diff options
Diffstat (limited to 'util-linux/mkswap.c')
| -rw-r--r-- | util-linux/mkswap.c | 59 |
1 files changed, 55 insertions, 4 deletions
diff --git a/util-linux/mkswap.c b/util-linux/mkswap.c index 167b9ee..c4e30fd 100644 --- a/util-linux/mkswap.c +++ b/util-linux/mkswap.c @@ -53,14 +53,65 @@ static void mkswap_selinux_setcontext(int fd, const char *path) #if ENABLE_DESKTOP static void mkswap_generate_uuid(uint8_t *buf) { + pid_t pid; unsigned i; char uuid_string[32]; - /* rand() is guaranteed to generate at least [0, 2^15) range, + /* http://www.ietf.org/rfc/rfc4122.txt + * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + * | time_low | + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + * | time_mid | time_hi_and_version | + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + * |clk_seq__and_variant | node (0-1) | + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + * | node (2-5) | + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + * IOW, uuid has this layout: + * uint32_t time_low (big endian) + * uint16_t time_mid (big endian) + * uint16_t time_hi_and_version (big endian) + * version is a 4-bit field: + * 1 Time-based version + * 2 DCE Security version, with embedded POSIX UIDs + * 3 Name-based version (MD5) + * 4 Randomly generated version + * 5 Name-based version (SHA-1) + * uint16_t clk_seq_and_variant (big endian) + * variant is a 3-bit field: + * 0xx Reserved, NCS backward compatibility + * 10x The variant specified in rfc4122 + * 110 Reserved, Microsoft backward compatibility + * 111 Reserved for future definition + * uint8_t node[6] + * + * For version 4, these bits are set/cleared: + * time_hi_and_version & 0x0fff | 0x4000 + * clk_seq_and_variant & 0x3fff | 0x8000 + */ + + i = open("/dev/urandom", O_RDONLY); + if (i >= 0) { + read(i, buf, 16); + close(i); + } + /* Paranoia. /dev/urandom may be missing. + * rand() is guaranteed to generate at least [0, 2^15) range, * but lowest bits in some libc are not so "random". */ - srand((unsigned)monotonic_us() + getpid()); - for (i = 0; i < 16; i++) - buf[i] = rand() >> 5; + srand(monotonic_us()); + pid = getpid(); + while (1) { + for (i = 0; i < 16; i++) + buf[i] ^= rand() >> 5; + if (pid == 0) + break; + srand(pid); + pid = 0; + } + + buf[4 + 2 ] = (buf[4 + 2 ] & 0x0f) | 0x40; /* time_hi_and_version */ + buf[4 + 2 + 2] = (buf[4 + 2 + 2] & 0x3f) | 0x80; /* clk_seq_and_variant */ bin2hex(uuid_string, (void*) buf, 16); /* f.e. UUID=dfd9c173-be52-4d27-99a5-c34c6c2ff55f */ |