nwaku/waku/v2/waku_noise/noise_utils.nim

579 lines
23 KiB
Nim

# Waku Noise Protocols for Waku Payload Encryption
# Noise utilities module
## See spec for more details:
## https://github.com/vacp2p/rfc/tree/master/content/docs/rfcs/35
when (NimMajor, NimMinor) < (1, 4):
{.push raises: [Defect].}
else:
{.push raises: [].}
import std/[algorithm, base64, oids, options, strutils, tables, sequtils]
import chronos
import chronicles
import bearssl/rand
import stew/[results, endians2, byteutils]
import nimcrypto/[sha2, hmac]
import libp2p/crypto/[chacha20poly1305, curve25519, hkdf]
import ./noise_types
import ./noise
logScope:
topics = "waku noise"
#################################################################
#################################
# Generic Utilities
#################################
# Generates random byte sequences of given size
proc randomSeqByte*(rng: var HmacDrbgContext, size: int): seq[byte] =
var output = newSeq[byte](size.uint32)
hmacDrbgGenerate(rng, output)
return output
# Pads a payload according to PKCS#7 as per RFC 5652 https://datatracker.ietf.org/doc/html/rfc5652#section-6.3
proc pkcs7_pad*(payload: seq[byte], paddingSize: int): seq[byte] =
assert(paddingSize<256)
let k = paddingSize - (payload.len mod paddingSize)
var padding: seq[byte]
if k != 0:
padding = newSeqWith(k, k.byte)
else:
padding = newSeqWith(paddingSize, paddingSize.byte)
let padded = concat(payload, padding)
return padded
# Unpads a payload according to PKCS#7 as per RFC 5652 https://datatracker.ietf.org/doc/html/rfc5652#section-6.3
proc pkcs7_unpad*(payload: seq[byte], paddingSize: int): seq[byte] =
let k = payload[payload.high]
let unpadded = payload[0..payload.high-k.int]
return unpadded
proc seqToDigest256*(sequence: seq[byte]): MDigest[256] =
var digest: MDigest[256]
for i in 0..<digest.data.len:
digest.data[i] = sequence[i]
return digest
proc digestToSeq*[T](digest: MDigest[T]): seq[byte] =
var sequence: seq[byte]
for i in 0..<digest.data.len:
sequence.add digest.data[i]
return sequence
# Serializes input parameters to a base64 string for exposure through QR code (used by WakuPairing)
proc toQr*(applicationName: string, applicationVersion: string, shardId: string, ephemeralKey: EllipticCurveKey, committedStaticKey: MDigest[256]): string =
var qr: string
qr.add encode(applicationName, safe=true) & ":"
qr.add encode(applicationVersion, safe=true) & ":"
qr.add encode(shardId, safe=true) & ":"
qr.add encode(ephemeralKey, safe=true) & ":"
qr.add encode(committedStaticKey.data, safe=true)
return qr
# Deserializes input string in base64 to the corresponding (applicationName, applicationVersion, shardId, ephemeralKey, committedStaticKey)
proc fromQr*(qr: string): (string, string, string, EllipticCurveKey, MDigest[256]) {.raises: [Defect, ValueError].} =
let values = qr.split(":")
assert(values.len == 5)
let applicationName: string = decode(values[0])
let applicationVersion: string = decode(values[1])
let shardId: string = decode(values[2])
let decodedEphemeralKey = decode(values[3]).toBytes
var ephemeralKey: EllipticCurveKey
for i in 0..<ephemeralKey.len:
ephemeralKey[i] = decodedEphemeralKey[i]
let committedStaticKey = seqToDigest256(decode(values[4]).toBytes)
