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Fix unmarshal bugs #409

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merged 6 commits into from
Jul 5, 2024
Merged

Fix unmarshal bugs #409

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09755bd
[evm precompiles] do *not* ignore `unmarshal` return value
Vindaar Jun 28, 2024
abddc2b
[io_limbs] handle `unmarshal` for sources longer, but smaller
Vindaar Jun 28, 2024
a1ae4fe
[tests] explicitly pass output size for EVM precompiles, chk exp err
Vindaar Jul 3, 2024
91b2fbb
revert checking of "upper" bytes in `io_limbs.nim`
Vindaar Jul 3, 2024
5d085d2
[evm precompiles] return invalid input size for MSM input.len == 0
Vindaar Jul 3, 2024
51d64b5
[evm precompiles] split parsing of field coords by curve
Vindaar Jul 3, 2024
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53 changes: 46 additions & 7 deletions constantine/ethereum_evm_precompiles.nim
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Original file line number Diff line number Diff line change
Expand Up @@ -196,20 +196,59 @@ func eth_evm_modexp*(r: var openArray[byte], inputs: openArray[byte]): CttEVMSta
# Elliptic Curves
# ----------------------------------------------------------------

func parseRawUint[Name: static Algebra](
dst: var Fp[Name],
src: openarray[byte]): CttEVMStatus =
proc parseEip2537(dst: var Fp[BLS12_381], src: openArray[byte]): CttEvmStatus {.inline.} =
## Parses a curve point following the encoding rules defined in EIP-2537,
## i.e. requiring the input to be exactly 64 bytes, with the 'upper' 16 bytes
## required to be empty.
## The input is required to be a coordinate of a point on the BLS12-381 curve and
## stored in Big Endian format.
##
## For points on the quadratic extension field Fp2 the individual terms are
## byte concatenated and the caller takes care of splitting the input for a
## before calling this.
##
## Ref: https://eips.ethereum.org/EIPS/eip-2537#fine-points-and-encoding-of-base-elements

var big {.noInit.}: Fp[BLS12_381].getBigInt()
if src.len != 64:
return cttEVM_InvalidInputSize

# Parse the subslice of 48 bytes using regular `unmarshal`
var success = big.unmarshal(src.toOpenArray(16, 63), bigEndian)

# Now check that all lower bytes are empty
var allZero = success # if `success` already false we still continue
for i in 0 ..< 15: # order irrelevant
allZero = allZero and (src[i] == 0)
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As mentioned in discussion, even if we don't require constant-time here, it is fine not to return early on a non-zero.

The difference is likely a couple nanoseconds. It's also an exceptional path.
Furthermore with an exact 16 bytes check, the compiler can transform this into a vector load + vector zero check and it may very well be faster than having an if branch in a hot path.


if not allZero or not bool(big < Fp[BLS12_381].getModulus()):
return cttEVM_IntLargerThanModulus

# assign result
dst.fromBig(big)
result = cttEVM_Success

func parseRawUint(dst: var Fp[BLS12_381], src: openarray[byte]): CttEVMStatus =
## Parse an unsigned integer from its canonical
## big-endian or little-endian unsigned representation
## And store it into a field element for
##
## Return false if the integer is larger than the field modulus.
## Returns true on success.
result = dst.parseEip2537(src)

func parseRawUint(dst: var Fp[BN254_Snarks], src: openarray[byte]): CttEVMStatus =
## Parse an unsigned integer from its canonical
## big-endian or little-endian unsigned representation
## And store it into a field element.
##
## Return false if the integer is larger than the field modulus.
## Returns true on success.
var big {.noInit.}: Fp[Name].getBigInt()
var big {.noInit.}: Fp[BN254_Snarks].getBigInt()
if not big.unmarshal(src, bigEndian):
return cttEVM_IntLargerThanModulus # `dst` too small for `src`!

if not bool(big < Fp[Name].getModulus()):
if not bool(big < Fp[BN254_Snarks].getModulus()):
return cttEVM_IntLargerThanModulus

dst.fromBig(big)
Expand Down Expand Up @@ -820,7 +859,7 @@ func eth_evm_bls12381_g1msm*(r: var openArray[byte], inputs: openarray[byte]): C
## cttEVM_PointNotOnCurve
##
## Spec https://eips.ethereum.org/EIPS/eip-2537
if inputs.len mod 160 != 0:
if inputs.len == 0 or inputs.len mod 160 != 0:
return cttEVM_InvalidInputSize

if r.len != 128:
Expand Down Expand Up @@ -903,7 +942,7 @@ func eth_evm_bls12381_g2msm*(r: var openArray[byte], inputs: openarray[byte]): C
## cttEVM_PointNotOnCurve
##
## Spec https://eips.ethereum.org/EIPS/eip-2537
if inputs.len mod 288 != 0:
if inputs.len == 0 or inputs.len mod 288 != 0:
return cttEVM_InvalidInputSize

if r.len != 256:
Expand Down
26 changes: 4 additions & 22 deletions constantine/serialization/io_limbs.nim
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Expand Up @@ -63,17 +63,8 @@ func unmarshalLE[T](

