/* One way encryption based on MD5 sum. Compatible with the behavior of MD5 crypt introduced in FreeBSD 2.0. Copyright (C) 1996, 1997, 1999, 2000, 2001, 2002, 2004 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Ulrich Drepper , 1996. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. The GNU C Library 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 Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU C Library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. */ #include "crypt-port.h" #include "crypt-private.h" #include "alg-md5.h" #include #include /* Define our magic string to mark salt for MD5 "encryption" replacement. This is meant to be the same as for other MD5 based encryption implementations. */ static const char md5_salt_prefix[] = "$1$"; /* Table with characters for base64 transformation. */ static const char b64t[64] = "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"; /* The maximum length of an MD5 salt string (just the actual salt, not the entire prefix). */ #define SALT_LEN_MAX 8 /* The length of an MD5-hashed password string, including the terminating NUL character. Prefix (including its NUL) + 8 bytes of salt + separator + 22 bytes of hashed password. */ #define MD5_HASH_LENGTH \ (sizeof (md5_salt_prefix) + SALT_LEN_MAX + 1 + 22) static_assert (MD5_HASH_LENGTH <= CRYPT_OUTPUT_SIZE, "CRYPT_OUTPUT_SIZE is too small for MD5"); /* An md5_buffer holds all of the sensitive intermediate data. */ struct md5_buffer { struct md5_ctx ctx; uint8_t result[16]; }; static_assert (sizeof (struct md5_buffer) <= ALG_SPECIFIC_SIZE, "ALG_SPECIFIC_SIZE is too small for MD5"); /* This entry point is equivalent to the `crypt' function in Unix libcs. */ void crypt_md5_rn (const char *phrase, const char *setting, uint8_t *output, size_t o_size, void *scratch, size_t s_size) { /* This shouldn't ever happen, but... */ if (o_size < MD5_HASH_LENGTH || s_size < sizeof (struct md5_buffer)) { errno = ERANGE; return; } struct md5_buffer *buf = scratch; struct md5_ctx *ctx = &buf->ctx; uint8_t *result = buf->result; char *cp = (char *)output; const char *salt = setting; size_t salt_len; size_t phrase_len; size_t cnt; /* Find beginning of salt string. The prefix should normally always be present. Just in case it is not. */ if (strncmp (md5_salt_prefix, salt, sizeof (md5_salt_prefix) - 1) == 0) /* Skip salt prefix. */ salt += sizeof (md5_salt_prefix) - 1; salt_len = strcspn (salt, "$"); if (salt_len > SALT_LEN_MAX) salt_len = SALT_LEN_MAX; phrase_len = strlen (phrase); /* Compute alternate MD5 sum with input PHRASE, SALT, and PHRASE. The final result will be added to the first context. */ md5_init_ctx (ctx); /* Add phrase. */ md5_process_bytes (phrase, phrase_len, ctx); /* Add salt. */ md5_process_bytes (salt, salt_len, ctx); /* Add phrase again. */ md5_process_bytes (phrase, phrase_len, ctx); /* Now get result of this (16 bytes). */ md5_finish_ctx (ctx, result); /* Prepare for the real work. */ md5_init_ctx (ctx); /* Add the phrase string. */ md5_process_bytes (phrase, phrase_len, ctx); /* Because the SALT argument need not always have the salt prefix we add it separately. */ md5_process_bytes (md5_salt_prefix, sizeof (md5_salt_prefix) - 1, ctx); /* The last part is the salt string. This must be at most 8 characters and it ends at the first `$' character (for compatibility with existing implementations). */ md5_process_bytes (salt, salt_len, ctx); /* Add for any character in the phrase one byte of the alternate sum. */ for (cnt = phrase_len; cnt > 16; cnt -= 16) md5_process_bytes (result, 16, ctx); md5_process_bytes (result, cnt, ctx); /* For the following code we need a NUL byte. */ *result = '\0'; /* The original implementation now does something weird: for every 1 bit in the phrase the first 0 is added to the buffer, for every 0 bit the first character of the phrase. This does not seem to be what was intended but we have to follow this to be compatible. */ for (cnt = phrase_len; cnt > 0; cnt >>= 1) md5_process_bytes ((cnt & 1) != 0 ? (const char *) result : phrase, 1, ctx); /* Create intermediate result. */ md5_finish_ctx (ctx, result); /* Now comes another weirdness. In fear of password crackers here comes a quite long loop which just processes the output of the previous round again. We cannot ignore this here. */ for (cnt = 0; cnt < 1000; ++cnt) { /* New context. */ md5_init_ctx (ctx); /* Add phrase or last result. */ if ((cnt & 1) != 0) md5_process_bytes (phrase, phrase_len, ctx); else md5_process_bytes (result, 16, ctx); /* Add salt for numbers not divisible by 3. */ if (cnt % 3 != 0) md5_process_bytes (salt, salt_len, ctx); /* Add phrase for numbers not divisible by 7. */ if (cnt % 7 != 0) md5_process_bytes (phrase, phrase_len, ctx); /* Add phrase or last result. */ if ((cnt & 1) != 0) md5_process_bytes (result, 16, ctx); else md5_process_bytes (phrase, phrase_len, ctx); /* Create intermediate result. */ md5_finish_ctx (ctx, result); } /* Now we can construct the result string. It consists of three parts. We already know that there is enough space at CP. */ memcpy (cp, md5_salt_prefix, sizeof (md5_salt_prefix) - 1); cp += sizeof (md5_salt_prefix) - 1; memcpy (cp, salt, salt_len); cp += salt_len; *cp++ = '$'; #define b64_from_24bit(B2, B1, B0, N) \ do { \ unsigned int w = ((((unsigned int)(B2)) << 16) | \ (((unsigned int)(B1)) << 8) | \ ((unsigned int)(B0))); \ int n = (N); \ while (n-- > 0) \ { \ *cp++ = b64t[w & 0x3f]; \ w >>= 6; \ } \ } while (0) b64_from_24bit (result[0], result[6], result[12], 4); b64_from_24bit (result[1], result[7], result[13], 4); b64_from_24bit (result[2], result[8], result[14], 4); b64_from_24bit (result[3], result[9], result[15], 4); b64_from_24bit (result[4], result[10], result[5], 4); b64_from_24bit (0, 0, result[11], 2); *cp = '\0'; } void gensalt_md5_rn (unsigned long count, const uint8_t *rbytes, size_t nrbytes, uint8_t *output, size_t output_size) { gensalt_sha_rn ('1', 8, 1000, 1000, 1000, count, rbytes, nrbytes, output, output_size); }