return (applicationName, applicationVersion, shardId, ephemeralKey, committedStaticKey)
# Converts a sequence or array (arbitrary size) to a MessageNametag
proc toMessageNametag*(input: openArray[byte]): MessageNametag =
var byte_seq: seq[byte] = @input
# We set its length to the default message nametag length (will be truncated or 0-padded)
byte_seq.setLen(MessageNametagLength)
# We copy it to a MessageNametag
var messageNametag: MessageNametag
for i in 0..<MessageNametagLength:
messageNametag[i] = byte_seq[i]
return messageNametag
# Uses the cryptographic information stored in the input handshake state to generate a random message nametag
# In current implementation the messageNametag = HKDF(handshake hash value), but other derivation mechanisms can be implemented
proc toMessageNametag*(hs: HandshakeState): MessageNametag =
var output: array[1, array[MessageNametagLength, byte]]
sha256.hkdf(hs.ss.h.data, [], [], output)
return output[0]
proc genMessageNametagSecrets*(hs: HandshakeState): (array[MessageNametagSecretLength, byte], array[MessageNametagSecretLength, byte]) =
var output: array[2, array[MessageNametagSecretLength, byte]]
sha256.hkdf(hs.ss.h.data, [], [], output)
return (output[0], output[1])
# Simple utility that checks if the given variable is "default",
# Therefore, it has not been initialized
proc isDefault*[T](value: T): bool =
value == static(default(T))
#################################################################
#################################
# Noise Handhshake Utilities
#################################
# Generate random (public, private) Elliptic Curve key pairs
proc genKeyPair*(rng: var HmacDrbgContext): KeyPair =
var keyPair: KeyPair
keyPair.privateKey = EllipticCurveKey.random(rng)
keyPair.publicKey = keyPair.privateKey.public()
return keyPair
# Gets private key from a key pair
proc getPrivateKey*(keypair: KeyPair): EllipticCurveKey =
return keypair.privateKey
# Gets public key from a key pair
proc getPublicKey*(keypair: KeyPair): EllipticCurveKey =
return keypair.publicKey
# Prints Handshake Patterns using Noise pattern layout
proc print*(self: HandshakePattern)
{.raises: [IOError, NoiseMalformedHandshake].}=
try:
if self.name != "":
stdout.write self.name, ":\n"
stdout.flushFile()
# We iterate over pre message patterns, if any
if self.preMessagePatterns != EmptyPreMessage:
for pattern in self.preMessagePatterns:
stdout.write " ", pattern.direction
var first = true
for token in pattern.tokens:
if first:
stdout.write " ", token
first = false
else:
stdout.write ", ", token
stdout.write "\n"
stdout.flushFile()
stdout.write " ...\n"
stdout.flushFile()
# We iterate over message patterns
for pattern in self.messagePatterns:
stdout.write " ", pattern.direction
var first = true
for token in pattern.tokens:
if first:
stdout.write " ", token
first = false
else:
stdout.write ", ", token
stdout.write "\n"
stdout.flushFile()
except CatchableError:
raise newException(NoiseMalformedHandshake, "HandshakePattern malformed")
# Hashes a Noise protocol name using SHA256
proc hashProtocol*(protocolName: string): MDigest[256] =
# The output hash value
var hash: MDigest[256]
