ghsa-cqvm-j2r2-hwpg
Vulnerability from github
Summary
Diffie-Hellman key validation is insufficient, which can lead to insecure shared secrets and therefore breaks confidentiality.
Details
Russh does not validate Diffie-Hellman keys.
It accepts received DH public keys $e$ where $e<0$, $e=1$, or $e \geq p-1$ from a misbehaving peer annd successfully performs key exchange.
This is a violation of RFC 4253, section 8 and RFC 8268, section 4, which state that:
DH Public Key values MUST be checked and both conditions:
- $1 < e < p-1$
- $1 < f < p-1$
MUST be true. Values not within these bounds MUST NOT be sent or accepted by either side. If either one of these conditions is violated, then the key exchange fails.
For example, a DH client public key $e=1$ would mean that the shared secret that the server calculates is always $K = e^y \mod{p} = 1^y \mod{p} = 1$. In other cases, an insecure order-2 subgroup may be used.
Also, the code does not look like it ensures that the generated secret key $y$ is in the valid interval $0 < y < q$ (or, if russh is the client, that the secret key $x$ satisfies $1 < x < q$):
https://github.com/warp-tech/russh/blob/master/russh/src/kex/dh/groups.rs#L72-L76
For example, rng.gen_biguint() might return a number consisting of zeroes, so that $y = 0$.
The public key is not validated either: https://github.com/warp-tech/russh/blob/master/russh/src/kex/dh/groups.rs#L78-L81
Impact
Due to the issues in the DH key generation, I think any connection that uses Diffie-Hellman key exchange is affected. Connections between a russh client and server or those of a russh peer with some other misbehaving peer are most likely to be problematic. These may vulnerable to eavesdropping.
Most other implementations reject such keys, so this is mainly an interoperability issue in such a case.
{
"affected": [
{
"package": {
"ecosystem": "crates.io",
"name": "russh"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.36.2"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "crates.io",
"name": "russh"
},
"ranges": [
{
"events": [
{
"introduced": "0.37.0"
},
{
"fixed": "0.37.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2023-28113"
],
"database_specific": {
"cwe_ids": [
"CWE-20",
"CWE-347"
],
"github_reviewed": true,
"github_reviewed_at": "2023-03-17T14:42:45Z",
"nvd_published_at": "2023-03-16T21:15:00Z",
"severity": "MODERATE"
},
"details": "### Summary\n\nDiffie-Hellman key validation is insufficient, which can lead to insecure shared secrets and therefore breaks confidentiality.\n\n### Details\n\nRussh does not validate Diffie-Hellman keys.\n\nIt accepts received DH public keys $e$ where $e\u003c0$, $e=1$, or $e \\geq p-1$ from a misbehaving peer annd successfully performs key exchange.\n\nThis is a violation of [RFC 4253, section 8](https://www.rfc-editor.org/rfc/rfc4253#section-8) and [RFC 8268, section 4](https://www.rfc-editor.org/rfc/rfc8268#section-4), which state that:\n\n\u003eDH Public Key values MUST be checked and both conditions:\n\u003e\n\u003e - $1 \u003c e \u003c p-1$\n\u003e - $1 \u003c f \u003c p-1$\n\u003e\n\u003e MUST be true. Values not within these bounds MUST NOT be sent or\n\u003e accepted by either side. If either one of these conditions is\n\u003e violated, then the key exchange fails.\n\nFor example, a DH client public key $e=1$ would mean that the shared secret that the server calculates is always $K = e^y \\mod{p} = 1^y \\mod{p} = 1$.\nIn other cases, an insecure order-2 subgroup may be used.\n\nAlso, the code does not look like it ensures that the generated secret key $y$ is in the valid interval $0 \u003c y \u003c q$ (or, if russh is the client, that the secret key $x$ satisfies $1 \u003c x \u003c q$):\nhttps://github.com/warp-tech/russh/blob/master/russh/src/kex/dh/groups.rs#L72-L76\nFor example, `rng.gen_biguint()` might return a number consisting of zeroes, so that $y = 0$.\n\nThe public key is not validated either:\nhttps://github.com/warp-tech/russh/blob/master/russh/src/kex/dh/groups.rs#L78-L81\n\n### Impact\n\nDue to the issues in the DH key generation, I think any connection that uses Diffie-Hellman key exchange is affected.\nConnections between a russh client and server or those of a russh peer with some other misbehaving peer are most likely to be problematic. These may vulnerable to eavesdropping.\n\nMost other implementations reject such keys, so this is mainly an interoperability issue in such a case.\n",
"id": "GHSA-cqvm-j2r2-hwpg",
"modified": "2023-03-17T14:42:45Z",
"published": "2023-03-17T14:42:45Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/warp-tech/russh/security/advisories/GHSA-cqvm-j2r2-hwpg"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2023-28113"
},
{
"type": "WEB",
"url": "https://github.com/warp-tech/russh/commit/45d2d82930bf4a675bd57abfafec8fe4065befcd"
},
{
"type": "WEB",
"url": "https://github.com/warp-tech/russh/commit/d831a3716d3719dc76f091fcea9d94bd4ef97c6e"
},
{
"type": "PACKAGE",
"url": "https://github.com/warp-tech/russh"
},
{
"type": "WEB",
"url": "https://github.com/warp-tech/russh/blob/master/russh/src/kex/dh/groups.rs#L72-L76"
},
{
"type": "WEB",
"url": "https://github.com/warp-tech/russh/blob/master/russh/src/kex/dh/groups.rs#L78-L81"
},
{
"type": "WEB",
"url": "https://github.com/warp-tech/russh/releases/tag/v0.36.2"
},
{
"type": "WEB",
"url": "https://github.com/warp-tech/russh/releases/tag/v0.37.1"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
],
"summary": "russh may use insecure Diffie-Hellman keys"
}
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.
- 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.