aboutsummaryrefslogtreecommitdiffstats
path: root/cmd/git-lfs-server/main.go
blob: c76c5d9af8383d44652995e907ee1b9c5d528834 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
package main

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"mime"
	"net/http"
	"net/http/cgi"
	"net/url"
	"os"
	"os/exec"
	"path"
	"regexp"
	"slices"
	"strings"
	"time"
	"unicode"

	"github.com/minio/minio-go/v7"
	"github.com/minio/minio-go/v7/pkg/credentials"
	"github.com/rs/xid"
)

type operation string
type transferAdapter string
type hashAlgo string

const (
	operationDownload    operation       = "download"
	operationUpload      operation       = "upload"
	transferAdapterBasic transferAdapter = "basic"
	hashAlgoSHA256       hashAlgo        = "sha256"
)

const lfsMIME = "application/vnd.git-lfs+json"

type batchRef struct {
	Name string `json:"name"`
}

type batchRequestObject struct {
	OID  string `json:"oid"`
	Size uint64 `json:"size"`
}

type batchRequest struct {
	Operation operation            `json:"operation"`
	Transfers []transferAdapter    `json:"transfers,omitempty"`
	Ref       *batchRef            `json:"ref,omitempty"`
	Objects   []batchRequestObject `json:"objects"`
	HashAlgo  hashAlgo             `json:"hash_algo,omitempty"`
}

type batchAction struct {
	HRef   string            `json:"href"`
	Header map[string]string `json:"header,omitempty"`
	// In seconds.
	ExpiresIn int64 `json:"expires_in,omitempty"`
	// expires_at (RFC3339) could also be used, but we leave it out since we
	// don't use it.
}

type batchError struct {
	Code    int    `json:"code"`
	Message string `json:"message"`
}

type batchResponseObject struct {
	OID           string                    `json:"oid"`
	Size          uint64                    `json:"size"`
	Authenticated *bool                     `json:"authenticated"`
	Actions       map[operation]batchAction `json:"actions,omitempty"`
	Error         *batchError               `json:"error,omitempty"`
}

type batchResponse struct {
	Transfer transferAdapter       `json:"transfer,omitempty"`
	Objects  []batchResponseObject `json:"objects"`
	HashAlgo hashAlgo              `json:"hash_algo,omitempty"`
}

type handler struct {
	mc           *minio.Client
	bucket       string
	anonUser     string
	gitolitePath string
}

// Requires lowercase hash
func isValidSHA256Hash(hash string) bool {
	if len(hash) != 64 {
		return false
	}
	for _, c := range hash {
		if !unicode.Is(unicode.ASCII_Hex_Digit, c) {
			return false
		}
	}
	return true
}

type lfsError struct {
	Message          string `json:"message"`
	DocumentationURL string `json:"documentation_url,omitempty"`
	RequestID        string `json:"request_id,omitempty"`
}

func makeRespError(ctx context.Context, w http.ResponseWriter, message string, code int) {
	err := lfsError{Message: message}
	if val := ctx.Value(requestIDKey); val != nil {
		err.RequestID = val.(string)
	}
	w.Header().Set("Content-Type", lfsMIME+"; charset=utf-8")
	w.WriteHeader(code)
	json.NewEncoder(w).Encode(err)
}

func makeObjError(obj parsedBatchObject, message string, code int) batchResponseObject {
	return batchResponseObject{
		OID:  obj.fullHash,
		Size: obj.size,
		Error: &batchError{
			Message: message,
			Code:    code,
		},
	}
}

func (h *handler) handleDownloadObject(ctx context.Context, repo string, obj parsedBatchObject) batchResponseObject {
	fullPath := path.Join(repo+".git", "lfs/objects", obj.firstByte, obj.secondByte, obj.fullHash)
	expiresIn := time.Hour * 24

	info, err := h.mc.StatObject(ctx, h.bucket, fullPath, minio.StatObjectOptions{Checksum: true})
	if err != nil {
		var resp minio.ErrorResponse
		if errors.As(err, &resp) && resp.StatusCode == http.StatusNotFound {
			return makeObjError(obj, "Object does not exist", http.StatusNotFound)
		}
		// TODO: consider not making this an object-specific, but rather a
		// generic error such that the entire Batch API request fails.
		reqlog(ctx, "Failed to query object information (full path: %s): %s", fullPath, err)
		return makeObjError(obj, "Failed to query object information", http.StatusInternalServerError)
	}
	if info.ChecksumSHA256 != "" && strings.ToLower(info.ChecksumSHA256) != obj.fullHash {
		return makeObjError(obj, "Corrupted file", http.StatusUnprocessableEntity)
	}
	if uint64(info.Size) != obj.size {
		return makeObjError(obj, "Incorrect size specified for object", http.StatusUnprocessableEntity)
	}

