login_access.c revision 87173
1 /* 2 * This module implements a simple but effective form of login access 3 * control based on login names and on host (or domain) names, internet 4 * addresses (or network numbers), or on terminal line names in case of 5 * non-networked logins. Diagnostics are reported through syslog(3). 6 * 7 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands. 8 * $FreeBSD: head/lib/libpam/modules/pam_login_access/login_access.c 87173 2001-12-01 17:46:46Z markm $ 9 */ 10 11#ifdef LOGIN_ACCESS 12#ifndef lint 13static const char sccsid[] = "%Z% %M% %I% %E% %U%"; 14#endif 15 16#include <stdio.h> 17#include <syslog.h> 18#include <ctype.h> 19#include <sys/types.h> 20#include <grp.h> 21#include <errno.h> 22#include <string.h> 23#include <unistd.h> 24#include <stdlib.h> 25 26#include "login.h" 27#include "pathnames.h" 28 29 /* Delimiters for fields and for lists of users, ttys or hosts. */ 30 31static char fs[] = ":"; /* field separator */ 32static char sep[] = ", \t"; /* list-element separator */ 33 34 /* Constants to be used in assignments only, not in comparisons... */ 35 36#define YES 1 37#define NO 0 38 39static int list_match __P((char *, char *, int (*)(char *, char *))); 40static int user_match __P((char *, char *)); 41static int from_match __P((char *, char *)); 42static int string_match __P((char *, char *)); 43static int netgroup_match __P((char *, char *, char *)); 44 45/* login_access - match username/group and host/tty with access control file */ 46 47int 48login_access(user, from) 49char *user; 50char *from; 51{ 52 FILE *fp; 53 char line[BUFSIZ]; 54 char *perm; /* becomes permission field */ 55 char *users; /* becomes list of login names */ 56 char *froms; /* becomes list of terminals or hosts */ 57 int match = NO; 58 int end; 59 int lineno = 0; /* for diagnostics */ 60 61 /* 62 * Process the table one line at a time and stop at the first match. 63 * Blank lines and lines that begin with a '#' character are ignored. 64 * Non-comment lines are broken at the ':' character. All fields are 65 * mandatory. The first field should be a "+" or "-" character. A 66 * non-existing table means no access control. 67 */ 68 69 if ((fp = fopen(_PATH_LOGACCESS, "r")) != NULL) { 70 while (!match && fgets(line, sizeof(line), fp)) { 71 lineno++; 72 if (line[end = strlen(line) - 1] != '\n') { 73 syslog(LOG_ERR, "%s: line %d: missing newline or line too long", 74 _PATH_LOGACCESS, lineno); 75 continue; 76 } 77 if (line[0] == '#') 78 continue; /* comment line */ 79 while (end > 0 && isspace(line[end - 1])) 80 end--; 81 line[end] = 0; /* strip trailing whitespace */ 82 if (line[0] == 0) /* skip blank lines */ 83 continue; 84 if (!(perm = strtok(line, fs)) 85 || !(users = strtok((char *) 0, fs)) 86 || !(froms = strtok((char *) 0, fs)) 87 || strtok((char *) 0, fs)) { 88 syslog(LOG_ERR, "%s: line %d: bad field count", _PATH_LOGACCESS, 89 lineno); 90 continue; 91 } 92 if (perm[0] != '+' && perm[0] != '-') { 93 syslog(LOG_ERR, "%s: line %d: bad first field", _PATH_LOGACCESS, 94 lineno); 95 continue; 96 } 97 match = (list_match(froms, from, from_match) 98 && list_match(users, user, user_match)); 99 } 100 (void) fclose(fp); 101 } else if (errno != ENOENT) { 102 syslog(LOG_ERR, "cannot open %s: %m", _PATH_LOGACCESS); 103 } 104 return (match == 0 || (line[0] == '+')); 105} 106 107/* list_match - match an item against a list of tokens with exceptions */ 108 109static int list_match(list, item, match_fn) 110char *list; 111char *item; 112int (*match_fn) __P((char *, char *)); 113{ 114 char *tok; 115 int match = NO; 116 117 /* 118 * Process tokens one at a time. We have exhausted all possible matches 119 * when we reach an "EXCEPT" token or the end of the list. If we do find 120 * a match, look for an "EXCEPT" list and recurse to determine whether 121 * the match is affected by any exceptions. 