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author | Jason A. Donenfeld <Jason@zx2c4.com> | 2017-01-06 19:32:01 +0100 |
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committer | Theodore Ts'o <tytso@mit.edu> | 2017-01-27 14:25:06 -0500 |
commit | f5b98461cb8167ba362ad9f74c41d126b7becea7 (patch) | |
tree | a03acbf2b6426dc27d642bacedd567611896d709 /include | |
parent | 5d0e5ea343a0f70351428476bcf8715e0731f26a (diff) | |
download | linux-stable-f5b98461cb8167ba362ad9f74c41d126b7becea7.tar.gz linux-stable-f5b98461cb8167ba362ad9f74c41d126b7becea7.tar.bz2 linux-stable-f5b98461cb8167ba362ad9f74c41d126b7becea7.zip |
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 'include')
-rw-r--r-- | include/linux/random.h | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/include/linux/random.h b/include/linux/random.h index 7bd2403e4fef..16ab429735a7 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -37,7 +37,6 @@ extern void get_random_bytes(void *buf, int nbytes); extern int add_random_ready_callback(struct random_ready_callback *rdy); extern void del_random_ready_callback(struct random_ready_callback *rdy); extern void get_random_bytes_arch(void *buf, int nbytes); -extern int random_int_secret_init(void); #ifndef MODULE extern const struct file_operations random_fops, urandom_fops; |