Add support for serializing/deserializing caching_sha2_password auth strings

go/mysql/auth_server.go

@@ -618,13 +618,18 @@ func (n *mysqlCachingSha2AuthMethod) HandleAuthPluginData(c *Conn, user string,
 		return result, nil
 	}
 	if !c.TLSEnabled() && !c.IsUnixSocket() {
-		return nil, NewSQLError(ERAccessDeniedError, SSAccessDeniedError, "Access denied for user '%v'", user)
+		return nil, NewSQLError(ERAccessDeniedError, SSAccessDeniedError,
+			"Access denied for user '%v' (not using TLS or Unix socket)", user)
 	}
-	data := c.startEphemeralPacket(1)
+
+	data := c.startEphemeralPacket(2)
 	pos := 0
 	pos = writeByte(data, pos, AuthMoreDataPacket)
 	writeByte(data, pos, CachingSha2FullAuth)
-	c.writeEphemeralPacket()
+	if err = c.writeEphemeralPacket(); err != nil {
+		return nil, err
+	}
+
 	password, err := readPacketPasswordString(c)
 	if err != nil {
 		return nil, err

go/mysql/auth_server_utils.go

@@ -0,0 +1,243 @@
+/*
+Copyright ApeCloud, Inc.
+Licensed under the Apache v2(found in the LICENSE file in the root directory).
+*/
+
+// NOTE: The logic in SerializeCachingSha2PasswordAuthString, and the b64From24bit and sha256Hash functions
+//       were taken from the wesql/wescale project (https://github.com/wesql/wescale) and is copyright ApeCloud, Inc.
+//       All other code in this file is copyright DoltHub, Inc.
+
+package mysql
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"fmt"
+	"strconv"
+)
+
+const (
+	// DefaultCachingSha2PasswordHashIterations is the default number of hashing iterations used (before the
+	// iterationMultiplier is applied) when hashing a password using the caching_sha2_password auth plugin.
+	DefaultCachingSha2PasswordHashIterations = 5
+
+	// mixChars is the number of characters to use in the mix
+	mixChars = 32
+
+	// iterationMultiplier is the multiplier applied to the number of hashing iterations the user has requested.
+	// For example, if the user requests 10 iterations, the actual number of iterations will be 10 * iterationMultiplier.
+	iterationMultiplier = 1000
+
+	// delimiter is used to separate the metadata fields in a caching_sha2_password authentication string.
+	delimiter = '$'
+
+	// saltLength is the length of the salt used in the caching_sha2_password authentication protocol.
+	saltLength = 20
+
+	// storedSha256DigestLength is the length of the base64 encoded sha256 digest in an auth string
+	storedSha256DigestLength = 43
+
+	// maxIterations is the maximum iterations (before the iterationMultiplier is applied) that can be used
+	// in the hasing process for the caching_sha2_password auth plugin. The iterations applied are not directly
+	// user-controllable, so realistically, this limit can't be breached.
+	maxIterations = 0xFFF
+)
+
+// DeserializeCachingSha2PasswordAuthString takes in |authStringBytes|, a caching_sha2_password auth plugin generated
+// authentication string, and parses out the individual components: the digest type, number of iterations, salt, and
+// the password hash. |iterations| is the number of iterations the hashing function has been through (not including
+// the internal iteration multiplier, 1,000). If any errors are encountered during parsing, such as the authentication
+// string bytes not having the expected format, an error is returned.
+//
+// The protocol for generating an auth string for the caching_sha2_password plugin is not documented, but the MySQL
+// source code can be found here: https://github.com/mysql/mysql-server/blob/trunk/sql/auth/sha2_password.cc#L440
+func DeserializeCachingSha2PasswordAuthString(authStringBytes []byte) (digestType string, iterations int, salt, digest []byte, err error) {
