On 18 November 2014 01:45, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > 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. Well, clang should support it as well, according to [1]. But still, a compiler independent solution would be nice. Anyway, the __COUNTER__ support is gcc >= 4.3 only. So, according to Documentation/Changes, stating gcc 3.2 is the minimum supported version for compiling the kernel, this would be a no-go, too. [1] http://clang.llvm.org/docs/LanguageExtensions.html#builtin-macros > > 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? Unfortunately, I do not ... beside this, maybe: #define MODULE_ALIAS_CRYPTO(name) \ __MODULE_INFO(alias, alias_userland, name); \ __MODULE_INFO(alias, alias_crypto, "crypto-" name) Looks ugly, but works. ;) Regards, Mathias -- 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
