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util: add UTI_GetRandomBytesUrandom()

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This function always uses /dev/urandom, even if arc4random() is
available, and is intended for generating long-term keys.
This commit is contained in:
Miroslav Lichvar 2016-01-13 11:57:36 +01:00
parent 0d12410eaa
commit 32ac6ffa26
2 changed files with 19 additions and 5 deletions
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17
util.c
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@ -1141,17 +1141,26 @@ UTI_DropRoot(uid_t uid, gid_t gid)
#define DEV_URANDOM "/dev/urandom"
void
UTI_GetRandomBytes(void *buf, unsigned int len)
UTI_GetRandomBytesUrandom(void *buf, unsigned int len)
{
#ifdef HAVE_ARC4RANDOM
arc4random_buf(buf, len);
#else
static FILE *f = NULL;
if (!f)
f = fopen(DEV_URANDOM, "r");
if (!f)
LOG_FATAL(LOGF_Util, "Can't open %s : %s", DEV_URANDOM, strerror(errno));
if (fread(buf, 1, len, f) != len)
LOG_FATAL(LOGF_Util, "Can't read from %s", DEV_URANDOM);
}
/* ================================================== */
void
UTI_GetRandomBytes(void *buf, unsigned int len)
{
#ifdef HAVE_ARC4RANDOM
arc4random_buf(buf, len);
#else
UTI_GetRandomBytesUrandom(buf, len);
#endif
}

7
util.h
View file

@ -148,7 +148,12 @@ extern int UTI_CheckDirPermissions(const char *path, mode_t perm, uid_t uid, gid
/* Set process user/group IDs and drop supplementary groups */
extern void UTI_DropRoot(uid_t uid, gid_t gid);
/* Fill buffer with random bytes */
/* Fill buffer with random bytes from /dev/urandom */
extern void UTI_GetRandomBytesUrandom(void *buf, unsigned int len);
/* Fill buffer with random bytes from /dev/urandom or a faster source if it's
available (e.g. arc4random()), which may not necessarily be suitable for
generating long-term keys */
extern void UTI_GetRandomBytes(void *buf, unsigned int len);
/* Macros to get maximum and minimum of two values */