all: initial files

2022-12-05 01:53:52 +07:00 · 2022-12-05 01:53:52 +07:00 · 44173e65f5
commit 44173e65f5
23 changed files with 1054 additions and 0 deletions
--- a/.config/example.env
+++ b/.config/example.env
@ -0,0 +1,19 @@
+## obs-access-signer
+#
+HTTP_ADDR=0.0.0.0:9002
+OBS_ENDPOINT=minio:9000
+OBS_BUCKET_NAME=test-bucket
+OBS_SECURE=false
+LOG_LEVEL=DEBUG
+AWS_ACCESS_KEY=example-minio-access
+AWS_SECRET_KEY=example-minio-secret
+# AWS_SESSION_TOKEN
+
+# accessible S3 gateway
+OBS_HOST_REDIRECT=127.0.0.1:9000
+
+
+## Infra
+# minio, mc
+MINIO_ACCESS_KEY=example-minio-access
+MINIO_SECRET_KEY=example-minio-secret
--- a/.dockerignore
+++ b/.dockerignore
@ -0,0 +1 @@
+.git/
--- a/.drone.yml
+++ b/.drone.yml
@ -0,0 +1,5 @@
+kind: pipeline
+type: docker
+name: default
+
+steps: []
--- a/.env.example
+++ b/.env.example
@ -0,0 +1,13 @@
+## obs-access-signer
+#
+HTTP_ADDR=127.0.0.1:9003
+OBS_ENDPOINT=127.0.0.1:9000
+OBS_BUCKET_NAME=test-bucket
+OBS_SECURE=false
+LOG_LEVEL=DEBUG
+AWS_ACCESS_KEY=example-minio-access
+AWS_SECRET_KEY=example-minio-secret
+# AWS_SESSION_TOKEN
+
+# accessible S3 gateway
+OBS_HOST_REDIRECT=127.0.0.1:9000
--- a/.gitignore
+++ b/.gitignore
@ -0,0 +1 @@
+.env
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@ -0,0 +1,22 @@
+{
+    "configurations": [
+        {
+            "name": "Launch server on external",
+            "type": "go",
+            "request": "launch",
+            "mode": "auto",
+            "program": "${workspaceFolder}",
+            "host": "127.0.0.1",
+            "port": 10500,
+            "showGlobalVariables": true,
+        },
+        {
+            "name": "Launch server",
+            "type": "go",
+            "request": "launch",
+            "mode": "auto",
+            "program": "${workspaceFolder}",
+            "showGlobalVariables": true,
+        }
+    ]
+}
--- a/.vscode/tasks.json
+++ b/.vscode/tasks.json
@ -0,0 +1,11 @@
+{
+    "version": "2.0.0",
+    "tasks": [
+        {
+            "label": "Run dlv",
+            "type": "shell",
+            "command": "dlv dap --check-go-version --listen 127.0.0.1:10500",
+            "group": "build",
+        },
+    ],
+}
--- a/18
+++ b/18
@ -0,0 +1,18 @@
+FROM ii64/golang-zig:go1.18-alpine3.15-zig AS builder
+
+WORKDIR /build
+COPY . /build
+
+RUN apk add --no-cache \
+    make
+
+RUN --mount=type=cache,mode=0755,target=/go/pkg/mod make dep
+RUN make build
+
+
+FROM gcr.io/distroless/static-debian11
+
+WORKDIR /app
+COPY --from=builder /build/obs-access-signer /app/obs-access-signer
+
+ENTRYPOINT [ "/app/obs-access-signer" ]
--- a/201
+++ b/201
@ -0,0 +1,201 @@
+                                 Apache License
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--- a/24
+++ b/24
@ -0,0 +1,24 @@
+all: build
+
+export DOCKER_BUILDKIT=1
+
+IMAGE := obs-access-signer:dev
+
+# use zig cc/c++ to statically link deps
+TARGET_TRIPLE := x86_64-linux
+
+CFLAGS ?=
+CFLAGS += -target $(TARGET_TRIPLE)
+CXXFLAGS ?=
+CXXFLAGS += -target $(TARGET_TRIPLE)
+GOFLAGS ?=
+GOFLAGS += -x -trimpath
+
+dep:
+	go mod download
+
+build:
+	CGO_ENABLED=0 CC="zig cc $(CFLAGS)" CXX="zig c++ $(CXXFLAGS)" go build $(GOFLAGS) .
