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authorJason A. Donenfeld <Jason@zx2c4.com>2017-01-06 19:32:01 +0100
committerTheodore Ts'o <tytso@mit.edu>2017-01-27 14:25:06 -0500
commitf5b98461cb8167ba362ad9f74c41d126b7becea7 (patch)
treea03acbf2b6426dc27d642bacedd567611896d709 /init
parent5d0e5ea343a0f70351428476bcf8715e0731f26a (diff)
random: use chacha20 for get_random_int/long
Now that our crng uses chacha20, we can rely on its speedy characteristics for replacing MD5, while simultaneously achieving a higher security guarantee. Before the idea was to use these functions if you wanted random integers that aren't stupidly insecure but aren't necessarily secure either, a vague gray zone, that hopefully was "good enough" for its users. With chacha20, we can strengthen this claim, since either we're using an rdrand-like instruction, or we're using the same crng as /dev/urandom. And it's faster than what was before. We could have chosen to replace this with a SipHash-derived function, which might be slightly faster, but at the cost of having yet another RNG construction in the kernel. By moving to chacha20, we have a single RNG to analyze and verify, and we also already get good performance improvements on all platforms. Implementation-wise, rather than use a generic buffer for both get_random_int/long and memcpy based on the size needs, we use a specific buffer for 32-bit reads and for 64-bit reads. This way, we're guaranteed to always have aligned accesses on all platforms. While slightly more verbose in C, the assembly this generates is a lot simpler than otherwise. Finally, on 32-bit platforms where longs and ints are the same size, we simply alias get_random_int to get_random_long. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Suggested-by: Theodore Ts'o <tytso@mit.edu> Cc: Theodore Ts'o <tytso@mit.edu> Cc: Hannes Frederic Sowa <hannes@stressinduktion.org> Cc: Andy Lutomirski <luto@amacapital.net> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'init')
-rw-r--r--init/main.c1
1 files changed, 0 insertions, 1 deletions
diff --git a/init/main.c b/init/main.c
index b0c9d6facef9..09beb7fc6e8c 100644
--- a/init/main.c
+++ b/init/main.c
@@ -879,7 +879,6 @@ static void __init do_basic_setup(void)
do_ctors();
usermodehelper_enable();
do_initcalls();
- random_int_secret_init();
}
static void __init do_pre_smp_initcalls(void)