Unify hashing for avatar (#22289)
- Unify the hashing code for repository and user avatars into a function. - Use a sane hash function instead of MD5. - Only require hashing once instead of twice(w.r.t. hashing for user avatar). - Improve the comment for the hashing code of why it works. Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com> Co-authored-by: Yarden Shoham <hrsi88@gmail.com>
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4 changed files with 32 additions and 11 deletions
28
modules/avatar/hash.go
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28
modules/avatar/hash.go
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@ -0,0 +1,28 @@
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// Copyright 2023 The Gitea Authors. All rights reserved.
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// SPDX-License-Identifier: MIT
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package avatar
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import (
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"crypto/sha256"
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"encoding/hex"
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"strconv"
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)
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// HashAvatar will generate a unique string, which ensures that when there's a
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// different unique ID while the data is the same, it will generate a different
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// output. It will generate the output according to:
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// HEX(HASH(uniqueID || - || data))
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// The hash being used is SHA256.
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// The sole purpose of the unique ID is to generate a distinct hash Such that
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// two unique IDs with the same data will have a different hash output.
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// The "-" byte is important to ensure that data cannot be modified such that
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// the first byte is a number, which could lead to a "collision" with the hash
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// of another unique ID.
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func HashAvatar(uniqueID int64, data []byte) string {
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h := sha256.New()
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h.Write([]byte(strconv.FormatInt(uniqueID, 10)))
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h.Write([]byte{'-'})
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h.Write(data)
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return hex.EncodeToString(h.Sum(nil))
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}
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@ -5,7 +5,6 @@ package repository
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import (
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"context"
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"crypto/md5"
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"fmt"
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"image/png"
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"io"
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@ -27,7 +26,7 @@ func UploadAvatar(repo *repo_model.Repository, data []byte) error {
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return err
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}
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newAvatar := fmt.Sprintf("%d-%x", repo.ID, md5.Sum(data))
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newAvatar := avatar.HashAvatar(repo.ID, data)
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if repo.Avatar == newAvatar { // upload the same picture
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return nil
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}
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@ -5,14 +5,13 @@ package repository
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import (
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"bytes"
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"crypto/md5"
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"fmt"
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"image"
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"image/png"
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"testing"
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repo_model "code.gitea.io/gitea/models/repo"
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"code.gitea.io/gitea/models/unittest"
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"code.gitea.io/gitea/modules/avatar"
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"github.com/stretchr/testify/assert"
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)
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@ -28,7 +27,7 @@ func TestUploadAvatar(t *testing.T) {
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err := UploadAvatar(repo, buff.Bytes())
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assert.NoError(t, err)
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assert.Equal(t, fmt.Sprintf("%d-%x", 10, md5.Sum(buff.Bytes())), repo.Avatar)
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assert.Equal(t, avatar.HashAvatar(10, buff.Bytes()), repo.Avatar)
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}
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func TestUploadBigAvatar(t *testing.T) {
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@ -5,7 +5,6 @@ package user
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import (
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"context"
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"crypto/md5"
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"fmt"
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"image/png"
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"io"
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@ -241,11 +240,7 @@ func UploadAvatar(u *user_model.User, data []byte) error {
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defer committer.Close()
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u.UseCustomAvatar = true
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// Different users can upload same image as avatar
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// If we prefix it with u.ID, it will be separated
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// Otherwise, if any of the users delete his avatar
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// Other users will lose their avatars too.
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u.Avatar = fmt.Sprintf("%x", md5.Sum([]byte(fmt.Sprintf("%d-%x", u.ID, md5.Sum(data)))))
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u.Avatar = avatar.HashAvatar(u.ID, data)
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if err = user_model.UpdateUserCols(ctx, u, "use_custom_avatar", "avatar"); err != nil {
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return fmt.Errorf("updateUser: %w", err)
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}
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