ghsa-498w-5j49-vqjg
Vulnerability from github
Impact
For some in-circuit values, it is possible to construct two valid decomposition to bits. In addition to the canonical decomposition of a, for small values there exists a second decomposition for a+r (where r is the modulus the values are being reduced by). The second decomposition was possible due to overflowing the field where the values are defined.
Internally, the comparison methods frontend.API.Cmp and frontend.API.IsLess used binary decomposition and checked the bitwise differences. This allows a malicious prover to construct a valid proof for a statement a < b even if a > b.
The issue impacts all users using API.Cmp or API.IsLess methods. Additionally, it impacts the users using bits.ToBinary or API.ToBinary methods if full-width decomposition is requested (the default behaviour if no options are given).
The issues does not impact comparison methods in field emulation (package std/math/emulated) and dedicated comparison package (std/math/cmp).
Patches
Fix has been implemented in pull request #835 and merged in commit 59a4087261a6c73f13e80d695c17b398c3d0934f to master branch. The release v0.9.0 and onwards include the fix.
The fix added additional comparison of the decomposed bit-vector to the modulus of the in-circuit values.
Workarounds
Upgrading to version v0.9.0 should fix the issue without needing to change the calls to value comparison methods.
Alternatively, users can use the std/math/cmp gadget, which additionally allows to bound the number of bits being compared, making the comparisons more efficient if the bound on the absolute difference of the values is known.
References
- https://github.com/Consensys/gnark/pull/835
- https://github.com/zkopru-network/zkopru/issues/116
- https://github.com/iden3/circomlib/pull/48
Acknowledgement
The vulnerability was reported by Marcin Kostrzewa @ Reilabs.
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/consensys/gnark"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.9.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2023-44378"
],
"database_specific": {
"cwe_ids": [
"CWE-191",
"CWE-697"
],
"github_reviewed": true,
"github_reviewed_at": "2023-10-04T14:44:08Z",
"nvd_published_at": "2023-10-09T14:15:10Z",
"severity": "MODERATE"
},
"details": "### Impact\n\nFor some in-circuit values, it is possible to construct two valid decomposition to bits. In addition to the canonical decomposition of `a`, for small values there exists a second decomposition for `a+r` (where `r` is the modulus the values are being reduced by). The second decomposition was possible due to overflowing the field where the values are defined.\n\nInternally, the comparison methods `frontend.API.Cmp` and `frontend.API.IsLess` used binary decomposition and checked the bitwise differences. This allows a malicious prover to construct a valid proof for a statement `a \u003c b` even if `a \u003e b`.\n\nThe issue impacts all users using `API.Cmp` or `API.IsLess` methods. Additionally, it impacts the users using `bits.ToBinary` or `API.ToBinary` methods if full-width decomposition is requested (the default behaviour if no options are given).\n\nThe issues does not impact comparison methods in field emulation (package `std/math/emulated`) and dedicated comparison package (`std/math/cmp`).\n\n### Patches\n\nFix has been implemented in pull request #835 and merged in commit 59a4087261a6c73f13e80d695c17b398c3d0934f to master branch. The release v0.9.0 and onwards include the fix.\n\nThe fix added additional comparison of the decomposed bit-vector to the modulus of the in-circuit values. \n\n### Workarounds\n\nUpgrading to version v0.9.0 should fix the issue without needing to change the calls to value comparison methods.\n\nAlternatively, users can use the `std/math/cmp` gadget, which additionally allows to bound the number of bits being compared, making the comparisons more efficient if the bound on the absolute difference of the values is known.\n\n### References\n\n* https://github.com/Consensys/gnark/pull/835\n* https://github.com/zkopru-network/zkopru/issues/116\n* https://github.com/iden3/circomlib/pull/48\n\n### Acknowledgement\n\nThe vulnerability was reported by [Marcin Kostrzewa](https://github.com/kustosz) @ [Reilabs](https://reilabs.io/).",
"id": "GHSA-498w-5j49-vqjg",
"modified": "2023-10-13T23:13:57Z",
"published": "2023-10-04T14:44:08Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/Consensys/gnark/security/advisories/GHSA-498w-5j49-vqjg"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2023-44378"
},
{
"type": "WEB",
"url": "https://github.com/zkopru-network/zkopru/issues/116"
},
{
"type": "WEB",
"url": "https://github.com/Consensys/gnark/pull/835"
},
{
"type": "WEB",
"url": "https://github.com/Consensys/gnark/commit/59a4087261a6c73f13e80d695c17b398c3d0934f"
},
{
"type": "PACKAGE",
"url": "https://github.com/Consensys/gnark"
},
{
"type": "ADVISORY",
"url": "https://github.com/advisories/GHSA-498w-5j49-vqjg"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N",
"type": "CVSS_V3"
}
],
"summary": "gnark unsoundness in variable comparison / non-unique binary decomposition"
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.