GHSA-wvcv-832q-fjg7
Vulnerability from github
Published
2020-12-21 16:56
Modified
2024-11-13 23:01
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
8.7 (High) - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
Summary
RSA weakness in tslite-ng
Details

Impact

The code that performs decryption and padding check in RSA PKCS#1 v1.5 decryption is data dependant. In particular, code in current (as of 0.8.0-alpha38) master https://github.com/tlsfuzzer/tlslite-ng/blob/0812ed60860fa61a6573b2c0e18771414958f46d/tlslite/utils/rsakey.py#L407-L441 and code in 0.7.5 branch https://github.com/tlsfuzzer/tlslite-ng/blob/acdde3161124d6ae37c506b3476aea9996d12e97/tlslite/utils/rsakey.py#L394-L425 has multiple ways in which it leaks information (for one, it aborts as soon as the plaintext doesn't start with 0x00, 0x02) about the decrypted ciphertext (both the bit length of the decrypted message as well as where the first unexpected byte lays).

All TLS servers that enable RSA key exchange as well as applications that use the RSA decryption API directly are vulnerable.

All previous versions of tlslite-ng are vulnerable.

Patches

The patches to fix it are proposed in https://github.com/tlsfuzzer/tlslite-ng/pull/438 https://github.com/tlsfuzzer/tlslite-ng/pull/439

Note: the patches depend on Python processing the individual bytes in side-channel free manner, this is known to not be the case: https://securitypitfalls.wordpress.com/2018/08/03/constant-time-compare-in-python/ As such, users that require side-channel resistance are recommended to use different TLS implementations, as stated in the security policy of tlslite-ng.

Workarounds

There is no way to workaround this issue.

References

https://securitypitfalls.wordpress.com/2018/08/03/constant-time-compare-in-python/

For more information

If you have any questions or comments about this advisory please open an issue in tlslite-ng.

Show details on source website

To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "tlslite-ng"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.7.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2020-26263"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-326"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2020-12-21T16:55:47Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Impact\nThe code that performs decryption and padding check in RSA PKCS#1 v1.5 decryption is data dependant.\nIn particular, code in current (as of 0.8.0-alpha38) master\nhttps://github.com/tlsfuzzer/tlslite-ng/blob/0812ed60860fa61a6573b2c0e18771414958f46d/tlslite/utils/rsakey.py#L407-L441\nand code in 0.7.5 branch\nhttps://github.com/tlsfuzzer/tlslite-ng/blob/acdde3161124d6ae37c506b3476aea9996d12e97/tlslite/utils/rsakey.py#L394-L425\nhas multiple ways in which it leaks information (for one, it aborts as soon as the plaintext doesn\u0027t start with 0x00, 0x02) about the decrypted ciphertext (both the bit length of the decrypted message as well as where the first unexpected byte lays).\n\nAll TLS servers that enable RSA key exchange as well as applications that use the RSA decryption API directly are vulnerable.\n\nAll previous versions of tlslite-ng are vulnerable.\n\n### Patches\nThe patches to fix it are proposed in \nhttps://github.com/tlsfuzzer/tlslite-ng/pull/438\nhttps://github.com/tlsfuzzer/tlslite-ng/pull/439\n\nNote: the patches depend on Python processing the individual bytes in side-channel free manner, this is known to not be the case: https://securitypitfalls.wordpress.com/2018/08/03/constant-time-compare-in-python/\nAs such, users that require side-channel resistance are recommended to use different TLS implementations, as stated in the [security policy](https://github.com/tlsfuzzer/tlslite-ng/blob/master/SECURITY.md) of tlslite-ng.\n\n### Workarounds\nThere is no way to workaround this issue.\n\n### References\nhttps://securitypitfalls.wordpress.com/2018/08/03/constant-time-compare-in-python/\n\n### For more information\nIf you have any questions or comments about this advisory please open an issue in [tlslite-ng](https://github.com/tlsfuzzer/tlslite-ng/issues).",
  "id": "GHSA-wvcv-832q-fjg7",
  "modified": "2024-11-13T23:01:33Z",
  "published": "2020-12-21T16:56:37Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/tlsfuzzer/tlslite-ng/security/advisories/GHSA-wvcv-832q-fjg7"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2020-26263"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tlsfuzzer/tlslite-ng/pull/438"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tlsfuzzer/tlslite-ng/pull/439"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tlsfuzzer/tlslite-ng/commit/c28d6d387bba59d8bd5cb3ba15edc42edf54b368"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/tlslite-ng/PYSEC-2020-143.yaml"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/tlsfuzzer/tlslite-ng"
    },
    {
      "type": "WEB",
      "url": "https://pypi.org/project/tlslite-ng"
    },
    {
      "type": "WEB",
      "url": "https://securitypitfalls.wordpress.com/2018/08/03/constant-time-compare-in-python"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "RSA weakness in tslite-ng"
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




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.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • 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.