lib/libpam/modules/pam_login_access/login_access.c

   1 /*      $NetBSD: login_access.c,v 1.4 2006/11/03 18:03:23 christos Exp $        */
   2
   3 /*
   4  * This module implements a simple but effective form of login access
   5  * control based on login names and on host (or domain) names, internet
   6  * addresses (or network numbers), or on terminal line names in case of
   7  * non-networked logins. Diagnostics are reported through syslog(3).
   8  *
   9  * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
  10  */
  11
  12 #if 0
  13 #ifndef lint
  14 static char sccsid[] = "%Z% %M% %I% %E% %U%";
  15 #endif
  16 #endif
  17
  18 #include <sys/cdefs.h>
  19 #ifdef __FreeBSD__
  20 __FBSDID("$FreeBSD: src/lib/libpam/modules/pam_login_access/login_access.c,v 1.12 2004/03/05 08:10:18 markm Exp $");
  21 #else
  22 __RCSID("$NetBSD: login_access.c,v 1.4 2006/11/03 18:03:23 christos Exp $");
  23 #endif
  24
  25 #include <sys/types.h>
  26 #include <ctype.h>
  27 #include <errno.h>
  28 #include <grp.h>
  29 #include <stdio.h>
  30 #include <stdlib.h>
  31 #include <string.h>
  32 #include <syslog.h>
  33 #include <unistd.h>
  34 #include <stdarg.h>
  35
  36 #include "pam_login_access.h"
  37
  38 #define _PATH_LOGACCESS         "/etc/login.access"
  39
  40  /* Delimiters for fields and for lists of users, ttys or hosts. */
  41
  42 static char fs[] = ":";                 /* field separator */
  43 static char sep[] = ", \t";             /* list-element separator */
  44
  45  /* Constants to be used in assignments only, not in comparisons... */
  46
  47 #define YES             1
  48 #define NO              0
  49
  50 static int      from_match(const char *, const char *);
  51 static int      list_match(char *, const char *,
  52                                 int (*)(const char *, const char *));
  53 static int      netgroup_match(const char *, const char *, const char *);
  54 static int      string_match(const char *, const char *);
  55 static int      user_match(const char *, const char *);
  56
  57 /* login_access - match username/group and host/tty with access control file */
  58
  59 static void
  60 logit(int level, const char *fmt, ...)
  61 {
  62         va_list ap;
  63         struct syslog_data data = SYSLOG_DATA_INIT;
  64
  65         openlog_r("pam_login_access", LOG_PID, LOG_AUTHPRIV, &data);
  66         va_start(ap, fmt);
  67         vsyslog_r(level, &data, fmt, ap);
  68         va_end(ap);
  69         closelog_r(&data);
  70 }
  71
  72 int
  73 login_access(const char *user, const char *from)
  74 {
  75     FILE   *fp;
  76     char    line[BUFSIZ];
  77     char   *perm;                       /* becomes permission field */
  78     char   *users;                      /* becomes list of login names */
  79     char   *froms;                      /* becomes list of terminals or hosts */
  80     int     match = NO;
  81     int     end;
  82     int     lineno = 0;                 /* for diagnostics */
  83
  84     /*
  85      * Process the table one line at a time and stop at the first match.
  86      * Blank lines and lines that begin with a '#' character are ignored.
  87      * Non-comment lines are broken at the ':' character. All fields are
  88      * mandatory. The first field should be a "+" or "-" character. A
  89      * non-existing table means no access control.
  90      */
  91
  92     if ((fp = fopen(_PATH_LOGACCESS, "r")) != NULL) {
  93         while (!match && fgets(line, sizeof(line), fp)) {
  94             lineno++;
  95             if (line[end = strlen(line) - 1] != '\n') {
  96                 logit(LOG_ERR, "%s: line %d: missing newline or line too long",
  97                        _PATH_LOGACCESS, lineno);
  98                 continue;
  99             }
 100             if (line[0] == '#')
 101                 continue;                       /* comment line */
 102             while (end > 0 && isspace((unsigned char)line[end - 1]))
 103                 end--;
 104             line[end] = 0;                      /* strip trailing whitespace */
 105             if (line[0] == 0)                   /* skip blank lines */
 106                 continue;
 107             if (!(perm = strtok(line, fs))
 108                 || !(users = strtok((char *) 0, fs))
 109                 || !(froms = strtok((char *) 0, fs))
 110                 || strtok((char *) 0, fs)) {
 111                 logit(LOG_ERR, "%s: line %d: bad field count", _PATH_LOGACCESS,
 112                        lineno);
 113                 continue;
 114             }
 115             if (perm[0] != '+' && perm[0] != '-') {
 116                 logit(LOG_ERR, "%s: line %d: bad first field", _PATH_LOGACCESS,
 117                        lineno);
 118                 continue;
 119             }
 120             match = (list_match(froms, from, from_match)
 121                      && list_match(users, user, user_match));
 122         }
 123         (void) fclose(fp);
 124     } else if (errno != ENOENT) {
 125         logit(LOG_ERR, "cannot open %s: %m", _PATH_LOGACCESS);
 126     }
 127     return (match == 0 || (line[0] == '+'));
 128 }
 129
 130 /* list_match - match an item against a list of tokens with exceptions */
 131
 132 static int
 133 list_match(char *list, const char *item,
 134     int (*match_fn)(const char *, const char *))
 135 {
 136     char   *tok;
 137     int     match = NO;
 138
 139     /*
 140      * Process tokens one at a time. We have exhausted all possible matches
 141      * when we reach an "EXCEPT" token or the end of the list. If we do find
 142      * a match, look for an "EXCEPT" list and recurse to determine whether
 143      * the match is affected by any exceptions.