+
+build.docker:
+	"docker" build --progress=plain -t $(IMAGE) .
--- a/README.md
+++ b/README.md
@ -0,0 +1,16 @@
+# obs-access-signer
+
+S3 Object Storage access signer.
+
+Run `obs-access-signer` behind a gateway/cache proxy is preferred as the response is static.
+
+There's an example of using it with Varnish Cache, you can see [here](docker/docker-compose.yaml).
+
+## Why?
+
+Some S3-compatible gateway might not support ACL endpoints but they are support presigned access. Currently, the behavior of `obs-access-signer` is similar to `public-read` ACL where clients can access objects anonymously and redirect them (permanently) to presigned url with `Expires` set to the max signed value of `int64` which has roughly 250yrs lifetime since unix time started.
+
+
+## License
+
+Apache-2.0
--- a/docker/.gitkeep
+++ b/docker/.gitkeep
--- a/docker/Makefile
+++ b/docker/Makefile
@ -0,0 +1,4 @@
+
+
+gen-minio-access:
+	docker compose run --rm minio 
--- a/docker/default.vcl
+++ b/docker/default.vcl
@ -0,0 +1,113 @@
+#
+# This is an example VCL file for Varnish.
+#
+# It does not do anything by default, delegating control to the
+# builtin VCL. The builtin VCL is called when there is no explicit
+# return statement.
+#
+# See the VCL chapters in the Users Guide at https://www.varnish-cache.org/docs/
+# and https://www.varnish-cache.org/trac/wiki/VCLExamples for more examples.
+
+# Marker to tell the VCL compiler that this VCL has been adapted to the
+# new 4.0 format.
+vcl 4.0;
+
+# Default backend definition. Set this to point to your content server.
+backend default {
+    .host = "obs-access-signer";
+    .port = "9002";
+    .connect_timeout = 300s;
+    .first_byte_timeout = 300s;
+    .between_bytes_timeout = 300s;
+    .max_connections = 800;
+}
+
+sub vcl_hash {
+    hash_data(req.url);
+    if (req.http.Host) {
+        hash_data(req.http.Host);
+    } else {
+        hash_data(server.ip);
+    }
+}
+
+sub vcl_recv {
+    # Happens before we check if we have this in cache already.
+    #
+    # Typically you clean up the request here, removing cookies you don't need,
+    # rewriting the request, etc.
+    
+    if (req.method == "PRI") {
+        /* We do not support SPDY or HTTP/2.0 */
+        return (synth(405));
+    }
+
+    # remove port from Host
+    set req.http.Host = regsub(req.http.Host, ":[0-9]+", "");
+
+    /* Backend accept HEAD and GET only */
+    if (req.method != "GET" && req.method != "HEAD") {
+        return (synth(405));
+    }
+
+    # Ignore the query string
+    set req.url = regsub(req.url, "\?.*$", "");
+
+    return (hash);
+}
+
+sub vcl_backend_response {
+    # Happens after we have read the response headers from the backend.
+    #
+    # Here you clean the response headers, removing silly Set-Cookie headers
+    # and other mistakes your backend does.
+
+    # Don't cache 400s
+    if (beresp.status >= 400) {
+        set beresp.uncacheable = true;
+        set beresp.http.X-Cacheable = "NO: beresp.status";
+        set beresp.ttl = 0s;
+        return (deliver);
+    }
+
+    # keep last content in case backend goes down.
+    set beresp.grace = 6h;
+
+    # cache timeout
+    set beresp.ttl = 1h;
+
+    return (deliver);
+}
+
+sub vcl_deliver {
+    # Happens when we have all the pieces we need, and are about to send the
+    # response to the client.
+    #
+    # You can do accounting or modifying the final object here.
