Vulnerability-Lookup

GHSA-M9C9-MC2H-9WJW

Vulnerability from github – Published: 2025-01-14 22:04 – Updated: 2025-01-14 22:04

Summary

Lodestar snappy checksum issue

Details

Impact

Unintended permanent chain split affecting greater than or equal to 25% of the network, requiring hard fork (network partition requiring hard fork)

Lodestar does not verify checksum in snappy framing uncompressed chunks.

Vulnerability Details

In Req/Resp protocol the messages are encoded by using ssz_snappy encoding, which is a snappy framing compression over ssz encoded message.

In snappy framing format there are uncompressed chunks, each such chunk is prefixed with a checksum.

Let's see how golang implementation parses such chunks - https://github.com/golang/snappy/blob/master/decode.go#L176

    case chunkTypeUncompressedData:
            // Section 4.3. Uncompressed data (chunk type 0x01).
            if chunkLen < checksumSize {
                r.err = ErrCorrupt
                return r.err
            }
            buf := r.buf[:checksumSize]
            if !r.readFull(buf, false) {
                return r.err
            }
            checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
            // Read directly into r.decoded instead of via r.buf.
            n := chunkLen - checksumSize
            if n > len(r.decoded) {
                r.err = ErrCorrupt
                return r.err
            }
            if !r.readFull(r.decoded[:n], false) {
                return r.err
            }
            if crc(r.decoded[:n]) != checksum {
                r.err = ErrCorrupt
                return r.err
            }
            r.i, r.j = 0, n
            continue

As you can see, if checksum is incorrect, decoder fails and returns error.

Now let's look at lodestar decoder https://github.com/ChainSafe/lodestar/blob/unstable/packages/reqresp/src/encodingStrategies/sszSnappy/snappyFrames/uncompress.ts#L17

uncompress(chunk: Uint8ArrayList): Uint8ArrayList | null {
    this.buffer.append(chunk);
    const result = new Uint8ArrayList();
    while (this.buffer.length > 0) {
      if (this.buffer.length < 4) break;

      const type = getChunkType(this.buffer.get(0));
      const frameSize = getFrameSize(this.buffer, 1);

      if (this.buffer.length - 4 < frameSize) {
        break;
      }

      const data = this.buffer.subarray(4, 4 + frameSize);
      this.buffer.consume(4 + frameSize);

      if (!this.state.foundIdentifier && type !== ChunkType.IDENTIFIER) {
        throw "malformed input: must begin with an identifier";
      }

      if (type === ChunkType.IDENTIFIER) {
        if (!Buffer.prototype.equals.call(data, IDENTIFIER)) {
          throw "malformed input: bad identifier";
        }
        this.state.foundIdentifier = true;
        continue;
      }

      if (type === ChunkType.COMPRESSED) {
        result.append(uncompress(data.subarray(4)));
      }
      if (type === ChunkType.UNCOMPRESSED) {
1)        result.append(data.subarray(4));
      }
    }
    if (result.length === 0) {
      return null;
    }
    return result;
  }

As you can see, checksum is not verified, bytes are appended to 'result'

Proof of Concept

How to reproduce:

get poc via gist link and run it:

$ node dec1.mjs 
checking chunk type=255
checking chunk type=1
got uncompressed chunk..
Decompressed ok 124 bytes

