s3: keep verifying the request host when externalUrl is set (#10970)

* s3: keep verifying the request host when externalUrl is set

externalUrl was the only host candidate once set, so a client that dialed
the gateway directly instead of through the proxy always got
SignatureDoesNotMatch. Make it lead the candidate walk instead: every
candidate still needs a valid signature, and the request-derived hosts are
already trusted when the flag is unset, so a mixed proxy plus in-cluster
topology can now advertise a public endpoint and verify both planes.

* s3: cover virtual-hosted addressing behind externalUrl

The old pin also rejected an external client that signed
bucket.api.example.com, since only the bare externalUrl host was ever
tried. The candidate walk covers it; pin the case down.

weed/command/filer.go

@@ -158,7 +158,7 @@ func init() {
 	filerS3Options.iamReadOnly = cmdFiler.Flag.Bool("s3.iam.readOnly", true, "disable IAM write operations on this server")
 	filerS3Options.portIceberg = cmdFiler.Flag.Int("s3.port.iceberg", 8181, "Iceberg REST Catalog server listen port (0 to disable)")
 	filerS3Options.portLance = cmdFiler.Flag.Int("s3.port.lance", 9101, "Lance Namespace server listen port (0 to disable)")
-	filerS3Options.externalUrl = cmdFiler.Flag.String("s3.externalUrl", "", "the external URL clients use to connect (e.g. https://api.example.com:9000). Used for S3 signature verification behind a reverse proxy. Falls back to S3_EXTERNAL_URL env var.")
+	filerS3Options.externalUrl = cmdFiler.Flag.String("s3.externalUrl", "", "the external URL clients use to connect (e.g. https://api.example.com:9000). Advertised to Iceberg and Lance clients, and tried first when verifying S3 signatures behind a reverse proxy. Falls back to S3_EXTERNAL_URL env var.")
 	filerS3Options.defaultFileMode = cmdFiler.Flag.String("s3.defaultFileMode", "", "default file mode for S3 uploaded objects, e.g. 0660, 0644, 0666")
 	filerS3Options.cacheSizeMB = cmdFiler.Flag.Int64("s3.cacheCapacityMB", 0, "in-memory chunk cache capacity in MB for S3 GETs shared across requests (0 disables)")
 

weed/command/mini.go

@@ -526,7 +526,7 @@ func initMiniS3Flags() {
 	miniS3Options.auditLogConfig = cmdMini.Flag.String("s3.auditLogConfig", "", "path to the audit log config file")
 	miniS3Options.allowDeleteBucketNotEmpty = miniS3AllowDeleteBucketNotEmpty
 	miniS3Options.autoCreateBucket = miniS3AutoCreateBucket
-	miniS3Options.externalUrl = cmdMini.Flag.String("s3.externalUrl", "", "the external URL clients use to connect (e.g. https://api.example.com:9000). Used for S3 signature verification behind a reverse proxy. Falls back to S3_EXTERNAL_URL env var.")
+	miniS3Options.externalUrl = cmdMini.Flag.String("s3.externalUrl", "", "the external URL clients use to connect (e.g. https://api.example.com:9000). Advertised to Iceberg and Lance clients, and tried first when verifying S3 signatures behind a reverse proxy. Falls back to S3_EXTERNAL_URL env var.")
 	miniS3Options.defaultFileMode = cmdMini.Flag.String("s3.defaultFileMode", "", "default file mode for S3 uploaded objects, e.g. 0660, 0644, 0666")
 	miniS3Options.cacheSizeMB = cmdMini.Flag.Int64("s3.cacheCapacityMB", 0, "in-memory chunk cache capacity in MB for S3 GETs shared across requests (0 disables)")
 	// In mini mode, S3 uses the shared debug server started at line 681, not its own separate debug server

weed/command/s3.go

@@ -124,7 +124,7 @@ func init() {
 	s3StandaloneOptions.debug = cmdS3.Flag.Bool("debug", false, "serves runtime profiling data via pprof on the port specified by -debug.port")
 	s3StandaloneOptions.debugPort = cmdS3.Flag.Int("debug.port", 6060, "http port for debugging")
 	s3StandaloneOptions.cipher = cmdS3.Flag.Bool("encryptVolumeData", false, "encrypt data on volume servers")
-	s3StandaloneOptions.externalUrl = cmdS3.Flag.String("externalUrl", "", "the external URL clients use to connect (e.g. https://api.example.com:9000). Used for S3 signature verification behind a reverse proxy. Falls back to S3_EXTERNAL_URL env var.")
+	s3StandaloneOptions.externalUrl = cmdS3.Flag.String("externalUrl", "", "the external URL clients use to connect (e.g. https://api.example.com:9000). Advertised to Iceberg and Lance clients, and tried first when verifying S3 signatures behind a reverse proxy. Falls back to S3_EXTERNAL_URL env var.")
 	s3StandaloneOptions.defaultFileMode = cmdS3.Flag.String("defaultFileMode", "", "default file mode for S3 uploaded objects, e.g. 0660, 0644, 0666")
 	s3StandaloneOptions.cacheSizeMB = cmdS3.Flag.Int64("cacheCapacityMB", 0, "in-memory chunk cache capacity in MB for S3 GETs shared across requests (0 disables)")
 }

weed/command/server.go

@@ -187,7 +187,7 @@ func init() {
 	s3Options.enableIam = cmdServer.Flag.Bool("s3.iam", true, "enable embedded IAM API on the same S3 port")
 	s3Options.iamReadOnly = cmdServer.Flag.Bool("s3.iam.readOnly", true, "disable IAM write operations on this server")
 	s3Options.cipher = cmdServer.Flag.Bool("s3.encryptVolumeData", false, "encrypt data on volume servers for S3 uploads")
-	s3Options.externalUrl = cmdServer.Flag.String("s3.externalUrl", "", "the external URL clients use to connect (e.g. https://api.example.com:9000). Used for S3 signature verification behind a reverse proxy. Falls back to S3_EXTERNAL_URL env var.")
+	s3Options.externalUrl = cmdServer.Flag.String("s3.externalUrl", "", "the external URL clients use to connect (e.g. https://api.example.com:9000). Advertised to Iceberg and Lance clients, and tried first when verifying S3 signatures behind a reverse proxy. Falls back to S3_EXTERNAL_URL env var.")
 	s3Options.defaultFileMode = cmdServer.Flag.String("s3.defaultFileMode", "", "default file mode for S3 uploaded objects, e.g. 0660, 0644, 0666")
 	s3Options.cacheSizeMB = cmdServer.Flag.Int64("s3.cacheCapacityMB", 0, "in-memory chunk cache capacity in MB for S3 GETs shared across requests (0 disables)")