+
+    set resp.http.Via = regsuball(resp.http.Via, "\s\([a-zA-Z0-9\/.]+\)", "");
+    set resp.http.Server = "VOAS";
+
+    # Debug header to see if it's a HIT/MISS and the number of hits
+    if (obj.hits > 0) {
+        set resp.http.X-Cache = "HIT";
+    } else {
+        set resp.http.X-Cache = "MISS";
+    }
+
+    # Please note that obj.hits behaviour changed in 4.0, now it counts per objecthead, not per object
+    # and obj.hits may not be reset in some cases where bans are in use. See bug 1492 for details.
+    # So take hits with a grain of salt
+    set resp.http.X-Cache-Hits = obj.hits;
+
+    unset resp.http.Date;
+    unset resp.http.Age;
+    # unset resp.http.Server;
+    # unset resp.http.Via;
+
+    return (deliver);
+}
+
+sub vcl_backend_error {
+    return (retry);
+}
--- a/docker/docker-compose.yaml
+++ b/docker/docker-compose.yaml
@ -0,0 +1,62 @@
+version: '3'
+
+services:
+  # obs access signer
+  obs-access-signer:
+    image: obs-access-signer:dev
+    networks:
+      - obs
+    build:
+      context: ..
+    env_file:
+      - ../.config/example.env
+    ports:
+      - "127.0.0.1:9002:9002"
+
+  # Varnish cache proxy
+  varnish:
+    image: varnish:stable
+    networks:
+      - obs
+    volumes:
+      - ./default.vcl:/etc/varnish/default.vcl:ro
+    ports:
+      - "127.0.0.1:8080:80"
+      - "127.0.0.1:8443:8443"
+
+  # intended as S3-compatible gateway test
+  minio:
+    image: quay.io/minio/minio
+    networks:
+      - obs
+    env_file:
+      - ../.config/example.env
+    command:
+      - server
+      - /data
+      - --console-address
+      - :9001
+    ports:
+      - "127.0.0.1:9000:9000"
+      - "127.0.0.1:9001:9001"
+  
+  # setup minio bucket
+  mc-create-bucket:
+    image: minio/mc
+    networks:
+      - obs
+    env_file:
+      - ../.config/example.env
+    entrypoint:
+      - sh
+      - -c
+      - |
+        mc config host add min http://minio:9000 $$MINIO_ACCESS_KEY $$MINIO_SECRET_KEY
+        mc rm -r --force min/$$OBS_BUCKET_NAME
+        mc mb min/$$OBS_BUCKET_NAME
+        mc policy download min/$$OBS_BUCKET_NAME
+    depends_on:
+      - minio
+
+networks:
+  obs: {}
--- a/go.mod
+++ b/go.mod
@ -0,0 +1,34 @@
+module github.com/ii64/obs-access-signer
+
+go 1.19
+
+require (
+	github.com/joho/godotenv v1.4.0
+	github.com/minio/minio-go/v7 v7.0.45
+	github.com/valyala/fasthttp v1.43.0
+	go.uber.org/zap v1.24.0
+)
+
+require (
+	github.com/andybalholm/brotli v1.0.4 // indirect
+	github.com/dustin/go-humanize v1.0.0 // indirect
+	github.com/google/uuid v1.3.0 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/klauspost/compress v1.15.9 // indirect
+	github.com/klauspost/cpuid/v2 v2.1.0 // indirect
+	github.com/minio/md5-simd v1.1.2 // indirect
+	github.com/minio/sha256-simd v1.0.0 // indirect
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.2 // indirect
+	github.com/rs/xid v1.4.0 // indirect
+	github.com/sirupsen/logrus v1.9.0 // indirect
+	github.com/valyala/bytebufferpool v1.0.0 // indirect
+	go.uber.org/atomic v1.7.0 // indirect
+	go.uber.org/goleak v1.1.12 // indirect
+	go.uber.org/multierr v1.6.0 // indirect
