NetBSD/lib/libskey/skeylogin.c

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2003-03-09 03:42:56 +03:00
/* $NetBSD: skeylogin.c,v 1.18 2003/03/09 00:46:07 lukem Exp $ */
1996-09-19 23:39:36 +04:00
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/* S/KEY v1.1b (skeylogin.c)
*
* Authors:
* Neil M. Haller <nmh@thumper.bellcore.com>
* Philip R. Karn <karn@chicago.qualcomm.com>
* John S. Walden <jsw@thumper.bellcore.com>
* Scott Chasin <chasin@crimelab.com>
*
* Modifications:
* Todd C. Miller <Todd.Miller@courtesan.com>
* Angelos D. Keromytis <adk@adk.gr>
*
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* S/KEY verification check, lookups, and authentication.
*/
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#include <sys/cdefs.h>
__RCSID("$NetBSD: skeylogin.c,v 1.18 2003/03/09 00:46:07 lukem Exp $");
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#include <sys/param.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/types.h>
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#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <paths.h>
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#include <stdio.h>
#include <stdlib.h>
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#include <string.h>
#include <time.h>
#include <unistd.h>
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#include "skey.h"
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#define OTP_FMT "otp-%.*s %d %.*s"
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/* Issue a skey challenge for user 'name'. If successful,
* fill in the caller's skey structure and return 0. If unsuccessful
* (e.g., if name is unknown) return -1.
*
* The file read/write pointer is left at the start of the
* record.
*/
int getskeyprompt(struct skey *mp, char *name, char *prompt)
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{
int rval;
sevenbit(name);
rval = skeylookup(mp, name);
*prompt = '\0';
switch (rval) {
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case -1: /* File error */
return -1;
case 0: /* Lookup succeeded, return challenge */
sprintf(prompt, OTP_FMT "\n",
SKEY_MAX_HASHNAME_LEN, skey_get_algorithm(),
mp->n - 1, SKEY_MAX_SEED_LEN, mp->seed);
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return 0;
case 1: /* User not found */
fclose(mp->keyfile);
mp->keyfile = NULL;
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return -1;
}
return -1; /* Can't happen */
}
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/* Return a skey challenge string for user 'name'. If successful,
* fill in the caller's skey structure and return 0. If unsuccessful
* (e.g., if name is unknown) return -1.
*
* The file read/write pointer is left at the start of the
* record.
*/
int skeychallenge(struct skey *mp, const char *name, char *ss, size_t sslen)
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{
int rval;
rval = skeylookup(mp, name);
*ss = '\0';
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switch(rval){
case -1: /* File error */
return -1;
case 0: /* Lookup succeeded, issue challenge */
snprintf(ss, sslen, OTP_FMT, SKEY_MAX_HASHNAME_LEN,
skey_get_algorithm(), mp->n - 1,
SKEY_MAX_SEED_LEN, mp->seed);
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return 0;
case 1: /* User not found */
fclose(mp->keyfile);
mp->keyfile = NULL;
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return -1;
}
return -1; /* Can't happen */
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}
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static FILE *openSkey(void)
{
struct stat statbuf;
FILE *keyfile = NULL;
/* Open _PATH_SKEYKEYS if it exists, else return an error */
if (stat(_PATH_SKEYKEYS, &statbuf) == 0 &&
(keyfile = fopen(_PATH_SKEYKEYS, "r+"))) {
if ((statbuf.st_mode & 0007777) != 0600)
fchmod(fileno(keyfile), 0600);
} else {
keyfile = NULL;
}
return keyfile;
}
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/* Find an entry in the One-time Password database.
