rustsec-2023-0035
Vulnerability from osv_rustsec
Published
2023-04-17 12:00
Modified
2023-06-13 13:10
Summary
Adverserial use of `make_bitflags!` macro can cause undefined behavior
Details

The macro relied on an expression of the form Enum::Variant always being a variant of the enum. However, it may also be an associated integer constant, in which case there's no guarantee that the value of said constant consists only of bits valid for this bitflag type.

Thus, code like this could create an invalid BitFlags<Test>, which would cause iterating over it to trigger undefined behavior. As the debug formatter internally iterates over the value, it is also affected.

use enumflags2::{bitflags, make_bitflags};

#[bitflags]
#[repr(u8)]
#[derive(Copy, Clone, Debug)]
enum Test {
    A = 1,
    B = 2,
}

impl Test {
    const C: u8 = 69;
}

fn main() {
    let x = make_bitflags!(Test::{C});
    // printing or iterating over x is UB
}
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "categories": [],
        "cvss": null,
        "informational": "unsound"
      },
      "ecosystem_specific": {
        "affected_functions": null,
        "affects": {
          "arch": [],
          "functions": [],
          "os": []
        }
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "enumflags2",
        "purl": "pkg:cargo/enumflags2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.7.0"
            },
            {
              "fixed": "0.7.7"
            }
          ],
          "type": "SEMVER"
        }
      ],
      "versions": []
    }
  ],
  "aliases": [
    "GHSA-qvc4-78gw-pv8p"
  ],
  "database_specific": {
    "license": "CC0-1.0"
  },
  "details": "The macro relied on an expression of the form `Enum::Variant` always being a\nvariant of the enum. However, it may also be an associated integer constant, in\nwhich case there\u0027s no guarantee that the value of said constant consists only of\nbits valid for this bitflag type.\n\nThus, code like this could create an invalid `BitFlags\u003cTest\u003e`, which would cause\niterating over it to trigger undefined behavior. As the debug formatter\ninternally iterates over the value, it is also affected.\n\n```rust\nuse enumflags2::{bitflags, make_bitflags};\n\n#[bitflags]\n#[repr(u8)]\n#[derive(Copy, Clone, Debug)]\nenum Test {\n    A = 1,\n    B = 2,\n}\n\nimpl Test {\n    const C: u8 = 69;\n}\n\nfn main() {\n    let x = make_bitflags!(Test::{C});\n    // printing or iterating over x is UB\n}\n```",
  "id": "RUSTSEC-2023-0035",
  "modified": "2023-06-13T13:10:24Z",
  "published": "2023-04-17T12:00:00Z",
  "references": [
    {
      "type": "PACKAGE",
      "url": "https://crates.io/crates/enumflags2"
    },
    {
      "type": "ADVISORY",
      "url": "https://rustsec.org/advisories/RUSTSEC-2023-0035.html"
    },
    {
      "type": "WEB",
      "url": "https://github.com/meithecatte/enumflags2/releases/tag/v0.7.7"
    }
  ],
  "related": [],
  "severity": [],
  "summary": "Adverserial use of `make_bitflags!` macro can cause undefined behavior"
}


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