+	golang.org/x/crypto v0.0.0-20220722155217-630584e8d5aa // indirect
+	golang.org/x/net v0.0.0-20220906165146-f3363e06e74c // indirect
+	golang.org/x/sys v0.0.0-20220728004956-3c1f35247d10 // indirect
+	golang.org/x/text v0.3.7 // indirect
+	gopkg.in/ini.v1 v1.66.6 // indirect
+)
--- a/go.sum
+++ b/go.sum
@ -0,0 +1,107 @@
+github.com/andybalholm/brotli v1.0.4 h1:V7DdXeJtZscaqfNuAdSRuRFzuiKlHSC/Zh3zl9qY3JY=
+github.com/andybalholm/brotli v1.0.4/go.mod h1:fO7iG3H7G2nSZ7m0zPUDn85XEX2GTukHGRSepvi9Eig=
+github.com/benbjohnson/clock v1.1.0 h1:Q92kusRqC1XV2MjkWETPvjJVqKetz1OzxZB7mHJLju8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/dustin/go-humanize v1.0.0 h1:VSnTsYCnlFHaM2/igO1h6X3HA71jcobQuxemgkq4zYo=
+github.com/dustin/go-humanize v1.0.0/go.mod h1:HtrtbFcZ19U5GC7JDqmcUSB87Iq5E25KnS6fMYU6eOk=
+github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
+github.com/google/uuid v1.3.0 h1:t6JiXgmwXMjEs8VusXIJk2BXHsn+wx8BZdTaoZ5fu7I=
+github.com/google/uuid v1.3.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/joho/godotenv v1.4.0 h1:3l4+N6zfMWnkbPEXKng2o2/MR5mSwTrBih4ZEkkz1lg=
+github.com/joho/godotenv v1.4.0/go.mod h1:f4LDr5Voq0i2e/R5DDNOoa2zzDfwtkZa6DnEwAbqwq4=
+github.com/json-iterator/go v1.1.12 h1:PV8peI4a0ysnczrg+LtxykD8LfKY9ML6u2jnxaEnrnM=
+github.com/json-iterator/go v1.1.12/go.mod h1:e30LSqwooZae/UwlEbR2852Gd8hjQvJoHmT4TnhNGBo=
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--- a/main.go
+++ b/main.go
@ -0,0 +1,88 @@
+package main
+
+import (
+	"flag"
+	"os"
+	"strconv"
+
+	_ "github.com/joho/godotenv/autoload"
+	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
+)
+
+var (
+	httpAddr string
+	logLevel string
+	// obsSignedUrlExpiry time.Duration
+	zapLogLevel   zapcore.Level
+	postFlagParse = []func(){}
+)
+
+func init() {
+	var err error
+	_ = err
+
+	// app
+	flag.StringVar(&httpAddr, "addr", os.Getenv("HTTP_ADDR"), "Server address")
+
+	// log
+	flag.StringVar(&logLevel, "log-level", os.Getenv("LOG_LEVEL"), "Log level")
+	qpostFlagParse(func() {
+		err := zapLogLevel.UnmarshalText([]byte(logLevel))
+		if err != nil {
+			zapLogLevel = zapcore.InfoLevel
+		}
+	})
+
+	// OBS
+	flag.StringVar(&defaultObsOpts.Endpoint, "obs-endpoint", os.Getenv("OBS_ENDPOINT"), "OBS host")
+	flag.StringVar(&defaultObsOpts.Region, "obs-region", os.Getenv("OBS_REGION"), "OBS region")
+	flag.BoolVar(&defaultObsOpts.Secure, "obs-secure", ok1(strconv.ParseBool(os.Getenv("OBS_SECURE"))), "OBS secure transport")
+	flag.StringVar(&defaultObsOpts.BucketName, "obs-bucket", os.Getenv("OBS_BUCKET_NAME"), "OBS bucket name")
+
+	flag.StringVar(&defaultObsOpts.HostRedirect, "obs-host-redirect", os.Getenv("OBS_HOST_REDIRECT"), "OBS host redirect")
+
+	// obsSignedUrlExpiry, err = time.ParseDuration(os.Getenv("OBS_SIGNED_URL_EXPIRY"))
+	// if err != nil {
+	// 	// max signed value
+	// 	obsSignedUrlExpiry = time.Duration(^uint64(0) / 2)
+	// }
+	// flag.DurationVar(&obsSignedUrlExpiry, "obs-signed-url-expiry", obsSignedUrlExpiry, "OBS ")
+}
+
+func qpostFlagParse(f func()) {
+	postFlagParse = append(postFlagParse, f)
+}
+func qpostFlagParseInvoke() {
+	for _, f := range postFlagParse {
