GHSA-77hh-43cm-v8j6: tuf's Metadata API Targets.get_delegated_role() Is Missing Input Validation Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-77hh-43cm-v8j6",
  "modified" : "2024-02-16T23:35:39Z",
  "published" : "2024-02-16T23:35:39Z",
  "aliases" : [ ],
  "summary" : "tuf's Metadata API:  Targets.get_delegated_role() is missing input validation",
  "details" : "The security of both a TUF client and repository implementations depend on the concept of trusted Metadata objects verifying the signatures over other Metadata that it delegates to. This verification process uses `Targets.get_delegated_role(delegated_role: str)` to find the delegation information.\n\n`tuf.api.metadata.Targets.get_delegated_role()` should ensure that the given `delegated_rolename` is actually a name of a role that is delegated by that Targets, but in the case of \"succinct delegation\" this does not happen.\n\n`tuf.ngclient` users are **not** impacted but direct users of `tuf.api.metadata` could be impacted.\n\n### Impact\n\nIf an attacker can make a Metadata API user run `Targets.get_delegated_role()` so that \n1. the `Targets` uses succinct delegation\n1. the `delegated_role` argument is not actually delegated by the `Targets`\n\nthe result will be incorrect.\n\nThis also means that if an attacker can make a Metadata API user run `Targets.verify_delegate()` or `Targets.get_verification_result()` so that\n1. the delegating `Targets` uses a succinct delegation\n1. the `delegated_role` argument is the name of some unrelated Metadata\n1. that other Metadata is correctly signed by the keys defined in the succinct delegation\n\nthe result would be a successful verification even though the `Targets` in question does not actually delegate to `delegated_role`.\n\nThe impact is estimated to be low for following reasons:\n\n* This cannot impact a TUF client that implements the client workflow as specified since the delegated role name is not an input but is collected from the (trusted) delegating Targets itself\n* Actual signature verification is not bypassed: The verified metadata _must_ still be correctly signed by the keys specified in the delegating role.\n* The described situations are somewhat hypothetical: there does not seem to be any reason for a python-tuf user (whether client or a repository) to use `tuf.api.metadata` in this way.\n\nAll users of `tuf.ngclient` are specifically **not** impacted. Users of `tuf.api.metadata` could be impacted if they use succinct delegations in a way described above.\n\n### Patches\n\nA fix is available in python-tuf 3.1.1 as commit 77cb66bc and in later releases as commit eb4834d9._\n\n### Workarounds\n\n`tuf.api.metadata` users should only call `Targets.get_delegated_role()`, `Targets.verify_delegate()` or `Targets.get_verification_result()` with `delegated_role` argument that is known to be delegated by the `Targets` in question.\n",
  "severity" : [ ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "tuf"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.0.0"
      }, {
        "fixed" : "3.1.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/theupdateframework/python-tuf/security/advisories/GHSA-77hh-43cm-v8j6"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/theupdateframework/python-tuf/commit/77cb66bc879d108c449ba4c46dfb0e3a9e57a785"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/theupdateframework/python-tuf/commit/eb4834d9205d07ae164bc6c5b97787585c0acfdc"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/theupdateframework/python-tuf"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/theupdateframework/python-tuf/releases/tag/v3.1.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-02-16T23:35:39Z",
    "nvd_published_at" : null
  }
}