> On Sat, Jan 08, 2011 at 03:23:04PM +0200, Nikos Mavrogiannopoulos wrote: > > On Fri, Jan 7, 2011 at 2:04 PM, Neil Horman <nhorman@xxxxxxxxxxxxx> > > wrote: > > > > > > Btw, it doesn't have to be about performance per se. Does this > > > > allow people to use keys without actually _seeing_ those keys? > > > > Your example implies that that is not the case, but that's > > > > actually one of the few reasons to actually support a kernel > > > > crypto interface - the ability to have private personal keys > > > > around, but not having to actually let possibly untrusted programs > > > > see them. > > > This actually is an indirect feature of this interface. ÂUsing it, > > > you can open a algorithm socket, select a specific alg, assign a > > > key, and then pass that socket descriptor over a unix socket to an > > > another process using an SCM_RIGHTS ancilliary message. ÂThe > > > receiving process can then use children acceppted from that passed > > > socket to preform the configured crypto operation without any > > > knoweldge of the keys used in it. ÂI can write a demo app if you > > > like. > > > > Several things have to be considered when extending an interface like > > that. For example, do the algorithm implementations protect against > > timing attacks, or keys can be recovered, using them? What is the > No, the kernel does not implement any protection against timing attacks > in the algorithms per-se, but preforming a timing attack against a > kernel crypto operation is going to be near impossible anyway, as > precise timing measurements are going to get obscured by interupts, > scheduling jitter, lock contention, and various other factors that will > make measuring syscall time fairly useless. Let me just point out that this is not near impossible at all; instead it has already been done more than 6 years ago. And it's not only syscall time that leaks information. One practical example is recovery of a full AES key in a couple of seconds, using cache attacks against an encrypted file system. AES-NI is immune to this kind of attack, but other algorithms typically implemented using lookup tables are at risk. Dag Arne -- 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
