615 lines
21 KiB
Nim
615 lines
21 KiB
Nim
# beacon_chain
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# Copyright (c) 2018-2023 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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# At the time of writing, the exact definitions of what should be used for
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# cryptography in the spec is in flux, with sizes and test vectors still being
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# hashed out. This layer helps isolate those chagnes.
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# BLS signatures can be combined such that multiple signatures are aggregated.
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# Each time a new signature is added, the corresponding public key must be
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# added to the verification key as well - if a key signs twice, it must be added
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# twice to the verification key. Aggregated signatures can be combined
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# arbitrarily (like addition) as long as public keys are aggregated in the same
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# way.
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#
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# In eth2, we use a single bit to record which keys have signed, thus we cannot
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# combined overlapping aggregates - ie if we have an aggregate of signatures of
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# A, B and C, and another with B, C and D, we cannot practically combine them
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# even if in theory it is possible to allow this in BLS.
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{.push raises: [].}
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import
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# Status
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stew/[bitseqs, endians2, objects, results, byteutils],
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blscurve,
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chronicles,
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bearssl/rand,
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json_serialization
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from std/hashes import Hash
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from std/sequtils import mapIt
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from std/tables import Table, withValue, `[]=`
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from nimcrypto/utils import burnMem
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export results, blscurve, rand, json_serialization
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# Type definitions
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# ----------------------------------------------------------------------
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const
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RawSigSize* = 96
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RawPubKeySize* = 48
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UncompressedPubKeySize* = 96
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# RawPrivKeySize* = 48 for Miracl / 32 for BLST
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type
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ValidatorPubKey* = object ##\
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## Compressed raw serialized key bytes - this type is used in so as to not
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## eagerly load keys - deserialization is slow, as are equality checks -
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## however, it is not guaranteed that the key is valid (except in some
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## cases, like the database state)
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##
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## It must be 8-byte aligned because `hash(ValidatorPubKey)` just casts a
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## ptr to one to a ptr to the other, so it needs a compatible alignment.
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blob* {.align: 16.}: array[RawPubKeySize, byte]
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UncompressedPubKey* = object
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## Uncompressed variation of ValidatorPubKey - this type is faster to
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## deserialize but doubles the storage footprint
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blob* {.align: 16.}: array[UncompressedPubKeySize, byte]
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CookedPubKey* = distinct blscurve.PublicKey ## Valid deserialized key
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ValidatorSig* = object
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blob* {.align: 16.}: array[RawSigSize, byte]
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ValidatorPrivKey* = distinct blscurve.SecretKey
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BlsCurveType* = ValidatorPrivKey | ValidatorPubKey | ValidatorSig
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BlsResult*[T] = Result[T, cstring]
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TrustedSig* = object
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data* {.align: 16.}: array[RawSigSize, byte]
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SomeSig* = TrustedSig | ValidatorSig
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CookedSig* = distinct blscurve.Signature ## \
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## Cooked signatures are those that have been loaded successfully from a
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## ValidatorSig and are used to avoid expensive reloading as well as error
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## checking
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SignatureShare* = object
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sign*: blscurve.Signature
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id*: uint32
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SecretShare* = object
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key*: ValidatorPrivKey
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id*: uint32
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export
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AggregateSignature
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# API
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# ----------------------------------------------------------------------
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# https://github.com/ethereum/consensus-specs/blob/v1.4.0-beta.1/specs/phase0/beacon-chain.md#bls-signatures
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func toPubKey*(privkey: ValidatorPrivKey): CookedPubKey =
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## Derive a public key from a private key
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# Un-specced in either hash-to-curve or Eth2
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var pubKey: blscurve.PublicKey
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let ok = publicFromSecret(pubKey, SecretKey privkey)
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doAssert ok, "The validator private key was a zero key. This should never happen."