# if full, dump
if acc_len >= wordBitWidth:
if dst_idx == dst.len: # return, however check if all remaining
# elements are 0 (more significant bits beyond `src_idx`)
# For example, given a
# `src = "DDCCBBAA0000"`
# and a 4 byte LittleEndian `BigInt`, `src` is fine, because the most
# significant two bytes are all zero.
var allZero = true
for jidx in src_idx ..< dst.len:
if src[jidx] != 0: allZero = false
if allZero: return true
else: return false
if dst_idx == dst.len:
return false

dst[dst_idx] = acc
inc dst_idx
Expand Down Expand Up @@ -127,17 +118,8 @@ func unmarshalBE[T](

# if full, dump
if acc_len >= wordBitWidth:
if dst_idx == dst.len: # return, however check if all remaining
# elements are 0 (more significant bits beyond `src_idx-1`)
# For examplle, given a
# `src = "0000AABBCCDD"`
# and a 4 byte BigEndian `BigInt`, `src` is fine, because the most
# significant two bytes are all zero.
var allZero = true
for jidx in countdown(src_idx, 0):
if src[jidx] != 0: allZero = false
if allZero: return true
else: return false
if dst_idx == dst.len:
return false

dst[dst_idx] = acc
inc dst_idx
Expand Down
70 changes: 39 additions & 31 deletions tests/t_ethereum_evm_precompiles.nim
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@ type
PrecompileTest = object
Input: HexString
Expected: HexString
ExpectedError: string
Name: string
Gas: int
NoBenchmark: bool
Expand All @@ -37,7 +38,7 @@ proc loadVectors(TestType: typedesc, filename: string): TestType =
let content = readFile(TestVectorsDir/filename)
result = content.fromJson(TestType)

template runPrecompileTests(filename: string, funcname: untyped) =
template runPrecompileTests(filename: string, funcname: untyped, outsize: int) =
block:
proc `PrecompileTestrunner _ funcname`() =
let vec = seq[PrecompileTest].loadVectors(filename)
Expand All @@ -53,16 +54,23 @@ template runPrecompileTests(filename: string, funcname: untyped) =
var expected = newSeq[byte](test.Expected.len div 2)
expected.paddedFromHex(test.Expected, bigEndian)

var r = newSeq[byte](test.Expected.len div 2)
## TODO: change to use `modexp_result_size` API after rebase
let outs = if outsize > 0: outsize else: test.Expected.len div 2
var r = newSeq[byte](outs)

let status = funcname(r, inputbytes)
if status != cttEVM_Success:
reset(r)

doAssert r == expected, "[Test Failure]\n" &
" " & funcname.astToStr & " status: " & $status & "\n" &
" " & "result: " & r.toHex() & "\n" &
" " & "expected: " & expected.toHex() & '\n'
doAssert test.ExpectedError.len > 0, "[Test Failure]\n" &
" " & test.Name & "\n" &
" " & funcname.astToStr & "\n" &
" " & "Nim proc returned failure, but test expected to pass.\n" &
" " & "Expected result: " & $expected.toHex()
else:
doAssert r == expected, "[Test Failure]\n" &
" " & test.Name & "\n" &
" " & funcname.astToStr & " status: " & $status & "\n" &
" " & "result: " & r.toHex() & "\n" &
" " & "expected: " & expected.toHex() & '\n'

stdout.write "Success\n"

Expand Down Expand Up @@ -99,32 +107,32 @@ proc testSha256() =

testSha256()

runPrecompileTests("modexp.json", eth_evm_modexp)
runPrecompileTests("modexp_eip2565.json", eth_evm_modexp)
runPrecompileTests("modexp.json", eth_evm_modexp, 0)
runPrecompileTests("modexp_eip2565.json", eth_evm_modexp, 0)

runPrecompileTests("bn256Add.json", eth_evm_bn254_g1add)
runPrecompileTests("bn256ScalarMul.json", eth_evm_bn254_g1mul)
runPrecompileTests("bn256Pairing.json", eth_evm_bn254_ecpairingcheck)
runPrecompileTests("bn256Add.json", eth_evm_bn254_g1add, 64)
runPrecompileTests("bn256ScalarMul.json", eth_evm_bn254_g1mul, 64)
runPrecompileTests("bn256Pairing.json", eth_evm_bn254_ecpairingcheck, 32)