+	if authStringBytes[0] != delimiter {
+		return "", 0, nil, nil, fmt.Errorf(
+			"authentication string does not start with the expected delimiter '$'")
+	}
+
+	// Digest Type
+	digestTypeCode := authStringBytes[1]
+	switch digestTypeCode {
+	case 'A':
+		digestType = "SHA256"
+	default:
+		return "", 0, nil, nil, fmt.Errorf(
+			"unsupported digest type: %v", digestTypeCode)
+	}
+
+	// Validate the delimiter
+	if authStringBytes[2] != delimiter {
+		return "", 0, nil, nil, fmt.Errorf(
+			"authentication string does not contain with the expected delimiter '$' between digest type and iterations")
+	}
+
+	// Iterations
+	iterationsString := string(authStringBytes[3:6])
+	iterations32bit, err := strconv.ParseInt(iterationsString, 16, 32)
+	if err != nil {
+		return "", 0, nil, nil, fmt.Errorf(
+			"iterations specified in authentication string is not a valid integer: %v", iterationsString)
+	}
+	iterations = int(iterations32bit)
+
+	// Validate the delimiter
+	if authStringBytes[6] != delimiter {
+		return "", 0, nil, nil, fmt.Errorf(
+			"authentication string does not contain with the expected delimiter '$' between iterations and salt")
+	}
+
+	// Salt
+	salt = authStringBytes[7 : 7+saltLength]
+
+	// Digest
+	digest = authStringBytes[7+saltLength:]
+	if len(digest) != storedSha256DigestLength {
+		return "", 0, nil, nil, fmt.Errorf("Unexpected digest length: %v", len(digest))
+	}
+
+	return digestType, iterations, salt, digest, nil
+}
+
+// SerializeCachingSha2PasswordAuthString uses SHA256 hashing algorithm to hash a plaintext password (|plaintext|)
+// with the specified |salt|. The hashing is repeated |iterations| times. Note that |iterations| is the external,
+// user-controllable number of iterations BEFORE the iterations multipler (i.e. 1000) is applied. The return bytes
+// represent an authentication string compatible with the caching_sha2_password plugin authentication method.
+func SerializeCachingSha2PasswordAuthString(plaintext string, salt []byte, iterations int) ([]byte, error) {
+	if iterations > maxIterations {
+		return nil, fmt.Errorf("iterations value (%d) is greater than max allowed iterations (%d)", iterations, maxIterations)
+	}
+
+	// 1, 2, 3
+	bufA := bytes.NewBuffer(make([]byte, 0, 4096))
+	bufA.WriteString(plaintext)
+	bufA.Write(salt)
+
+	// 4, 5, 6, 7, 8
+	bufB := bytes.NewBuffer(make([]byte, 0, 4096))
+	bufB.WriteString(plaintext)
+	bufB.Write(salt)
+	bufB.WriteString(plaintext)
+	sumB := sha256Hash(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.WriteString(plaintext)
+		} else {
+			bufA.Write(sumB[:])
+		}
+	}
+
+	// 12
+	sumA := sha256Hash(bufA.Bytes())
+	bufA.Reset()
+
+	// 13, 14, 15
+	bufDP := bufA
+	for range []byte(plaintext) {
+		bufDP.WriteString(plaintext)
+	}
+	sumDP := sha256Hash(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 := sha256Hash(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 []byte
+	for i = 0; i < iterations*iterationMultiplier; 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 = sha256Hash(bufC.Bytes())
+		sumA = sumC
+	}
+	// 22
+	buf := bytes.NewBuffer(make([]byte, 0, 100))
+	buf.Write([]byte{'$', 'A', '$'})
+	rounds := fmt.Sprintf("%03X", iterations)
+	buf.WriteString(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 []byte(buf.String()), nil
+}
+
+// sha256Hash is a util function to calculate a sha256 hash.
+func sha256Hash(input []byte) []byte {
+	res := sha256.Sum256(input)
+	return res[:]
+}
+
+// b64From24bit is a util function to base64 encode up to 24 bits at a time (|n|) from the
+// byte slice |b| and writes the encoded data to |buf|.
+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
+	}
+}