 144      */
 145
 146     for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) {
 147         if (strcasecmp(tok, "EXCEPT") == 0)     /* EXCEPT: give up */
 148             break;
 149         if ((match = (*match_fn)(tok, item)) != 0)      /* YES */
 150             break;
 151     }
 152     /* Process exceptions to matches. */
 153
 154     if (match != NO) {
 155         while ((tok = strtok((char *) 0, sep)) && strcasecmp(tok, "EXCEPT"))
 156              /* VOID */ ;
 157         if (tok == 0 || list_match((char *) 0, item, match_fn) == NO)
 158             return (match);
 159     }
 160     return (NO);
 161 }
 162
 163 /* netgroup_match - match group against machine or user */
 164
 165 static int
 166 netgroup_match(const char *group __unused,
 167     const char *machine __unused, const char *user __unused)
 168 {
 169     logit(LOG_ERR, "NIS netgroup support not configured");
 170     return 0;
 171 }
 172
 173 /* user_match - match a username against one token */
 174
 175 static int
 176 user_match(const char *tok, const char *string)
 177 {
 178     struct group grres, *group;
 179     char grbuf[1024];
 180     int     i;
 181
 182     /*
 183      * If a token has the magic value "ALL" the match always succeeds.
 184      * Otherwise, return YES if the token fully matches the username, or if
 185      * the token is a group that contains the username.
 186      */
 187
 188     if (tok[0] == '@') {                        /* netgroup */
 189         return (netgroup_match(tok + 1, (char *) 0, string));
 190     } else if (string_match(tok, string)) {     /* ALL or exact match */
 191         return (YES);
 192     } else if (getgrnam_r(tok, &grres, grbuf, sizeof(grbuf), &group) == 0 &&
 193         group != NULL) {/* try group membership */
 194         for (i = 0; group->gr_mem[i]; i++)
 195             if (strcasecmp(string, group->gr_mem[i]) == 0)
 196                 return (YES);
 197     }
 198     return (NO);
 199 }
 200
 201 /* from_match - match a host or tty against a list of tokens */
 202
 203 static int
 204 from_match(const char *tok, const char *string)
 205 {
 206     int     tok_len;
 207     int     str_len;
 208
 209     /*
 210      * If a token has the magic value "ALL" the match always succeeds. Return
 211      * YES if the token fully matches the string. If the token is a domain
 212      * name, return YES if it matches the last fields of the string. If the
 213      * token has the magic value "LOCAL", return YES if the string does not
 214      * contain a "." character. If the token is a network number, return YES
 215      * if it matches the head of the string.
 216      */
 217
 218     if (tok[0] == '@') {                        /* netgroup */
 219         return (netgroup_match(tok + 1, string, (char *) 0));
 220     } else if (string_match(tok, string)) {     /* ALL or exact match */
 221         return (YES);
 222     } else if (tok[0] == '.') {                 /* domain: match last fields */
 223         if ((str_len = strlen(string)) > (tok_len = strlen(tok))
 224             && strcasecmp(tok, string + str_len - tok_len) == 0)
 225             return (YES);
 226     } else if (strcasecmp(tok, "LOCAL") == 0) { /* local: no dots */
 227         if (strchr(string, '.') == 0)
 228             return (YES);
 229     } else if (tok[(tok_len = strlen(tok)) - 1] == '.'  /* network */
 230                && strncmp(tok, string, tok_len) == 0) {
 231         return (YES);
 232     }
 233     return (NO);
 234 }
 235
 236 /* string_match - match a string against one token */
 237
 238 static int
 239 string_match(const char *tok, const char *string)
 240 {
 241
 242     /*
 243      * If the token has the magic value "ALL" the match always succeeds.
 244      * Otherwise, return YES if the token fully matches the string.
 245      */
 246
 247     if (strcasecmp(tok, "ALL") == 0) {          /* all: always matches */
 248         return (YES);
 249     } else if (strcasecmp(tok, string) == 0) {  /* try exact match */
 250         return (YES);
 251     }
 252     return (NO);
 253 }