nim-eth/eth/p2p/auth.nim

550 lines
18 KiB
Nim

#
# Ethereum P2P
# (c) Copyright 2018
# Status Research & Development GmbH
#
# Licensed under either of
# Apache License, version 2.0, (LICENSE-APACHEv2)
# MIT license (LICENSE-MIT)
#
## This module implements Ethereum authentication
{.push raises: [Defect].}
import
nimcrypto/[rijndael, keccak, utils],
stew/[arrayops, byteutils, endians2, objects, results],
".."/[keys, rlp],
./ecies
export results
const
SupportedRlpxVersion* = 4'u8
PlainAuthMessageV4Length* = 194
AuthMessageV4Length* = 307
PlainAuthMessageEIP8Length = 169
PlainAuthMessageMaxEIP8* = PlainAuthMessageEIP8Length + 255
AuthMessageEIP8Length* = 282 + 2
AuthMessageMaxEIP8* = AuthMessageEIP8Length + 255
PlainAckMessageV4Length* = 97
AckMessageV4Length* = 210
PlainAckMessageEIP8Length* = 102
PlainAckMessageMaxEIP8* = PlainAckMessageEIP8Length + 255
AckMessageEIP8Length* = 215 + 2
AckMessageMaxEIP8* = AckMessageEIP8Length + 255
type
Nonce* = array[KeyLength, byte]
AuthMessageV4* {.packed.} = object
signature: array[RawSignatureSize, byte]
keyhash: array[keccak256.sizeDigest, byte]
pubkey: array[RawPublicKeySize, byte]
nonce: array[keccak256.sizeDigest, byte]
flag: byte
AckMessageV4* {.packed.} = object
pubkey: array[RawPublicKeySize, byte]
nonce: array[keccak256.sizeDigest, byte]
flag: byte
HandshakeFlag* = enum
Initiator, ## `Handshake` owner is connection initiator
Responder, ## `Handshake` owner is connection responder
EIP8 ## Flag indicates that EIP-8 handshake is used
AuthError* = enum
EcdhError = "auth: ECDH shared secret could not be calculated"
BufferOverrun = "auth: buffer overrun"
SignatureError = "auth: signature could not be obtained"
EciesError = "auth: ECIES encryption/decryption error"
InvalidPubKey = "auth: invalid public key"
InvalidAuth = "auth: invalid Authentication message"
InvalidAck = "auth: invalid Authentication ACK message"
RlpError = "auth: error while decoding RLP stream"
IncompleteError = "auth: data incomplete"
Handshake* = object
version*: uint8 ## protocol version
flags*: set[HandshakeFlag] ## handshake flags
host*: KeyPair ## host keypair
ephemeral*: KeyPair ## ephemeral host keypair
remoteHPubkey*: PublicKey ## remote host public key
remoteEPubkey*: PublicKey ## remote host ephemeral public key
initiatorNonce*: Nonce ## initiator nonce
responderNonce*: Nonce ## responder nonce
expectedLength*: int ## expected incoming message length
ConnectionSecret* = object
aesKey*: array[aes256.sizeKey, byte]
macKey*: array[KeyLength, byte]
egressMac*: keccak256
ingressMac*: keccak256
AuthResult*[T] = Result[T, AuthError]
template toa(a, b, c: untyped): untyped =
toOpenArray((a), (b), (b) + (c) - 1)
proc mapErrTo[T, E](r: Result[T, E], v: static AuthError): AuthResult[T] =
r.mapErr(proc (e: E): AuthError = v)
