RUSTSEC-2021-0119: Out-of-bounds write in nix::unistd::getgrouplist

[github-actions]

Out-of-bounds write in nix::unistd::getgrouplist

Details
Package	nix
Version	0.19.1
URL	nix-rust/nix#1541
Date	2021-09-27
Patched versions	^0.20.2,^0.21.2,^0.22.2,>=0.23.0
Unaffected versions	<0.16.0

On certain platforms, if a user has more than 16 groups, the
nix::unistd::getgrouplist function will call the libc getgrouplist
function with a length parameter greater than the size of the buffer it
provides, resulting in an out-of-bounds write and memory corruption.

The libc getgrouplist function takes an in/out parameter ngroups
specifying the size of the group buffer. When the buffer is too small to
hold all of the reqested user's group memberships, some libc
implementations, including glibc and Solaris libc, will modify ngroups
to indicate the actual number of groups for the user, in addition to
returning an error. The version of nix::unistd::getgrouplist in nix
0.16.0 and up will resize the buffer to twice its size, but will not
read or modify the ngroups variable. Thus, if the user has more than
twice as many groups as the initial buffer size of 8, the next call to
getgrouplist will then write past the end of the buffer.

The issue would require editing /etc/groups to exploit, which is usually
only editable by the root user.

See advisory page for additional details.

[ClementTsang]

Seems like both heim and battery are on 0.19, which is both in the affected range and not patched. See:

• Could we get a release with a bumped version of nix? svartalf/rust-battery#91
• Would it be possible to do a release updating nix to >0.19? heim-rs/heim#351

Would prefer to not have to patch them manually in Cargo.toml, so I'll wait a bit and see if they get fixed upstream.

[ClementTsang]

FWIW this is likely not something that affects bottom, though it would be nice to fix. If it takes too long I'll just close this.

[ClementTsang]

First half addressed by #724, which moves to a more maintained fork of the battery crate.

The second half is likely either going to be addressed by looking for another fork, or the more likely case, just stripping out heim entirely.

[ClementTsang]

Resolved as heim, the dependency pulling in the problematic version, is removed.