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forgejo/modules/avatar/hash.go
Gusted 96797fed31
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>
2023-01-02 22:46:39 +01:00

28 lines
978 B
Go

// Copyright 2023 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package avatar
import (
"crypto/sha256"
"encoding/hex"
"strconv"
)
// HashAvatar will generate a unique string, which ensures that when there's a
// different unique ID while the data is the same, it will generate a different
// output. It will generate the output according to:
// HEX(HASH(uniqueID || - || data))
// The hash being used is SHA256.
// The sole purpose of the unique ID is to generate a distinct hash Such that
// two unique IDs with the same data will have a different hash output.
// The "-" byte is important to ensure that data cannot be modified such that
// the first byte is a number, which could lead to a "collision" with the hash
// of another unique ID.
func HashAvatar(uniqueID int64, data []byte) string {
h := sha256.New()
h.Write([]byte(strconv.FormatInt(uniqueID, 10)))
h.Write([]byte{'-'})
h.Write(data)
return hex.EncodeToString(h.Sum(nil))
}