/
caching_sha2.go
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/
caching_sha2.go
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// Copyright 2021 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package auth
// Resources:
// - https://dev.mysql.com/doc/refman/8.0/en/caching-sha2-pluggable-authentication.html
// - https://dev.mysql.com/doc/dev/mysql-server/latest/page_caching_sha2_authentication_exchanges.html
// - https://dev.mysql.com/doc/dev/mysql-server/latest/namespacesha2__password.html
// - https://www.akkadia.org/drepper/SHA-crypt.txt
// - https://dev.mysql.com/worklog/task/?id=9591
//
// CREATE USER 'foo'@'%' IDENTIFIED BY 'foobar';
// SELECT HEX(authentication_string) FROM mysql.user WHERE user='foo';
// 24412430303524031A69251C34295C4B35167C7F1E5A7B63091349503974624D34504B5A424679354856336868686F52485A736E4A733368786E427575516C73446469496537
//
// Format:
// Split on '$':
// - digest type ("A")
// - iterations (divided by ITERATION_MULTIPLIER)
// - salt+hash
//
import (
"bytes"
"crypto/rand"
"crypto/sha256"
"errors"
"fmt"
"strconv"
)
const (
// MIXCHARS is the number of characters to use in the mix
MIXCHARS = 32
// SALT_LENGTH is the length of the salt
SALT_LENGTH = 20 //nolint: revive
// ITERATION_MULTIPLIER is the number of iterations to use
ITERATION_MULTIPLIER = 1000 //nolint: revive
)
func b64From24bit(b []byte, n int, buf *bytes.Buffer) {
b64t := []byte("./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz")
w := (int64(b[0]) << 16) | (int64(b[1]) << 8) | int64(b[2])
for n > 0 {
n--
buf.WriteByte(b64t[w&0x3f])
w >>= 6
}
}
func sha256crypt(plaintext string, salt []byte, iterations int) string {
// Numbers in the comments refer to the description of the algorithm on https://www.akkadia.org/drepper/SHA-crypt.txt
// 1, 2, 3
bufA := bytes.NewBuffer(make([]byte, 0, 4096))
bufA.Write([]byte(plaintext))
bufA.Write(salt)
// 4, 5, 6, 7, 8
bufB := bytes.NewBuffer(make([]byte, 0, 4096))
bufB.Write([]byte(plaintext))
bufB.Write(salt)
bufB.Write([]byte(plaintext))
sumB := sha256.Sum256(bufB.Bytes())
bufB.Reset()
// 9, 10
var i int
for i = len(plaintext); i > MIXCHARS; i -= MIXCHARS {
bufA.Write(sumB[:MIXCHARS])
}
bufA.Write(sumB[:i])
// 11
for i = len(plaintext); i > 0; i >>= 1 {
if i%2 == 0 {
bufA.Write([]byte(plaintext))
} else {
bufA.Write(sumB[:])
}
}
// 12
sumA := sha256.Sum256(bufA.Bytes())
bufA.Reset()
// 13, 14, 15
bufDP := bufA
for range []byte(plaintext) {
bufDP.Write([]byte(plaintext))
}
sumDP := sha256.Sum256(bufDP.Bytes())
bufDP.Reset()
// 16
p := make([]byte, 0, sha256.Size)
for i = len(plaintext); i > 0; i -= MIXCHARS {
if i > MIXCHARS {
p = append(p, sumDP[:]...)
} else {
p = append(p, sumDP[0:i]...)
}
}
// 17, 18, 19
bufDS := bufA
for i = 0; i < 16+int(sumA[0]); i++ {
bufDS.Write(salt)
}
sumDS := sha256.Sum256(bufDS.Bytes())
bufDS.Reset()
// 20
s := make([]byte, 0, 32)
for i = len(salt); i > 0; i -= MIXCHARS {
if i > MIXCHARS {
s = append(s, sumDS[:]...)
} else {
s = append(s, sumDS[0:i]...)
}
}
// 21
bufC := bufA
var sumC [32]byte
for i = 0; i < iterations; i++ {
bufC.Reset()
if i&1 != 0 {
bufC.Write(p)
} else {
bufC.Write(sumA[:])
}
if i%3 != 0 {
bufC.Write(s)
}
if i%7 != 0 {
bufC.Write(p)
}
if i&1 != 0 {
bufC.Write(sumA[:])
} else {
bufC.Write(p)
}
sumC = sha256.Sum256(bufC.Bytes())
sumA = sumC
}
// 22
buf := bytes.NewBuffer(make([]byte, 0, 100))
buf.Write([]byte{'$', 'A', '$'})
rounds := fmt.Sprintf("%03d", iterations/ITERATION_MULTIPLIER)
buf.Write([]byte(rounds))
buf.Write([]byte{'$'})
buf.Write(salt)
b64From24bit([]byte{sumC[0], sumC[10], sumC[20]}, 4, buf)
b64From24bit([]byte{sumC[21], sumC[1], sumC[11]}, 4, buf)
b64From24bit([]byte{sumC[12], sumC[22], sumC[2]}, 4, buf)
b64From24bit([]byte{sumC[3], sumC[13], sumC[23]}, 4, buf)
b64From24bit([]byte{sumC[24], sumC[4], sumC[14]}, 4, buf)
b64From24bit([]byte{sumC[15], sumC[25], sumC[5]}, 4, buf)
b64From24bit([]byte{sumC[6], sumC[16], sumC[26]}, 4, buf)
b64From24bit([]byte{sumC[27], sumC[7], sumC[17]}, 4, buf)
b64From24bit([]byte{sumC[18], sumC[28], sumC[8]}, 4, buf)
b64From24bit([]byte{sumC[9], sumC[19], sumC[29]}, 4, buf)
b64From24bit([]byte{0, sumC[31], sumC[30]}, 3, buf)
return buf.String()
}
// CheckShaPassword is to checks if a MySQL style caching_sha2 authentication string matches a password
func CheckShaPassword(pwhash []byte, password string) (bool, error) {
pwhashParts := bytes.Split(pwhash, []byte("$"))
if len(pwhashParts) != 4 {
return false, errors.New("failed to decode hash parts")
}
hashType := string(pwhashParts[1])
if hashType != "A" {
return false, errors.New("digest type is incompatible")
}
iterations, err := strconv.Atoi(string(pwhashParts[2]))
if err != nil {
return false, errors.New("failed to decode iterations")
}
iterations = iterations * ITERATION_MULTIPLIER
salt := pwhashParts[3][:SALT_LENGTH]
newHash := sha256crypt(password, salt, iterations)
return bytes.Equal(pwhash, []byte(newHash)), nil
}
// NewSha2Password creates a new MySQL style caching_sha2 password hash
func NewSha2Password(pwd string) string {
salt := make([]byte, SALT_LENGTH)
rand.Read(salt)
// Restrict to 7-bit to avoid multi-byte UTF-8
for i := range salt {
salt[i] = salt[i] &^ 128
for salt[i] == 36 || salt[i] == 0 { // '$' or NUL
newval := make([]byte, 1)
rand.Read(newval)
salt[i] = newval[0] &^ 128
}
}
return sha256crypt(pwd, salt, 5*ITERATION_MULTIPLIER)
}