On Mon, Nov 17, 2014 at 3:20 PM, Mathias Krause <minipli@xxxxxxxxxxxxxx> wrote: > On 17 November 2014 21:02, Kees Cook <keescook@xxxxxxxxxxxx> wrote: >> This prefixes all crypto module loading with "crypto-" so we never run >> the risk of exposing module auto-loading to userspace via a crypto API, >> as demonstrated by Mathias Krause: >> >> https://lkml.org/lkml/2013/3/4/70 >> >> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> >> --- >> v2: >> - added missing #include, thanks to minipli >> - built with allmodconfig >> [...snip...] >> diff --git a/include/linux/crypto.h b/include/linux/crypto.h >> index d45e949699ea..d14230f6e977 100644 >> --- a/include/linux/crypto.h >> +++ b/include/linux/crypto.h >> @@ -26,6 +26,13 @@ >> #include <linux/uaccess.h> >> >> /* >> + * Autoloaded crypto modules should only use a prefixed name to avoid allowing >> + * arbitrary modules to be loaded. >> + */ >> +#define MODULE_ALIAS_CRYPTO(name) \ >> + MODULE_ALIAS("crypto-" name) > > This would break userland relying on the old aliases, e.g. 'modprobe > aes' no longer works. > > Why not have both aliases, one with the "crypto-" prefix for on-demand > loading within the crypto API and one without for manual loading from > userland? E.g., something like this: > > #define MODULE_ALIAS_CRYPTO(name) \ > MODULE_ALIAS(name); \ > MODULE_ALIAS("crypto-" name) > > That would prevent the userland breakage and still achieves the goal > of restricting the request_module() call offered by the means of the > AF_ALG API. That was my intention originally, and I should go back to it. The trouble is with the use of __UNIQUE_ID in the MODULE_ALIAS macro. It uses __LINE__ to produce the id, so the suggested macro expansion (which is what I started with) won't work on non-gcc compilers. I haven't found any solutions for C89 version of gcc's __COUNTER__, and I haven't found any C89 ways to force a macro to be expanded as being multi-line. I'd like to avoid having to open-code both MODULE_ALIAS and MODULE_ALIAS_CRYPTO in each module's source. Anyone see some sneaky way to accomplish this? -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
