login_access.c revision 22230
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 */ 9 10#ifdef LOGIN_ACCESS 11#ifndef lint 12static char sccsid[] = "%Z% %M% %I% %E% %U%"; 13#endif 14 15#include <stdio.h> 16#include <syslog.h> 17#include <ctype.h> 18#include <sys/types.h> 19#include <grp.h> 20#include <errno.h> 21#include <string.h> 22#include <unistd.h> 23#include <stdlib.h> 24 25#include "pathnames.h" 26 27 /* Delimiters for fields and for lists of users, ttys or hosts. */ 28 29static char fs[] = ":"; /* field separator */ 30static char sep[] = ", \t"; /* list-element separator */ 31 32 /* Constants to be used in assignments only, not in comparisons... */ 33 34#define YES 1 35#define NO 0 36 37static int list_match(); 38static int user_match(); 39static int from_match(); 40static int string_match(); 41 42/* login_access - match username/group and host/tty with access control file */ 43 44int 45login_access(user, from) 46char *user; 47char *from; 48{ 49 FILE *fp; 50 char line[BUFSIZ]; 51 char *perm; /* becomes permission field */ 52 char *users; /* becomes list of login names */ 53 char *froms; /* becomes list of terminals or hosts */ 54 int match = NO; 55 int end; 56 int lineno = 0; /* for diagnostics */ 57 58 /* 59 * Process the table one line at a time and stop at the first match. 60 * Blank lines and lines that begin with a '#' character are ignored. 61 * Non-comment lines are broken at the ':' character. All fields are 62 * mandatory. The first field should be a "+" or "-" character. A 63 * non-existing table means no access control. 64 */ 65 66 if ((fp = fopen(_PATH_LOGACCESS, "r")) != NULL) { 67 while (!match && fgets(line, sizeof(line), fp)) { 68 lineno++; 69 if (line[end = strlen(line) - 1] != '\n') { 70 syslog(LOG_ERR, "%s: line %d: missing newline or line too long", 71 _PATH_LOGACCESS, lineno); 72 continue; 73 } 74 if (line[0] == '#') 75 continue; /* comment line */ 76 while (end > 0 && isspace(line[end - 1])) 77 end--; 78 line[end] = 0; /* strip trailing whitespace */ 79 if (line[0] == 0) /* skip blank lines */ 80 continue; 81 if (!(perm = strtok(line, fs)) 82 || !(users = strtok((char *) 0, fs)) 83 || !(froms = strtok((char *) 0, fs)) 84 || strtok((char *) 0, fs)) { 85 syslog(LOG_ERR, "%s: line %d: bad field count", _PATH_LOGACCESS, 86 lineno); 87 continue; 88 } 89 if (perm[0] != '+' && perm[0] != '-') { 90 syslog(LOG_ERR, "%s: line %d: bad first field", _PATH_LOGACCESS, 91 lineno); 92 continue; 93 } 94 match = (list_match(froms, from, from_match) 95 && list_match(users, user, user_match)); 96 } 97 (void) fclose(fp); 98 } else if (errno != ENOENT) { 99 syslog(LOG_ERR, "cannot open %s: %m", _PATH_LOGACCESS); 100 } 101 return (match == 0 || (line[0] == '+')); 102} 103 104/* list_match - match an item against a list of tokens with exceptions */ 105 106static int list_match(list, item, match_fn) 107char *list; 108char *item; 109int (*match_fn) (); 110{ 111 char *tok; 112 int match = NO; 113 114 /* 115 * Process tokens one at a time. We have exhausted all possible matches 116 * when we reach an "EXCEPT" token or the end of the list. If we do find 117 * a match, look for an "EXCEPT" list and recurse to determine whether 118 * the match is affected by any exceptions. 119 */ 120 121 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) { 122 if (strcasecmp(tok, "EXCEPT") == 0) /* EXCEPT: give up */ 123 break; 124 if ((match = (*match_fn)(tok, item)) != NULL) /* YES */ 125 break; 126 } 127 /* Process exceptions to matches. */ 128 129 if (match != NO) { 130 while ((tok = strtok((char *) 0, sep)) && strcasecmp(tok, "EXCEPT")) 131 /* VOID */ ; 132 if (tok == 0 || list_match((char *) 0, item, match_fn) == NO) 133 return (match); 134 } 135 return (NO); 136} 137 138/* netgroup_match - match group against machine or user */ 139 140static int netgroup_match(group, machine, user) 141gid_t group; 142char *machine; 143char *user; 144{ 145#ifdef NIS 146 static char *mydomain = 0; 147 148 if (mydomain == 0) 149 yp_get_default_domain(&mydomain); 150 return (innetgr(group, machine, user, mydomain)); 151#else 152 syslog(LOG_ERR, "NIS netgroup support not configured"); 153 return 0; 154#endif 155} 156 157/* user_match - match a username against one token */ 158 159static int user_match(tok, string) 160char *tok; 161char *string; 162{ 163 struct group *group; 164 int i; 165 166 /* 167 * If a token has the magic value "ALL" the match always succeeds. 168 * Otherwise, return YES if the token fully matches the username, or if 169 * the token is a group that contains the username. 170 */ 171 172 if (tok[0] == '@') { /* netgroup */ 173 return (netgroup_match(tok + 1, (char *) 0, string)); 174 } else if (string_match(tok, string)) { /* ALL or exact match */ 175 return (YES); 176 } else if ((group = getgrnam(tok)) != NULL) {/* try group membership */ 177 for (i = 0; group->gr_mem[i]; i++) 178 if (strcasecmp(string, group->gr_mem[i]) == 0) 179 return (YES); 180 } 181 return (NO); 182} 183 184/* from_match - match a host or tty against a list of tokens */ 185 186static int from_match(tok, string) 187char *tok; 188char *string; 189{ 190 int tok_len; 191 int str_len; 192 193 /* 194 * If a token has the magic value "ALL" the match always succeeds. Return 195 * YES if the token fully matches the string. If the token is a domain 196 * name, return YES if it matches the last fields of the string. If the 197 * token has the magic value "LOCAL", return YES if the string does not 198 * contain a "." character. If the token is a network number, return YES 199 * if it matches the head of the string. 200 */ 201 202 if (tok[0] == '@') { /* netgroup */ 203 return (netgroup_match(tok + 1, string, (char *) 0)); 204 } else if (string_match(tok, string)) { /* ALL or exact match */ 205 return (YES); 206 } else if (tok[0] == '.') { /* domain: match last fields */ 207 if ((str_len = strlen(string)) > (tok_len = strlen(tok)) 208 && strcasecmp(tok, string + str_len - tok_len) == 0) 209 return (YES); 210 } else if (strcasecmp(tok, "LOCAL") == 0) { /* local: no dots */ 211 if (strchr(string, '.') == 0) 212 return (YES); 213 } else if (tok[(tok_len = strlen(tok)) - 1] == '.' /* network */ 214 && strncmp(tok, string, tok_len) == 0) { 215 return (YES); 216 } 217 return (NO); 218} 219 220/* string_match - match a string against one token */ 221 222static int string_match(tok, string) 223char *tok; 224char *string; 225{ 226 227 /* 228 * If the token has the magic value "ALL" the match always succeeds. 229 * Otherwise, return YES if the token fully matches the string. 230 */ 231 232 if (strcasecmp(tok, "ALL") == 0) { /* all: always matches */ 233 return (YES); 234 } else if (strcasecmp(tok, string) == 0) { /* try exact match */ 235 return (YES); 236 } 237 return (NO); 238} 239#endif /* LOGIN_ACCES */ 240