Token types, download verification

1 files changed, 138 insertions, 20 deletions

diff --git a/cmd/git-lfs-server/main.go b/cmd/git-lfs-server/main.go
index 191a696..c7feeff 100644
--- a/cmd/git-lfs-server/main.go
+++ b/cmd/git-lfs-server/main.go
@@ -163,19 +163,35 @@ func (h *handler) handleDownloadObject(ctx context.Context, repo string, obj par
                 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)
+                return makeObjError(obj, "Object corrupted", http.StatusUnprocessableEntity)
         }
         if info.Size != obj.size {
-                return makeObjError(obj, "Incorrect size specified for object", http.StatusUnprocessableEntity)
+                return makeObjError(obj, "Incorrect size specified for object or object currupted", http.StatusUnprocessableEntity)
         }
 
-        presigned, err := h.mc.PresignedGetObject(ctx, h.bucket, fullPath, expiresIn, url.Values{})
+        claims := handleObjectCustomClaims{
+                Gitolfs3: handleObjectGitolfs3Claims{
+                        Type:       "basic-transfer",
+                        Operation:  operationDownload,
+                        Repository: repo,
+                        OID:        obj.fullHash,
+                        Size:       obj.size,
+                },
+                RegisteredClaims: &jwt.RegisteredClaims{
+                        IssuedAt:  jwt.NewNumericDate(time.Now()),
+                        ExpiresAt: jwt.NewNumericDate(time.Now().Add(expiresIn)),
+                },
+        }
+
+        token := jwt.NewWithClaims(jwt.SigningMethodEdDSA, claims)
+        ss, err := token.SignedString(h.privateKey)
         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)
+                reqlog(ctx, "Fatal: failed to generate JWT: %s", err)
+                return makeObjError(obj, "Failed to generate token", http.StatusInternalServerError)
         }
+        uploadPath := path.Join(repo+".git", "info/lfs/objects", obj.firstByte, obj.secondByte, obj.fullHash)
 
         authenticated := true
         return batchResponseObject{
@@ -184,21 +200,26 @@ func (h *handler) handleDownloadObject(ctx context.Context, repo string, obj par
                 Authenticated: &authenticated,
                 Actions: map[operation]batchAction{
                         operationDownload: {
-                                HRef:      presigned.String(),
+                                Header: map[string]string{
+                                        "Authorization": "Bearer " + ss,
+                                },
+                                HRef:      h.baseURL.ResolveReference(&url.URL{Path: uploadPath}).String(),
                                 ExpiresIn: int64(expiresIn.Seconds()),
                         },
                 },
         }
 }
 
-type uploadObjectGitolfs3Claims struct {
-        Repository string `json:"repository"`
-        OID        string `json:"oid"`
-        Size       int64  `json:"size"`
+type handleObjectGitolfs3Claims struct {
+        Type       string    `json:"type"`
+        Operation  operation `json:"operation"`
+        Repository string    `json:"repository"`
+        OID        string    `json:"oid"`
+        Size       int64     `json:"size"`
 }
 
-type uploadObjectCustomClaims struct {
-        Gitolfs3 uploadObjectGitolfs3Claims `json:"gitolfs3"`
+type handleObjectCustomClaims struct {
+        Gitolfs3 handleObjectGitolfs3Claims `json:"gitolfs3"`
         *jwt.RegisteredClaims
 }
 
@@ -221,8 +242,10 @@ func (h *handler) handleUploadObject(ctx context.Context, repo string, obj parse
         }
 
         expiresIn := time.Hour * 24
-        claims := uploadObjectCustomClaims{
-                Gitolfs3: uploadObjectGitolfs3Claims{
+        claims := handleObjectCustomClaims{
+                Gitolfs3: handleObjectGitolfs3Claims{
+                        Type:       "basic-transfer",
+                        Operation:  operationUpload,
                         Repository: repo,
                         OID:        obj.fullHash,
                         Size:       obj.size,
@@ -327,7 +350,7 @@ func (h *handler) handlePutObject(w http.ResponseWriter, r *http.Request, repo,
         }
         authz = strings.TrimPrefix(authz, "Bearer ")
 
-        var claims uploadObjectCustomClaims
+        var claims handleObjectCustomClaims
         _, err := jwt.ParseWithClaims(authz, &claims, func(token *jwt.Token) (any, error) {
                 if _, ok := token.Method.(*jwt.SigningMethodEd25519); !ok {
                         return nil, fmt.Errorf("expected signing method EdDSA, got %s", token.Header["alg"])
@@ -338,6 +361,10 @@ func (h *handler) handlePutObject(w http.ResponseWriter, r *http.Request, repo,
                 makeRespError(ctx, w, "Invalid token", http.StatusUnauthorized)
                 return
         }
+        if claims.Gitolfs3.Type != "basic-transfer" {
+                makeRespError(ctx, w, "Invalid token", http.StatusUnauthorized)
+                return
+        }
         if claims.Gitolfs3.Repository != repo {
                 makeRespError(ctx, w, "Invalid token", http.StatusUnauthorized)
                 return
@@ -346,6 +373,10 @@ func (h *handler) handlePutObject(w http.ResponseWriter, r *http.Request, repo,
                 makeRespError(ctx, w, "Invalid token", http.StatusUnauthorized)
                 return
         }
+        if claims.Gitolfs3.Operation != operationUpload {
+                makeRespError(ctx, w, "Invalid token", http.StatusUnauthorized)
+                return
+        }
 
         // Check with claims
         if lengthStr := r.Header.Get("Content-Length"); lengthStr != "" {
@@ -387,6 +418,85 @@ func (h *handler) handlePutObject(w http.ResponseWriter, r *http.Request, repo,
         }
 }
 