+		f()
+	}
+}
+
+func main() {
+	flag.Parse()
+	qpostFlagParseInvoke()
+
+	zcfg := zap.NewProductionConfig()
+	zcfg.Level = zap.NewAtomicLevelAt(zapLogLevel)
+
+	logger := unwrap1(zcfg.Build())
+	defer logger.Sync()
+
+	sug := logger.Named("main").Sugar()
+	sug.Infow("starting",
+		"log_level", zapLogLevel,
+		"obs_endpoint", defaultObsOpts.Endpoint,
+		"obs_host_redirect", defaultObsOpts.HostRedirect,
+	)
+
+	client := unwrap1(newObsClient(defaultObsOpts))
+	srv.Init(serverOptions{
+		Addr:   httpAddr,
+		Logger: logger.Named("server"),
+		OBS:    &defaultObsOpts,
+		S3:     client,
+	})
+
+	srv.Run()
+}
--- a/obs.go
+++ b/obs.go
@ -0,0 +1,102 @@
+package main
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/url"
+	"reflect"
+	"unsafe"
+
+	"github.com/minio/minio-go/v7"
+	"github.com/minio/minio-go/v7/pkg/credentials"
+
+	_ "unsafe"
+)
+
+type obsOptions struct {
+	Endpoint   string
+	Region     string
+	Secure     bool
+	BucketName string
+
+	HostRedirect string
+}
+
+var defaultObsOpts obsOptions
+
+func newObsClient(opts obsOptions) (*minio.Client, error) {
+	client, err := minio.New(opts.Endpoint, &minio.Options{
+		Creds:        credentials.NewEnvAWS(),
+		BucketLookup: minio.BucketLookupAuto, // vhost / path
+		Region:       opts.Region,
+		Secure:       opts.Secure,
+	})
+	if err != nil {
+		return nil, err
+	}
+	setOverrideSignerType(client, credentials.SignatureV2)
+	return client, nil
+}
+
+var (
+	offsetCredsProvider      uintptr
+	offsetOverrideSignerType uintptr
+)
+
+func init() {
+	vt := reflect.TypeOf(minio.Client{})
+	if field, ok := vt.FieldByName("credsProvider"); ok {
+		offsetCredsProvider = field.Offset
+	} else {
+		panic("cannot find credsProvider field")
+	}
+
+	if field, ok := vt.FieldByName("overrideSignerType"); ok {
+		offsetOverrideSignerType = field.Offset
+	} else {
+		panic("cannot find overrideSignerType field")
+	}
+}
+
+func getCredsProvider(client *minio.Client) *credentials.Credentials {
+	return *(**credentials.Credentials)(unsafe.Add(unsafe.Pointer(client), offsetCredsProvider))
+}
+
+func setOverrideSignerType(client *minio.Client, signerType credentials.SignatureType) {
+	ptr := (*credentials.SignatureType)(unsafe.Add(unsafe.Pointer(client), offsetOverrideSignerType))
+	*ptr = signerType
+}
+
+//go:linkname isVirtualHostStyleRequest github.com/minio/minio-go/v7.(*Client).isVirtualHostStyleRequest
+func isVirtualHostStyleRequest(client *minio.Client, url url.URL, bucketName string) bool
+
+//go:linkname makeTargetURL github.com/minio/minio-go/v7.(*Client).makeTargetURL
+func makeTargetURL(client *minio.Client, bucketName, objectName, bucketLocation string, isVirtualHostStyle bool, queryValues url.Values) (*url.URL, error)
+
+// requestMetadata - is container for all the values to make a request.
+type requestMetadata struct {
+	// If set newRequest presigns the URL.
+	presignURL bool
+
+	// User supplied.
+	bucketName         string
+	objectName         string
+	queryValues        url.Values
+	customHeader       http.Header
+	extraPresignHeader http.Header
+	expires            int64
+
+	// Generated by our internal code.
