diff options
Diffstat (limited to 'lib/tempname.c')
| -rw-r--r-- | lib/tempname.c | 49 |
1 files changed, 30 insertions, 19 deletions
diff --git a/lib/tempname.c b/lib/tempname.c index cfb0fc42eca..b9f7cc8703d 100644 --- a/lib/tempname.c +++ b/lib/tempname.c @@ -47,9 +47,11 @@ #include <string.h> #include <fcntl.h> +#include <stdalign.h> #include <stdint.h> #include <sys/random.h> #include <sys/stat.h> +#include <time.h> #if _LIBC # define struct_stat64 struct stat64 @@ -60,27 +62,33 @@ # define __mkdir mkdir # define __open open # define __lxstat64(version, file, buf) lstat (file, buf) +# define __getrandom getrandom +# define __clock_gettime64 clock_gettime +# define __timespec64 timespec #endif -#ifdef _LIBC -# include <random-bits.h> -# define RANDOM_BITS(Var) ((Var) = random_bits ()) -typedef uint32_t random_value; -# define RANDOM_VALUE_MAX UINT32_MAX -# define BASE_62_DIGITS 5 /* 62**5 < UINT32_MAX */ -# define BASE_62_POWER (62 * 62 * 62 * 62 * 62) /* 2**BASE_62_DIGITS */ -#else /* Use getrandom if it works, falling back on a 64-bit linear - congruential generator that starts with whatever Var's value - happens to be. */ -# define RANDOM_BITS(Var) \ - ((void) (getrandom (&(Var), sizeof (Var), 0) == sizeof (Var) \ - || ((Var) = 2862933555777941757 * (Var) + 3037000493))) + congruential generator that starts with Var's value + mixed in with a clock's low-order bits if available. */ typedef uint_fast64_t random_value; -# define RANDOM_VALUE_MAX UINT_FAST64_MAX -# define BASE_62_DIGITS 10 /* 62**10 < UINT_FAST64_MAX */ -# define BASE_62_POWER (62LL * 62 * 62 * 62 * 62 * 62 * 62 * 62 * 62 * 62) +#define RANDOM_VALUE_MAX UINT_FAST64_MAX +#define BASE_62_DIGITS 10 /* 62**10 < UINT_FAST64_MAX */ +#define BASE_62_POWER (62LL * 62 * 62 * 62 * 62 * 62 * 62 * 62 * 62 * 62) + +static random_value +random_bits (random_value var) +{ + random_value r; + if (__getrandom (&r, sizeof r, 0) == sizeof r) + return r; +#if _LIBC || (defined CLOCK_MONOTONIC && HAVE_CLOCK_GETTIME) + /* Add entropy if getrandom is not supported. */ + struct __timespec64 tv; + __clock_gettime64 (CLOCK_MONOTONIC, &tv); + var ^= tv.tv_nsec; #endif + return 2862933555777941757 * var + 3037000493; +} #if _LIBC /* Return nonzero if DIR is an existent directory. */ @@ -250,8 +258,11 @@ try_tempname_len (char *tmpl, int suffixlen, void *args, unsigned int attempts = ATTEMPTS_MIN; #endif - /* A random variable. */ - random_value v; + /* A random variable. The initial value is used only the for fallback path + on 'random_bits' on 'getrandom' failure. Its initial value tries to use + some entropy from the ASLR and ignore possible bits from the stack + alignment. */ + random_value v = ((uintptr_t) &v) / alignof (max_align_t); /* How many random base-62 digits can currently be extracted from V. */ int vdigits = 0; @@ -279,7 +290,7 @@ try_tempname_len (char *tmpl, int suffixlen, void *args, if (vdigits == 0) { do - RANDOM_BITS (v); + v = random_bits (v); while (unfair_min <= v); vdigits = BASE_62_DIGITS; |