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CookedPubKey(pubKey)
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template toRaw*(x: CookedPubKey): auto =
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PublicKey(x).exportRaw()
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template toUncompressed*(x: CookedPubKey): auto =
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UncompressedPubKey(blob: PublicKey(x).exportUncompressed())
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func toPubKey*(pubKey: CookedPubKey): ValidatorPubKey =
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## Derive a public key from a private key
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# Un-specced in either hash-to-curve or Eth2
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ValidatorPubKey(blob: pubKey.toRaw())
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func load*(v: ValidatorPubKey): Opt[CookedPubKey] =
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## Parse signature blob - this may fail
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var val: blscurve.PublicKey
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if fromBytes(val, v.blob):
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Opt.some CookedPubKey(val)
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else:
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Opt.none CookedPubKey
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func load*(v: UncompressedPubKey): Opt[CookedPubKey] =
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## Parse signature blob - this may fail
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var val: blscurve.PublicKey
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if fromBytes(val, v.blob):
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Opt.some CookedPubKey(val)
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else:
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Opt.none CookedPubKey
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func loadValid*(v: UncompressedPubKey | ValidatorPubKey): CookedPubKey {.noinit.} =
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## Parse known-to-be-valid key - this is the case for any key that's passed
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## parsing once and is the output of serialization, such as those keys we
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## keep in the database or state.
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var val: blscurve.PublicKey
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let ok = fromBytesKnownOnCurve(val, v.blob)
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doAssert ok, "Valid key no longer parses, data corrupt? " & $v
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CookedPubKey(val)
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proc loadWithCache*(v: ValidatorPubKey): Opt[CookedPubKey] =
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## Parse public key blob - this may fail - this function uses a cache to
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## avoid the expensive deserialization - for now, external public keys only
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## come from deposits in blocks - when more sources are added, the memory
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## usage of the cache should be considered
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var cache {.threadvar.}: Table[typeof(v.blob), CookedPubKey]
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# Try to get parse value from cache - if it's not in there, try to parse it -
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# if that's not possible, it's broken
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cache.withValue(v.blob, key) do:
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return Opt.some key[]
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do:
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# Only valid keys are cached
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let cooked = v.load()
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if cooked.isSome():
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cache[v.blob] = cooked.get()
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return cooked
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func load*(v: ValidatorSig): Opt[CookedSig] =
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## Parse signature blob - this may fail
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var parsed: blscurve.Signature
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if fromBytes(parsed, v.blob):
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Opt.some(CookedSig(parsed))
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else:
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Opt.none(CookedSig)
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func init*(agg: var AggregatePublicKey, pubkey: CookedPubKey) {.inline.}=
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## Initializes an aggregate signature context
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agg.init(blscurve.PublicKey(pubkey))
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func init*(T: type AggregatePublicKey, pubkey: CookedPubKey): T =
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result.init(pubkey)
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func aggregate*(agg: var AggregatePublicKey, pubkey: CookedPubKey) {.inline.}=
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## Aggregate two valid Validator Public Keys
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agg.aggregate(blscurve.PublicKey(pubkey))
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func finish*(agg: AggregatePublicKey): CookedPubKey {.inline.} =
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## Canonicalize an AggregatePublicKey into a signature
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var pubkey: blscurve.PublicKey
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pubkey.finish(agg)
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CookedPubKey(pubkey)
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func init*(agg: var AggregateSignature, sig: CookedSig) {.inline.}=
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## Initializes an aggregate signature context
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agg.init(blscurve.Signature(sig))
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func init*(T: type AggregateSignature, sig: CookedSig): T =
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result.init(sig)
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func aggregate*(agg: var AggregateSignature, sig: CookedSig) {.inline.}=
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## Aggregate two valid Validator Signatures
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agg.aggregate(blscurve.Signature(sig))
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func finish*(agg: AggregateSignature): CookedSig {.inline.} =
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## Canonicalize an AggregateSignature into a signature
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var sig: blscurve.Signature
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sig.finish(agg)
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CookedSig(sig)
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# https://github.com/ethereum/consensus-specs/blob/v1.4.0-beta.1/specs/phase0/beacon-chain.md#bls-signatures
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func blsVerify*(
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pubkey: CookedPubKey, message: openArray[byte],
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signature: CookedSig): bool =
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## Check that a signature is valid for a message
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## under the provided public key.
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## returns `true` if the signature is valid, `false` otherwise.
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##
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## The proof-of-possession MUST be verified before calling this function.
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## It is recommended to use the overload that accepts a proof-of-possession
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## to enforce correct usage.