* Return codes:
* -1: error in opening database
* 0: entry found, file R/W pointer positioned at beginning of record
* 1: entry not found, file R/W pointer positioned at EOF
*/
int skeylookup(struct skey *mp, const char *name)
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{
int found = 0;
long recstart = 0;
const char *ht = NULL;
char *last;
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if(!(mp->keyfile = openSkey()))
return(-1);
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/* Look up user name in database */
while (!feof(mp->keyfile)) {
char *cp;
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recstart = ftell(mp->keyfile);
mp->recstart = recstart;
if (fgets(mp->buf, sizeof(mp->buf), mp->keyfile) != mp->buf)
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break;
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rip(mp->buf);
if (mp->buf[0] == '#')
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continue; /* Comment */
if ((mp->logname = strtok_r(mp->buf, " \t", &last)) == NULL)
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continue;
if ((cp = strtok_r(NULL, " \t", &last)) == NULL)
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continue;
/* Save hash type if specified, else use md4 */
if (isalpha((u_char) *cp)) {
ht = cp;
if ((cp = strtok_r(NULL, " \t", &last)) == NULL)
continue;
} else {
ht = "md4";
}
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mp->n = atoi(cp);
if ((mp->seed = strtok_r(NULL, " \t", &last)) == NULL)
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continue;
if ((mp->val = strtok_r(NULL, " \t", &last)) == NULL)
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continue;
if (strcmp(mp->logname, name) == 0) {
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found = 1;
break;
}
}
if (found) {
fseek(mp->keyfile, recstart, SEEK_SET);
/* Set hash type */
if (ht && skey_set_algorithm(ht) == NULL) {
warnx("Unknown hash algorithm %s, using %s", ht,
skey_get_algorithm());
}
return(0);
} else {
return(1);
}
}
/* Get the next entry in the One-time Password database.
* Return codes:
* -1: error in opening database
* 0: next entry found and stored in mp
* 1: no more entries, file R/W pointer positioned at EOF
*/
int skeygetnext(struct skey *mp)
{
long recstart = 0;
char *last;
/* Open _PATH_SKEYKEYS if it exists, else return an error */
if (mp->keyfile == NULL) {
if(!(mp->keyfile = openSkey()))
return(-1);
}
/* Look up next user in database */
while (!feof(mp->keyfile)) {
char *cp;
recstart = ftell(mp->keyfile);
mp->recstart = recstart;
if (fgets(mp->buf, sizeof(mp->buf), mp->keyfile) != mp->buf)
break;
rip(mp->buf);
if (mp->buf[0] == '#')
continue; /* Comment */
if ((mp->logname = strtok_r(mp->buf, " \t", &last)) == NULL)
continue;
if ((cp = strtok_r(NULL, " \t", &last)) == NULL)
continue;
/* Save hash type if specified, else use md4 */
if (isalpha((u_char) *cp)) {
if ((cp = strtok_r(NULL, " \t", &last)) == NULL)
continue;
}
mp->n = atoi(cp);
if ((mp->seed = strtok_r(NULL, " \t", &last)) == NULL)
continue;
if ((mp->val = strtok_r(NULL, " \t", &last)) == NULL)
continue;
/* Got a real entry */
break;
}
return(feof(mp->keyfile));
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}
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/* Verify response to a s/key challenge.
*
* Return codes:
* -1: Error of some sort; database unchanged
* 0: Verify successful, database updated
* 1: Verify failed, database unchanged
*
* The database file is always closed by this call.
*/
int skeyverify(struct skey *mp, char *response)
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{
char key[SKEY_BINKEY_SIZE];
char fkey[SKEY_BINKEY_SIZE];
char filekey[SKEY_BINKEY_SIZE];
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time_t now;
struct tm *tm;
char tbuf[27];
char *cp, *last;
int i, rval;
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time(&now);
tm = localtime(&now);
strftime(tbuf, sizeof(tbuf), " %b %d,%Y %T", tm);
if (response == NULL) {
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fclose(mp->keyfile);
mp->keyfile = NULL;
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return -1;
}
rip(response);
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/* Convert response to binary */
if (etob(key, response) != 1 && atob8(key, response) != 0) {
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/* Neither english words or ascii hex */
fclose(mp->keyfile);
mp->keyfile = NULL;
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return -1;
}
/* Compute fkey = f(key) */
memcpy(fkey, key, sizeof(key));
fflush(stdout);
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f(fkey);
/*
* Obtain an exclusive lock on the key file so the same password
* cannot be used twice to get in to the system.
