Fix argv injection in _create_user and gpasswd loop#4473
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svartkanin merged 2 commits intoarchlinux:masterfrom Apr 26, 2026
Merged
Fix argv injection in _create_user and gpasswd loop#4473svartkanin merged 2 commits intoarchlinux:masterfrom
svartkanin merged 2 commits intoarchlinux:masterfrom
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Use argv list with run() instead of f-string interpolation into SysCommand, add debug logging on failure.
svartkanin
reviewed
Apr 26, 2026
Address svartkanin's review on archlinux#4473: factor the ['arch-chroot', '-S', str(self.target), ...] boilerplate into a private Installer._chroot_argv() helper, and migrate the seven existing argv-form call sites to it (useradd, gpasswd, chpasswd, chsh, chown, snapper-create-config, grub-install). Two related hardening tweaks while in the area: - Raise gpasswd failure log from debug() to warn(). The group-add loop has no return-False feedback channel for the caller, so a silent debug() means a half-configured user looks like a successful install. - Add `--` end-of-options separator for useradd and chown so a username or path starting with `-` cannot smuggle flags. The TUI validates usernames, but parse_arguments() in models/users.py does not, so config.json is the residual hole; this closes it for these two sites at zero cost.
svartkanin
approved these changes
Apr 26, 2026
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Same class of bug as #4443, two sibling call sites that were missed back then.
_create_userand thegpasswdloop interpolateuser.usernameandgroupinto f-strings that reachSysCommand(f'arch-chroot -S {target} {cmd}'), whereshlex.splitparses the payload as argv. Ausernamelike--uid 0or-G wheel,rootis accepted asuseradd/gpasswdflags and gives trivial escalation. Vector is the same as #4443: custominstall.py, plugins, tampered--configJSON.Changes
_create_usernow builds an argv list and callsrun(). Failures are logged viadebug(), and theSystemErrorre-raise is kept so guided install still aborts.The
gpasswdloop gets the same switch. Also wrapped it intry/exceptwithdebug()- previously a failinggpasswdwas silently ignored.