go/mysql/auth_server_utils_test.go

@@ -0,0 +1,124 @@
+// Copyright 2024 Dolthub, 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,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mysql
+
+import (
+	"encoding/hex"
+	"strconv"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// TestDeserializeCachingSha2PasswordAuthString tests that MySQL-generated caching_sha2_password authentication strings
+// can be correctly deserialized into their component parts. We use a hex encoded string for the authentication string,
+// because it is binary data and displaying it as a string and copying/pasting it corrupts the data.
+func TestDeserializeCachingSha2PasswordAuthString(t *testing.T) {
+	tests := []struct {
+		hexEncodedAuthStringBytes string
+		expectedDigestType        string
+		expectedIterations        int
+		expectedSalt              []byte
+		expectedDigest            []byte
+		expectedErrorSubstring    string
+	}{
+		{
+			hexEncodedAuthStringBytes: "2441243030352434341F5017121D0420134615056D3519305C4C57507A4B4E584E482E5351544E324B2E44764B586566567243336F56367739736F61386E424B695741395443",
+			expectedDigestType:        "SHA256",
+			expectedIterations:        5,
+			expectedSalt:              []byte{52, 52, 31, 80, 23, 18, 29, 4, 32, 19, 70, 21, 5, 109, 53, 25, 48, 92, 76, 87},
+			expectedDigest: []byte{0x50, 0x7a, 0x4b, 0x4e, 0x58, 0x4e, 0x48, 0x2e, 0x53, 0x51, 0x54,
+				0x4e, 0x32, 0x4b, 0x2e, 0x44, 0x76, 0x4b, 0x58, 0x65, 0x66, 0x56, 0x72, 0x43, 0x33, 0x6f, 0x56,
+				0x36, 0x77, 0x39, 0x73, 0x6f, 0x61, 0x38, 0x6e, 0x42, 0x4b, 0x69, 0x57, 0x41, 0x39, 0x54, 0x43},
+		},
+		{
+			hexEncodedAuthStringBytes: "244124303035241A502F3D02576A0150494D096659325E017E08086E516B42326E5762733366615556756E6131666174354533594255684536356E79772F5971397876772F32",
+			expectedDigestType:        "SHA256",
+			expectedIterations:        5,
+			expectedSalt:              []byte{0x1a, 0x50, 0x2f, 0x3d, 0x2, 0x57, 0x6a, 0x1, 0x50, 0x49, 0x4d, 0x9, 0x66, 0x59, 0x32, 0x5e, 0x1, 0x7e, 0x8, 0x8},
+			expectedDigest: []byte{0x6e, 0x51, 0x6b, 0x42, 0x32, 0x6e, 0x57, 0x62, 0x73, 0x33, 0x66,
+				0x61, 0x55, 0x56, 0x75, 0x6e, 0x61, 0x31, 0x66, 0x61, 0x74, 0x35, 0x45, 0x33, 0x59, 0x42, 0x55,
+				0x68, 0x45, 0x36, 0x35, 0x6e, 0x79, 0x77, 0x2f, 0x59, 0x71, 0x39, 0x78, 0x76, 0x77, 0x2f, 0x32},
+		},
+
+		// TODO: Test malformed auth strings
+	}
+
+	for i, test := range tests {
+		t.Run(strconv.Itoa(i), func(t *testing.T) {
+			bytes, err := hex.DecodeString(test.hexEncodedAuthStringBytes)
+			require.NoError(t, err)
+
+			digestType, iterations, salt, digest, err := DeserializeCachingSha2PasswordAuthString(bytes)
+			if test.expectedErrorSubstring == "" {
+				require.NoError(t, err)
+				require.Equal(t, test.expectedDigestType, digestType)
+				require.Equal(t, test.expectedIterations, iterations)
+				require.Equal(t, test.expectedSalt, salt)
+				require.Equal(t, test.expectedDigest, digest)
+			} else {
+				require.Error(t, err)
+				require.Contains(t, err.Error(), test.expectedErrorSubstring)
+			}
+		})
+	}
+}
+
+// TestSerializeCachingSha2PasswordAuthString tests that we can generate a correct caching_sha2_password authentication
+// string from a password, salt, and number of iterations. We use a hex encoded string for the expected authentication
+// string, because it is binary data and displaying it as a string and copying/pasting it corrupts the data.
+func TestSerializeCachingSha2PasswordAuthString(t *testing.T) {
+	tests := []struct {
+		password                     string
+		salt                         []byte
+		iterations                   int
+		expectedHexEncodedAuthString string
+		expectedErrorSubstring       string
+	}{
+		{
+			password:                     "pass3",
+			salt:                         []byte{52, 52, 31, 80, 23, 18, 29, 4, 32, 19, 70, 21, 5, 109, 53, 25, 48, 92, 76, 87},
+			iterations:                   5,
+			expectedHexEncodedAuthString: "2441243030352434341F5017121D0420134615056D3519305C4C57507A4B4E584E482E5351544E324B2E44764B586566567243336F56367739736F61386E424B695741395443",
+		},
+		{
+			password:                     "pass1",
+			salt:                         []byte{0x1a, 0x50, 0x2f, 0x3d, 0x2, 0x57, 0x6a, 0x1, 0x50, 0x49, 0x4d, 0x9, 0x66, 0x59, 0x32, 0x5e, 0x1, 0x7e, 0x8, 0x8},
+			iterations:                   5,
+			expectedHexEncodedAuthString: "244124303035241A502F3D02576A0150494D096659325E017E08086E516B42326E5762733366615556756E6131666174354533594255684536356E79772F5971397876772F32",
+		},
+		{
+			// When an iteration count larger than 0xFFF is specified, an error should be returned
+			password:               "pass1",
+			salt:                   []byte{0x1a, 0x50, 0x2f, 0x3d, 0x2, 0x57, 0x6a, 0x1, 0x50, 0x49, 0x4d, 0x9, 0x66, 0x59, 0x32, 0x5e, 0x1, 0x7e, 0x8, 0x8},
+			iterations:             maxIterations + 1,
+			expectedErrorSubstring: "iterations value (4096) is greater than max allowed iterations (4095)",
+		},
+	}
+
+	for i, test := range tests {
+		t.Run(strconv.Itoa(i), func(t *testing.T) {
+			authStringBytes, err := SerializeCachingSha2PasswordAuthString(test.password, test.salt, test.iterations)
+			if test.expectedErrorSubstring == "" {
+				expectedBytes, err := hex.DecodeString(test.expectedHexEncodedAuthString)
+				require.NoError(t, err)
+				require.Equal(t, expectedBytes, authStringBytes)
+			} else {
+				require.Error(t, err)
+				require.Contains(t, err.Error(), test.expectedErrorSubstring)
+			}
+		})
+	}
+}