/* Unix SMB/CIFS implementation. Functions to create reasonable random numbers for crypto use. Copyright (C) Jeremy Allison 2001 This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. */ #include "includes.h" #include "system/filesys.h" #include "lib/crypto/crypto.h" #include "system/locale.h" /** * @file * @brief Random number generation */ static unsigned char hash[258]; static uint32_t counter; static bool done_reseed = false; static unsigned int bytes_since_reseed = 0; static int urand_fd = -1; static void (*reseed_callback)(int *newseed); /** Copy any user given reseed data. **/ _PUBLIC_ void set_rand_reseed_callback(void (*fn)(int *)) { reseed_callback = fn; set_need_random_reseed(); } /** * Tell the random number generator it needs to reseed. */ _PUBLIC_ void set_need_random_reseed(void) { done_reseed = false; bytes_since_reseed = 0; } static void get_rand_reseed_data(int *reseed_data) { if (reseed_callback) { reseed_callback(reseed_data); } else { *reseed_data = 0; } } /**************************************************************** Setup the seed. *****************************************************************/ static void seed_random_stream(unsigned char *seedval, size_t seedlen) { unsigned char j = 0; size_t ind; for (ind = 0; ind < 256; ind++) hash[ind] = (unsigned char)ind; for( ind = 0; ind < 256; ind++) { unsigned char tc; j += (hash[ind] + seedval[ind%seedlen]); tc = hash[ind]; hash[ind] = hash[j]; hash[j] = tc; } hash[256] = 0; hash[257] = 0; } /**************************************************************** Get datasize bytes worth of random data. *****************************************************************/ static void get_random_stream(unsigned char *data, size_t datasize) { unsigned char index_i = hash[256]; unsigned char index_j = hash[257]; size_t ind; for( ind = 0; ind < datasize; ind++) { unsigned char tc; unsigned char t; index_i++; index_j += hash[index_i]; tc = hash[index_i]; hash[index_i] = hash[index_j]; hash[index_j] = tc; t = hash[index_i] + hash[index_j]; data[ind] = hash[t]; } hash[256] = index_i; hash[257] = index_j; } /**************************************************************** Get a 16 byte hash from the contents of a file. Note that the hash is initialised, because the extra entropy is not worth the valgrind pain. *****************************************************************/ static void do_filehash(const char *fname, unsigned char *the_hash) { unsigned char buf[1011]; /* deliberate weird size */ unsigned char tmp_md4[16]; int fd, n; ZERO_STRUCT(tmp_md4); fd = open(fname,O_RDONLY,0); if (fd == -1) return; while ((n = read(fd, (char *)buf, sizeof(buf))) > 0) { mdfour(tmp_md4, buf, n); for (n=0;n<16;n++) the_hash[n] ^= tmp_md4[n]; } close(fd); } /************************************************************** Try and get a good random number seed. Try a number of different factors. Firstly, try /dev/urandom - use if exists. We use /dev/urandom as a read of /dev/random can block if the entropy pool dries up. This leads clients to timeout or be very slow on connect. If we can't use /dev/urandom then seed the stream random generator above... **************************************************************/ static int do_reseed(bool use_fd, int fd) { unsigned char seed_inbuf[40]; uint32_t v1, v2; struct timeval tval; pid_t mypid; int reseed_data = 0; if (use_fd) { if (fd == -1) { fd = open( "/dev/urandom", O_RDONLY,0); } if (fd != -1 && (read(fd, seed_inbuf, sizeof(seed_inbuf)) == sizeof(seed_inbuf))) { seed_random_stream(seed_inbuf, sizeof(seed_inbuf)); return fd; } } /* Add in some secret file contents */ do_filehash("/etc/shadow", &seed_inbuf[0]); /* * Add the counter, time of day, and pid. */ GetTimeOfDay(&tval); mypid = getpid(); v1 = (counter++) + mypid + tval.tv_sec; v2 = (counter++) * mypid + tval.tv_usec; SIVAL(seed_inbuf, 32, v1 ^ IVAL(seed_inbuf, 32)); SIVAL(seed_inbuf, 36, v2 ^ IVAL(seed_inbuf, 36)); /* * Add any user-given reseed data. */ get_rand_reseed_data(&reseed_data); if (reseed_data) { size_t i; for (i = 0; i < sizeof(seed_inbuf); i++) seed_inbuf[i] ^= ((char *)(&reseed_data))[i % sizeof(reseed_data)]; } seed_random_stream(seed_inbuf, sizeof(seed_inbuf)); return -1; } /** Interface to the (hopefully) good crypto random number generator. Will use our internal PRNG if more than 40 bytes of random generation has been requested, otherwise tries to read from /dev/random **/ _PUBLIC_ void generate_random_buffer(uint8_t *out, int len) { unsigned char md4_buf[64]; unsigned char tmp_buf[16]; unsigned char *p; if(!done_reseed) { bytes_since_reseed += len; /* Magic constant to try and avoid reading 40 bytes * and setting up the PRNG if the app only ever wants * a few bytes */ if (bytes_since_reseed < 40) { if (urand_fd == -1) { urand_fd = open( "/dev/urandom", O_RDONLY,0); } if(urand_fd != -1 && (read(urand_fd, out, len) == len)) { return; } } urand_fd = do_reseed(true, urand_fd); done_reseed = true; } /* * Generate random numbers in chunks of 64 bytes, * then md4 them & copy to the output buffer. * This way the raw state of the stream is never externally * seen. */ p = out; while(len > 0) { int copy_len = len > 16 ? 16 : len; get_random_stream(md4_buf, sizeof(md4_buf)); mdfour(tmp_buf, md4_buf, sizeof(md4_buf)); memcpy(p, tmp_buf, copy_len); p += copy_len; len -= copy_len; } } /** Interface to the (hopefully) good crypto random number generator. Will always use /dev/urandom if available. **/ _PUBLIC_ void generate_secret_buffer(uint8_t *out, int len) { if (urand_fd == -1) { urand_fd = open( "/dev/urandom", O_RDONLY,0); } if(urand_fd != -1 && (read(urand_fd, out, len) == len)) { return; } generate_random_buffer(out, len); } /** generate a single random uint32_t **/ _PUBLIC_ uint32_t generate_random(void) { uint8_t v[4]; generate_random_buffer(v, 4); return IVAL(v, 0); } /** very basic password quality checker **/ _PUBLIC_ bool check_password_quality(const char *s) { int has_digit=0, has_capital=0, has_lower=0, has_special=0, has_high=0; while (*s) { if (isdigit((unsigned char)*s)) { has_digit |= 1; } else if (isupper((unsigned char)*s)) { has_capital |= 1; } else if (islower((unsigned char)*s)) { has_lower |= 1; } else if (isascii((unsigned char)*s)) { has_special |= 1; } else { has_high++; } s++; } return ((has_digit + has_lower + has_capital + has_special) >= 3 || (has_high > strlen(s)/2)); } /** Use the random number generator to generate a random string. **/ _PUBLIC_ char *generate_random_str_list(TALLOC_CTX *mem_ctx, size_t len, const char *list) { size_t i; size_t list_len = strlen(list); char *retstr = talloc_array(mem_ctx, char, len + 1); if (!retstr) return NULL; generate_random_buffer((uint8_t *)retstr, len); for (i = 0; i < len; i++) { retstr[i] = list[retstr[i] % list_len]; } retstr[i] = '\0'; return retstr; } /** * Generate a random text string consisting of the specified length. * The returned string will be allocated. * * Characters used are: ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+_-#., */ _PUBLIC_ char *generate_random_str(TALLOC_CTX *mem_ctx, size_t len) { char *retstr; const char *c_list = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+_-#.,"; again: retstr = generate_random_str_list(mem_ctx, len, c_list); if (!retstr) return NULL; /* we need to make sure the random string passes basic quality tests or it might be rejected by windows as a password */ if (len >= 7 && !check_password_quality(retstr)) { talloc_free(retstr); goto again; } return retstr; }