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "@lodestar/reqresp"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.25.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-354"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2025-01-14T22:04:02Z",
    "nvd_published_at": null,
    "severity": "LOW"
  },
  "details": "### Impact\nUnintended permanent chain split affecting greater than or equal to 25% of the network, requiring hard fork (network partition requiring hard fork)\n\nLodestar does not verify checksum in snappy framing uncompressed chunks.\n\n### Vulnerability Details\nIn Req/Resp protocol the messages are encoded by using ssz_snappy encoding, which is a snappy framing compression over ssz encoded message.\n\nIn snappy framing format there are uncompressed chunks, each such chunk is prefixed with a checksum.\n\nLet\u0027s see how golang implementation parses such chunks - https://github.com/golang/snappy/blob/master/decode.go#L176\n\n```\n\tcase chunkTypeUncompressedData:\n\t\t\t// Section 4.3. Uncompressed data (chunk type 0x01).\n\t\t\tif chunkLen \u003c checksumSize {\n\t\t\t\tr.err = ErrCorrupt\n\t\t\t\treturn r.err\n\t\t\t}\n\t\t\tbuf := r.buf[:checksumSize]\n\t\t\tif !r.readFull(buf, false) {\n\t\t\t\treturn r.err\n\t\t\t}\n\t\t\tchecksum := uint32(buf[0]) | uint32(buf[1])\u003c\u003c8 | uint32(buf[2])\u003c\u003c16 | uint32(buf[3])\u003c\u003c24\n\t\t\t// Read directly into r.decoded instead of via r.buf.\n\t\t\tn := chunkLen - checksumSize\n\t\t\tif n \u003e len(r.decoded) {\n\t\t\t\tr.err = ErrCorrupt\n\t\t\t\treturn r.err\n\t\t\t}\n\t\t\tif !r.readFull(r.decoded[:n], false) {\n\t\t\t\treturn r.err\n\t\t\t}\n\t\t\tif crc(r.decoded[:n]) != checksum {\n\t\t\t\tr.err = ErrCorrupt\n\t\t\t\treturn r.err\n\t\t\t}\n\t\t\tr.i, r.j = 0, n\n\t\t\tcontinue\n```\n\nAs you can see, if checksum is incorrect, decoder fails and returns error.\n\nNow let\u0027s look at lodestar decoder https://github.com/ChainSafe/lodestar/blob/unstable/packages/reqresp/src/encodingStrategies/sszSnappy/snappyFrames/uncompress.ts#L17\n\n```\nuncompress(chunk: Uint8ArrayList): Uint8ArrayList | null {\n    this.buffer.append(chunk);\n    const result = new Uint8ArrayList();\n    while (this.buffer.length \u003e 0) {\n      if (this.buffer.length \u003c 4) break;\n\n      const type = getChunkType(this.buffer.get(0));\n      const frameSize = getFrameSize(this.buffer, 1);\n\n      if (this.buffer.length - 4 \u003c frameSize) {\n        break;\n      }\n\n      const data = this.buffer.subarray(4, 4 + frameSize);\n      this.buffer.consume(4 + frameSize);\n\n      if (!this.state.foundIdentifier \u0026\u0026 type !== ChunkType.IDENTIFIER) {\n        throw \"malformed input: must begin with an identifier\";\n      }\n\n      if (type === ChunkType.IDENTIFIER) {\n        if (!Buffer.prototype.equals.call(data, IDENTIFIER)) {\n          throw \"malformed input: bad identifier\";\n        }\n        this.state.foundIdentifier = true;\n        continue;\n      }\n\n      if (type === ChunkType.COMPRESSED) {\n        result.append(uncompress(data.subarray(4)));\n      }\n      if (type === ChunkType.UNCOMPRESSED) {\n1)        result.append(data.subarray(4));\n      }\n    }\n    if (result.length === 0) {\n      return null;\n    }\n    return result;\n  }\n```\n\nAs you can see, checksum is not verified, bytes are appended to \u0027result\u0027\n\n### Proof of Concept\n\nHow to reproduce:\n\nget poc via [gist link](https://gist.github.com/gln7/aab55674431b1c8d42a59ccf9d7cbf60) and run it:\n\n```\n$ node dec1.mjs \nchecking chunk type=255\nchecking chunk type=1\ngot uncompressed chunk..\nDecompressed ok 124 bytes\n```\n",
  "id": "GHSA-m9c9-mc2h-9wjw",
  "modified": "2025-01-14T22:04:02Z",
  "published": "2025-01-14T22:04:02Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ChainSafe/lodestar/security/advisories/GHSA-m9c9-mc2h-9wjw"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ChainSafe/lodestar/commit/18a0d681dbcc51fb2ac9456f31e91f4e31a18300"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ChainSafe/lodestar"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [],
  "summary": "Lodestar snappy checksum issue"
}

Sightings

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Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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