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Support short inputs with missing bytes

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This commit is contained in:
mratsim 2018-10-05 17:37:52 +02:00
parent 38b4d54815
commit 0494e2a877
1 changed files with 3 additions and 6 deletions
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9
nimbus/vm/precompiles.nim
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@ -96,9 +96,9 @@ proc modExp(computation: var BaseComputation) =
template rawMsg: untyped {.dirty.} =
computation.msg.data
let
base_len = rawMsg.toOpenArray(0, 31).readUintBE[:256].toInt
exp_len = rawMsg.toOpenArray(32, 63).readUintBE[:256].toInt
mod_len = rawMsg.toOpenArray(64, 95).readUintBE[:256].toInt
base_len = toInt Uint256.fromBytesBE(rawMsg.toOpenArray(0, 31), allowPadding = true)
exp_len = toInt Uint256.fromBytesBE(rawMsg.toOpenArray(32, 63), allowPadding = true)
mod_len = toInt Uint256.fromBytesBE(rawMsg.toOpenArray(64, 96), allowPadding = true)
start_exp = 96 + base_len
start_mod = start_exp + exp_len
@ -107,8 +107,6 @@ proc modExp(computation: var BaseComputation) =
exp = Uint256.fromBytesBE(rawMsg.toOpenArray(start_exp, start_mod - 1), allowPadding = true)
modulo = Uint256.fromBytesBE(rawMsg.toOpenArray(start_mod, start_mod + mod_len - 1), allowPadding = true)
# TODO: Whenever the input is too short, the missing bytes are considered to be zero.
block: # Gas cost
func gasModExp_f(x: Natural): int =
# x: maximum length in bytes between modulo and base
@ -124,7 +122,6 @@ proc modExp(computation: var BaseComputation) =
if exp.isZero(): 0
else: log2(exp)
else:
# TODO: deal with overflow
let extra = Uint256.fromBytesBE(rawMsg.toOpenArray(96 + base_len, 127 + base_len), allowPadding = true)
if not extra.isZero:
8 * (exp_len - 32) + extra.log2