+	bucketLocation   string
+	contentBody      io.Reader
+	contentLength    int64
+	contentMD5Base64 string // carries base64 encoded md5sum
+	contentSHA256Hex string // carries hex encoded sha256sum
+	streamSha256     bool
+	addCrc           bool
+	trailer          http.Header // (http.Request).Trailer. Requires v4 signature.
+}
+
+//go:linkname newRequest github.com/minio/minio-go/v7.(*Client).newRequest
+func newRequest(client *minio.Client, ctx context.Context, method string, metadata requestMetadata) (req *http.Request, err error)
--- a/obs_test.go
+++ b/obs_test.go
@ -0,0 +1,29 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"strconv"
+	"testing"
+
+	"github.com/minio/minio-go/v7/pkg/s3utils"
+	"github.com/minio/minio-go/v7/pkg/signer"
+)
+
+func TestObsSignerV2(t *testing.T) {
+	req, err := http.NewRequest(http.MethodGet, "/test/mk/603d83c0-5083-44b0-87cb-7030ef28c43f.jpg", nil)
+	if err != nil {
+		t.Fail()
+	}
+
+	exp := strconv.FormatInt(int64(^uint64(0)/2), 10) // ~250years
+	req.Header.Set("Expires", exp)
+	req.URL.RawQuery = ""
+	reqVal := signer.PreSignV2(*req, "asd", "asdasd", 0, true)
+	query := reqVal.URL.Query()
+	query.Set("Expires", exp)
+	reqVal.URL.RawQuery = s3utils.QueryEncode(query)
+
+	fmt.Println(reqVal.URL)
+
+}
--- a/server.go
+++ b/server.go
@ -0,0 +1,146 @@
+package main
+
+import (
+	"bytes"
+	"net/http"
+	"net/url"
+	"strconv"
+	"time"
+
+	"github.com/minio/minio-go/v7"
+	"github.com/minio/minio-go/v7/pkg/s3utils"
+	"github.com/minio/minio-go/v7/pkg/signer"
+	"github.com/valyala/fasthttp"
+	"go.uber.org/zap"
+)
+
+var (
+	MethodGet  = []byte(http.MethodGet)
+	MethodHead = []byte(http.MethodHead)
+)
+
+type serverOptions struct {
+	Addr   string
+	Logger *zap.Logger
+	OBS    *obsOptions
+
+	ObjectExpiry time.Duration
+
+	S3 *minio.Client
+}
+
+type server struct {
+	opts   serverOptions
+	logger *zap.SugaredLogger
+}
+
+var srv server
+
+func (s *server) Init(opts serverOptions) {
+	s.opts = opts
+	s.logger = opts.Logger.Sugar()
+}
+
+func (s *server) reportError(ctx *fasthttp.RequestCtx, errType string, err any) {
+	s.logger.Errorw("handler error",
+		"kind", errType,
+		"err", err)
+	ctx.Response.Header.Set("x-error-code", errType)
+	switch errVal := err.(type) {
+	case []byte:
+		ctx.Response.Header.Set("x-error-message", unsafeByteSliceToString(errVal))
+	case string:
+		ctx.Response.Header.Set("x-error-message", errVal)
+	case error:
+		ctx.Response.Header.Set("x-error-message", errVal.Error())
+	default:
+		ctx.Response.Header.Set("x-error-message", "unknown error")
+	}
+}
+
+var (
+	ErrKind_ResourceNotFound = "OBS_RESOURCE_NOT_FOUND"
+	ErrKind_MethodNotAllowed = "OBS_METHOD_NOT_ALLOWED"
+	ErrKind_S3ComposeRequest = "S3_COMPOSE_REQUEST"
+	ErrKind_S3CredsProvider  = "S3_CREDS_PROVIDER"
+)
+
+func (s *server) handle(ctx *fasthttp.RequestCtx) {
+	ctx.Response.Header.Set("server", "obs-access-signer")
+	isMethodGet := bytes.Equal(ctx.Method(), MethodGet)
+	isMethodHead := bytes.Equal(ctx.Method(), MethodHead)
+	if !isMethodGet && !isMethodHead {
+		ctx.SetStatusCode(http.StatusMethodNotAllowed)