*/
for (i = 0; i < 300; i++) {
if ((rval = flock(fileno(mp->keyfile), LOCK_EX|LOCK_NB)) == 0 ||
errno != EWOULDBLOCK)
break;
usleep(100000); /* Sleep for 0.1 seconds */
}
if (rval == -1) { /* Can't get exclusive lock */
errno = EAGAIN;
return(-1);
}
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/* Reread the file record NOW */
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fseek(mp->keyfile, mp->recstart, SEEK_SET);
if (fgets(mp->buf, sizeof(mp->buf), mp->keyfile) != mp->buf) {
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fclose(mp->keyfile);
mp->keyfile = NULL;
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return -1;
}
rip(mp->buf);
if ((mp->logname = strtok_r(mp->buf, " \t", &last)) == NULL)
goto verify_failure;
if ((cp = strtok_r(NULL, " \t", &last)) == NULL)
goto verify_failure;
if (isalpha((u_char) *cp))
if ((cp = strtok_r(NULL, " \t", &last)) == NULL)
goto verify_failure;
if ((mp->seed = strtok_r(NULL, " \t", &last)) == NULL)
goto verify_failure;
if ((mp->val = strtok_r(NULL, " \t", &last)) == NULL)
goto verify_failure;
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/* And convert file value to hex for comparison */
atob8(filekey, mp->val);
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/* Do actual comparison */
if (memcmp(filekey, fkey, SKEY_BINKEY_SIZE) != 0) {
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/* Wrong response */
fclose(mp->keyfile);
mp->keyfile = NULL;
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return 1;
}
/*
* Update key in database by overwriting entire record. Note
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* that we must write exactly the same number of bytes as in
* the original record (note fixed width field for N)
*/
btoa8(mp->val, key);
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mp->n--;
fseek(mp->keyfile, mp->recstart, SEEK_SET);
/* Don't save algorithm type for md4 (keep record length same) */
if (strcmp(skey_get_algorithm(), "md4") == 0)
(void)fprintf(mp->keyfile, "%s %04d %-16s %s %-21s\n",
mp->logname, mp->n, mp->seed, mp->val, tbuf);
else
(void)fprintf(mp->keyfile, "%s %s %04d %-16s %s %-21s\n",
mp->logname, skey_get_algorithm(), mp->n,
mp->seed, mp->val, tbuf);
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fclose(mp->keyfile);
mp->keyfile = NULL;
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return 0;
verify_failure:
fclose(mp->keyfile);
mp->keyfile = NULL;
return -1;
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}
/* Returns: 1 user doesnt exist, -1 file error, 0 user exists. */
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int skey_haskey(const char *username)
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{
struct skey skey;
int i;
i = skeylookup(&skey, username);
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if (skey.keyfile != NULL) {
fclose(skey.keyfile);
skey.keyfile = NULL;
}
return(i);
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}
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/*
* Returns the current sequence number and
* seed for the passed user.
*/
const char *skey_keyinfo(const char *username)
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{
int i;
static char str[SKEY_MAX_CHALLENGE];
struct skey skey;
i = skeychallenge(&skey, username, str, sizeof str);
if (i == -1)
return 0;
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if (skey.keyfile != NULL) {
fclose(skey.keyfile);
skey.keyfile = NULL;
}
return str;
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}
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/*
* Check to see if answer is the correct one to the current
* challenge.
*
* Returns: 0 success, -1 failure
*/
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int skey_passcheck (const char *username, char *passwd)
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{
int i;
struct skey skey;
i = skeylookup (&skey, username);
if (i == -1 || i == 1)
return -1;
if (skeyverify (&skey, passwd) == 0)
return skey.n;
return -1;
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}
#if DO_FAKE_CHALLENGE
#define ROUND(x) (((x)[0] << 24) + (((x)[1]) << 16) + (((x)[2]) << 8) + \
((x)[3]))
/*
* hash_collapse()
*/
static u_int32_t hash_collapse(u_char *s)
{
int len, target;
u_int32_t i;
int slen;
slen = strlen((char *)s);
if ((slen % sizeof(u_int32_t)) == 0)
target = slen; /* Multiple of 4 */
else
target = slen - slen % sizeof(u_int32_t);
for (i = 0, len = 0; len < target; len += 4)
i ^= ROUND(s + len);
return i;
}
#endif
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/*
* Used when calling program will allow input of the user's
* response to the challenge.
*
* Returns: 0 success, -1 failure
*/
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int skey_authenticate(const char *username)
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{
int i;
char pbuf[SKEY_MAX_PW_LEN+1], skeyprompt[SKEY_MAX_CHALLENGE+1];
struct skey skey;
#if DO_FAKE_CHALLENGE
u_int ptr;
u_char hseed[SKEY_MAX_SEED_LEN], flg = 1, *up;
size_t secretlen;
struct skey skey;
SHA1_CTX ctx;
#endif
/* Attempt a S/Key challenge */
i = skeychallenge(&skey, username, skeyprompt, sizeof skeyprompt);
#if DO_FAKE_CHALLENGE
/* Cons up a fake prompt if no entry in keys file */
if (i != 0) {
char *p, *u;
/*
* Base first 4 chars of seed on hostname.
