| Message ID | 20161214184605.24006-3-Jason@zx2c4.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Jason,
[auto build test ERROR on linus/master]
[also build test ERROR on next-20161214]
[cannot apply to v4.9]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Jason-A-Donenfeld/siphash-add-cryptographically-secure-hashtable-function/20161215-041458
config: i386-randconfig-i1-201650 (attached as .config)
compiler: gcc-4.8 (Debian 4.8.4-1) 4.8.4
reproduce:
# save the attached .config to linux build tree
make ARCH=i386
All errors (new ones prefixed by >>):
>> drivers/char/random.c:2046:1: error: requested alignment is not an integer constant
static u8 random_int_secret[SIPHASH24_KEY_LEN] __aligned(SIPHASH24_ALIGNMENT);
^
drivers/char/random.c: In function 'get_random_int':
drivers/char/random.c:2071:2: error: requested alignment is not an integer constant
} __aligned(SIPHASH24_ALIGNMENT) combined;
^
drivers/char/random.c: In function 'get_random_long':
drivers/char/random.c:2100:2: error: requested alignment is not an integer constant
} __aligned(SIPHASH24_ALIGNMENT) combined;
^
vim +2046 drivers/char/random.c
2040 },
2041 #endif
2042 { }
2043 };
2044 #endif /* CONFIG_SYSCTL */
2045
> 2046 static u8 random_int_secret[SIPHASH24_KEY_LEN] __aligned(SIPHASH24_ALIGNMENT);
2047
2048 int random_int_secret_init(void)
2049 {
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
Hi Jason,
[auto build test ERROR on linus/master]
[also build test ERROR on next-20161214]
[cannot apply to v4.9]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Jason-A-Donenfeld/siphash-add-cryptographically-secure-hashtable-function/20161215-041458
config: openrisc-or1ksim_defconfig (attached as .config)
compiler: or32-linux-gcc (GCC) 4.5.1-or32-1.0rc1
reproduce:
wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=openrisc
All errors (new ones prefixed by >>):
>> drivers/char/random.c:2046:1: error: requested alignment is not a constant
drivers/char/random.c: In function 'get_random_int':
drivers/char/random.c:2071:2: error: requested alignment is not a constant
drivers/char/random.c: In function 'get_random_long':
drivers/char/random.c:2100:2: error: requested alignment is not a constant
vim +2046 drivers/char/random.c
2040 },
2041 #endif
2042 { }
2043 };
2044 #endif /* CONFIG_SYSCTL */
2045
> 2046 static u8 random_int_secret[SIPHASH24_KEY_LEN] __aligned(SIPHASH24_ALIGNMENT);
2047
2048 int random_int_secret_init(void)
2049 {
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
From: Behalf Of Jason A. Donenfeld > Sent: 14 December 2016 18:46 ... > + ret = *chaining = siphash24((u8 *)&combined, offsetof(typeof(combined), end), If you make the first argument 'const void *' you won't need the cast on every call. I'd also suggest making the key u64[2]. David
Hi David, On Thu, Dec 15, 2016 at 11:14 AM, David Laight <David.Laight@aculab.com> wrote: > From: Behalf Of Jason A. Donenfeld >> Sent: 14 December 2016 18:46 > ... >> + ret = *chaining = siphash24((u8 *)&combined, offsetof(typeof(combined), end), > > If you make the first argument 'const void *' you won't need the cast > on every call. > > I'd also suggest making the key u64[2]. I'll do both. Thanks for the suggestion. Jason
diff --git a/drivers/char/random.c b/drivers/char/random.c index d6876d506220..b1c2e3b26430 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -262,6 +262,7 @@ #include <linux/syscalls.h> #include <linux/completion.h> #include <linux/uuid.h> +#include <linux/siphash.h> #include <crypto/chacha20.h> #include <asm/processor.h> @@ -2042,7 +2043,7 @@ struct ctl_table random_table[] = { }; #endif /* CONFIG_SYSCTL */ -static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned; +static u8 random_int_secret[SIPHASH24_KEY_LEN] __aligned(SIPHASH24_ALIGNMENT); int random_int_secret_init(void) { @@ -2050,8 +2051,7 @@ int random_int_secret_init(void) return 0; } -static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash) - __aligned(sizeof(unsigned long)); +static DEFINE_PER_CPU(u64, get_random_int_chaining); /* * Get a random word for internal kernel use only. Similar to urandom but @@ -2061,19 +2061,26 @@ static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash) */ unsigned int get_random_int(void) { - __u32 *hash; unsigned int ret; + struct { + u64 chaining; + unsigned long ts; + unsigned long entropy; + pid_t pid; + char end[]; + } __aligned(SIPHASH24_ALIGNMENT) combined; + u64 *chaining; if (arch_get_random_int(&ret)) return ret; - hash = get_cpu_var(get_random_int_hash); - - hash[0] += current->pid + jiffies + random_get_entropy(); - md5_transform(hash, random_int_secret); - ret = hash[0]; - put_cpu_var(get_random_int_hash); - + chaining = get_cpu_ptr(&get_random_int_chaining); + combined.chaining = *chaining; + combined.ts = jiffies; + combined.entropy = random_get_entropy(); + combined.pid = current->pid; + ret = *chaining = siphash24((u8 *)&combined, offsetof(typeof(combined), end), random_int_secret); + put_cpu_ptr(chaining); return ret; } EXPORT_SYMBOL(get_random_int); @@ -2083,19 +2090,26 @@ EXPORT_SYMBOL(get_random_int); */ unsigned long get_random_long(void) { - __u32 *hash; unsigned long ret; + struct { + u64 chaining; + unsigned long ts; + unsigned long entropy; + pid_t pid; + char end[]; + } __aligned(SIPHASH24_ALIGNMENT) combined; + u64 *chaining; if (arch_get_random_long(&ret)) return ret; - hash = get_cpu_var(get_random_int_hash); - - hash[0] += current->pid + jiffies + random_get_entropy(); - md5_transform(hash, random_int_secret); - ret = *(unsigned long *)hash; - put_cpu_var(get_random_int_hash); - + chaining = get_cpu_ptr(&get_random_int_chaining); + combined.chaining = *chaining; + combined.ts = jiffies; + combined.entropy = random_get_entropy(); + combined.pid = current->pid; + ret = *chaining = siphash24((u8 *)&combined, offsetof(typeof(combined), end), random_int_secret); + put_cpu_ptr(chaining); return ret; } EXPORT_SYMBOL(get_random_long);
This duplicates the current algorithm for get_random_int/long, but uses siphash24 instead. This comes with several benefits. It's certainly faster and more cryptographically secure than MD5. This patch also hashes the pid, entropy, and timestamp as fixed width fields, in order to increase diffusion. The previous md5 algorithm used a per-cpu md5 state, which caused successive calls to the function to chain upon each other. While it's not entirely clear that this kind of chaining is absolutely necessary when using a secure PRF like siphash24, it can't hurt, and the timing of the call chain does add a degree of natural entropy. So, in keeping with this design, instead of the massive per-cpu 64-byte md5 state, there is instead a per-cpu previously returned value for chaining. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Cc: Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com> Cc: Ted Tso <tytso@mit.edu> --- Changes from v2->v3: - Structs are no longer packed, to mitigate slow byte-by-byte assignment. drivers/char/random.c | 52 ++++++++++++++++++++++++++++++++------------------- 1 file changed, 33 insertions(+), 19 deletions(-)