+		s.reportError(ctx, ErrKind_MethodNotAllowed, "")
+		return
+	}
+
+	if isMethodHead {
+		// Doc: https://www.rfc-editor.org/rfc/rfc9110.html#section-9.3.2-1
+		ctx.Response.Header.Set("Content-Length", "0")
+	}
+
+	bucketName := s.opts.OBS.BucketName
+	isVirtualHostStyle := isVirtualHostStyleRequest(s.opts.S3, *s.opts.S3.EndpointURL(), bucketName)
+
+	path := ctx.Path()
+	_path := bytes.TrimLeft(path, "/")
+	objectName := unsafeByteSliceToString(_path)
+	if _, _objectName, found := bytes.Cut(_path, []byte(bucketName)); !isVirtualHostStyle &&
+		bytes.HasPrefix(_path, []byte(bucketName)) &&
+		found {
+		_objectName = bytes.TrimLeft(_objectName, "/")
+		objectName = unsafeByteSliceToString(_objectName)
+	}
+
+	// check if we had access to the object
+	if _, err := s.opts.S3.StatObject(ctx, bucketName, objectName, minio.GetObjectOptions{}); err != nil {
+		ctx.SetStatusCode(http.StatusNotFound)
+		s.reportError(ctx, ErrKind_ResourceNotFound, err)
+		return
+	}
+
+	// compose initial request
+	req, err := newRequest(s.opts.S3, ctx, http.MethodGet, requestMetadata{
+		presignURL:  true,
+		bucketName:  bucketName,
+		objectName:  objectName,
+		expires:     1, // to trigger presigned generator
+		queryValues: url.Values{},
+	})
+	if err != nil {
+		ctx.SetStatusCode(http.StatusInternalServerError)
+		s.reportError(ctx, ErrKind_S3ComposeRequest, err)
+		return
+	}
+
+	// grab creds from provider
+	value, err := getCredsProvider(s.opts.S3).Get()
+	if err != nil {
+		ctx.SetStatusCode(http.StatusInternalServerError)
+		s.reportError(ctx, ErrKind_S3CredsProvider, err)
+		return
+	}
+
+	// clear given params, set max signed value for expire, and re-presign.
+	exp := strconv.FormatInt(int64(^uint64(0)/2), 10) // ~250years
+	req.Header.Set("Expires", exp)
+	req.URL.RawQuery = ""
+	req = signer.PreSignV2(*req, value.AccessKeyID, value.SecretAccessKey, 0, isVirtualHostStyle)
+
+	// re-encode query string with Expires hack.
+	query := req.URL.Query()
+	query.Set("Expires", exp)
+	req.URL.RawQuery = s3utils.QueryEncode(query)
+	if hostRedirect := s.opts.OBS.HostRedirect; hostRedirect != "" {
+		req.URL.Host = hostRedirect
+	}
+
+	ctx.Redirect(req.URL.String(), http.StatusMovedPermanently)
+}
+
+func (s *server) Run() {
+	s.logger.Infow("running server",
+		"addr", s.opts.Addr)
+	fasthttp.ListenAndServe(s.opts.Addr, s.handle)
+}
--- a/util.go
+++ b/util.go
@ -0,0 +1,25 @@
+package main
+
+import "unsafe"
+
+func ok1[T any](res T, err error) T {
+	return res
+}
+
+func option1[T any](res T, err error) (T, bool) {
+	return res, err != nil
+}
+
+func unwrap0(err error) {
+	if err != nil {
+		panic(err)
+	}
+}
+func unwrap1[T any](res T, err error) T {
+	unwrap0(err)
+	return res
+}
+
+func unsafeByteSliceToString(b []byte) string {
+	return *(*string)(unsafe.Pointer(&b))
+}
--- a/util_test.go
+++ b/util_test.go
@ -0,0 +1,13 @@
+package main
+
+import "testing"
+
+func TestUnsafeByteSliceToString(t *testing.T) {
+	exp := "foo bar"
+	act := unsafeByteSliceToString([]byte(exp))
+	if exp != act { // cmp str
+		t.Fail()
+	}
+	println(&exp, &act)
+	println(exp, act)
+}