# From Noise specification: Section 5.2
# http://www.noiseprotocol.org/noise.html#the-symmetricstate-object
# If protocol_name is less than or equal to HASHLEN bytes in length,
# sets h equal to protocol_name with zero bytes appended to make HASHLEN bytes.
# Otherwise sets h = HASH(protocol_name).
if protocolName.len <= 32:
hash.data[0..protocolName.high] = protocolName.toBytes
else:
hash = sha256.digest(protocolName)
return hash
# Commits a public key pk for randomness r as H(pk || s)
proc commitPublicKey*(publicKey: EllipticCurveKey, r: seq[byte]): MDigest[256] =
var hashInput: seq[byte]
hashInput.add getBytes(publicKey)
hashInput.add r
# The output hash value
var hash: MDigest[256]
hash = sha256.digest(hashInput)
return hash
# Generates an 8 decimal digits authorization code using HKDF and the handshake state
proc genAuthcode*(hs: HandshakeState): string =
var output: array[1, array[8, byte]]
sha256.hkdf(hs.ss.h.data, [], [], output)
let code = cast[uint64](output[0]) mod 100_000_000
return $code
# Initializes the empty Message nametag buffer. The n-th nametag is equal to HKDF( secret || n )
proc initNametagsBuffer*(mntb: var MessageNametagBuffer) =
# We default the counter and buffer fields
mntb.counter = 0
mntb.buffer = default(array[MessageNametagBufferSize, MessageNametag])
if mntb.secret.isSome:
for i in 0..<mntb.buffer.len:
mntb.buffer[i] = toMessageNametag(sha256.digest(@(mntb.secret.get()) & @(toBytesLE(mntb.counter))).data)
mntb.counter += 1
else:
# We warn users if no secret is set
debug "The message nametags buffer has not a secret set"
# Deletes the first n elements in buffer and appends n new ones
proc delete*(mntb: var MessageNametagBuffer, n: int) =
if n <= 0:
return
# We ensure n is at most MessageNametagBufferSize (the buffer will be fully replaced)
let n = min(n, MessageNametagBufferSize)
# We update the last n values in the array if a secret is set
# Note that if the input MessageNametagBuffer is set to default, nothing is done here
if mntb.secret.isSome:
# We rotate left the array by n
mntb.buffer.rotateLeft(n)
for i in 0..<n:
mntb.buffer[mntb.buffer.len-n+i] = toMessageNametag(sha256.digest(@(mntb.secret.get()) & @(toBytesLE(mntb.counter))).data)
mntb.counter += 1
else:
# We warn users that no secret is set
debug "The message nametags buffer has no secret set"
# Checks if the input messageNametag is contained in the input MessageNametagBuffer
proc checkNametag*(messageNametag: MessageNametag, mntb: var MessageNametagBuffer): Result[bool, cstring]
{.raises: [Defect, NoiseMessageNametagError, NoiseSomeMessagesWereLost].} =
let index = mntb.buffer.find(messageNametag)
if index == -1:
raise newException(NoiseMessageNametagError, "Message nametag not found in buffer")
elif index > 0:
raise newException(NoiseSomeMessagesWereLost, "Message nametag is present in buffer but is not the next expected nametag. One or more messages were probably lost")
# index is 0, hence the read message tag is the next expected one
return ok(true)
# Deletes the first n elements in buffer and appends n new ones
proc pop*(mntb: var MessageNametagBuffer): MessageNametag =
# Note that if the input MessageNametagBuffer is set to default, an all 0 messageNametag is returned
let messageNametag = mntb.buffer[0]
delete(mntb, 1)
return messageNametag
# Performs a Diffie-Hellman operation between two elliptic curve keys (one private, one public)
proc dh*(private: EllipticCurveKey, public: EllipticCurveKey): EllipticCurveKey =
# The output result of the Diffie-Hellman operation
var output: EllipticCurveKey
# Since the EC multiplication writes the result to the input, we copy the input to the output variable
output = public
# We execute the DH operation
EllipticCurve.mul(output, private)
return output
#################################################################
#################################
# ChaChaPoly Cipher utilities
#################################
