prot_auth.go

/*
  The MIT License (MIT)

  Copyright (c) 2015 Nirbhay Choubey

  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/

package mysql

import (
	"crypto/sha1"
	"encoding/binary"
)

//<!-- connection phase packets -->

// parseGreetingPacket parses handshake initialization packet received from
// the server.
func (c *Conn) parseGreetingPacket(b []byte) {
	var (
		off, n                       int
		authData                     []byte // authentication plugin data
		authDataLength               int
		authDataOff_1, authDataOff_2 int
	)

	off++                                                 // [0a] protocol version
	c.serverVersion, n = getNullTerminatedString(b[off:]) // server version (null-terminated)
	off += n

	c.connectionId = binary.LittleEndian.Uint32(b[off : off+4]) // connection ID
	off += 4

	// auth-plugin-data-part-1 (8 bytes) : note the offset & length
	authDataOff_1 = off
	authDataLength = 8
	off += 8

	off++ // [00] filler

	// capacity flags (lower 2 bytes)
	c.serverCapabilities = uint32(binary.LittleEndian.Uint16(b[off : off+2]))
	off += 2

	if len(b) > off {
		c.serverCharset = uint8(b[off])
		off++

		c.statusFlags = binary.LittleEndian.Uint16(b[off : off+2]) // status flags
		off += 2
		// capacity flags (upper 2 bytes)
		c.serverCapabilities |= (uint32(binary.LittleEndian.Uint16(b[off:off+2])) << 16)
		off += 2

		if (c.serverCapabilities & _CLIENT_PLUGIN_AUTH) != 0 {
			// update the auth plugin data length
			authDataLength = int(b[off])
			off++
		} else {
			off++ // [00]
		}

		off += 10 // reserved (all [00])

		if (c.serverCapabilities & _CLIENT_SECURE_CONNECTION) != 0 {
			// auth-plugin-data-part-2 : note the offset & update
			// the length (max(13, authDataLength- 8)
			if (authDataLength - 8) > 13 {
				authDataLength = 13 + 8
			}
			authDataOff_2 = off
			off += (authDataLength - 8)
			authDataLength-- // ignore the 13th 0x00 byte
		}
		authData = make([]byte, authDataLength)
		copy(authData[0:8], b[authDataOff_1:authDataOff_1+8])
		if authDataLength > 8 {
			copy(authData[8:], b[authDataOff_2:authDataOff_2+(authDataLength-8)])
		}

		c.authPluginData = authData

		if (c.serverCapabilities & _CLIENT_PLUGIN_AUTH) != 0 {
			// auth-plugin name (null-terminated)
			c.authPluginName, n = getNullTerminatedString(b[off:])
			off += n
		}
	}
}

// createHandshakeResponsePacket generates the handshake response packet.
func (c *Conn) createHandshakeResponsePacket() ([]byte, error) {
	var (
		authData           []byte // auth response data
		b                  []byte
		off, payloadLength int
		err                error
	)

	payloadLength = (4 + 4 + 1 + 23)

	authData = c.authResponseData()
	payloadLength += c.handshakeResponse2Length(len(authData))

	if b, err = c.buff.Reset(4 + payloadLength); err != nil {
		return nil, err
	}

	off += 4 // placeholder for protocol packet header
	off += c.populateHandshakeResponse1(b[off:])
	off += c.populateHandshakeResponse2(b[off:], authData)

	return b[0:off], nil
}

// createSSLRequestPacket generates the SSL request packet to initiate SSL
// handshake. It is sent to the server over plain connection after which the
// communication switches to SSL.
func (c *Conn) createSSLRequestPacket() ([]byte, error) {
	var (
		b                  []byte
		off, payloadLength int
		err                error
	)

	payloadLength = (4 + 4 + 1 + 23)

	if b, err = c.buff.Reset(4 + payloadLength); err != nil {
		return nil, err
	}

	off += 4
	off += c.populateHandshakeResponse1(b[4:])

	return b[0:off], nil
}

// populateHandshakeResponse1 populates the specified slice with the
// information from 1st part of protocol's handshake response packet
// (before user name) and returns the final offset.
func (c *Conn) populateHandshakeResponse1(b []byte) int {
	var off int

	// client capability flags
	binary.LittleEndian.PutUint32(b[off:off+4], c.p.clientCapabilities)
	off += 4

	// max packet size
	binary.LittleEndian.PutUint32(b[off:off+4], c.p.maxPacketSize)
	off += 4

