersioning
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetBucketVersioningHandler, ACTION_READ)), "GET")).Queries("versioning", "")
		bucket.Methods(http.MethodPut).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutBucketVersioningHandler, ACTION_WRITE)), "PUT")).Queries("versioning", "")

		// GetObjectLockConfiguration / PutObjectLockConfiguration (bucket-level operations)
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetObjectLockConfigurationHandler, ACTION_READ)), "GET")).Queries("object-lock", "")
		bucket.Methods(http.MethodPut).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutObjectLockConfigurationHandler, ACTION_WRITE)), "PUT")).Queries("object-lock", "")

		// GetBucketTagging
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetBucketTaggingHandler, ACTION_TAGGING)), "GET")).Queries("tagging", "")
		bucket.Methods(http.MethodPut).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutBucketTaggingHandler, ACTION_TAGGING)), "PUT")).Queries("tagging", "")
		bucket.Methods(http.MethodDelete).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.DeleteBucketTaggingHandler, ACTION_TAGGING)), "DELETE")).Queries("tagging", "")

		// GetBucketEncryption
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetBucketEncryptionHandler, ACTION_ADMIN)), "GET")).Queries("encryption", "")
		bucket.Methods(http.MethodPut).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutBucketEncryptionHandler, ACTION_ADMIN)), "PUT")).Queries("encryption", "")
		bucket.Methods(http.MethodDelete).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.DeleteBucketEncryptionHandler, ACTION_ADMIN)), "DELETE")).Queries("encryption", "")

		// GetPublicAccessBlockHandler
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.GetPublicAccessBlockHandler, ACTION_ADMIN)), "GET")).Queries("publicAccessBlock", "")
		bucket.Methods(http.MethodPut).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutPublicAccessBlockHandler, ACTION_ADMIN)), "PUT")).Queries("publicAccessBlock", "")
		bucket.Methods(http.MethodDelete).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.DeletePublicAccessBlockHandler, ACTION_ADMIN)), "DELETE")).Queries("publicAccessBlock", "")

		// ListObjectsV2
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.AuthWithPublicRead(func(w http.ResponseWriter, r *http.Request) {
			limitedHandler, _ := s3a.cb.Limit(s3a.ListObjectsV2Handler, ACTION_LIST)
			limitedHandler(w, r)
		}, ACTION_LIST), "LIST")).Queries("list-type", "2")

		// ListObjectVersions
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.ListObjectVersionsHandler, ACTION_LIST)), "LIST")).Queries("versions", "")

		// buckets with query
		// PutBucketOwnershipControls
		bucket.Methods(http.MethodPut).HandlerFunc(track(s3a.iam.Auth(s3a.PutBucketOwnershipControls, ACTION_ADMIN), "PUT")).Queries("ownershipControls", "")

		//GetBucketOwnershipControls
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.iam.Auth(s3a.GetBucketOwnershipControls, ACTION_READ), "GET")).Queries("ownershipControls", "")

		//DeleteBucketOwnershipControls
		bucket.Methods(http.MethodDelete).HandlerFunc(track(s3a.iam.Auth(s3a.DeleteBucketOwnershipControls, ACTION_ADMIN), "DELETE")).Queries("ownershipControls", "")

		// raw buckets

		// PostPolicy
		bucket.Methods(http.MethodPost).HeadersRegexp("Content-Type", "multipart/form-data*").HandlerFunc(track(s3a.iam.AuthPostPolicy(s3a.cb.Limit(s3a.PostPolicyBucketHandler, ACTION_WRITE)), "POST"))

		// HeadBucket
		bucket.Methods(http.MethodHead).HandlerFunc(track(s3a.AuthWithPublicRead(func(w http.ResponseWriter, r *http.Request) {
			limitedHandler, _ := s3a.cb.Limit(s3a.HeadBucketHandler, ACTION_READ)
			limitedHandler(w, r)
		}, ACTION_READ), "GET"))

		// PutBucket
		bucket.Methods(http.MethodPut).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.PutBucketHandler, ACTION_ADMIN)), "PUT"))

		// DeleteBucket
		bucket.Methods(http.MethodDelete).HandlerFunc(track(s3a.iam.Auth(s3a.cb.Limit(s3a.DeleteBucketHandler, ACTION_DELETE_BUCKET)), "DELETE"))

		// ListObjectsV1 (Legacy)
		bucket.Methods(http.MethodGet).HandlerFunc(track(s3a.AuthWithPublicRead(func(w http.ResponseWriter, r *http.Request) {
			limitedHandler, _ := s3a.cb.Limit(s3a.ListObjectsV1Handler, ACTION_LIST)
			limitedHandler(w, r)
		}, ACTION_LIST), "LIST"))