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PublicKey(pubkey).verify(message, blscurve.Signature(signature))
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# https://github.com/ethereum/consensus-specs/blob/v1.4.0-beta.1/specs/phase0/beacon-chain.md#bls-signatures
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proc blsVerify*(
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pubkey: ValidatorPubKey, message: openArray[byte],
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signature: CookedSig): bool =
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## Check that a signature is valid for a message
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## under the provided public key.
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## returns `true` if the signature and the pubkey is valid, `false` otherwise.
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##
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## The proof-of-possession MUST be verified before calling this function.
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## It is recommended to use the overload that accepts a proof-of-possession
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## to enforce correct usage.
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let
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parsedKey = pubkey.loadWithCache()
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# Guard against invalid signature blobs that fail to parse
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parsedKey.isSome() and blsVerify(parsedKey.get(), message, signature)
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proc blsVerify*(
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pubkey: ValidatorPubKey | CookedPubKey, message: openArray[byte],
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signature: ValidatorSig): bool =
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let
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parsedSig = signature.load()
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# Guard against invalid signature blobs that fail to parse
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parsedSig.isSome() and blsVerify(pubkey, message, parsedSig.get())
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func blsVerify*(sigSet: SignatureSet): bool =
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## Unbatched verification
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## of 1 SignatureSet
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## tuple[pubkey: blscurve.PublicKey, message: array[32, byte], blscurve.signature: Signature]
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verify(
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sigSet.pubkey,
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sigSet.message,
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sigSet.signature
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)
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func blsSign*(privkey: ValidatorPrivKey, message: openArray[byte]): CookedSig =
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## Computes a signature from a secret key and a message
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CookedSig(SecretKey(privkey).sign(message))
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func blsFastAggregateVerify*(
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publicKeys: openArray[CookedPubKey],
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message: openArray[byte],
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signature: CookedSig
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): bool =
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## Verify the aggregate of multiple signatures on the same message
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## This function is faster than AggregateVerify
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##
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## The proof-of-possession MUST be verified before calling this function.
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## It is recommended to use the overload that accepts a proof-of-possession
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## to enforce correct usage.
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# TODO: Note: `invalid` in the following paragraph means invalid by construction
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# The keys/signatures are not even points on the elliptic curves.
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# To respect both the IETF API and the fact that
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# we can have invalid public keys (as in not point on the elliptic curve),
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# requiring a wrapper indirection,
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# we need a first pass to extract keys from the wrapper
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# and then call fastAggregateVerify.
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# Instead:
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# - either we expose a new API: context + init-update-finish
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# in blscurve which already exists internally
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# - or at network/databases/serialization boundaries we do not
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# allow invalid BLS objects to pollute consensus routines
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let keys = mapIt(publicKeys, PublicKey(it))
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fastAggregateVerify(keys, message, blscurve.Signature(signature))
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proc blsFastAggregateVerify*(
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publicKeys: openArray[ValidatorPubKey],
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message: openArray[byte],
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signature: CookedSig
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): bool =
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var unwrapped: seq[PublicKey]
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for pubkey in publicKeys:
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let realkey = pubkey.loadWithCache()
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if realkey.isNone:
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return false
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unwrapped.add PublicKey(realkey.get)
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fastAggregateVerify(unwrapped, message, blscurve.Signature(signature))
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func blsFastAggregateVerify*(
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publicKeys: openArray[CookedPubKey],
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message: openArray[byte],
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signature: ValidatorSig
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): bool =
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let parsedSig = signature.load()
