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Date: Mon, 6 Nov 2023 00:08:10 +0100
From: Solar Designer <solar@...nwall.com>
To: oss-security@...ts.openwall.com
Cc: Pietro Albini <pietro@...troalbini.org>
Subject: Re: CVE-2022-46176: Cargo does not check SSH host keys
Hi,
On Tue, Jan 10, 2023 at 05:45:06PM +0100, Pietro Albini wrote:
> The Rust Security Response WG was notified that Cargo did not perform SSH host
> key verification when cloning indexes and dependencies via SSH. An attacker
> could exploit this to perform man-in-the-middle (MITM) attacks.
>
> This vulnerability has been assigned CVE-2022-46176.
In the distros thread leading to the above oss-security posting, Pietro
Albini also wrote:
> Note that while investigating this we discovered that the underlying library
> Cargo uses for git operations, libgit2, does not perform SSH host key checking
> either. We've been coordinating with them, and they'll also release a fix on
> 2023-01-10.
I think the libgit2 issue was never brought to oss-security, so I am
passing its mention to here now. Also per that thread, CVE-2022-46176
is only for the Cargo issue. libgit2 was supposed to get its own CVE,
but no one in the thread knew whether they actually did.
I don't know whether libgit2 was actually fixed on that date as planned.
Alexander
P.S. I'm quoting the rest of the oss-security posting I'm "replying" to
below, for context since it's been a while.
On Tue, Jan 10, 2023 at 05:45:06PM +0100, Pietro Albini wrote:
> The Rust Security Response WG was notified that Cargo did not perform SSH host
> key verification when cloning indexes and dependencies via SSH. An attacker
> could exploit this to perform man-in-the-middle (MITM) attacks.
>
> This vulnerability has been assigned CVE-2022-46176.
>
> ## Overview
>
> When an SSH client establishes communication with a server, to prevent MITM
> attacks the client should check whether it already communicated with that
> server in the past and what the server's public key was back then. If the key
> changed since the last connection, the connection must be aborted as a MITM
> attack is likely taking place.
>
> It was discovered that Cargo never implemented such checks, and performed no
> validation on the server's public key, leaving Cargo users vulnerable to MITM
> attacks.
>
> ## Affected Versions
>
> All Rust versions containing Cargo before 1.66.1 are vulnerable.
>
> Note that even if you don't explicitly use SSH for alternate registry indexes
> or crate dependencies, you might be affected by this vulnerability if you have
> configured git to replace HTTPS connections to GitHub with SSH (through git's
> [`url.<base>.insteadOf`][1] setting), as that'd cause you to clone the
> crates.io index through SSH.
>
> ## Mitigations
>
> We will be releasing Rust 1.66.1 today, 2023-01-10, changing Cargo to check the
> SSH host key and abort the connection if the server's public key is not already
> trusted. We recommend everyone to upgrade as soon as possible.
>
> Patch files for Rust 1.66.0 are also available [here][2] for custom-built
> toolchains.
>
> For the time being Cargo will not ask the user whether to trust a server's
> public key during the first connection. Instead, Cargo will show an error
> message detailing how to add that public key to the list of trusted keys. Note
> that this might break your automated builds if the hosts you clone dependencies
> or indexes from are not already trusted.
>
> ## Acknowledgments
>
> Thanks to the Julia Security Team for disclosing this to us according to our
> [security policy][1]!
>
> We also want to thank the members of the Rust project who contributed to fixing
> this issue. Thanks to Eric Huss and Weihang Lo for writing and reviewing the
> patch, Pietro Albini for coordinating the disclosure and writing this advisory,
> and Josh Stone, Josh Triplett and Jacob Finkelman for advising during the
> disclosure.
>
> [1]: https://git-scm.com/docs/git-config#Documentation/git-config.txt-urlltbasegtinsteadOf
> [2]: https://github.com/rust-lang/wg-security-response/tree/main/patches/CVE-2022-46176
> [3]: https://www.rust-lang.org/policies/security
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