GHSA-XW37-57QP-9MM4

Vulnerability from github – Published: 2021-06-29 21:14 – Updated: 2023-02-09 19:40
VLAI
Summary
Consensus flaw during block processing in github.com/ethereum/go-ethereum
Details

Impact

A consensus-vulnerability in Geth could cause a chain split, where vulnerable versions refuse to accept the canonical chain.

Description

A flaw was repoted at 2020-08-11 by John Youngseok Yang (Software Platform Lab), where a particular sequence of transactions could cause a consensus failure.

  • Tx 1:
  • sender invokes caller.
  • caller invokes 0xaa. 0xaa has 3 wei, does a self-destruct-to-self

  • caller does a 1 wei -call to 0xaa, who thereby has 1 wei (the code in 0xaa still executed, since the tx is still ongoing, but doesn't redo the selfdestruct, it takes a different path if callvalue is non-zero)

  • Tx 2:

  • sender does a 5-wei call to 0xaa. No exec (since no code).

In geth, the result would be that 0xaa had 6 wei, whereas OE reported (correctly) 5 wei. Furthermore, in geth, if the second tx was not executed, the 0xaa would be destructed, resulting in 0 wei. Thus obviously wrong.

It was determined that the root cause was this commit from this PR. The semantics of createObject was subtly changd, into returning a non-nil object (with deleted=true) where it previously did not if the account had been destructed. This return value caused the new object to inherit the old balance:

func (s *StateDB) CreateAccount(addr common.Address) {
    newObj, prev := s.createObject(addr)
    if prev != nil {
        newObj.setBalance(prev.data.Balance)
    }
}

It was determined that the minimal possible correct fix was

+++ b/core/state/statedb.go
@@ -589,7 +589,10 @@ func (s *StateDB) createObject(addr common.Address) (newobj, prev *stateObject)
                s.journal.append(resetObjectChange{prev: prev, prevdestruct: prevdestruct})
        }
        s.setStateObject(newobj)
-       return newobj, prev
+       if prev != nil && !prev.deleted {
+               return newobj, prev
+       }
+       return newobj, nil

Patches

See above. The fix was included in Geth v1.9.20 "Paragade".

Credits

The bug was found by @johnyangk and reported via bounty@ethereum.org.

For more information

If you have any questions or comments about this advisory: * Open an issue in go-ethereum * Email us at security@ethereum.org

Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/ethereum/go-ethereum"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.9.4"
            },
            {
              "fixed": "1.9.20"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2020-26265"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-682"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2021-05-21T21:15:07Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Impact\n\nA consensus-vulnerability in Geth could cause a chain split, where vulnerable versions refuse to accept the canonical chain. \n\n### Description\n\n\nA flaw was repoted at 2020-08-11 by John Youngseok Yang (Software Platform Lab), where a particular sequence of transactions could cause a consensus failure.\n\n- Tx 1:\n  - `sender` invokes `caller`.\n  - `caller` invokes `0xaa`. `0xaa` has 3 wei, does a self-destruct-to-self\n  - `caller` does a  `1 wei` -call to `0xaa`, who thereby has 1 wei (the code in `0xaa` still executed, since the tx is still ongoing, but doesn\u0027t redo the selfdestruct, it takes a different path if callvalue is non-zero)\n\n- Tx 2:\n  - `sender` does a 5-wei call to 0xaa. No exec (since no code). \n\nIn geth, the result would be that `0xaa` had `6 wei`, whereas OE reported (correctly) `5` wei. Furthermore, in geth, if the second tx was not executed, the `0xaa` would be destructed, resulting in `0 wei`. Thus obviously wrong. \n\nIt was determined that the root cause was this [commit](https://github.com/ethereum/go-ethereum/commit/223b950944f494a5b4e0957fd9f92c48b09037ad) from [this PR](https://github.com/ethereum/go-ethereum/pull/19953). The semantics of `createObject` was subtly changd, into returning a non-nil object (with `deleted=true`) where it previously did not if the account had been destructed. This return value caused the new object to inherit the old `balance`:\n\n```golang\nfunc (s *StateDB) CreateAccount(addr common.Address) {\n\tnewObj, prev := s.createObject(addr)\n\tif prev != nil {\n\t\tnewObj.setBalance(prev.data.Balance)\n\t}\n}\n```\n\nIt was determined that the minimal possible correct fix was\n\n```diff\n+++ b/core/state/statedb.go\n@@ -589,7 +589,10 @@ func (s *StateDB) createObject(addr common.Address) (newobj, prev *stateObject)\n                s.journal.append(resetObjectChange{prev: prev, prevdestruct: prevdestruct})\n        }\n        s.setStateObject(newobj)\n-       return newobj, prev\n+       if prev != nil \u0026\u0026 !prev.deleted {\n+               return newobj, prev\n+       }\n+       return newobj, nil\n```\n\n### Patches\n\nSee above. The fix was included in Geth `v1.9.20` \"Paragade\".\n\n### Credits\n\nThe bug was found by @johnyangk and reported via bounty@ethereum.org.\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [go-ethereum](https://github.com/ethereum/go-ethereum)\n* Email us at [security@ethereum.org](mailto:security@ethereum.org)",
  "id": "GHSA-xw37-57qp-9mm4",
  "modified": "2023-02-09T19:40:33Z",
  "published": "2021-06-29T21:14:16Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ethereum/go-ethereum/security/advisories/GHSA-xw37-57qp-9mm4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2020-26265"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ethereum/go-ethereum/pull/21080"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ethereum/go-ethereum/pull/21409"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ethereum/go-ethereum/commit/87c0ba92136a75db0ab2aba1046d4a9860375d6a"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ethereum/go-ethereum"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ethereum/go-ethereum/releases/tag/v1.9.20"
    },
    {
      "type": "WEB",
      "url": "https://pkg.go.dev/vuln/GO-2021-0105"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Consensus flaw during block processing in github.com/ethereum/go-ethereum"
}



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