* Add some filler for short hostnames if necessary.
*/
if (gethostname(pbuf, sizeof(pbuf)) == -1)
*(p = pbuf) = '.';
else
for (p = pbuf; *p && isalnum((u_char) *p); p++)
if (isalpha((u_char)*p) && isupper((u_char)*p))
*p = tolower((u_char)*p);
if (*p && pbuf - p < 4)
(void)strncpy(p, "asjd", 4 - (pbuf - p));
pbuf[4] = '\0';
/* Hash the username if possible */
if ((up = SHA1Data(username, strlen(username), NULL)) != NULL) {
struct stat sb;
time_t t;
int fd;
/* Collapse the hash */
ptr = hash_collapse(up);
memset(up, 0, strlen(up));
/* See if the random file's there, else use ctime */
if ((fd = open(_SKEY_RAND_FILE_PATH_, O_RDONLY)) != -1
&& fstat(fd, &sb) == 0 &&
sb.st_size > (off_t)SKEY_MAX_SEED_LEN &&
lseek(fd, ptr % (sb.st_size - SKEY_MAX_SEED_LEN),
SEEK_SET) != -1 && read(fd, hseed,
SKEY_MAX_SEED_LEN) == SKEY_MAX_SEED_LEN) {
close(fd);
fd = -1;
secret = hseed;
secretlen = SKEY_MAX_SEED_LEN;
flg = 0;
} else if (!stat(_PATH_MEM, &sb) || !stat("/", &sb)) {
t = sb.st_ctime;
secret = ctime(&t);
secretlen = strlen(secret);
flg = 0;
}
if (fd != -1)
close(fd);
}
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/* Put that in your pipe and smoke it */
if (flg == 0) {
/* Hash secret value with username */
SHA1Init(&ctx);
SHA1Update(&ctx, secret, secretlen);
SHA1Update(&ctx, username, strlen(username));
SHA1End(&ctx, up);
/* Zero out */
memset(secret, 0, secretlen);
/* Now hash the hash */
SHA1Init(&ctx);
SHA1Update(&ctx, up, strlen(up));
SHA1End(&ctx, up);
ptr = hash_collapse(up + 4);
for (i = 4; i < 9; i++) {
pbuf[i] = (ptr % 10) + '0';
ptr /= 10;
}
pbuf[i] = '\0';
/* Sequence number */
ptr = ((up[2] + up[3]) % 99) + 1;
memset(up, 0, 20); /* SHA1 specific */
free(up);
(void)sprintf(skeyprompt,
"otp-%.*s %d %.*s",
SKEY_MAX_HASHNAME_LEN,
skey_get_algorithm(),
ptr, SKEY_MAX_SEED_LEN,
pbuf);
} else {
/* Base last 8 chars of seed on username */
u = username;
i = 8;
p = &pbuf[4];
do {
if (*u == 0) {
/* Pad remainder with zeros */
while (--i >= 0)
*p++ = '0';
break;
}
*p++ = (*u++ % 10) + '0';
} while (--i != 0);
pbuf[12] = '\0';
(void)sprintf(skeyprompt, "otp-%.*s %d %.*s",
SKEY_MAX_HASHNAME_LEN,
skey_get_algorithm(),
99, SKEY_MAX_SEED_LEN, pbuf);
}
}
#endif
fprintf(stderr, "[%s]\n", skeyprompt);
fflush(stderr);
fputs("Response: ", stderr);
readskey(pbuf, sizeof(pbuf));
/* Is it a valid response? */
if (i == 0 && skeyverify(&skey, pbuf) == 0) {
if (skey.n < 5) {
fprintf(stderr,
"\nWarning! Key initialization needed soon. (%d logins left)\n",
skey.n);
}
return 0;
}
return -1;
}
/* Comment out user's entry in the s/key database
*
* Return codes:
* -1: Write error; database unchanged
* 0: Database updated
*
* The database file is always closed by this call.
*/
/* ARGSUSED */
int skeyzero(struct skey *mp, char *response)
{
/*
* Seek to the right place and write comment character
* which effectively zero's out the entry.
*/
fseek(mp->keyfile, mp->recstart, SEEK_SET);
if (fputc('#', mp->keyfile) == EOF) {
fclose(mp->keyfile);
mp->keyfile = NULL;
return(-1);
}
fclose(mp->keyfile);
mp->keyfile = NULL;
return(0);
}