		// raw buckets

	}

	// Global OPTIONS handler for service-level requests (non-bucket requests)
	// This handles requests like OPTIONS /, OPTIONS /status, OPTIONS /healthz
	// Place this after bucket handlers to avoid interfering with bucket CORS middleware
	apiRouter.Methods(http.MethodOptions).PathPrefix("/").HandlerFunc(
		func(w http.ResponseWriter, r *http.Request) {
			// Only handle if this is not a bucket-specific request
			vars := mux.Vars(r)
			bucket := vars["bucket"]
			if bucket != "" {
				// This is a bucket-specific request, let bucket CORS middleware handle it
				http.NotFound(w, r)
				return
			}

			if s3a.handleCORSOriginValidation(w, r) {
				writeSuccessResponseEmpty(w, r)
			}
		})

	// STS API endpoint for AssumeRoleWithWebIdentity
	// POST /?Action=AssumeRoleWithWebIdentity&WebIdentityToken=...
	if s3a.stsHandlers != nil {
		// 1. Explicit query param match (highest priority)
		apiRouter.Methods(http.MethodPost).Path("/").Queries("Action", "AssumeRoleWithWebIdentity").
			HandlerFunc(track(s3a.stsHandlers.HandleSTSRequest, "STS"))

		// AssumeRole - requires SigV4 authentication
		apiRouter.Methods(http.MethodPost).Path("/").Queries("Action", "AssumeRole").
			HandlerFunc(track(s3a.stsHandlers.HandleSTSRequest, "STS-AssumeRole"))

		// AssumeRoleWithLDAPIdentity - uses LDAP credentials
		apiRouter.Methods(http.MethodPost).Path("/").Queries("Action", "AssumeRoleWithLDAPIdentity").
			HandlerFunc(track(s3a.stsHandlers.HandleSTSRequest, "STS-LDAP"))

		// GetCallerIdentity - returns caller identity based on SigV4 authentication
		apiRouter.Methods(http.MethodPost).Path("/").Queries("Action", "GetCallerIdentity").
			HandlerFunc(track(s3a.stsHandlers.HandleSTSRequest, "STS-GetCallerIdentity"))

		// GetFederationToken - requires SigV4 authentication (long-term IAM user credentials)
		apiRouter.Methods(http.MethodPost).Path("/").Queries("Action", "GetFederationToken").
			HandlerFunc(track(s3a.stsHandlers.HandleSTSRequest, "STS-GetFederationToken"))

		glog.V(1).Infof("STS API enabled on S3 port (AssumeRole, AssumeRoleWithWebIdentity, AssumeRoleWithLDAPIdentity, GetCallerIdentity, GetFederationToken)")
	}

	// Embedded IAM API endpoint
	// POST / (without specific query parameters)
	// Uses AuthIam for granular permission checking
	if s3a.embeddedIam != nil {

		// 2. Authenticated IAM/STS Post requests
		// Only match if the request appears to be authenticated (AWS Signature)
		// We use a UnifiedPostHandler to dispatch based on Action (STS vs IAM)
		iamMatcher := func(r *http.Request, rm *mux.RouteMatch) bool {
			if getRequestAuthType(r) == authTypeAnonymous {
				return false
			}

			// IMPORTANT: We do NOT parse the body here.
			// UnifiedPostHandler will handle authentication and body parsing.
			// We only filter out requests that are explicitly targeted at STS via Query params
			// to avoid double-handling, although UnifiedPostHandler would handle them correctly anyway.

			// Action in Query String is handled by explicit STS routes above
			action := r.URL.Query().Get("Action")
			if action == "AssumeRole" || action == "AssumeRoleWithWebIdentity" || action == "AssumeRoleWithLDAPIdentity" || action == "GetCallerIdentity" || action == "GetFederationToken" {
				return false
			}

			return true
		}

		apiRouter.Methods(http.MethodPost).Path("/").MatcherFunc(iamMatcher).
			HandlerFunc(track(s3a.UnifiedPostHandler, "IAM-Unified"))

		glog.V(1).Infof("Embedded IAM API enabled on S3 port")
	}

	// 3. Fallback STS handler (lowest priority)
	// Catches unauthenticated POST / requests that didn't match specific query params.
	// This primarily handles AssumeRoleWithWebIdentity where parameters are in the POST body.
	if s3a.stsHandlers != nil {
		glog.V(1).Infof("Registering fallback STS handler for unauthenticated POST requests")
		apiRouter.Methods(http.MethodPost).Path("/").
			HandlerFunc(track(s3a.stsHandlers.HandleSTSRequest, "STS-Fallback"))
	}