# Generates a random ChaChaPolyKey for testing encryption/decryption
proc randomChaChaPolyKey*(rng: var HmacDrbgContext): ChaChaPolyKey =
var key: ChaChaPolyKey
hmacDrbgGenerate(rng, key)
return key
# Generates a random ChaChaPoly Cipher State for testing encryption/decryption
proc randomChaChaPolyCipherState*(rng: var HmacDrbgContext): ChaChaPolyCipherState =
var randomCipherState: ChaChaPolyCipherState
randomCipherState.k = randomChaChaPolyKey(rng)
hmacDrbgGenerate(rng, randomCipherState.nonce)
randomCipherState.ad = newSeq[byte](32)
hmacDrbgGenerate(rng, randomCipherState.ad)
return randomCipherState
#################################################################
#################################
# Noise Public keys utilities
#################################
# Checks equality between two Noise public keys
proc `==`*(k1, k2: NoisePublicKey): bool =
return (k1.flag == k2.flag) and (k1.pk == k2.pk)
# Converts a public Elliptic Curve key to an unencrypted Noise public key
proc toNoisePublicKey*(publicKey: EllipticCurveKey): NoisePublicKey =
var noisePublicKey: NoisePublicKey
noisePublicKey.flag = 0
noisePublicKey.pk = getBytes(publicKey)
return noisePublicKey
# Generates a random Noise public key
proc genNoisePublicKey*(rng: var HmacDrbgContext): NoisePublicKey =
var noisePublicKey: NoisePublicKey
# We generate a random key pair
let keyPair: KeyPair = genKeyPair(rng)
# Since it is unencrypted, flag is 0
noisePublicKey.flag = 0
# We copy the public X coordinate of the key pair to the output Noise public key
noisePublicKey.pk = getBytes(keyPair.publicKey)
return noisePublicKey
# Converts a Noise public key to a stream of bytes as in
# https://rfc.vac.dev/spec/35/#public-keys-serialization
proc serializeNoisePublicKey*(noisePublicKey: NoisePublicKey): seq[byte] =
var serializedNoisePublicKey: seq[byte]
# Public key is serialized as (flag || pk)
# Note that pk contains the X coordinate of the public key if unencrypted
# or the encryption concatenated with the authorization tag if encrypted
serializedNoisePublicKey.add noisePublicKey.flag
serializedNoisePublicKey.add noisePublicKey.pk
return serializedNoisePublicKey
# Converts a serialized Noise public key to a NoisePublicKey object as in
# https://rfc.vac.dev/spec/35/#public-keys-serialization
proc intoNoisePublicKey*(serializedNoisePublicKey: seq[byte]): NoisePublicKey
{.raises: [Defect, NoisePublicKeyError].} =
var noisePublicKey: NoisePublicKey
# We retrieve the encryption flag
noisePublicKey.flag = serializedNoisePublicKey[0]
# If not 0 or 1 we raise a new exception
if not (noisePublicKey.flag == 0 or noisePublicKey.flag == 1):
raise newException(NoisePublicKeyError, "Invalid flag in serialized public key")
# We set the remaining sequence to the pk value (this may be an encrypted or not encrypted X coordinate)
noisePublicKey.pk = serializedNoisePublicKey[1..<serializedNoisePublicKey.len]
return noisePublicKey
# Encrypts a Noise public key using a ChaChaPoly Cipher State
proc encryptNoisePublicKey*(cs: ChaChaPolyCipherState, noisePublicKey: NoisePublicKey): NoisePublicKey
{.raises: [Defect, NoiseEmptyChaChaPolyInput, NoiseNonceMaxError].} =
var encryptedNoisePublicKey: NoisePublicKey
# We proceed with encryption only if
# - a key is set in the cipher state
# - the public key is unencrypted
if cs.k != EmptyKey and noisePublicKey.flag == 0:
let encPk = encrypt(cs, noisePublicKey.pk)
# We set the flag to 1, since encrypted
encryptedNoisePublicKey.flag = 1
# Authorization tag is appendend to the ciphertext
encryptedNoisePublicKey.pk = encPk.data
encryptedNoisePublicKey.pk.add encPk.tag
# Otherwise we return the public key as it is
else:
encryptedNoisePublicKey = noisePublicKey
return encryptedNoisePublicKey
# Decrypts a Noise public key using a ChaChaPoly Cipher State
proc decryptNoisePublicKey*(cs: ChaChaPolyCipherState, noisePublicKey: NoisePublicKey): NoisePublicKey
{.raises: [Defect, NoiseEmptyChaChaPolyInput, NoiseDecryptTagError].} =
var decryptedNoisePublicKey: NoisePublicKey
