Out-of-bounds write in nix::unistd::getgrouplist
High severity
GitHub Reviewed
Published
Jun 17, 2022
to the GitHub Advisory Database
•
Updated Jun 13, 2023
Package
Affected versions
>= 0.16.0, < 0.20.2
>= 0.21.0, < 0.21.2
>= 0.22.0, < 0.22.2
Patched versions
0.20.2
0.21.2
0.22.2
Description
Published to the GitHub Advisory Database
Jun 17, 2022
Reviewed
Jun 17, 2022
Last updated
Jun 13, 2023
On certain platforms, if a user has more than 16 groups, the
nix::unistd::getgrouplistfunction will call the libcgetgrouplistfunction 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
getgrouplistfunction takes an in/out parameterngroupsspecifying 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
ngroupsto indicate the actual number of groups for the user, in addition to
returning an error. The version of
nix::unistd::getgrouplistin nix0.16.0 and up will resize the buffer to twice its size, but will not
read or modify the
ngroupsvariable. Thus, if the user has more thantwice as many groups as the initial buffer size of 8, the next call to
getgrouplistwill 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.
References