	// ListBuckets
	apiRouter.Methods(http.MethodGet).Path("/").HandlerFunc(track(s3a.iam.Auth(s3a.ListBucketsHandler, ACTION_LIST), "LIST"))

	// NotFound
	apiRouter.NotFoundHandler = http.HandlerFunc(s3err.NotFoundHandler)

}

// loadIAMManagerFromConfig loads the advanced IAM manager from configuration file
func loadIAMManagerFromConfig(configPath string, filerAddressProvider func() string, getFilerSigningKey func() string) (*integration.IAMManager, error) {
	var configRoot struct {
		STS       *sts.STSConfig                `json:"sts"`
		Policy    *policy.PolicyEngineConfig    `json:"policy"`
		Providers []map[string]interface{}      `json:"providers"`
		Roles     []*integration.RoleDefinition `json:"roles"`
		Policies  []struct {
			Name     string                 `json:"name"`
			Document *policy.PolicyDocument `json:"document"`
		} `json:"policies"`
	}

	if configPath != "" {
		// Read configuration file
		configData, err := os.ReadFile(configPath)
		if err != nil {
			return nil, fmt.Errorf("failed to read config file: %w", err)
		}

		if err := json.Unmarshal(configData, &configRoot); err != nil {
			return nil, fmt.Errorf("failed to parse config: %w", err)
		}
	} else {
		glog.V(1).Infof("No IAM config file provided; using defaults")
		// Initialize with empty config which will trigger defaults below
	}

	// Ensure STS config exists so we can apply defaults later
	if configRoot.STS == nil {
		configRoot.STS = &sts.STSConfig{}
	}

	// Ensure a valid policy engine config exists
	if configRoot.Policy == nil {
		configRoot.Policy = &policy.PolicyEngineConfig{}
	}
	if configRoot.Policy.StoreType == "" {
		configRoot.Policy.StoreType = sts.StoreTypeMemory
	}
	if configRoot.Policy.DefaultEffect == "" {
		// Secure default when an explicit IAM config file is provided:
		// omitted defaultEffect should be Deny to avoid unintentional privilege escalation.
		// Keep zero-config startup behavior (no config file path) open for memory store.
		if configPath == "" && configRoot.Policy.StoreType == sts.StoreTypeMemory {
			configRoot.Policy.DefaultEffect = sts.EffectAllow
		} else {
			configRoot.Policy.DefaultEffect = sts.EffectDeny
		}
		glog.V(1).Infof("Using policy defaults: DefaultEffect=%s, StoreType=%s", configRoot.Policy.DefaultEffect, configRoot.Policy.StoreType)
	}

	// Create IAM configuration
	iamConfig := &integration.IAMConfig{
		STS:    configRoot.STS,
		Policy: configRoot.Policy,
		Roles: &integration.RoleStoreConfig{
			StoreType: sts.StoreTypeMemory, // Use memory store for JSON config-based setup
		},
	}

	// Apply default signing key if not present in config
	if iamConfig.STS != nil && len(iamConfig.STS.SigningKey) == 0 {
		// 1. Try server-configured signing key (security.toml / CLI)
		if key := getFilerSigningKey(); key != "" {
			iamConfig.STS.SigningKey = []byte(key)
			glog.V(1).Infof("Using default filer signing key for STS service")
		} else {
			// 2. Try cluster-wide SSE-S3 Master Key (KEK) from Filer
			// This ensures zero-config consistency across the cluster
			if kek := GetSSES3KeyManager().GetMasterKey(); len(kek) > 0 {
				iamConfig.STS.SigningKey = kek
				glog.V(1).Infof("Using SSE-S3 Master Key (KEK) for STS service")
			} else {
				// 3. Fail if no signing key is available
				// This ensures consistency across multiple S3 servers and secure operation
				return nil, fmt.Errorf("no signing key found for STS service; please provide 'signingKey' in IAM config, configure 'jwt.filer_signing.key' in security.toml, or ensure SSE-S3 is initialized")
			}
		}
	}

	// Initialize IAM manager
	iamManager := integration.NewIAMManager()
	if err := iamManager.Initialize(iamConfig, filerAddressProvider); err != nil {
		return nil, fmt.Errorf("failed to initialize IAM manager: %w", err)
	}

	// Load identity providers
	providerFactory := sts.NewProviderFactory()
	for _, providerConfig := range configRoot.Providers {
		// Check for required fields with explicit type assertion
		name, ok := providerConfig["name"].(string)
		if !ok || name == "" {
			glog.Warningf("Skipping provider with invalid or missing name: %+v", providerConfig)
			continue
		}
		providerType, ok := providerConfig["type"].(string)
		if !ok || providerType == "" {
			glog.Warningf("Skipping provider %s with invalid or missing type", name)
			continue
		}

