login_access.c revision 1.2
1 /* $NetBSD: login_access.c,v 1.2 2004/12/12 08:18:46 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 1.2 2004/12/12 08:18:46 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 35 #include "pam_login_access.h" 36 37 #define _PATH_LOGACCESS "/etc/login.access" 38 39 /* Delimiters for fields and for lists of users, ttys or hosts. */ 40 41 static char fs[] = ":"; /* field separator */ 42 static char sep[] = ", \t"; /* list-element separator */ 43 44 /* Constants to be used in assignments only, not in comparisons... */ 45 46 #define YES 1 47 #define NO 0 48 49 static int from_match(const char *, const char *); 50 static int list_match(char *, const char *, 51 int (*)(const char *, const char *)); 52 static int netgroup_match(const char *, const char *, const char *); 53 static int string_match(const char *, const char *); 54 static int user_match(const char *, const char *); 55 56 /* login_access - match username/group and host/tty with access control file */ 57 58 int 59 login_access(const char *user, const char *from) 60 { 61 FILE *fp; 62 char line[BUFSIZ]; 63 char *perm; /* becomes permission field */ 64 char *users; /* becomes list of login names */ 65 char *froms; /* becomes list of terminals or hosts */ 66 int match = NO; 67 int end; 68 int lineno = 0; /* for diagnostics */ 69 70 /* 71 * Process the table one line at a time and stop at the first match. 72 * Blank lines and lines that begin with a '#' character are ignored. 73 * Non-comment lines are broken at the ':' character. All fields are 74 * mandatory. The first field should be a "+" or "-" character. A 75 * non-existing table means no access control. 76 */ 77 78 if ((fp = fopen(_PATH_LOGACCESS, "r")) != NULL) { 79 while (!match && fgets(line, sizeof(line), fp)) { 80 lineno++; 81 if (line[end = strlen(line) - 1] != '\n') { 82 syslog(LOG_ERR, "%s: line %d: missing newline or line too long", 83 _PATH_LOGACCESS, lineno); 84 continue; 85 } 86 if (line[0] == '#') 87 continue; /* comment line */ 88 while (end > 0 && isspace((unsigned char)line[end - 1])) 89 end--; 90 line[end] = 0; /* strip trailing whitespace */ 91 if (line[0] == 0) /* skip blank lines */ 92 continue; 93 if (!(perm = strtok(line, fs)) 94 || !(users = strtok((char *) 0, fs)) 95 || !(froms = strtok((char *) 0, fs)) 96 || strtok((char *) 0, fs)) { 97 syslog(LOG_ERR, "%s: line %d: bad field count", _PATH_LOGACCESS, 98 lineno); 99 continue; 100 } 101 if (perm[0] != '+' && perm[0] != '-') { 102 syslog(LOG_ERR, "%s: line %d: bad first field", _PATH_LOGACCESS, 103 lineno); 104 continue; 105 } 106 match = (list_match(froms, from, from_match) 107 && list_match(users, user, user_match)); 108 } 109 (void) fclose(fp); 110 } else if (errno != ENOENT) { 111 syslog(LOG_ERR, "cannot open %s: %m", _PATH_LOGACCESS); 112 } 113 return (match == 0 || (line[0] == '+')); 114 } 115 116 /* list_match - match an item against a list of tokens with exceptions */ 117 118 static int 119 list_match(char *list, const char *item, 120 int (*match_fn)(const char *, const char *)) 121 { 122 char *tok; 123 int match = NO; 124 125 /* 126 * Process tokens one at a time. We have exhausted all possible matches 127 * when we reach an "EXCEPT" token or the end of the list. If we do find 128 * a match, look for an "EXCEPT" list and recurse to determine whether 129 * the match is affected by any exceptions. 130 */ 131 132 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) { 133 if (strcasecmp(tok, "EXCEPT") == 0) /* EXCEPT: give up */ 134 break; 135 if ((match = (*match_fn)(tok, item)) != 0) /* YES */ 136 break; 137 } 138 /* Process exceptions to matches. */ 139 140 if (match != NO) { 141 while ((tok = strtok((char *) 0, sep)) && strcasecmp(tok, "EXCEPT")) 142 /* VOID */ ; 143 if (tok == 0 || list_match((char *) 0, item, match_fn) == NO) 144 return (match); 145 } 146 return (NO); 147 } 148 149 /* netgroup_match - match group against machine or user */ 150 151 static int 152 netgroup_match(const char *group __unused, 153 const char *machine __unused, const char *user __unused) 154 { 155 syslog(LOG_ERR, "NIS netgroup support not configured"); 156 return 0; 157 } 158 159 /* user_match - match a username against one token */ 160 161 static int 162 user_match(const char *tok, const char *string) 163 { 164 struct group *group; 165 int i; 166 167 /* 168 * If a token has the magic value "ALL" the match always succeeds. 169 * Otherwise, return YES if the token fully matches the username, or if 170 * the token is a group that contains the username. 171 */ 172 173 if (tok[0] == '@') { /* netgroup */ 174 return (netgroup_match(tok + 1, (char *) 0, string)); 175 } else if (string_match(tok, string)) { /* ALL or exact match */ 176 return (YES); 177 } else if ((group = getgrnam(tok)) != NULL) {/* try group membership */ 178 for (i = 0; group->gr_mem[i]; i++) 179 if (strcasecmp(string, group->gr_mem[i]) == 0) 180 return (YES); 181 } 182 return (NO); 183 } 184 185 /* from_match - match a host or tty against a list of tokens */ 186 187 static int 188 from_match(const char *tok, const char *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 */ 221 222 static int 223 string_match(const char *tok, const char *string) 224 { 225 226 /* 227 * If the token has the magic value "ALL" the match always succeeds. 228 * Otherwise, return YES if the token fully matches the string. 229 */ 230 231 if (strcasecmp(tok, "ALL") == 0) { /* all: always matches */ 232 return (YES); 233 } else if (strcasecmp(tok, string) == 0) { /* try exact match */ 234 return (YES); 235 } 236 return (NO); 237 } 238
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