nimbus-eth1/nimbus/vm/precompiles.nim

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import
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../vm_types, interpreter/[gas_meter, gas_costs, utils/utils_numeric, vm_forks],
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../errors, stint, eth/[keys, common], chronicles, tables, macros,
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math, nimcrypto, bncurve/[fields, groups], blake2b_f
type
PrecompileAddresses* = enum
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# Frontier to Spurious Dragron
paEcRecover = 1,
paSha256,
paRipeMd160,
paIdentity,
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# Byzantium and Constantinople
paModExp,
paEcAdd,
paEcMul,
paPairing,
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# Istanbul
paBlake2bf = 9
proc getSignature(computation: Computation): (array[32, byte], Signature) =
# input is Hash, V, R, S
template data: untyped = computation.msg.data
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var bytes: array[65, byte] # will hold R[32], S[32], V[1], in that order
let maxPos = min(data.high, 127)
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# if we don't have at minimum 64 bytes, there can be no valid V
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if maxPos >= 63:
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let v = data[63]
# check if V[32] is 27 or 28
if not (v.int in 27..28):
raise newException(ValidationError, "Invalid V in getSignature")
for x in 32..<63:
if data[x] != 0:
raise newException(ValidationError, "Invalid V in getSignature")
bytes[64] = v - 27
# if there is more data for R and S, copy it. Else, defaulted zeroes are
# used for R and S
if maxPos >= 64:
# Copy message data to buffer
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bytes[0..(maxPos-64)] = data[64..maxPos]
let sig = Signature.fromRaw(bytes)
if sig.isErr:
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raise newException(ValidationError, "Could not recover signature computation")
result[1] = sig[]
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# extract message hash, only need to copy when there is a valid signature
result[0][0..31] = data[0..31]
else:
raise newException(ValidationError, "Invalid V in getSignature")
proc getPoint[T: G1|G2](t: typedesc[T], data: openarray[byte]): Point[T] =
when T is G1:
const nextOffset = 32
var px, py: FQ
else:
const nextOffset = 64
var px, py: FQ2
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if not px.fromBytes2(data.toOpenArray(0, nextOffset - 1)):
raise newException(ValidationError, "Could not get point value")
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if not py.fromBytes2(data.toOpenArray(nextOffset, nextOffset * 2 - 1)):
raise newException(ValidationError, "Could not get point value")
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# "ecpairing_perturb_g2_by_field_modulus_again.json",
# "ecpairing_perturb_zeropoint_by_field_modulus.json",
# "ecpairing_perturb_g2_by_field_modulus.json",
# modulus comparion in FQ2.fromBytes produce different result
const
modulus = Uint256.fromHex("30644e72e131a029b85045b68181585d97816a916871ca8d3c208c16d87cfd47")
let a = Uint256.fromBytesBE(data.toOpenArray(0, 31), false)
let b = Uint256.fromBytesBE(data.toOpenArray(32, 63), false)
when T is G2:
let c = Uint256.fromBytesBE(data.toOpenArray(64, 95), false)
let d = Uint256.fromBytesBE(data.toOpenArray(96, 127), false)
if a >= modulus or b >= modulus or c >= modulus or d >= modulus:
raise newException(ValidationError, "value greater than field modulus")
else:
if a >= modulus or b >= modulus:
raise newException(ValidationError, "value greater than field modulus")
if px.isZero() and py.isZero():
result = T.zero()
else:
var ap: AffinePoint[T]
if not ap.init(px, py):
raise newException(ValidationError, "Point is not on curve")
result = ap.toJacobian()
proc getFR(data: openarray[byte]): FR =
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if not result.fromBytes2(data):
raise newException(ValidationError, "Could not get FR value")
proc ecRecover*(computation: Computation) =
computation.gasMeter.consumeGas(
GasECRecover,
reason="ECRecover Precompile")
var
(msgHash, sig) = computation.getSignature()
var pubkey = recover(sig, SkMessage(data: msgHash))
if pubkey.isErr:
raise newException(ValidationError, "Could not derive public key from computation")
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computation.output.setLen(32)
computation.output[12..31] = pubkey[].toCanonicalAddress()
trace "ECRecover precompile", derivedKey = pubkey[].toCanonicalAddress()
proc sha256*(computation: Computation) =
let
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wordCount = wordCount(computation.msg.data.len)
gasFee = GasSHA256 + wordCount * GasSHA256Word
computation.gasMeter.consumeGas(gasFee, reason="SHA256 Precompile")
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computation.output = @(nimcrypto.sha_256.digest(computation.msg.data).data)
trace "SHA256 precompile", output = computation.output.toHex
proc ripemd160*(computation: Computation) =
let
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wordCount = wordCount(computation.msg.data.len)
gasFee = GasRIPEMD160 + wordCount * GasRIPEMD160Word
computation.gasMeter.consumeGas(gasFee, reason="RIPEMD160 Precompile")
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computation.output.setLen(32)
computation.output[12..31] = @(nimcrypto.ripemd160.digest(computation.msg.data).data)
trace "RIPEMD160 precompile", output = computation.output.toHex
proc identity*(computation: Computation) =
let
wordCount = wordCount(computation.msg.data.len)
gasFee = GasIdentity + wordCount * GasIdentityWord
computation.gasMeter.consumeGas(gasFee, reason="Identity Precompile")
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computation.output = computation.msg.data
trace "Identity precompile", output = computation.output.toHex
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proc modExpInternal(computation: Computation, baseLen, expLen, modLen: int, T: type StUint) =
template data: untyped {.dirty.} =
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computation.msg.data
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let
base = data.rangeToPadded[:T](96, 95 + baseLen, baseLen)
exp = data.rangeToPadded[:T](96 + baseLen, 95 + baseLen + expLen, expLen)
modulo = data.rangeToPadded[:T](96 + baseLen + expLen, 95 + baseLen + expLen + modLen, modLen)
# TODO: specs mentions that we should return in "M" format
# i.e. if Base and exp are uint512 and Modulo an uint256
# we should return a 256-bit big-endian byte array
# Force static evaluation
func zero(): array[T.bits div 8, byte] {.compileTime.} = discard
func one(): array[T.bits div 8, byte] {.compileTime.} =
when cpuEndian == bigEndian:
result[0] = 1
else:
result[^1] = 1
# Start with EVM special cases
let output = if modulo <= 1:
# If m == 0: EVM returns 0.
# If m == 1: we can shortcut that to 0 as well
zero()
elif exp.isZero():
# If 0^0: EVM returns 1
# For all x != 0, x^0 == 1 as well
one()
else:
powmod(base, exp, modulo).toByteArrayBE
# maximum output len is the same as modLen
# if it less than modLen, it will be zero padded at left
if output.len >= modLen:
computation.output = @(output[^modLen..^1])
else:
computation.output = newSeq[byte](modLen)
computation.output[^output.len..^1] = output[0..^1]
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proc modExpFee(c: Computation, baseLen, expLen, modLen: Uint256): GasInt =
template data: untyped {.dirty.} =
c.msg.data
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func gasModExp(x: Uint256): Uint256 =
## Estimates the difficulty of Karatsuba multiplication
if x <= 64.u256: x * x
elif x <= 1024.u256: x * x div 4.u256 + 96.u256 * x - 3072.u256
else: x * x div 16.u256 + 480.u256 * x - 199680.u256
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let adjExpLen = block:
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let
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baseL = baseLen.safeInt
expL = expLen.safeInt
first32 = if baseL.uint64 + expL.uint64 < high(int32).uint64 and baseL < data.len:
data.rangeToPadded2[:Uint256](96 + baseL, 95 + baseL + expL, min(expL, 32))
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else:
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0.u256
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if expLen <= 32:
if first32.isZero(): 0.u256
else: first32.log2.u256 # highest-bit in exponent
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else:
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if not first32.isZero:
8.u256 * (expLen - 32.u256) + first32.log2.u256
else:
8.u256 * (expLen - 32.u256)
let gasFee = (
max(modLen, baseLen).gasModExp *
max(adjExpLen, 1.u256)
) div GasQuadDivisor
if gasFee > high(GasInt).u256:
raise newException(OutOfGas, "modExp gas overflow")
result = gasFee.truncate(GasInt)
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proc modExp*(computation: Computation) =
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## Modular exponentiation precompiled contract
## Yellow Paper Appendix E
## EIP-198 - https://github.com/ethereum/EIPs/blob/master/EIPS/eip-198.md
# Parsing the data
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template data: untyped {.dirty.} =
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computation.msg.data
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let # lengths Base, Exponent, Modulus
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baseL = data.rangeToPadded[:Uint256](0, 31)
expL = data.rangeToPadded[:Uint256](32, 63)
modL = data.rangeToPadded[:Uint256](64, 95)
baseLen = baseL.safeInt
expLen = expL.safeInt
modLen = modL.safeInt
let gasFee = modExpFee(computation, baseL, expL, modL)
computation.gasMeter.consumeGas(gasFee, reason="ModExp Precompile")
if baseLen == 0 and modLen == 0:
# This is a special case where expLength can be very big.
computation.output = @[]
return
let maxBytes = max(baseLen, max(expLen, modLen))
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if maxBytes <= 32:
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computation.modExpInternal(baseLen, expLen, modLen, UInt256)
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elif maxBytes <= 64:
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computation.modExpInternal(baseLen, expLen, modLen, StUint[512])
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elif maxBytes <= 128:
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computation.modExpInternal(baseLen, expLen, modLen, StUint[1024])
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elif maxBytes <= 256:
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computation.modExpInternal(baseLen, expLen, modLen, StUint[2048])
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elif maxBytes <= 512:
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computation.modExpInternal(baseLen, expLen, modLen, StUint[4096])
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elif maxBytes <= 1024:
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computation.modExpInternal(baseLen, expLen, modLen, StUint[8192])
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else:
raise newException(EVMError, "The Nimbus VM doesn't support modular exponentiation with numbers larger than uint8192")
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proc bn256ecAdd*(computation: Computation, fork: Fork = FkByzantium) =
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let gasFee = if fork < FkIstanbul: GasECAdd else: GasECAddIstanbul
computation.gasMeter.consumeGas(gasFee, reason = "ecAdd Precompile")
var
input: array[128, byte]
output: array[64, byte]
# Padding data
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let len = min(computation.msg.data.len, 128) - 1
input[0..len] = computation.msg.data[0..len]
var p1 = G1.getPoint(input.toOpenArray(0, 63))
var p2 = G1.getPoint(input.toOpenArray(64, 127))
var apo = (p1 + p2).toAffine()
if isSome(apo):
# we can discard here because we supply proper buffer
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discard apo.get().toBytes(output)
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computation.output = @output
proc bn256ecMul*(computation: Computation, fork: Fork = FkByzantium) =
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let gasFee = if fork < FkIstanbul: GasECMul else: GasECMulIstanbul
computation.gasMeter.consumeGas(gasFee, reason="ecMul Precompile")
var
input: array[96, byte]
output: array[64, byte]
# Padding data
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let len = min(computation.msg.data.len, 96) - 1
input[0..len] = computation.msg.data[0..len]
var p1 = G1.getPoint(input.toOpenArray(0, 63))
var fr = getFR(input.toOpenArray(64, 95))
var apo = (p1 * fr).toAffine()
if isSome(apo):
# we can discard here because we supply buffer of proper size
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discard apo.get().toBytes(output)
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computation.output = @output
proc bn256ecPairing*(computation: Computation, fork: Fork = FkByzantium) =
let msglen = len(computation.msg.data)
if msglen mod 192 != 0:
raise newException(ValidationError, "Invalid input length")
let numPoints = msglen div 192
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let gasFee = if fork < FkIstanbul:
GasECPairingBase + numPoints * GasECPairingPerPoint
else:
GasECPairingBaseIstanbul + numPoints * GasECPairingPerPointIstanbul
computation.gasMeter.consumeGas(gasFee, reason="ecPairing Precompile")
var output: array[32, byte]
if msglen == 0:
# we can discard here because we supply buffer of proper size
discard BNU256.one().toBytes(output)
else:
# Calculate number of pairing pairs
let count = msglen div 192
# Pairing accumulator
var acc = FQ12.one()
for i in 0..<count:
let s = i * 192
# Loading AffinePoint[G1], bytes from [0..63]
var p1 = G1.getPoint(computation.msg.data.toOpenArray(s, s + 63))
# Loading AffinePoint[G2], bytes from [64..191]
var p2 = G2.getPoint(computation.msg.data.toOpenArray(s + 64, s + 191))
# Accumulate pairing result
acc = acc * pairing(p1, p2)
if acc == FQ12.one():
# we can discard here because we supply buffer of proper size
discard BNU256.one().toBytes(output)
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computation.output = @output
proc blake2bf*(computation: Computation) =
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template input(): untyped =
computation.msg.data
if len(input) == blake2FInputLength:
let gasFee = GasInt(beLoad32(input, 0))
computation.gasMeter.consumeGas(gasFee, reason="ecPairing Precompile")
var output: array[64, byte]
if not blake2b_F(input, output):
raise newException(ValidationError, "Blake2b F function invalid input")
else:
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computation.output = @output
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proc getMaxPrecompileAddr(fork: Fork): PrecompileAddresses =
if fork < FkByzantium: paIdentity
elif fork < FkIstanbul: paPairing
else: PrecompileAddresses.high
proc execPrecompiles*(computation: Computation, fork: Fork): bool {.inline.} =
for i in 0..18:
if computation.msg.codeAddress[i] != 0: return
let lb = computation.msg.codeAddress[19]
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let maxPrecompileAddr = getMaxPrecompileAddr(fork)
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if lb in PrecompileAddresses.low.byte .. maxPrecompileAddr.byte:
result = true
let precompile = PrecompileAddresses(lb)
trace "Call precompile", precompile = precompile, codeAddr = computation.msg.codeAddress
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try:
case precompile
of paEcRecover: ecRecover(computation)
of paSha256: sha256(computation)
of paRipeMd160: ripeMd160(computation)
of paIdentity: identity(computation)
of paModExp: modExp(computation)
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of paEcAdd: bn256ecAdd(computation, fork)
of paEcMul: bn256ecMul(computation, fork)
of paPairing: bn256ecPairing(computation, fork)
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of paBlake2bf: blake2bf(computation)
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except OutOfGas as e:
# cannot use setError here, cyclic dependency
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computation.error = Error(info: e.msg, burnsGas: true)
except CatchableError as e:
if fork >= FKByzantium and precompile > paIdentity:
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computation.error = Error(info: e.msg, burnsGas: true)
else:
# swallow any other precompiles errors
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debug "execPrecompiles validation error", msg=e.msg