Add POS36-C runtime safety check to setuid and security documentation#817
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mcepl wants to merge 4 commits intoluvit:masterfrom
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Add POS36-C runtime safety check to setuid and security documentation#817mcepl wants to merge 4 commits intoluvit:masterfrom
mcepl wants to merge 4 commits intoluvit:masterfrom
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Expose POSIX getgroups(), setgroups(), and initgroups() as Lua-callable functions (Unix-only). These are needed to properly manage supplementary group IDs when dropping privileges, addressing the security concern raised in issue luvit#341 (CERT POS36-C). New functions: - uv.getgroups(): returns table of supplementary group IDs - uv.setgroups(groups): sets supplementary group IDs from a table - uv.initgroups(user, group): sets groups from the group database References: luvit#341
Add a runtime check in luv_setuid() that prevents dropping from root
(euid 0) to an unprivileged user while supplementary groups are still
set. This addresses the CERT POS36-C vulnerability where setuid()
alone does not revoke supplementary group privileges.
The check returns an error instructing users to call uv.setgroups({})
or uv.initgroups() before uv.setuid(). Non-root callers and
root-to-root transitions are unaffected.
Also adds security warnings to setuid/setgid documentation in all
three doc files (docs.md, docs.lua, meta.lua) explaining the correct
privilege-dropping order.
See: https://wiki.sei.cmu.edu/confluence/display/c/POS36-C
Fixes: luvit#341
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So, they shouldn't be in git at all? |
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Where else would they be 😆 |
Bilal2453
reviewed
Mar 18, 2026
Bilal2453
reviewed
Mar 18, 2026
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Add a runtime check in
luv_setuid()that prevents dropping from root (euid 0) to an unprivileged user while supplementary groups are still set. This addresses the CERT POS36-C vulnerability wheresetuid()alone does not revoke supplementary group privileges.The check returns an error instructing users to call
uv.setgroups({})oruv.initgroups()beforeuv.setuid(). Non-root callers androot-to-root transitions are unaffected.
Also adds security warnings to
setuid/setgiddocumentation in allthree doc files (
docs.md,docs.lua,meta.lua) explaining the correctprivilege-dropping order.
See: https://wiki.sei.cmu.edu/confluence/display/c/POS36-C
Fixes: #341