fix: harden EIP-712 typed data encoding against amplification and malformed types - #214
fix: harden EIP-712 typed data encoding against amplification and malformed types#214patrislav wants to merge 1 commit into
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…formed types Follow-up to #210. Retesting surfaced a value-driven amplification path that the schema-only cycle check does not cover, plus a panic reachable from any caller that decodes untrusted typed data. - Memoize EncodeType/TypeHash per Encode call. HashStruct previously recomputed a type's hash for every array element, so a message holding an array of custom structs multiplied schema-processing cost by the element count. The cache is shared across the whole call tree, domain and message alike, so type-dependent work happens at most once per distinct type. - Add functional Options bounding both the schema and the message: WithMaxTypes, WithMaxFieldsPerType, WithMaxWalkVisits, WithMaxArrayElements, WithMaxRecursionDepth and WithMaxTotalValues. The zero value means unlimited, so existing callers are unaffected. Value-driven checks run before allocating or recursing, so an oversized array is rejected up front. - Fix a panic in typedDataDecodePrimitiveValue. ABIUnmarshalStringValuesAny returns fewer values than requested, with a nil error, for a type token it does not recognize; the caller then indexed out[0] and panicked on input as simple as {"type": ""} or {"type": "foobar"}. - Make ValidateTypeGraph's walk an explicit-stack DFS and cap nesting at maxTypeGraphDepth. The encoders below it still recurse one frame per level, and a long enough type chain overflowed the goroutine stack fatally. The ceiling is measured from each type's longest downward path rather than the live DFS stack, which memoization can cut short depending on map iteration order. - Reject field types no encoder can handle (unknown names, uint0/uint7/uint2560, bytes0/bytes33, bare uint/int, malformed array suffixes) instead of letting them fail deep inside the encoders. Note: schema validation is stricter than before. A schema declaring a type with an invalid field type previously decoded and only failed if that type was actually encoded; it is now rejected at decode. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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| // WithMaxWalkVisits, WithMaxArrayElements, WithMaxRecursionDepth, and | ||
| // WithMaxTotalValues. With no opts, behavior is unbounded, matching prior | ||
| // versions of this function. | ||
| func (t *TypedData) Encode(opts ...Option) ([]byte, []byte, error) { |
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Changing this public method from Encode() ([]byte, []byte, error) to Encode(...Option) ([]byte, []byte, error) keeps direct td.Encode() calls working, but it changes the method set: downstream code that stores *TypedData behind an interface requiring Encode(), or assigns td.Encode to a func(), no longer compiles. Since this package is consumed as a library and the option-bearing path can be exposed with a separate helper/method, keeping the original signature avoids a source-compatibility break for existing callers.
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Follow-up to #210. End-to-end retesting of that fix surfaced a residual value-driven amplification path the schema-only cycle check cannot cover, and auditing the surrounding code turned up a reachable panic and a latent stack overflow.
What's here
1. Memoize
EncodeType/TypeHashperEncodecallHashStructrecomputed a type'sTypeHash— and thereforeEncodeTypeover its whole dependency DAG — for every array element. A message with an array of custom structs multiplied schema-processing cost by the element count.A
typeInfocache is now created once perEncodeand shared across the entire call tree (domain and message alike), so type-dependent work happens at most once per distinct type. This also fixes a second-order case unrelated to arrays: a diamond-shaped DAG previously re-expanded shared sub-types multiple times within a singleEncodeTypecall.Measured on a depth-6 diamond struct in an array — scaling is now flat per element (~57µs), i.e. linear in encoded values:
Public signatures of
EncodeType,TypeHashandHashStructare unchanged; they delegate to the cached core with a fresh cache.2. Functional options for schema and value budgets
WithMaxTypes,WithMaxFieldsPerType,WithMaxWalkVisits,WithMaxArrayElements,WithMaxRecursionDepth,WithMaxTotalValues— accepted byValidateTypeGraph,EncodeandEncodeDigest.The zero value of every option means unlimited, so existing callers are unaffected. Value-driven checks run before allocating or recursing, so an oversized array is rejected up front rather than after the work is done. This consolidates limits that downstream services were otherwise reimplementing on top of ethkit.
3. Fix a reachable panic in
typedDataDecodePrimitiveValueABIUnmarshalStringValuesAnyreturns fewer values than requested — with a nil error — for a type token matching none of its branches, silently violating its positional contract. The caller then indexedout[0]:Triggered by input as simple as
{"name":"x","type":""}or"type":"foobar","tuple","byte","String","address ". Any service decoding untrusted typed data without a panic barrier crashes on it.4. Iterative type-graph DFS + unconditional depth ceiling
ValidateTypeGraph's walk was recursive, one frame per type. An acyclic linear type chain therefore still overflowed the goroutine stack — fatally, not recoverably — at roughly 2M types. Cycle detection did not help; the graph is a valid DAG.The walk is now an explicit-stack DFS, and type nesting is capped at
maxTypeGraphDepth = 1024. The cap is unconditional rather than anOptionbecauseUnmarshalJSONvalidates without options, and it protects the encoders below it (encodeTypeCached,hashStruct,encodeValue), which still recurse one frame per level.The ceiling is measured from each type's longest downward path, not the live DFS stack: memoization can cut that stack short depending on map iteration order, which would let an over-deep chain through non-deterministically. Verified exact and stable at the 1024/1025 boundary across repeated runs.
5. Reject field types no encoder can handle
ValidateTypeGraphnow validates every field type up front instead of letting bad ones fail deep inside the encoders: unknown names,uint0/uint7/uint2560,bytes0/bytes33, bareuint/int(EIP-712 requires the canonicaluint256/int256, and the packer cannot size them), and malformed array suffixes such asuint256[,uint256[a],[]uint256.Schema validation is stricter than before. A schema declaring a type with an invalid field type previously decoded fine and only failed if that type was actually encoded — it is now rejected at decode.
The existing corpus is unaffected: all real-world payloads in the test suite (including the Seaport cases) pass unchanged, and the typed-data tests only use
address,bytes,bytes32,string,uint8/128/256, arrays and custom types.Testing
ethcodersuite passes, including under-race.TestTypedDataMemoization,TestTypedDataBudgetLimits,TestTypedDataInvalidPrimitiveType,TestTypedDataTypeGraphHardening.bytesN, null values, nested arrays, scalar/array/struct mismatches) — all return errors, none panic.Known issues left alone (pre-existing, out of scope)
uintNfield encodes as its absolute value with no error, because the 128/256 path builds abig.IntviaSetStringwithout a sign or range check (the 8/16/32/64 paths do check, viaParseUint).chainIdsuch as"0xzz"silently parses to0—UnmarshalJSONignoresSetString's ok bool.EncodeType/TypeHash/HashStructcalled directly still skipValidateTypeGraph, so a cyclic graph recurses without bound.Encode/EncodeDigestand the JSON decode path all validate first.Happy to fold any of those into this PR or file them separately.
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