proc init*(
T: type Handshake, rng: var HmacDrbgContext, host: KeyPair,
flags: set[HandshakeFlag] = {Initiator},
version: uint8 = SupportedRlpxVersion): T =
## Create new `Handshake` object.
var
initiatorNonce: Nonce
responderNonce: Nonce
expectedLength: int
ephemeral = KeyPair.random(rng)
if Initiator in flags:
expectedLength = AckMessageV4Length
rng.generate(initiatorNonce)
else:
expectedLength = AuthMessageV4Length
rng.generate(responderNonce)
return T(
version: version,
flags: flags,
host: host,
ephemeral: ephemeral,
initiatorNonce: initiatorNonce,
responderNonce: responderNonce,
expectedLength: expectedLength
)
proc authMessagePreEIP8(h: var Handshake,
rng: var HmacDrbgContext,
pubkey: PublicKey,
output: var openArray[byte],
outlen: var int,
flag: byte = 0,
encrypt: bool = true): AuthResult[void] =
## Create plain pre-EIP8 authentication message.
var
buffer: array[PlainAuthMessageV4Length, byte]
outlen = 0
let header = cast[ptr AuthMessageV4](addr buffer[0])
var secret = ecdhRaw(h.host.seckey, pubkey)
secret.data = secret.data xor h.initiatorNonce
let signature = sign(h.ephemeral.seckey, SkMessage(secret.data))
secret.clear()
h.remoteHPubkey = pubkey
header.signature = signature.toRaw()
header.keyhash = keccak256.digest(h.ephemeral.pubkey.toRaw()).data
header.pubkey = h.host.pubkey.toRaw()
header.nonce = h.initiatorNonce
header.flag = flag
if encrypt:
if len(output) < AuthMessageV4Length:
return err(AuthError.BufferOverrun)
if eciesEncrypt(rng, buffer, output, h.remoteHPubkey).isErr:
return err(AuthError.EciesError)
outlen = AuthMessageV4Length
else:
if len(output) < PlainAuthMessageV4Length:
return err(AuthError.BufferOverrun)
copyMem(addr output[0], addr buffer[0], PlainAuthMessageV4Length)
outlen = PlainAuthMessageV4Length
ok()
proc authMessageEIP8(h: var Handshake,
rng: var HmacDrbgContext,
pubkey: PublicKey,
output: var openArray[byte],
outlen: var int,
flag: byte = 0,
encrypt: bool = true): AuthResult[void] =
## Create EIP8 authentication message.
var
buffer: array[PlainAuthMessageMaxEIP8, byte]
doAssert(EIP8 in h.flags)
outlen = 0
var secret = ecdhRaw(h.host.seckey, pubkey)
secret.data = secret.data xor h.initiatorNonce
let signature = sign(h.ephemeral.seckey, SkMessage(secret.data))
secret.clear()
h.remoteHPubkey = pubkey
var payload = rlp.encodeList(signature.toRaw(),
h.host.pubkey.toRaw(),
h.initiatorNonce,
[byte(h.version)])
doAssert(len(payload) == PlainAuthMessageEIP8Length)
let
pencsize = eciesEncryptedLength(len(payload))
var padsize = int(rng.generate(byte)) # aka rand(max)
while padsize <= (AuthMessageV4Length - (pencsize + 2)):
padsize = int(rng.generate(byte))
# It is possible to make packet size constant by uncommenting this line
# padsize = 24
let
wosize = pencsize + padsize
fullsize = wosize + 2
rng.generate(toa(buffer, PlainAuthMessageEIP8Length, padsize))
if encrypt:
if len(output) < fullsize:
return err(AuthError.BufferOverrun)
copyMem(addr buffer[0], addr payload[0], len(payload))
let wosizeBE = uint16(wosize).toBytesBE()
output[0..<2] = wosizeBE
if eciesEncrypt(rng, toa(buffer, 0, len(payload) + padsize),
toa(output, 2, wosize), pubkey,
toa(output, 0, 2)).isErr:
return err(AuthError.EciesError)
outlen = fullsize
else:
let plainsize = len(payload) + padsize
if len(output) < plainsize:
return err(AuthError.BufferOverrun)
copyMem(addr output[0], addr buffer[0], plainsize)
outlen = plainsize
ok()