	presigned, err := h.mc.PresignedGetObject(ctx, h.bucket, fullPath, expiresIn, url.Values{})
	if err != nil {
		// TODO: consider not making this an object-specific, but rather a
		// generic error such that the entire Batch API request fails.
		reqlog(ctx, "Failed to generate action href (full path: %s): %s", fullPath, err)
		return makeObjError(obj, "Failed to generate action href", http.StatusInternalServerError)
	}

	authenticated := true
	return batchResponseObject{
		OID:           obj.fullHash,
		Size:          obj.size,
		Authenticated: &authenticated,
		Actions: map[operation]batchAction{
			operationDownload: {
				HRef:      presigned.String(),
				ExpiresIn: int64(expiresIn.Seconds()),
			},
		},
	}
}

type parsedBatchObject struct {
	firstByte  string
	secondByte string
	fullHash   string
	size       uint64
}

func isLFSMediaType(t string) bool {
	if mediaType, params, err := mime.ParseMediaType(t); err == nil {
		if mediaType == lfsMIME {
			if params["charset"] == "" || strings.ToLower(params["charset"]) == "utf-8" {
				return true
			}
		}
	}
	return false
}

var re = regexp.MustCompile(`^([a-zA-Z0-9-_/]+)\.git/info/lfs/objects/batch$`)

type requestID struct{}

var requestIDKey requestID

func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	ctx := context.WithValue(r.Context(), requestIDKey, xid.New().String())

	reqPath := os.Getenv("PATH_INFO")
	if reqPath == "" {
		reqPath = r.URL.Path
	}
	reqlog(ctx, "reqPath: %s", reqPath)
	reqPath = strings.TrimPrefix(path.Clean(reqPath), "/")
	reqlog(ctx, "Cleaned reqPath: %s", reqPath)
	submatches := re.FindStringSubmatch(reqPath)
	if len(submatches) != 2 {
		reqlog(ctx, "Got path: %s, did not match regex", reqPath)
		makeRespError(ctx, w, "Not found", http.StatusNotFound)
		return
	}
	repo := strings.TrimPrefix(path.Clean(submatches[1]), "/")
	reqlog(ctx, "Repository: %s", repo)

	if !slices.ContainsFunc(r.Header.Values("Accept"), isLFSMediaType) {
		makeRespError(ctx, w, "Expected "+lfsMIME+" (with UTF-8 charset) in list of acceptable response media types", http.StatusNotAcceptable)
		return
	}
	if !isLFSMediaType(r.Header.Get("Content-Type")) {
		makeRespError(ctx, w, "Expected request Content-Type to be "+lfsMIME+" (with UTF-8 charset)", http.StatusUnsupportedMediaType)
		return
	}

	var body batchRequest
	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
		makeRespError(ctx, w, "Failed to parse request body as JSON", http.StatusBadRequest)
		return
	}

	if body.HashAlgo != hashAlgoSHA256 {
		makeRespError(ctx, w, "Unsupported hash algorithm specified", http.StatusConflict)
		return
	}

	// TODO: handle authentication
	// right now, we're just trying to make everything publically accessible
	if body.Operation == operationUpload {
		makeRespError(ctx, w, "Upload operations are currently not supported", http.StatusForbidden)
		return
	}

	if len(body.Transfers) != 0 && !slices.Contains(body.Transfers, transferAdapterBasic) {
		makeRespError(ctx, w, "Unsupported transfer adapter specified (supported: basic)", http.StatusConflict)
		return
	}