	// client character set
	b[off] = byte(c.clientCharset) // client character set
	off++

	zerofy(b[off : off+23])
	off += 23 // reserved (all [0])

	return off
}

// populateHandshakeResponse2 populates the specified slice with the
// information from 2st part of protocol's handshake response packet
// (starting user name) and returns the final offset.
func (c *Conn) populateHandshakeResponse2(b []byte, authData []byte) int {
	var off int

	off += putNullTerminatedString(b[off:], c.p.username)

	if (c.serverCapabilities & _CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA) != 0 {
		off += putLenencString(b[off:], string(authData))
	} else if (c.serverCapabilities & _CLIENT_SECURE_CONNECTION) != 0 {
		b[off] = byte(len(authData))
		off++
		off += copy(b[off:], authData)
	} else {
		off += putNullTerminatedString(b[off:], string(authData))
	}

	if (c.p.schema != "") && ((c.serverCapabilities & _CLIENT_CONNECT_WITH_DB) != 0) {
		off += putNullTerminatedString(b[off:], c.p.schema)
	}

	if (c.serverCapabilities & _CLIENT_PLUGIN_AUTH) != 0 {
		off += putNullTerminatedString(b[off:], c.authPluginName)
	}

	if (c.serverCapabilities & _CLIENT_CONNECT_ATTRS) != 0 {
		// TODO: handle connection attributes
	}
	return off
}

// handshakeResponse2Length returns the extra payload length of the handshake
// response packet starting user name.
func (c *Conn) handshakeResponse2Length(authLength int) (length int) {
	length += (len(c.p.username) + 1) // null-terminated username
	length += authLength

	if (c.serverCapabilities & _CLIENT_CONNECT_WITH_DB) != 0 {
		length += (len(c.p.schema) + 1) // null-terminated schema name
	}

	if (c.serverCapabilities & _CLIENT_PLUGIN_AUTH) != 0 {
		length += (len(c.authPluginName) + 1) // null-terminated authentication plugin name
	}

	if (c.serverCapabilities & _CLIENT_CONNECT_ATTRS) != 0 {
		// TODO: handle connection attributes
	}
	return
}

// handshake performs handshake during connection establishment
func (c *Conn) handshake() error {
	var (
		b              []byte
		useSSL         bool
		useCompression bool
		err            error
	)

	// read handshake initialization packet.
	if b, err = c.readPacket(); err != nil {
		return err
	}

	c.parseGreetingPacket(b)

	// note : server capabilities can only be checked after receiving the
	// "greeting" packet
	if c.p.clientCapabilities&_CLIENT_SSL != 0 {
		if c.serverCapabilities&_CLIENT_SSL == 0 {
			// error: client requested for SSL but server doesn't
			// support SSL.
			return myError(ErrSSLSupport)
		} else {
			useSSL = true
		}
	}

	if c.p.clientCapabilities&_CLIENT_COMPRESS != 0 {
		if c.serverCapabilities&_CLIENT_COMPRESS == 0 {
			// error: client requested for packet compression but server doesn't
			// support compression protocol.
			return myError(ErrCompressionSupport)
		} else {
			useCompression = true
		}
	}

	if !useSSL {
		// send plain handshake response packet
		if b, err = c.createHandshakeResponsePacket(); err != nil {
			return err
		}
		if err = c.writePacket(b); err != nil {
			return err
		}
	} else {
		// send SSL request packet (1st part of handshake response
		// packet)
		if b, err = c.createSSLRequestPacket(); err != nil {
			return err
		}
		if err = c.writePacket(b); err != nil {
			return err
		}

		// switch to tls
		if err = c.sslConnect(); err != nil {
			return err
		}

		// <!-- SSL activated -->

		// now send the entire handshake response packet
		if b, err = c.createHandshakeResponsePacket(); err != nil {
			return err
		}
		if err = c.writePacket(b); err != nil {
			return err
		}
	}

	// read server response
	if b, err = c.readPacket(); err != nil {
		return err
	}

	switch b[0] {
	case _PACKET_ERR:
		c.parseErrPacket(b)
		return &c.e
	case _PACKET_OK:
		c.parseOkPacket(b)
	default:
		// TODO: invalid packet
	}

	if useCompression { // switch to compression protocol
		c.rw = &compressRW{}
		c.rw.init(c)
		// <!-- Compression activated -->
	}
	return nil
}

// authResponseData returns the authentication response data to be sent to the
// server.
func (c *Conn) authResponseData() []byte {
	return scramble41(c.p.password, c.authPluginData)
}

// scraamble41 returns a scramble buffer based on the following formula:
// SHA1(password) XOR SHA1("20-byte public seed from server" <concat> SHA1( SHA1( password)))
func scramble41(password string, seed []byte) (buf []byte) {
	if len(password) == 0 {
		return
	}

	hash := sha1.New()

	// stage 1: SHA1(password)
	hash.Write([]byte(password))
	hashStage1 := hash.Sum(nil)

	// stage 2: SHA1(SHA1(password))
	hash.Reset()
	hash.Write(hashStage1)
	hashStage2 := hash.Sum(nil)

	// SHA1("20-byte public seed from server" <concat> SHA1(SHA1(password)))
	hash.Reset()
	hash.Write(seed)
	hash.Write(hashStage2)
	buf = hash.Sum(nil)

	for i := 0; i < sha1.Size; i++ {
		buf[i] ^= hashStage1[i]
	}
	return
}