proc ackMessagePreEIP8(h: var Handshake,
rng: var HmacDrbgContext,
output: var openArray[byte],
outlen: var int,
flag: byte = 0,
encrypt: bool = true): AuthResult[void] =
## Create plain pre-EIP8 authentication ack message.
var buffer: array[PlainAckMessageV4Length, byte]
outlen = 0
let header = cast[ptr AckMessageV4](addr buffer[0])
header.pubkey = h.ephemeral.pubkey.toRaw()
header.nonce = h.responderNonce
header.flag = flag
if encrypt:
if len(output) < AckMessageV4Length:
return err(AuthError.BufferOverrun)
if eciesEncrypt(rng, buffer, output, h.remoteHPubkey).isErr:
return err(AuthError.EciesError)
outlen = AckMessageV4Length
else:
if len(output) < PlainAckMessageV4Length:
return err(AuthError.BufferOverrun)
copyMem(addr output[0], addr buffer[0], PlainAckMessageV4Length)
outlen = PlainAckMessageV4Length
ok()
proc ackMessageEIP8(h: var Handshake,
rng: var HmacDrbgContext,
output: var openArray[byte],
outlen: var int,
flag: byte = 0,
encrypt: bool = true): AuthResult[void] =
## Create EIP8 authentication ack message.
var
buffer: array[PlainAckMessageMaxEIP8, byte]
padsize: array[1, byte]
doAssert(EIP8 in h.flags)
var payload = rlp.encodeList(h.ephemeral.pubkey.toRaw(),
h.responderNonce,
[byte(h.version)])
doAssert(len(payload) == PlainAckMessageEIP8Length)
outlen = 0
let pencsize = eciesEncryptedLength(len(payload))
while true:
generate(rng, padsize)
if int(padsize[0]) > (AckMessageV4Length - (pencsize + 2)):
break
# It is possible to make packet size constant by uncommenting this line
# padsize = 0
let wosize = pencsize + int(padsize[0])
let fullsize = wosize + 2
if int(padsize[0]) > 0:
rng.generate(toa(buffer, PlainAckMessageEIP8Length, int(padsize[0])))
copyMem(addr buffer[0], addr payload[0], len(payload))
if encrypt:
if len(output) < fullsize:
return err(AuthError.BufferOverrun)
output[0..<2] = uint16(wosize).toBytesBE()
if eciesEncrypt(rng, toa(buffer, 0, len(payload) + int(padsize[0])),
toa(output, 2, wosize), h.remoteHPubkey,
toa(output, 0, 2)).isErr:
return err(AuthError.EciesError)
outlen = fullsize
else:
let plainsize = len(payload) + int(padsize[0])
if len(output) < plainsize:
return err(AuthError.BufferOverrun)
copyMem(addr output[0], addr buffer[0], plainsize)
outlen = plainsize
ok()
template authSize*(h: Handshake, encrypt: bool = true): int =
## Get number of bytes needed to store AuthMessage.
if EIP8 in h.flags:
if encrypt: (AuthMessageMaxEIP8) else: (PlainAuthMessageMaxEIP8)
else:
if encrypt: (AuthMessageV4Length) else: (PlainAuthMessageV4Length)
template ackSize*(h: Handshake, encrypt: bool = true): int =
## Get number of bytes needed to store AckMessage.
if EIP8 in h.flags:
if encrypt: (AckMessageMaxEIP8) else: (PlainAckMessageMaxEIP8)
else:
if encrypt: (AckMessageV4Length) else: (PlainAckMessageV4Length)
proc authMessage*(h: var Handshake, rng: var HmacDrbgContext,
pubkey: PublicKey,
output: var openArray[byte],
outlen: var int, flag: byte = 0,
encrypt: bool = true): AuthResult[void] =
## Create new AuthMessage for specified `pubkey` and store it inside
## of `output`, size of generated AuthMessage will stored in `outlen`.
if EIP8 in h.flags:
authMessageEIP8(h, rng, pubkey, output, outlen, flag, encrypt)
else:
authMessagePreEIP8(h, rng, pubkey, output, outlen, flag, encrypt)
