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Message-ID: <510D7953.50308@opensource.dyc.edu> Date: Sat, 02 Feb 2013 15:38:43 -0500 From: "Anthony G. Basile" <basile@...nsource.dyc.edu> To: musl@...ts.openwall.com Subject: Re: [PATCH] Add support for mkostemp, mkstemps and mkostemps Okay let me try those fixes. Some points: 1. I forgot to remove a group of headers when I refactorized. So mkostemp.c mkostemps.c mkstemp.c and mkstemps.c only need #include <fcntl.h> #include "libc.h" or #define _GNU_SOURCE #include "libc.h" 2. This is from uclibc. Clearly, static is critical here, but still they never initialize a value of 'value' on first entry into the function, so that memory is dirty to start. Mine is worse, but I wonder if this is still a bug there. static void brain_damaged_fillrand(unsigned char *buf, unsigned int len) { ... static uint64_t value; gettimeofday(&tv, NULL); value += ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec ^ getpid(); ... 3. I retested your address approach. I like it but it only maps to upper and lower case letters, no numbers which uclibc and glibc do. clock_gettime(CLOCK_REALTIME, &ts); r = ts.tv_nsec*65537 ^ (uintptr_t)&ts / 16 + (uintptr_t)template; for (i=0; i<6; i++, r>>=5) template[i] = 'A'+(r&15)+(r&16)*2; On 02/02/2013 03:14 PM, Szabolcs Nagy wrote: > * Anthony G. Basile <basile@...nsource.dyc.edu> [2013-02-02 13:45:31 -0500]: >> + /* Null terminate the template before the suffix, >> + and save the char for adding back the suffix */ >> + char suffix = template[l]; >> + template[l] = '\0'; > > if you set only the XXXXXX part in __randname, then the \0 is unnecessary > >> + int fd, retries = 100; >> + while (retries--) { >> + if (!*__randname(template)) return -1; > > __randname cannot fail, so the check is unnecessary > >> +/* This assumes that a check for the >> + template size has alrady been made */ >> +char *__randname(char *template) >> +{ >> + struct timespec ts; >> + size_t i, l = strlen(template); >> + >> + /* r is intentially uninialized and 'dirty' */ >> + unsigned long r; >> + > > it's undefined behaviour so the compiler is allowed to > completely remove the code of this function > > if you seen this kind of code somewhere, that's a critical > bug that should be reported > > the original address based entropy source was ok > >> + clock_gettime(CLOCK_REALTIME, &ts); >> + r += ((uint64_t) ts.tv_nsec << 16) ^ ts.tv_sec; >> + for (i=1; i<=6; i++, r>>=6) >> + template[l-i] = __map_letter(r); >> + >> + return template; >> +} -- Anthony G. Basile, Ph. D. Chair of Information Technology D'Youville College Buffalo, NY 14201 (716) 829-8197
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