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parsedSig.isSome and blsFastAggregateVerify(publicKeys, message, parsedSig.get())
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proc blsFastAggregateVerify*(
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publicKeys: openArray[ValidatorPubKey],
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message: openArray[byte],
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signature: ValidatorSig
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): bool =
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let parsedSig = signature.load()
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parsedSig.isSome and blsFastAggregateVerify(publicKeys, message, parsedSig.get())
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proc blsFastAggregateVerify*(
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fullParticipationAggregatePublicKey: ValidatorPubKey,
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nonParticipatingPublicKeys: openArray[ValidatorPubKey],
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message: openArray[byte],
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signature: CookedSig
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): bool =
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let unwrappedFull = fullParticipationAggregatePublicKey.loadWithCache.valueOr:
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return false
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var unwrapped = newSeqOfCap[PublicKey](nonParticipatingPublicKeys.len)
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for pubkey in nonParticipatingPublicKeys:
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let realkey = pubkey.loadWithCache.valueOr:
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return false
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unwrapped.add PublicKey(realkey)
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fastAggregateVerify(
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PublicKey(unwrappedFull), unwrapped,
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message, blscurve.Signature(signature))
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proc blsFastAggregateVerify*(
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fullParticipationAggregatePublicKey: ValidatorPubKey,
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nonParticipatingPublicKeys: openArray[ValidatorPubKey],
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message: openArray[byte],
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signature: ValidatorSig
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): bool =
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let parsedSig = signature.load()
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parsedSig.isSome and blsFastAggregateVerify(
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fullParticipationAggregatePublicKey, nonParticipatingPublicKeys,
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message, parsedSig.get())
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proc blsFastAggregateVerify*(
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allPublicKeys: openArray[ValidatorPubKey],
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fullParticipationAggregatePublicKey: ValidatorPubKey,
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participantBits: BitArray,
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message: openArray[byte],
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signature: ValidatorSig
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): bool =
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const maxParticipants = participantBits.bits
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var numParticipants = 0
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for idx in 0 ..< maxParticipants:
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if participantBits[idx]:
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inc numParticipants
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return
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if numParticipants < 1:
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false
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elif numParticipants > maxParticipants div 2:
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var nonParticipatingPublicKeys = newSeqOfCap[ValidatorPubKey](
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maxParticipants - numParticipants)
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for idx, pubkey in allPublicKeys:
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if not participantBits[idx]:
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nonParticipatingPublicKeys.add pubkey
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blsFastAggregateVerify(
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fullParticipationAggregatePublicKey, nonParticipatingPublicKeys,
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message, signature)
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else:
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var publicKeys = newSeqOfCap[ValidatorPubKey](numParticipants)
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for idx, pubkey in allPublicKeys:
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if participantBits[idx]:
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publicKeys.add pubkey
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blsFastAggregateVerify(publicKeys, message, signature)
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# Codecs
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# ----------------------------------------------------------------------
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func `$`*(x: ValidatorPrivKey): string =
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"<private key>"
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func `$`*(x: ValidatorPubKey | ValidatorSig): string =
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x.blob.toHex()
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func toRaw*(x: ValidatorPrivKey): array[32, byte] =
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# TODO: distinct type - see https://github.com/status-im/nim-blscurve/pull/67
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when BLS_BACKEND == BLST:
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result = SecretKey(x).exportRaw()
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else:
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# Miracl exports to 384-bit arrays, but Curve order is 256-bit
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let raw = SecretKey(x).exportRaw()
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result[0..32-1] = raw.toOpenArray(48-32, 48-1)
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template toRaw*(x: ValidatorPubKey | ValidatorSig): auto =
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x.blob
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template toRaw*(x: TrustedSig): auto =
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x.data
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func toHex*(x: BlsCurveType): string =
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toHex(toRaw(x))