proc ackMessage*(h: var Handshake, rng: var HmacDrbgContext,
output: var openArray[byte],
outlen: var int, flag: byte = 0,
encrypt: bool = true): AuthResult[void] =
## Create new AckMessage and store it inside of `output`, size of generated
## AckMessage will stored in `outlen`.
if EIP8 in h.flags:
ackMessageEIP8(h, rng, output, outlen, flag, encrypt)
else:
ackMessagePreEIP8(h, rng, output, outlen, flag, encrypt)
proc decodeAuthMessageV4(h: var Handshake, m: openArray[byte]): AuthResult[void] =
## Decodes V4 AuthMessage.
var
buffer: array[PlainAuthMessageV4Length, byte]
doAssert(Responder in h.flags)
if eciesDecrypt(m, buffer, h.host.seckey).isErr:
return err(EciesError)
let
header = cast[ptr AuthMessageV4](addr buffer[0])
pubkey = ? PublicKey.fromRaw(header.pubkey).mapErrTo(InvalidPubKey)
signature = ? Signature.fromRaw(header.signature).mapErrTo(SignatureError)
var secret = ecdhRaw(h.host.seckey, pubkey)
secret.data = secret.data xor header.nonce
var recovered = recover(signature, SkMessage(secret.data))
secret.clear()
h.remoteEPubkey = ? recovered.mapErrTo(SignatureError)
h.initiatorNonce = header.nonce
h.remoteHPubkey = pubkey
ok()
proc decodeAuthMessageEIP8(h: var Handshake, m: openArray[byte]): AuthResult[void] =
## Decodes EIP-8 AuthMessage.
let size = uint16.fromBytesBE(m)
h.expectedLength = int(size) + 2
if h.expectedLength > len(m):
return err(AuthError.IncompleteError)
var buffer = newSeq[byte](eciesDecryptedLength(int(size)))
if eciesDecrypt(toa(m, 2, int(size)), buffer, h.host.seckey,
toa(m, 0, 2)).isErr:
return err(AuthError.EciesError)
try:
var reader = rlpFromBytes(buffer)
if not reader.isList() or reader.listLen() < 4:
return err(AuthError.InvalidAuth)
if reader.listElem(0).blobLen != RawSignatureSize:
return err(AuthError.InvalidAuth)
if reader.listElem(1).blobLen != RawPublicKeySize:
return err(AuthError.InvalidAuth)
if reader.listElem(2).blobLen != KeyLength:
return err(AuthError.InvalidAuth)
if reader.listElem(3).blobLen != 1:
return err(AuthError.InvalidAuth)
let
signatureBr = reader.listElem(0).toBytes()
pubkeyBr = reader.listElem(1).toBytes()
nonceBr = reader.listElem(2).toBytes()
versionBr = reader.listElem(3).toBytes()
let
signature = ? Signature.fromRaw(signatureBr).mapErrTo(SignatureError)
pubkey = ? PublicKey.fromRaw(pubkeyBr).mapErrTo(InvalidPubKey)
nonce = toArray(KeyLength, nonceBr)
var secret = ecdhRaw(h.host.seckey, pubkey)
secret.data = secret.data xor nonce
let recovered = recover(signature, SkMessage(secret.data))
secret.clear()
h.remoteEPubkey = ? recovered.mapErrTo(SignatureError)
h.initiatorNonce = nonce
h.remoteHPubkey = pubkey
h.version = versionBr[0]
ok()
except CatchableError:
err(AuthError.RlpError)
proc decodeAckMessageEIP8*(h: var Handshake, m: openArray[byte]): AuthResult[void] =
## Decodes EIP-8 AckMessage.
let size = uint16.fromBytesBE(m)
h.expectedLength = 2 + int(size)
if h.expectedLength > len(m):
return err(AuthError.IncompleteError)
var buffer = newSeq[byte](eciesDecryptedLength(int(size)))
if eciesDecrypt(toa(m, 2, int(size)), buffer, h.host.seckey,
toa(m, 0, 2)).isErr:
return err(AuthError.EciesError)
try:
var reader = rlpFromBytes(buffer)
if not reader.isList() or reader.listLen() < 3:
return err(AuthError.InvalidAck)
if reader.listElem(0).blobLen != RawPublicKeySize:
return err(AuthError.InvalidAck)
if reader.listElem(1).blobLen != KeyLength:
return err(AuthError.InvalidAck)
if reader.listElem(2).blobLen != 1:
return err(AuthError.InvalidAck)
let
pubkeyBr = reader.listElem(0).toBytes()
nonceBr = reader.listElem(1).toBytes()
versionBr = reader.listElem(2).toBytes()
h.remoteEPubkey = ? PublicKey.fromRaw(pubkeyBr).mapErrTo(InvalidPubKey)
h.responderNonce = toArray(KeyLength, nonceBr)
h.version = versionBr[0]
ok()
except CatchableError:
err(AuthError.RlpError)
proc decodeAckMessageV4(h: var Handshake, m: openArray[byte]): AuthResult[void] =
