142 lines
4.4 KiB
Nim
142 lines
4.4 KiB
Nim
# beacon_chain
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# Copyright (c) 2018-2022 Status Research & Development GmbH
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# Licensed and distributed under either of
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# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
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# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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# Serenity hash function / digest
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#
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# https://github.com/ethereum/consensus-specs/blob/v1.2.0-rc.1/specs/phase0/beacon-chain.md#hash
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#
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# In Phase 0 the beacon chain is deployed with SHA256 (SHA2-256).
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# Note that is is different from Keccak256 (often mistakenly called SHA3-256)
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# and SHA3-256.
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#
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# In Eth1.0, the default hash function is Keccak256 and SHA256 is available as a precompiled contract.
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#
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# In our code base, to enable a smooth transition
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# (already did Blake2b --> Keccak256 --> SHA2-256),
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# we call this function `eth2digest`, and it outputs a `Eth2Digest`. Easy to sed :)
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{.push raises: [Defect].}
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import
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# Standard library
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std/hashes,
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# Status libraries
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chronicles,
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nimcrypto/[sha2, hash],
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stew/[byteutils, endians2, objects],
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json_serialization
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export
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# Exports from sha2 / hash are explicit to avoid exporting upper-case `$` and
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# constant-time `==`
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hash.fromHex, json_serialization
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type
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Eth2Digest* = MDigest[32 * 8] ## `hash32` from spec
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const PREFER_BLST_SHA256* {.booldefine.} = true
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when PREFER_BLST_SHA256:
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import blscurve
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when BLS_BACKEND == BLST:
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const USE_BLST_SHA256 = true
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else:
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const USE_BLST_SHA256 = false
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else:
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const USE_BLST_SHA256 = false
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when USE_BLST_SHA256:
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export blscurve.update
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type Eth2DigestCtx* = BLST_SHA256_CTX
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else:
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export sha2.update
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type Eth2DigestCtx* = sha2.sha256
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func `$`*(x: Eth2Digest): string =
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x.data.toHex()
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func shortLog*(x: Eth2Digest): string =
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x.data.toOpenArray(0, 3).toHex()
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chronicles.formatIt Eth2Digest:
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shortLog(it)
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# TODO: expose an in-place digest function
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# when hashing in loop or into a buffer
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# See: https://github.com/cheatfate/nimcrypto/blob/b90ba3abd/nimcrypto/sha2.nim#L570
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func eth2digest*(v: openArray[byte]): Eth2Digest {.noinit.} =
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## Apply the Eth2 Hash function
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## Do NOT use for secret data.
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when USE_BLST_SHA256:
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# BLST has a fast assembly optimized SHA256
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result.data.bls_sha256_digest(v)
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else:
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# We use the init-update-finish interface to avoid
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# the expensive burning/clearing memory (20~30% perf)
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var ctx {.noinit.}: Eth2DigestCtx
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ctx.init()
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ctx.update(v)
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ctx.finish()
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template withEth2Hash*(body: untyped): Eth2Digest =
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## This little helper will init the hash function and return the sliced
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## hash:
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## let hashOfData = withHash: h.update(data)
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when nimvm:
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# In SSZ, computeZeroHashes require compile-time SHA256
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block:
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var h {.inject.}: sha256
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init(h)
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body
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finish(h)
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else:
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when USE_BLST_SHA256:
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block:
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var h {.inject, noinit.}: Eth2DigestCtx
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init(h)
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body
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var res {.noinit.}: Eth2Digest
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finalize(res.data, h)
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res
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else:
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block:
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var h {.inject, noinit.}: Eth2DigestCtx
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init(h)
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body
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finish(h)
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template hash*(x: Eth2Digest): Hash =
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## Hash for digests for Nim hash tables
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# digests are already good hashes
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cast[ptr Hash](unsafeAddr x.data[0])[]
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func `==`*(a, b: Eth2Digest): bool =
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when nimvm:
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a.data == b.data
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else:
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# nimcrypto uses a constant-time comparison for all MDigest types which for
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# Eth2Digest is unnecessary - the type should never hold a secret!
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equalMem(unsafeAddr a.data[0], unsafeAddr b.data[0], sizeof(a.data))
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func isZero*(x: Eth2Digest): bool =
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x.isZeroMemory
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proc writeValue*(w: var JsonWriter, a: Eth2Digest) {.raises: [Defect, IOError, SerializationError].} =
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w.writeValue $a
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proc readValue*(r: var JsonReader, a: var Eth2Digest) {.raises: [Defect, IOError, SerializationError].} =
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try:
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a = fromHex(type(a), r.readValue(string))
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except ValueError:
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raiseUnexpectedValue(r, "Hex string expected")
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func toGaugeValue*(hash: Eth2Digest): int64 =
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# Only the last 8 bytes are taken into consideration in accordance
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# to the ETH2 metrics spec:
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# https://github.com/ethereum/beacon-metrics/blob/6a79914cb31f7d54858c7dd57eee75b6162ec737/metrics.md#interop-metrics
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cast[int64](uint64.fromBytesLE(hash.data.toOpenArray(24, 31)))
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