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Fix shell quoting and add username validation #355

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Fix shell quoting and add username validation #355

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8 changes: 4 additions & 4 deletions usr/libexec/security-misc/build-fm-shim-backend#security-misc-shared
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Original file line number Diff line number Diff line change
Expand Up @@ -46,12 +46,12 @@ gcc_hardening_options+=(

gcc \
-g \
$(pkg-config --cflags dbus-1) \
$(pkg-config --cflags libsystemd) \
"$(pkg-config --cflags dbus-1)" \
"$(pkg-config --cflags libsystemd)" \
/usr/src/security-misc/fm-shim-backend.c \
-o /usr/bin/fm-shim-backend \
$(pkg-config --libs dbus-1) \
$(pkg-config --libs libsystemd) \
"$(pkg-config --libs dbus-1)" \
"$(pkg-config --libs libsystemd)" \
Comment on lines -49 to +54
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@ArrayBolt3 ArrayBolt3 Apr 5, 2026

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Rejected. Quotes are absent here on purpose, because pkg-config may return multiple parameters at once. For instance, pkg-config --cflags dbus-1 returns -I/usr/include/dbus-1.0 -I/usr/lib/x86_64-linux-gnu/dbus-1.0/include. Those would get smashed into one argument by this.

"${gcc_hardening_options[@]}" \
|| {
printf "%s\n" 'Could not compile fm-shim-backend executable!'
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5 changes: 5 additions & 0 deletions usr/libexec/security-misc/virusforget#security-misc-shared
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Expand Up @@ -85,6 +85,11 @@ parse_cmd_options() {
echo "ERROR: must set --user username" >&2
exit 1
fi

if [[ ! "$user_name" =~ ^[a-zA-Z0-9._-]+$ ]]; then
echo "ERROR: Invalid username format. Only alphanumeric characters, dots, underscores, and hyphens are allowed." >&2
exit 1
fi
Comment on lines +88 to +92
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@ArrayBolt3 ArrayBolt3 Apr 5, 2026

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This doesn't seem like it adds much value IMO. Usernames might not always match this pattern, and the input here is trusted (I think?) so we probably shouldn't be concerned about invalid usernames being passed here. What we can do here is make sure the specified user actually exists though.

}

variables() {
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