		// Fix: providerConfig["roleMapping"] might be missing from "config" map if configured externally
		// We inject it into the config map so the factory can find it
		configMap, ok := providerConfig["config"].(map[string]interface{})
		if !ok {
			glog.Warningf("Validation failed for provider %s: config must be a map", name)
			continue
		}

		if roleMapping, ok := providerConfig["roleMapping"]; ok {
			configMap["roleMapping"] = roleMapping
		}

		provider, err := providerFactory.CreateProvider(&sts.ProviderConfig{
			Name:    name,
			Type:    providerType,
			Enabled: true,
			Config:  configMap,
		})
		if err != nil {
			glog.Warningf("Failed to create provider %s: %v", providerConfig["name"], err)
			continue
		}
		if provider != nil {
			if err := iamManager.RegisterIdentityProvider(provider); err != nil {
				glog.Warningf("Failed to register provider %s: %v", providerConfig["name"], err)
			} else {
				glog.V(1).Infof("Registered identity provider: %s", providerConfig["name"])
			}
		}
	}

	// Load policies
	for _, policyDef := range configRoot.Policies {
		if err := iamManager.CreatePolicy(context.Background(), "", policyDef.Name, policyDef.Document); err != nil {
			glog.Warningf("Failed to create policy %s: %v", policyDef.Name, err)
		}
	}

	// Load roles
	for _, roleDef := range configRoot.Roles {
		if err := iamManager.CreateRole(context.Background(), "", roleDef.RoleName, roleDef); err != nil {
			glog.Warningf("Failed to create role %s: %v", roleDef.RoleName, err)
		}
	}

	glog.V(1).Infof("Loaded %d providers, %d policies and %d roles from config", len(configRoot.Providers), len(configRoot.Policies), len(configRoot.Roles))

	return iamManager, nil
}

// AuthenticateRequest authenticates the request and returns the identity name and object
func (s3a *S3ApiServer) AuthenticateRequest(r *http.Request) (string, interface{}, s3err.ErrorCode) {
	if s3a.iam == nil {
		return "", nil, s3err.ErrAccessDenied
	}
	identity, err := s3a.iam.AuthenticateRequest(r)
	if identity != nil {
		return identity.Name, identity, err
	}
	return "", nil, err
}

// DefaultAllow returns whether access is allowed by default when no policy is found
func (s3a *S3ApiServer) DefaultAllow() bool {
	if s3a.iam == nil || s3a.iam.iamIntegration == nil {
		return false
	}
	return s3a.iam.iamIntegration.DefaultAllow()
}

// ValidateS3Credential validates an S3 access key / secret key pair.
// Returns the identity name and identity object on success.
func (s3a *S3ApiServer) ValidateS3Credential(accessKey, secretKey string) (string, interface{}, error) {
	if s3a.iam == nil {
		return "", nil, fmt.Errorf("IAM not configured")
	}
	identity, cred, found := s3a.iam.LookupByAccessKey(accessKey)
	if !found {
		return "", nil, fmt.Errorf("access key not found")
	}
	if cred.SecretKey != secretKey {
		return "", nil, fmt.Errorf("invalid secret key")
	}
	if identity.Disabled {
		return "", nil, fmt.Errorf("identity is disabled")
	}
	if cred.isCredentialExpired() {
		return "", nil, fmt.Errorf("credential expired")
	}
	if cred.Status == "Inactive" {
		return "", nil, fmt.Errorf("credential is inactive")
	}
	return identity.Name, identity, nil
}

// GetCredentialByAccessKey looks up a credential by access key.
// Returns the identity name, identity object, and secret key.
// Used for verifying Iceberg OAuth Bearer tokens with the exact credential
// that was used to sign the token.
func (s3a *S3ApiServer) GetCredentialByAccessKey(accessKey string) (string, interface{}, string, error) {
	if s3a.iam == nil {
		return "", nil, "", fmt.Errorf("IAM not configured")
	}
	identity, cred, found := s3a.iam.LookupByAccessKey(accessKey)
	if !found {
		return "", nil, "", fmt.Errorf("access key not found")
	}
	if identity.Disabled {
		return "", nil, "", fmt.Errorf("identity is disabled")
	}
	if cred.isCredentialExpired() {
		return "", nil, "", fmt.Errorf("credential expired")
	}
	if cred.Status == "Inactive" {
		return "", nil, "", fmt.Errorf("credential is inactive")
	}
	return identity.Name, identity, cred.SecretKey, nil
}