	gitoliteArgs := []string{"access", "-q", repo, h.anonUser, "R"}
	if body.Ref != nil && body.Ref.Name != "" {
		gitoliteArgs = append(gitoliteArgs, body.Ref.Name)
	}
	cmd := exec.Command(h.gitolitePath, gitoliteArgs...)
	err := cmd.Run()
	permGranted := err == nil
	var exitErr *exec.ExitError
	if err != nil && !errors.As(err, &exitErr) {
		reqlog(ctx, "Error checking access info (running %s): %s", cmd, err)
		makeRespError(ctx, w, "Failed to query access information", http.StatusInternalServerError)
		return
	}
	if !permGranted {
		// TODO: when handling authorization, make sure to return 403 Forbidden
		// here when the user *does* have read permissions, but is not allowed
		// to write when requesting an upload operation.
		makeRespError(ctx, w, "Repository not found", http.StatusNotFound)
		return
	}

	var objects []parsedBatchObject
	for _, obj := range body.Objects {
		oid := strings.ToLower(obj.OID)
		if !isValidSHA256Hash(oid) {
			makeRespError(ctx, w, "Invalid hash format in object ID", http.StatusBadRequest)
			return
		}
		objects = append(objects, parsedBatchObject{
			firstByte:  oid[:2],
			secondByte: oid[2:4],
			fullHash:   oid,
			size:       obj.Size,
		})
	}

	resp := batchResponse{
		Transfer: transferAdapterBasic,
		HashAlgo: hashAlgoSHA256,
	}
	for _, obj := range objects {
		resp.Objects = append(resp.Objects, h.handleDownloadObject(ctx, repo, obj))
	}

	w.Header().Set("Content-Type", lfsMIME)
	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(resp)
}

func reqlog(ctx context.Context, msg string, args ...any) {
	fmt.Fprint(os.Stderr, "[gitolfs3] ")
	if val := ctx.Value(requestIDKey); val != nil {
		fmt.Fprintf(os.Stderr, "[%s] ", val.(string))
	}
	fmt.Fprintf(os.Stderr, msg, args...)
	fmt.Fprint(os.Stderr, "\n")
}

func log(msg string, args ...any) {
	fmt.Fprint(os.Stderr, "[gitolfs3] ")
	fmt.Fprintf(os.Stderr, msg, args...)
	fmt.Fprint(os.Stderr, "\n")
}

func die(msg string, args ...any) {
	log(msg, args...)
	os.Exit(1)
}

func main() {
	log("Environment variables:")
	for _, s := range os.Environ() {
		log("  %s", s)
	}

	anonUser := os.Getenv("ANON_USER")
	endpoint := os.Getenv("S3_ENDPOINT")
	bucket := os.Getenv("S3_BUCKET")
	accessKeyIDFile := os.Getenv("S3_ACCESS_KEY_ID_FILE")
	secretAccessKeyFile := os.Getenv("S3_SECRET_ACCESS_KEY_FILE")
	gitolitePath := os.Getenv("GITOLITE_PATH")

	if gitolitePath == "" {
		gitolitePath = "gitolite"
	}

	if anonUser == "" {
		die("Fatal: expected environment variable ANON_USER to be set")
	}
	if endpoint == "" {
		die("Fatal: expected environment variable S3_ENDPOINT to be set")
	}
	if bucket == "" {
		die("Fatal: expected environment variable S3_BUCKET to be set")
	}

	if accessKeyIDFile == "" {
		die("Fatal: expected environment variable S3_ACCESS_KEY_ID_FILE to be set")
	}
	if secretAccessKeyFile == "" {
		die("Fatal: expected environment variable S3_SECRET_ACCESS_KEY_FILE to be set")
	}

	accessKeyID, err := os.ReadFile(accessKeyIDFile)
	if err != nil {
		die("Fatal: failed to read access key ID from specified file: %s", err)
	}
	secretAccessKey, err := os.ReadFile(secretAccessKeyFile)
	if err != nil {
		die("Fatal: failed to read secret access key from specified file: %s", err)
	}

	mc, err := minio.New(endpoint, &minio.Options{
		Creds:  credentials.NewStaticV4(string(accessKeyID), string(secretAccessKey), ""),
		Secure: true,
	})
	if err != nil {
		die("Fatal: failed to create S3 client: %s", err)
	}

	if err = cgi.Serve(&handler{mc, bucket, anonUser, gitolitePath}); err != nil {
		die("Fatal: failed to serve CGI: %s", err)
	}
}

// Directory stucture:
// - lfs/
//   - locks/
//   - objects/
//     - <1st OID byte>
//       - <2nd OID byte>
//         - <OID hash> <- this is the object