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Diffstat (limited to 'modules/pam_unix/bigcrypt.c')
| -rw-r--r-- | modules/pam_unix/bigcrypt.c | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/modules/pam_unix/bigcrypt.c b/modules/pam_unix/bigcrypt.c new file mode 100644 index 0000000..e08e409 --- /dev/null +++ b/modules/pam_unix/bigcrypt.c @@ -0,0 +1,159 @@ +/* + * This function implements the "bigcrypt" algorithm specifically for + * Linux-PAM. + * + * This algorithm is algorithm 0 (default) shipped with the C2 secure + * implementation of Digital UNIX. + * + * Disclaimer: This work is not based on the source code to Digital + * UNIX, nor am I connected to Digital Equipment Corp, in any way + * other than as a customer. This code is based on published + * interfaces and reasonable guesswork. + * + * Description: The cleartext is divided into blocks of SEGMENT_SIZE=8 + * characters or less. Each block is encrypted using the standard UNIX + * libc crypt function. The result of the encryption for one block + * provides the salt for the succeeding block. + * + * Restrictions: The buffer used to hold the encrypted result is + * statically allocated. (see MAX_PASS_LEN below). This is necessary, + * as the returned pointer points to "static data that are overwritten + * by each call", (XPG3: XSI System Interface + Headers pg 109), and + * this is a drop in replacement for crypt(); + * + * Andy Phillips <atp@mssl.ucl.ac.uk> + */ + +#include "config.h" + +#include <string.h> +#include <stdlib.h> +#include <security/_pam_macros.h> +#ifdef HAVE_LIBXCRYPT +#include <xcrypt.h> +#elif defined(HAVE_CRYPT_H) +#include <crypt.h> +#endif + +#include "bigcrypt.h" + +/* + * Max cleartext password length in segments of 8 characters this + * function can deal with (16 segments of 8 chars= max 128 character + * password). + */ + +#define MAX_PASS_LEN 16 +#define SEGMENT_SIZE 8 +#define SALT_SIZE 2 +#define KEYBUF_SIZE ((MAX_PASS_LEN*SEGMENT_SIZE)+SALT_SIZE) +#define ESEGMENT_SIZE 11 +#define CBUF_SIZE ((MAX_PASS_LEN*ESEGMENT_SIZE)+SALT_SIZE+1) + +char *bigcrypt(const char *key, const char *salt) +{ + char *dec_c2_cryptbuf; +#ifdef HAVE_CRYPT_R + struct crypt_data *cdata; +#endif + unsigned long int keylen, n_seg, j; + char *cipher_ptr, *plaintext_ptr, *tmp_ptr, *salt_ptr; + char keybuf[KEYBUF_SIZE + 1]; + + D(("called with key='%s', salt='%s'.", key, salt)); + + /* reset arrays */ + dec_c2_cryptbuf = malloc(CBUF_SIZE); + if (!dec_c2_cryptbuf) { + return NULL; + } +#ifdef HAVE_CRYPT_R + cdata = malloc(sizeof(*cdata)); + if(!cdata) { + free(dec_c2_cryptbuf); + return NULL; + } + cdata->initialized = 0; +#endif + memset(keybuf, 0, KEYBUF_SIZE + 1); + memset(dec_c2_cryptbuf, 0, CBUF_SIZE); + + /* fill KEYBUF_SIZE with key */ + strncpy(keybuf, key, KEYBUF_SIZE); + + /* deal with case that we are doing a password check for a + conventially encrypted password: the salt will be + SALT_SIZE+ESEGMENT_SIZE long. */ + if (strlen(salt) == (SALT_SIZE + ESEGMENT_SIZE)) + keybuf[SEGMENT_SIZE] = '\0'; /* terminate password early(?) */ + + keylen = strlen(keybuf); + + if (!keylen) { + n_seg = 1; + } else { + /* work out how many segments */ + n_seg = 1 + ((keylen - 1) / SEGMENT_SIZE); + } + + if (n_seg > MAX_PASS_LEN) + n_seg = MAX_PASS_LEN; /* truncate at max length */ + + /* set up some pointers */ + cipher_ptr = dec_c2_cryptbuf; + plaintext_ptr = keybuf; + + /* do the first block with supplied salt */ +#ifdef HAVE_CRYPT_R + tmp_ptr = crypt_r(plaintext_ptr, salt, cdata); /* libc crypt_r() */ +#else + tmp_ptr = crypt(plaintext_ptr, salt); /* libc crypt() */ +#endif + if (tmp_ptr == NULL) { + free(dec_c2_cryptbuf); + return NULL; + } + /* and place in the static area */ + strncpy(cipher_ptr, tmp_ptr, 13); + cipher_ptr += ESEGMENT_SIZE + SALT_SIZE; + plaintext_ptr += SEGMENT_SIZE; /* first block of SEGMENT_SIZE */ + + /* change the salt (1st 2 chars of previous block) - this was found + by dowsing */ + + salt_ptr = cipher_ptr - ESEGMENT_SIZE; + + /* so far this is identical to "return crypt(key, salt);", if + there is more than one block encrypt them... */ + + if (n_seg > 1) { + for (j = 2; j <= n_seg; j++) { + +#ifdef HAVE_CRYPT_R + tmp_ptr = crypt_r(plaintext_ptr, salt_ptr, cdata); +#else + tmp_ptr = crypt(plaintext_ptr, salt_ptr); +#endif + if (tmp_ptr == NULL) { + _pam_overwrite(dec_c2_cryptbuf); + free(dec_c2_cryptbuf); + return NULL; + } + + /* skip the salt for seg!=0 */ + strncpy(cipher_ptr, (tmp_ptr + SALT_SIZE), ESEGMENT_SIZE); + + cipher_ptr += ESEGMENT_SIZE; + plaintext_ptr += SEGMENT_SIZE; + salt_ptr = cipher_ptr - ESEGMENT_SIZE; + } + } + D(("key=|%s|, salt=|%s|\nbuf=|%s|\n", key, salt, dec_c2_cryptbuf)); + +#ifdef HAVE_CRYPT_R + free(cdata); +#endif + + /* this is the <NUL> terminated encrypted password */ + return dec_c2_cryptbuf; +} |