# We proceed with decryption only if
# - a key is set in the cipher state
# - the public key is encrypted
if cs.k != EmptyKey and noisePublicKey.flag == 1:
# Since the pk field would contain an encryption + tag, we retrieve the ciphertext length
let pkLen = noisePublicKey.pk.len - ChaChaPolyTag.len
# We isolate the ciphertext and the authorization tag
let pk = noisePublicKey.pk[0..<pkLen]
let pkAuth = intoChaChaPolyTag(noisePublicKey.pk[pkLen..<pkLen+ChaChaPolyTag.len])
# We convert it to a ChaChaPolyCiphertext
let ciphertext = ChaChaPolyCiphertext(data: pk, tag: pkAuth)
# We run decryption and store its value to a non-encrypted Noise public key (flag = 0)
decryptedNoisePublicKey.pk = decrypt(cs, ciphertext)
decryptedNoisePublicKey.flag = 0
# Otherwise we return the public key as it is
else:
decryptedNoisePublicKey = noisePublicKey
return decryptedNoisePublicKey
#################################################################
#################################
# Payload encoding/decoding procedures
#################################
# Checks equality between two PayloadsV2 objects
proc `==`*(p1, p2: PayloadV2): bool =
return (p1.messageNametag == p2.messageNametag) and
(p1.protocolId == p2.protocolId) and
(p1.handshakeMessage == p2.handshakeMessage) and
(p1.transportMessage == p2.transportMessage)
# Generates a random PayloadV2
proc randomPayloadV2*(rng: var HmacDrbgContext): PayloadV2 =
var payload2: PayloadV2
# We set a random messageNametag
let randMessageNametag = randomSeqByte(rng, MessageNametagLength)
for i in 0..<MessageNametagLength:
payload2.messageNametag[i] = randMessageNametag[i]
# To generate a random protocol id, we generate a random 1-byte long sequence, and we convert the first element to uint8
payload2.protocolId = randomSeqByte(rng, 1)[0].uint8
# We set the handshake message to three unencrypted random Noise Public Keys
payload2.handshakeMessage = @[genNoisePublicKey(rng), genNoisePublicKey(rng), genNoisePublicKey(rng)]
# We set the transport message to a random 128-bytes long sequence
payload2.transportMessage = randomSeqByte(rng, 128)
return payload2
# Serializes a PayloadV2 object to a byte sequences according to https://rfc.vac.dev/spec/35/.
# The output serialized payload concatenates the input PayloadV2 object fields as
# payload = ( protocolId || serializedHandshakeMessageLen || serializedHandshakeMessage || transportMessageLen || transportMessage)
# The output can be then passed to the payload field of a WakuMessage https://rfc.vac.dev/spec/14/
proc serializePayloadV2*(self: PayloadV2): Result[seq[byte], cstring] =
# We collect public keys contained in the handshake message
var
# According to https://rfc.vac.dev/spec/35/, the maximum size for the handshake message is 256 bytes, that is
# the handshake message length can be represented with 1 byte only. (its length can be stored in 1 byte)
# However, to ease public keys length addition operation, we declare it as int and later cast to uit8
serializedHandshakeMessageLen: int = 0
# This variables will store the concatenation of the serializations of all public keys in the handshake message
serializedHandshakeMessage = newSeqOfCap[byte](256)
# A variable to store the currently processed public key serialization
serializedPk: seq[byte]
# For each public key in the handshake message
for pk in self.handshakeMessage:
# We serialize the public key
serializedPk = serializeNoisePublicKey(pk)
# We sum its serialized length to the total
serializedHandshakeMessageLen += serializedPk.len
# We add its serialization to the concatenation of all serialized public keys in the handshake message
serializedHandshakeMessage.add serializedPk
# If we are processing more than 256 byte, we return an error
if serializedHandshakeMessageLen > uint8.high.int:
debug "PayloadV2 malformed: too many public keys contained in the handshake message"
return err("Too many public keys in handshake message")
