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Lines 62-68
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static inline uintptr_t __attribute__ ((always_inline)) |
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static inline uintptr_t __attribute__ ((always_inline)) |
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_dl_setup_stack_chk_guard (void *dl_random) |
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_dl_setup_stack_chk_guard (void *dl_random) |
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{ |
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{ |
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uintptr_t ret; |
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uintptr_t ret = 0; |
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/* Having a leading zero byte protects the stack guard from |
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being exposed by an unterminated str* read operation. */ |
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unsigned char *p = ((unsigned char *) &ret) + 1; |
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int size = sizeof (ret) - 1; |
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#ifndef __ASSUME_AT_RANDOM |
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#ifndef __ASSUME_AT_RANDOM |
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if (__builtin_expect (dl_random == NULL, 0)) |
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if (__builtin_expect (dl_random == NULL, 0)) |
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{ |
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{ |
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Lines 70-92
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int fd = __open ("/dev/urandom", O_RDONLY); |
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int fd = __open ("/dev/urandom", O_RDONLY); |
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if (fd >= 0) |
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if (fd >= 0) |
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{ |
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{ |
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ssize_t reslen = __read (fd, &ret, sizeof (ret)); |
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ssize_t reslen = __read (fd, p, size); |
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__close (fd); |
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__close (fd); |
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if (reslen == (ssize_t) sizeof (ret)) |
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if (reslen == (ssize_t) size) |
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return ret; |
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return ret; |
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} |
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} |
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# endif |
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# endif |
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ret = 0; |
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/* Lacking any other form of randomized stack guard, add other |
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unsigned char *p = (unsigned char *) &ret; |
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terminators in an attempt to block things like fgets, etc. */ |
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p[sizeof (ret) - 1] = 255; |
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p[size - 1] = 255; |
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p[sizeof (ret) - 2] = '\n'; |
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p[size - 2] = '\n'; |
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} |
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} |
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else |
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else |
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#endif |
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#endif |
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/* We need in the moment only 8 bytes on 32-bit platforms and 16 |
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/* We need in the moment only 8 bytes on 32-bit platforms and 16 |
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bytes on 64-bit platforms. Therefore we can use the data |
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bytes on 64-bit platforms. Therefore we can use the data |
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directly and not use the kernel-provided data to seed a PRNG. */ |
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directly and not use the kernel-provided data to seed a PRNG. */ |
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memcpy (&ret, dl_random, sizeof (ret)); |
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memcpy (p, dl_random, size); |
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return ret; |
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return ret; |
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} |
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} |
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