Boris, ----- Ursprüngliche Mail ----- > Von: "Boris Kolpackov" <boris@xxxxxxxxxxxxxxxxx> > An: "richard" <richard@xxxxxx> > CC: "masahiroy" <masahiroy@xxxxxxxxxx>, "linux-kernel" <linux-kernel@xxxxxxxxxxxxxxx>, "linux-kbuild" > <linux-kbuild@xxxxxxxxxxxxxxx> > Gesendet: Mittwoch, 22. September 2021 17:18:43 > Betreff: Re: [PATCH 2/2] kconfig: Deny command substitution in string values > Richard Weinberger <richard@xxxxxx> writes: > >> > So effectively it's now impossible to include ` or $ in kconfig >> > string values. Seems like a major, backwards-incompatible >> > restriction. >> >> Do you have a working example? > > You mean of a project that uses kconfig and that is capable of > handling string values with these characters? If so, then yes, > see for example, libbuild2-kconfig[1] which is a build system > module that implements kconfig-based configuration support for > build2. In particular, it exposes values from .config as > buildfile variables but it doesn't do this by sourcing .config. > Instead it loads .config using the kconfig API and then sets > the corresponding buildfile variables programmatically. I had a config setting of Linux in mind. :-) > >> Since the config is sourced in the scripts/setlocalversion it will >> not work correctly anyway. > > The actual file being sources is include/config/auto.conf, not > .config, right? > Yes. auto.conf is .config post processed. This is exactly where my mitigation takes place. >> > I think if this is really desired, then it should be re-done with >> > escaping (similar to ") rather than outright banning inconvenient >> > characters. >> >> Escaping is not so easy since the very same content is included >> in shell scripts (sertlocalversion), in Makefiles and in C files. > > Again, I don't think it's .config that gets included in C files but > rather include/generated/autoconf.h, right? > Yes. But the key/values are taken as-is. Just add some odd characters to your .config, build the kernel and observe the breakage at different levels. Or something like CONFIG_DEFAULT_HOSTNAME="`touch owned`". ;-) >> At least I didn't find find a good way to escape these characters >> such that all three programming environments will accept it. > > If my understanding is correct, then you are concerned with the > autoconf functionality: the auto.conf makefile and autoconf.h > header, and not the .config file itself. Perhaps it will be less > disruptive to do the escaping (or banning) at that level? My concern is that currently a .config file can contain hostile content that will get executed at build time. .config files are often blindly shared across untrusted developers. So I thought that mitigating this whole is worth it. > Specifically: > > 1. If you do escaping at that level, then you can do it differently > for auto.conf and autoconf.h. Though auto.conf still seems to be > read by both make and shell. I need to think about that. Thanks for the pointer. Thanks, //richard