# We get the transport message byte length
let transportMessageLen = self.transportMessage.len
# The output payload as in https://rfc.vac.dev/spec/35/. We concatenate all the PayloadV2 fields as
# payload = ( protocolId || serializedHandshakeMessageLen || serializedHandshakeMessage || transportMessageLen || transportMessage)
# We declare it as a byte sequence of length accordingly to the PayloadV2 information read
var payload = newSeqOfCap[byte](MessageNametagLength + #MessageNametagLength bytes for messageNametag
1 + # 1 byte for protocol ID
1 + # 1 byte for length of serializedHandshakeMessage field
serializedHandshakeMessageLen + # serializedHandshakeMessageLen bytes for serializedHandshakeMessage
8 + # 8 bytes for transportMessageLen
transportMessageLen # transportMessageLen bytes for transportMessage
)
# We concatenate all the data
# The protocol ID (1 byte) and handshake message length (1 byte) can be directly casted to byte to allow direct copy to the payload byte sequence
payload.add @(self.messageNametag)
payload.add self.protocolId.byte
payload.add serializedHandshakeMessageLen.byte
payload.add serializedHandshakeMessage
# The transport message length is converted from uint64 to bytes in Little-Endian
payload.add toBytesLE(transportMessageLen.uint64)
payload.add self.transportMessage
return ok(payload)
# Deserializes a byte sequence to a PayloadV2 object according to https://rfc.vac.dev/spec/35/.
# The input serialized payload concatenates the output PayloadV2 object fields as
# payload = ( messageNametag || protocolId || serializedHandshakeMessageLen || serializedHandshakeMessage || transportMessageLen || transportMessage)
proc deserializePayloadV2*(payload: seq[byte]): Result[PayloadV2, cstring]
{.raises: [Defect, NoisePublicKeyError].} =
# The output PayloadV2
var payload2: PayloadV2
# i is the read input buffer position index
var i: uint64 = 0
# We start by reading the messageNametag
for j in 0..<MessageNametagLength:
payload2.messageNametag[j] = payload[i+j.uint64]
i += MessageNametagLength
# We read the Protocol ID
# TODO: when the list of supported protocol ID is defined, check if read protocol ID is supported
payload2.protocolId = payload[i].uint8
i += 1
# We read the Handshake Message lenght (1 byte)
var handshakeMessageLen = payload[i].uint64
if handshakeMessageLen > uint8.high.uint64:
debug "Payload malformed: too many public keys contained in the handshake message"
return err("Too many public keys in handshake message")
i += 1
# We now read for handshakeMessageLen bytes the buffer and we deserialize each (encrypted/unencrypted) public key read
var
# In handshakeMessage we accumulate the read deserialized Noise Public keys
handshakeMessage: seq[NoisePublicKey]
flag: byte
pkLen: uint64
written: uint64 = 0
# We read the buffer until handshakeMessageLen are read
while written != handshakeMessageLen:
# We obtain the current Noise Public key encryption flag
flag = payload[i]
# If the key is unencrypted, we only read the X coordinate of the EC public key and we deserialize into a Noise Public Key
if flag == 0:
pkLen = 1 + EllipticCurveKey.len
handshakeMessage.add intoNoisePublicKey(payload[i..<i+pkLen])
i += pkLen
written += pkLen
# If the key is encrypted, we only read the encrypted X coordinate and the authorization tag, and we deserialize into a Noise Public Key
elif flag == 1:
pkLen = 1 + EllipticCurveKey.len + ChaChaPolyTag.len
handshakeMessage.add intoNoisePublicKey(payload[i..<i+pkLen])
i += pkLen
written += pkLen
else:
return err("Invalid flag for Noise public key")
# We save in the output PayloadV2 the read handshake message
payload2.handshakeMessage = handshakeMessage
# We read the transport message length (8 bytes) and we convert to uint64 in Little Endian
let transportMessageLen = fromBytesLE(uint64, payload[i..(i+8-1)])
i += 8
# We read the transport message (handshakeMessage bytes)
payload2.transportMessage = payload[i..i+transportMessageLen-1]
i += transportMessageLen
return ok(payload2)