+func (h *handler) handleGetObject(w http.ResponseWriter, r *http.Request, repo, oid string) {
+        ctx := r.Context()
+
+        authz := r.Header.Get("Authorization")
+        if authz == "" {
+                makeRespError(ctx, w, "Missing Authorization header", http.StatusBadRequest)
+                return
+        }
+        if !strings.HasPrefix(authz, "Bearer ") {
+                makeRespError(ctx, w, "Invalid Authorization header", http.StatusBadRequest)
+                return
+        }
+        authz = strings.TrimPrefix(authz, "Bearer ")
+
+        var claims handleObjectCustomClaims
+        _, err := jwt.ParseWithClaims(authz, &claims, func(token *jwt.Token) (any, error) {
+                if _, ok := token.Method.(*jwt.SigningMethodEd25519); !ok {
+                        return nil, fmt.Errorf("expected signing method EdDSA, got %s", token.Header["alg"])
+                }
+                return h.privateKey.Public(), nil
+        })
+        if err != nil {
+                makeRespError(ctx, w, "Invalid token", http.StatusUnauthorized)
+                return
+        }
+        if claims.Gitolfs3.Type != "basic-transfer" {
+                makeRespError(ctx, w, "Invalid token", http.StatusUnauthorized)
+                return
+        }
+        if claims.Gitolfs3.Repository != repo {
+                makeRespError(ctx, w, "Invalid token", http.StatusUnauthorized)
+                return
+        }
+        if claims.Gitolfs3.OID != oid {
+                makeRespError(ctx, w, "Invalid token", http.StatusUnauthorized)
+                return
+        }
+        if claims.Gitolfs3.Operation != operationDownload {
+                makeRespError(ctx, w, "Invalid token", http.StatusUnauthorized)
+                return
+        }
+
+        sha256Raw, err := hex.DecodeString(oid)
+        if err != nil || len(sha256Raw) != sha256.Size {
+                makeRespError(ctx, w, "Invalid OID", http.StatusBadRequest)
+                return
+        }
+
+        fullPath := path.Join(repo+".git", "lfs/objects", oid[:2], oid[2:4], oid)
+        obj, err := h.mc.GetObject(ctx, h.bucket, fullPath, minio.GetObjectOptions{})
+
+        var resp minio.ErrorResponse
+        if errors.As(err, &resp) && resp.StatusCode != http.StatusNotFound {
+                makeRespError(ctx, w, "Not found", http.StatusNotFound)
+                return
+        } else if err != nil {
+                reqlog(ctx, "Failed to get object: %s", err)
+                makeRespError(ctx, w, "Failed to get object", http.StatusInternalServerError)
+                return
+        }
+
+        stat, err := obj.Stat()
+        if err != nil {
+                reqlog(ctx, "Failed to stat: %s", err)
+                makeRespError(ctx, w, "Internal server error", http.StatusInternalServerError)
+        }
+
+        if stat.Size != claims.Gitolfs3.Size {
+                reqlog(ctx, "Claims size does not match S3 object size")
+                makeRespError(ctx, w, "Internal server error", http.StatusInternalServerError)
+        }
+
+        vr := newValidatingReader(claims.Gitolfs3.Size, sha256Raw, obj)
+        _, err = io.Copy(w, vr)
+        if errors.Is(err, errBadSum) {
+                reqlog(ctx, "Bad object checksum")
+        }
+}
+
 type parsedBatchObject struct {
         firstByte  string
         secondByte string
@@ -414,6 +524,7 @@ var requestIDKey requestID
 
 // TODO: make a shared package for this
 type lfsAuthGitolfs3Claims struct {
+        Type       string    `json:"type"`
         Repository string    `json:"repository"`
         Permission operation `json:"permission"`
 }
@@ -448,7 +559,7 @@ func (h *handler) getGitoliteAccess(repo, user, gitolitePerm string, refspec *st
         return true, nil
 }
 
-func (h *handler) authorize(w http.ResponseWriter, r *http.Request, or operationRequest) bool {
+func (h *handler) authorizeBatchAPI(w http.ResponseWriter, r *http.Request, or operationRequest) bool {
         user := h.anonUser
         ctx := r.Context()
 
@@ -471,6 +582,10 @@ func (h *handler) authorize(w http.ResponseWriter, r *http.Request, or operation
                         return false
                 }
 
+                if claims.Gitolfs3.Type != "batch-api" {
+                        makeRespError(ctx, w, "Invalid token", http.StatusUnauthorized)
+                        return false
+                }
                 if claims.Gitolfs3.Repository != or.repository {
                         makeRespError(ctx, w, "Invalid token", http.StatusUnauthorized)
                         return false
@@ -539,7 +654,7 @@ func (h *handler) handleBatchAPI(w http.ResponseWriter, r *http.Request, repo st
         if body.Ref != nil {
                 or.refspec = &body.Ref.Name
         }
-        if !h.authorize(w, r.WithContext(ctx), or) {
+        if !h.authorizeBatchAPI(w, r.WithContext(ctx), or) {
                 return
         }
 
@@ -632,12 +747,15 @@ func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
                 repo := strings.TrimPrefix(path.Clean(submatches[1]), "/")
                 reqlog(ctx, "Handling object PUT for repository: %s, OID: %s", repo, oid)
 
-                if r.Method != http.MethodPut {
+                switch r.Method {
+                case http.MethodGet:
+                        h.handleGetObject(w, r.WithContext(ctx), repo, oid)
+                case http.MethodPut:
+                        h.handlePutObject(w, r.WithContext(ctx), repo, oid)
+                default:
                         makeRespError(ctx, w, "Method not allowed", http.StatusMethodNotAllowed)
-                        return
                 }
 
-                h.handlePutObject(w, r.WithContext(ctx), repo, oid)
                 return
         }