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func toHex*(x: CookedPubKey): string =
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toHex(x.toPubKey())
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func `$`*(x: CookedPubKey): string =
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$(x.toPubKey())
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func toValidatorSig*(x: CookedSig): ValidatorSig =
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ValidatorSig(blob: blscurve.Signature(x).exportRaw())
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func fromRaw*(T: type ValidatorPrivKey, bytes: openArray[byte]): BlsResult[T] =
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var val: SecretKey
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if val.fromBytes(bytes):
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ok ValidatorPrivKey(val)
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else:
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err "bls: invalid private key"
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func fromRaw*(BT: type[ValidatorPubKey | ValidatorSig], bytes: openArray[byte]): BlsResult[BT] =
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# Signatures and keys are deserialized lazily
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if bytes.len() != sizeof(BT):
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err "bls: invalid bls length"
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else:
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ok BT(blob: toArray(sizeof(BT), bytes))
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func fromHex*(T: type BlsCurveType, hexStr: string): BlsResult[T] {.inline.} =
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## Initialize a BLSValue from its hex representation
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try:
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T.fromRaw(hexStr.hexToSeqByte())
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except ValueError:
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err "bls: cannot parse value"
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func `==`*(a, b: ValidatorPubKey | ValidatorSig): bool =
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equalMem(unsafeAddr a.blob[0], unsafeAddr b.blob[0], sizeof(a.blob))
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func `==`*(a, b: ValidatorPrivKey): bool {.error: "Secret keys should stay secret".}
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# Hashing
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# ----------------------------------------------------------------------
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template hash*(x: ValidatorPubKey | ValidatorSig): Hash =
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static: doAssert sizeof(Hash) <= x.blob.len div 2
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# We use rough "middle" of blob for the hash, assuming this is where most of
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# the entropy is found
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cast[ptr Hash](unsafeAddr x.blob[x.blob.len div 2])[]
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# Comparison/Sorting
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# ----------------------------------------------------------------------
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template `<`*(x, y: ValidatorPubKey): bool =
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x.blob < y.blob
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# Serialization
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# ----------------------------------------------------------------------
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{.pragma: serializationRaises, raises: [SerializationError, IOError].}
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proc writeValue*(
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writer: var JsonWriter, value: ValidatorPubKey | CookedPubKey
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) {.inline, raises: [IOError].} =
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writer.writeValue(value.toHex())
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proc readValue*(reader: var JsonReader, value: var ValidatorPubKey)
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{.serializationRaises.} =
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let key = ValidatorPubKey.fromHex(reader.readValue(string))
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if key.isOk:
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value = key.get
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else:
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# TODO: Can we provide better diagnostic?
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raiseUnexpectedValue(reader, "Valid hex-encoded public key expected")
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proc writeValue*(
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writer: var JsonWriter, value: ValidatorSig
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) {.inline, raises: [IOError].} =
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# Workaround: https://github.com/status-im/nimbus-eth2/issues/374
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writer.writeValue(value.toHex())
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proc readValue*(reader: var JsonReader, value: var ValidatorSig)
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{.serializationRaises.} =
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let sig = ValidatorSig.fromHex(reader.readValue(string))
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if sig.isOk:
|
|
value = sig.get
|
|
else:
|
|
# TODO: Can we provide better diagnostic?
|
|
raiseUnexpectedValue(reader, "Valid hex-encoded signature expected")
|
|
|
|
proc writeValue*(
|
|
writer: var JsonWriter, value: ValidatorPrivKey
|
|
) {.inline, raises: [IOError].} =
|
|
writer.writeValue(value.toHex())
|
|
|
|
proc readValue*(reader: var JsonReader, value: var ValidatorPrivKey)
|
|
{.serializationRaises.} =
|
|
let key = ValidatorPrivKey.fromHex(reader.readValue(string))
|
|
if key.isOk:
|
|
value = key.get
|
|
else:
|
|
# TODO: Can we provide better diagnostic?
|
|
raiseUnexpectedValue(reader, "Valid hex-encoded private key expected")
|
|
|
|
template fromSszBytes*(T: type[ValidatorPubKey | ValidatorSig], bytes: openArray[byte]): auto =
|
|
let v = fromRaw(T, bytes)
|
|
if v.isErr:
|
|
raise newException(MalformedSszError, $v.error)
|
|
v[]
|
|
|
|
# Logging
|
|
# ----------------------------------------------------------------------
|
|
|
|
func shortLog*(x: ValidatorPubKey | ValidatorSig): string =
|
|
## Logging for wrapped BLS types
|
|
## that may contain valid or non-validated data
|
|
byteutils.toHex(x.blob.toOpenArray(0, 3))
|
|
|
|
func shortLog*(x: CookedPubKey): string =
|
|
let raw = x.toRaw()
|
|
byteutils.toHex(raw.toOpenArray(0, 3))
|
|
|
|
func shortLog*(x: ValidatorPrivKey): string =
|
|
## Logging for raw unwrapped BLS types
|
|
"<private key>"
|
|
|
|
func shortLog*(x: TrustedSig): string =
|
|
byteutils.toHex(x.data.toOpenArray(0, 3))