## Decodes V4 AckMessage.
var
buffer: array[PlainAckMessageV4Length, byte]
doAssert(Initiator in h.flags)
if eciesDecrypt(m, buffer, h.host.seckey).isErr:
return err(AuthError.EciesError)
var header = cast[ptr AckMessageV4](addr buffer[0])
h.remoteEPubkey = ? PublicKey.fromRaw(header.pubkey).mapErrTo(InvalidPubKey)
h.responderNonce = header.nonce
ok()
proc decodeAuthMessage*(h: var Handshake, input: openArray[byte]): AuthResult[void] =
## Decodes AuthMessage from `input`.
if len(input) < AuthMessageV4Length:
return err(AuthError.IncompleteError)
if len(input) == AuthMessageV4Length:
let res = h.decodeAuthMessageV4(input)
if res.isOk(): return res
let res = h.decodeAuthMessageEIP8(input)
if res.isOk():
h.flags.incl(EIP8)
res
proc decodeAckMessage*(h: var Handshake, input: openArray[byte]): AuthResult[void] =
## Decodes AckMessage from `input`.
if len(input) < AckMessageV4Length:
return err(AuthError.IncompleteError)
if len(input) == AckMessageV4Length:
let res = h.decodeAckMessageV4(input)
if res.isOk(): return res
let res = h.decodeAckMessageEIP8(input)
if res.isOk(): h.flags.incl(EIP8)
res
proc getSecrets*(
h: Handshake, authmsg: openArray[byte],
ackmsg: openArray[byte]): ConnectionSecret =
## Derive secrets from handshake `h` using encrypted AuthMessage `authmsg` and
## encrypted AckMessage `ackmsg`.
var
ctx0: keccak256
ctx1: keccak256
mac1: MDigest[256]
secret: ConnectionSecret
# ecdhe-secret = ecdh.agree(ephemeral-privkey, remote-ephemeral-pubk)
var shsec = ecdhRaw(h.ephemeral.seckey, h.remoteEPubkey)
# shared-secret = keccak(ecdhe-secret || keccak(nonce || initiator-nonce))
ctx0.init()
ctx1.init()
ctx1.update(h.responderNonce)
ctx1.update(h.initiatorNonce)
mac1 = ctx1.finish()
ctx1.clear()
ctx0.update(shsec.data)
ctx0.update(mac1.data)
mac1 = ctx0.finish()
# aes-secret = keccak(ecdhe-secret || shared-secret)
ctx0.init()
ctx0.update(shsec.data)
ctx0.update(mac1.data)
mac1 = ctx0.finish()
# mac-secret = keccak(ecdhe-secret || aes-secret)
ctx0.init()
ctx0.update(shsec.data)
ctx0.update(mac1.data)
secret.aesKey = mac1.data
mac1 = ctx0.finish()
secret.macKey = mac1.data
clear(shsec)
# egress-mac = keccak256(mac-secret ^ recipient-nonce || auth-sent-init)
var xornonce = mac1.data xor h.responderNonce
ctx0.init()
ctx0.update(xornonce)
ctx0.update(authmsg)
# ingress-mac = keccak256(mac-secret ^ initiator-nonce || auth-recvd-ack)
xornonce = secret.macKey xor h.initiatorNonce
ctx1.init()
ctx1.update(xornonce)
ctx1.update(ackmsg)
burnMem(xornonce)
if Initiator in h.flags:
secret.egressMac = ctx0
secret.ingressMac = ctx1
else:
secret.ingressMac = ctx0
secret.egressMac = ctx1
ctx0.clear()
ctx1.clear()
secret