runPrecompileTests("eip-2537/add_G1_bls.json", eth_evm_bls12381_g1add)
runPrecompileTests("eip-2537/fail-add_G1_bls.json", eth_evm_bls12381_g1add)
runPrecompileTests("eip-2537/add_G2_bls.json", eth_evm_bls12381_g2add)
runPrecompileTests("eip-2537/fail-add_G2_bls.json", eth_evm_bls12381_g2add)
runPrecompileTests("eip-2537/add_G1_bls.json", eth_evm_bls12381_g1add, 128)
runPrecompileTests("eip-2537/fail-add_G1_bls.json", eth_evm_bls12381_g1add, 128)
runPrecompileTests("eip-2537/add_G2_bls.json", eth_evm_bls12381_g2add, 256)
runPrecompileTests("eip-2537/fail-add_G2_bls.json", eth_evm_bls12381_g2add, 256)

runPrecompileTests("eip-2537/mul_G1_bls.json", eth_evm_bls12381_g1mul)
runPrecompileTests("eip-2537/fail-mul_G1_bls.json", eth_evm_bls12381_g1mul)
runPrecompileTests("eip-2537/mul_G2_bls.json", eth_evm_bls12381_g2mul)
runPrecompileTests("eip-2537/fail-mul_G2_bls.json", eth_evm_bls12381_g2mul)
runPrecompileTests("eip-2537/mul_G1_bls.json", eth_evm_bls12381_g1mul, 128)
runPrecompileTests("eip-2537/fail-mul_G1_bls.json", eth_evm_bls12381_g1mul, 128)
runPrecompileTests("eip-2537/mul_G2_bls.json", eth_evm_bls12381_g2mul, 256)
runPrecompileTests("eip-2537/fail-mul_G2_bls.json", eth_evm_bls12381_g2mul, 256)

runPrecompileTests("eip-2537/multiexp_G1_bls.json", eth_evm_bls12381_g1msm)
runPrecompileTests("eip-2537/fail-multiexp_G1_bls.json", eth_evm_bls12381_g1msm)
runPrecompileTests("eip-2537/multiexp_G2_bls.json", eth_evm_bls12381_g2msm)
runPrecompileTests("eip-2537/fail-multiexp_G2_bls.json", eth_evm_bls12381_g2msm)
runPrecompileTests("eip-2537/multiexp_G1_bls.json", eth_evm_bls12381_g1msm, 128)
runPrecompileTests("eip-2537/fail-multiexp_G1_bls.json", eth_evm_bls12381_g1msm, 128)
runPrecompileTests("eip-2537/multiexp_G2_bls.json", eth_evm_bls12381_g2msm, 256)
runPrecompileTests("eip-2537/fail-multiexp_G2_bls.json", eth_evm_bls12381_g2msm, 256)

runPrecompileTests("eip-2537/pairing_check_bls.json", eth_evm_bls12381_pairingcheck)
runPrecompileTests("eip-2537/fail-pairing_check_bls.json", eth_evm_bls12381_pairingcheck)
runPrecompileTests("eip-2537/pairing_check_bls.json", eth_evm_bls12381_pairingcheck, 32)
runPrecompileTests("eip-2537/fail-pairing_check_bls.json", eth_evm_bls12381_pairingcheck, 32)

runPrecompileTests("eip-2537/map_fp_to_G1_bls.json", eth_evm_bls12381_map_fp_to_g1)
runPrecompileTests("eip-2537/fail-map_fp_to_G1_bls.json", eth_evm_bls12381_map_fp_to_g1)
runPrecompileTests("eip-2537/map_fp2_to_G2_bls.json", eth_evm_bls12381_map_fp2_to_g2)
runPrecompileTests("eip-2537/fail-map_fp2_to_G2_bls.json", eth_evm_bls12381_map_fp2_to_g2)
runPrecompileTests("eip-2537/map_fp_to_G1_bls.json", eth_evm_bls12381_map_fp_to_g1, 128)
runPrecompileTests("eip-2537/fail-map_fp_to_G1_bls.json", eth_evm_bls12381_map_fp_to_g1, 128)
runPrecompileTests("eip-2537/map_fp2_to_G2_bls.json", eth_evm_bls12381_map_fp2_to_g2, 256)
runPrecompileTests("eip-2537/fail-map_fp2_to_G2_bls.json", eth_evm_bls12381_map_fp2_to_g2, 256)
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