|
|
|
|
# Initialization
|
|
# ----------------------------------------------------------------------
|
|
|
|
# TODO more specific exceptions? don't raise?
|
|
|
|
# For confutils
|
|
func init*(T: typedesc[ValidatorPrivKey], hex: string): T {.noinit, raises: [ValueError].} =
|
|
let v = T.fromHex(hex)
|
|
if v.isErr:
|
|
raise (ref ValueError)(msg: $v.error)
|
|
v[]
|
|
|
|
# For mainchain monitor
|
|
func init*(T: typedesc[ValidatorPubKey], data: array[RawPubKeySize, byte]): T {.noinit, raises: [ValueError].} =
|
|
let v = T.fromRaw(data)
|
|
if v.isErr:
|
|
raise (ref ValueError)(msg: $v.error)
|
|
v[]
|
|
|
|
# For mainchain monitor
|
|
func init*(T: typedesc[ValidatorSig], data: array[RawSigSize, byte]): T {.noinit, raises: [ValueError].} =
|
|
let v = T.fromRaw(data)
|
|
if v.isErr:
|
|
raise (ref ValueError)(msg: $v.error)
|
|
v[]
|
|
|
|
func infinity*(T: type ValidatorSig): T =
|
|
result.blob[0] = byte 0xC0
|
|
|
|
func burnMem*(key: var ValidatorPrivKey) =
|
|
burnMem(addr key, sizeof(ValidatorPrivKey))
|
|
|
|
{.push warning[ProveField]:off.} # https://github.com/nim-lang/Nim/issues/22060
|
|
proc keyGen(rng: var HmacDrbgContext): BlsResult[blscurve.SecretKey] =
|
|
var
|
|
pubkey: blscurve.PublicKey
|
|
let bytes = rng.generate(array[32, byte])
|
|
result.ok default(blscurve.SecretKey)
|
|
if not keyGen(bytes, pubkey, result.value):
|
|
return err "key generation failed"
|
|
{.pop.}
|
|
|
|
proc secretShareId(x: uint32) : blscurve.ID =
|
|
let bytes: array[8, uint32] = [uint32 x, 0, 0, 0, 0, 0, 0, 0]
|
|
blscurve.ID.fromUint32(bytes)
|
|
|
|
func generateSecretShares*(sk: ValidatorPrivKey,
|
|
rng: var HmacDrbgContext,
|
|
k: uint32, n: uint32): BlsResult[seq[SecretShare]] =
|
|
doAssert k > 0 and k <= n
|
|
|
|
var originPts: seq[blscurve.SecretKey]
|
|
originPts.add(blscurve.SecretKey(sk))
|
|
for i in 1 ..< k:
|
|
originPts.add(? keyGen(rng))
|
|
|
|
var shares: seq[SecretShare]
|
|
for i in uint32(0) ..< n:
|
|
let numericShareId = i + 1 # the share id must not be zero
|
|
let blsShareId = secretShareId(numericShareId)
|
|
let secret = genSecretShare(originPts, blsShareId)
|
|
let share = SecretShare(key: ValidatorPrivKey(secret), id: numericShareId)
|
|
shares.add(share)
|
|
|
|
return ok shares
|
|
|
|
func toSignatureShare*(sig: CookedSig, id: uint32): SignatureShare =
|
|
result.sign = blscurve.Signature(sig)
|
|
result.id = id
|
|
|
|
func recoverSignature*(sings: seq[SignatureShare]): CookedSig =
|
|
let signs = sings.mapIt(it.sign)
|
|
let ids = sings.mapIt(secretShareId(it.id))
|
|
CookedSig blscurve.recover(signs, ids).expect(
|
|
"valid shares (validated when loading the keystore)")
|
|
|
|
proc confirmShares*(pubKey: ValidatorPubKey,
|
|
shares: seq[SecretShare],
|
|
rng: var HmacDrbgContext): bool =
|
|
let confirmationData = rng.generate(array[32, byte])
|
|
var signs: seq[SignatureShare]
|
|
for share in items(shares):
|
|
let signature = share.key.blsSign(confirmationData).toSignatureShare(share.id);
|
|
signs.add(signature)
|
|
let recovered = signs.recoverSignature()
|
|
return pubKey.blsVerify(confirmationData, recovered)
|