122 */ 123 124 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) { 125 if (strcasecmp(tok, "EXCEPT") == 0) /* EXCEPT: give up */ 126 break; 127 if ((match = (*match_fn)(tok, item)) != NULL) /* YES */ 128 break; 129 } 130 /* Process exceptions to matches. */ 131 132 if (match != NO) { 133 while ((tok = strtok((char *) 0, sep)) && strcasecmp(tok, "EXCEPT")) 134 /* VOID */ ; 135 if (tok == 0 || list_match((char *) 0, item, match_fn) == NO) 136 return (match); 137 } 138 return (NO); 139} 140 141/* netgroup_match - match group against machine or user */ 142 143static int netgroup_match(group, machine, user) 144char *group __unused; 145char *machine __unused; 146char *user __unused; 147{ 148 syslog(LOG_ERR, "NIS netgroup support not configured"); 149 return 0; 150} 151 152/* user_match - match a username against one token */ 153 154static int user_match(tok, string) 155char *tok; 156char *string; 157{ 158 struct group *group; 159 int i; 160 161 /* 162 * If a token has the magic value "ALL" the match always succeeds. 163 * Otherwise, return YES if the token fully matches the username, or if 164 * the token is a group that contains the username. 165 */ 166 167 if (tok[0] == '@') { /* netgroup */ 168 return (netgroup_match(tok + 1, (char *) 0, string)); 169 } else if (string_match(tok, string)) { /* ALL or exact match */ 170 return (YES); 171 } else if ((group = getgrnam(tok)) != NULL) {/* try group membership */ 172 for (i = 0; group->gr_mem[i]; i++) 173 if (strcasecmp(string, group->gr_mem[i]) == 0) 174 return (YES); 175 } 176 return (NO); 177} 178 179/* from_match - match a host or tty against a list of tokens */ 180 181static int from_match(tok, string) 182char *tok; 183char *string; 184{ 185 int tok_len; 186 int str_len; 187 188 /* 189 * If a token has the magic value "ALL" the match always succeeds. Return 190 * YES if the token fully matches the string. If the token is a domain 191 * name, return YES if it matches the last fields of the string. If the 192 * token has the magic value "LOCAL", return YES if the string does not 193 * contain a "." character. If the token is a network number, return YES 194 * if it matches the head of the string. 195 */ 196 197 if (tok[0] == '@') { /* netgroup */ 198 return (netgroup_match(tok + 1, string, (char *) 0)); 199 } else if (string_match(tok, string)) { /* ALL or exact match */ 200 return (YES); 201 } else if (tok[0] == '.') { /* domain: match last fields */ 202 if ((str_len = strlen(string)) > (tok_len = strlen(tok)) 203 && strcasecmp(tok, string + str_len - tok_len) == 0) 204 return (YES); 205 } else if (strcasecmp(tok, "LOCAL") == 0) { /* local: no dots */ 206 if (strchr(string, '.') == 0) 207 return (YES); 208 } else if (tok[(tok_len = strlen(tok)) - 1] == '.' /* network */ 209 && strncmp(tok, string, tok_len) == 0) { 210 return (YES); 211 } 212 return (NO); 213} 214 215/* string_match - match a string against one token */ 216 217static int string_match(tok, string) 218char *tok; 219char *string; 220{ 221 222 /* 223 * If the token has the magic value "ALL" the match always succeeds. 224 * Otherwise, return YES if the token fully matches the string. 225 */ 226 227 if (strcasecmp(tok, "ALL") == 0) { /* all: always matches */ 228 return (YES); 229 } else if (strcasecmp(tok, string) == 0) { /* try exact match */ 230 return (YES); 231 } 232 return (NO); 233} 234#endif /* LOGIN_ACCES */ 235