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 #if 0 11 #ifndef lint 12 static char sccsid[] = "%Z% %M% %I% %E% %U%"; 13 #endif 14 #endif 15 16 #include <sys/cdefs.h> 17 __FBSDID("$FreeBSD$"); 18 19 #include <sys/types.h> 20 #include <sys/param.h> 21 #include <ctype.h> 22 #include <errno.h> 23 #include <grp.h> 24 #include <netdb.h> 25 #include <pwd.h> 26 #include <stdio.h> 27 #include <stdlib.h> 28 #include <string.h> 29 #include <syslog.h> 30 #include <unistd.h> 31 32 #include "pam_login_access.h" 33 34 /* Constants to be used in assignments only, not in comparisons... */ 35 36 #define YES 1 37 #define NO 0 38 39 static int from_match(const char *, const char *, struct pam_login_access_options *); 40 static int list_match(char *, const char *, 41 int (*)(const char *, const char *, 42 struct pam_login_access_options *), 43 struct pam_login_access_options *); 44 static int netgroup_match(const char *, const char *, const char *); 45 static int string_match(const char *, const char *); 46 static int user_match(const char *, const char *, struct pam_login_access_options *); 47 static int group_match(const char *, const char *); 48 49 /* login_access - match username/group and host/tty with access control file */ 50 51 int 52 login_access(const char *user, const char *from, 53 struct pam_login_access_options *login_access_opts) 54 { 55 FILE *fp; 56 char line[BUFSIZ]; 57 char *perm; /* becomes permission field */ 58 char *users; /* becomes list of login names */ 59 char *froms; /* becomes list of terminals or hosts */ 60 int match = NO; 61 int end; 62 int lineno = 0; /* for diagnostics */ 63 const char *fieldsep = login_access_opts->fieldsep; 64 65 /* 66 * Process the table one line at a time and stop at the first match. 67 * Blank lines and lines that begin with a '#' character are ignored. 68 * Non-comment lines are broken at the ':' character. All fields are 69 * mandatory. The first field should be a "+" or "-" character. A 70 * non-existing table means no access control. 71 */ 72 73 if ((fp = fopen(login_access_opts->accessfile, "r")) != NULL) { 74 while (!match && fgets(line, sizeof(line), fp)) { 75 lineno++; 76 if (line[end = strlen(line) - 1] != '\n') { 77 syslog(LOG_ERR, "%s: line %d: missing newline or line too long", 78 login_access_opts->accessfile, lineno); 79 continue; 80 } 81 if (line[0] == '#') 82 continue; /* comment line */ 83 while (end > 0 && isspace(line[end - 1])) 84 end--; 85 line[end] = 0; /* strip trailing whitespace */ 86 if (line[0] == 0) /* skip blank lines */ 87 continue; 88 if (!(perm = strtok(line, fieldsep)) 89 || !(users = strtok((char *) 0, fieldsep)) 90 || !(froms = strtok((char *) 0, fieldsep)) 91 || strtok((char *) 0, fieldsep)) { 92 syslog(LOG_ERR, "%s: line %d: bad field count", login_access_opts->accessfile, 93 lineno); 94 continue; 95 } 96 if (perm[0] != '+' && perm[0] != '-') { 97 syslog(LOG_ERR, "%s: line %d: bad first field", login_access_opts->accessfile, 98 lineno); 99 continue; 100 } 101 match = (list_match(froms, from, from_match, login_access_opts) 102 && list_match(users, user, user_match, login_access_opts)); 103 } 104 (void) fclose(fp); 105 } else if (errno != ENOENT) { 106 syslog(LOG_ERR, "cannot open %s: %m", login_access_opts->accessfile); 107 } 108 return (match == 0 || (line[0] == '+')); 109 } 110 111 /* list_match - match an item against a list of tokens with exceptions */ 112 113 static int 114 list_match(char *list, const char *item, 115 int (*match_fn)(const char *, const char *, struct pam_login_access_options *), 116 struct pam_login_access_options *login_access_opts) 117 { 118 char *tok; 119 int match = NO; 120 const char *listsep = login_access_opts->listsep; 121 122 /* 123 * Process tokens one at a time. We have exhausted all possible matches 124 * when we reach an "EXCEPT" token or the end of the list. If we do find 125 * a match, look for an "EXCEPT" list and recurse to determine whether 126 * the match is affected by any exceptions. 127 */ 128 129 for (tok = strtok(list, listsep); tok != NULL; tok = strtok((char *) 0, listsep)) { 130 if (strcmp(tok, "EXCEPT") == 0) /* EXCEPT: give up */ 131 break; 132 if ((match = (*match_fn)(tok, item, login_access_opts)) != 0) /* YES */ 133 break; 134 } 135 /* Process exceptions to matches. */ 136 137 if (match != NO) { 138 while ((tok = strtok((char *) 0, listsep)) && strcmp(tok, "EXCEPT")) { 139 /* VOID */ ; 140 if (tok == NULL || list_match((char *) 0, item, match_fn, 141 login_access_opts) == NO) { 142 return (match); 143 } 144 } 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, const char *machine, const char *user) 153 { 154 char domain[1024]; 155 unsigned int i; 156 157 if (getdomainname(domain, sizeof(domain)) != 0 || *domain == '\0') { 158 syslog(LOG_ERR, "NIS netgroup support disabled: no NIS domain"); 159 return (NO); 160 } 161 162 /* getdomainname() does not reliably terminate the string */ 163 for (i = 0; i < sizeof(domain); ++i) 164 if (domain[i] == '\0') 165 break; 166 if (i == sizeof(domain)) { 167 syslog(LOG_ERR, "NIS netgroup support disabled: invalid NIS domain"); 168 return (NO); 169 } 170 171 if (innetgr(group, machine, user, domain) == 1) 172 return (YES); 173 return (NO); 174 } 175 176 /* group_match - match a group against one token */ 177 178 int 179 group_match(const char *tok, const char *username) 180 { 181 struct group *group; 182 struct passwd *passwd; 183 gid_t *grouplist; 184 int i, ret, ngroups = NGROUPS; 185 186 if ((passwd = getpwnam(username)) == NULL) 187 return (NO); 188 errno = 0; 189 if ((group = getgrnam(tok)) == NULL) { 190 if (errno != 0) 191 syslog(LOG_ERR, "getgrnam() failed for %s: %s", username, strerror(errno)); 192 else 193 syslog(LOG_NOTICE, "group not found: %s", username); 194 return (NO); 195 } 196 if ((grouplist = calloc(ngroups, sizeof(gid_t))) == NULL) { 197 syslog(LOG_ERR, "cannot allocate memory for grouplist: %s", username); 198 return (NO); 199 } 200 ret = NO; 201 if (getgrouplist(username, passwd->pw_gid, grouplist, &ngroups) != 0) 202 syslog(LOG_ERR, "getgrouplist() failed for %s", username); 203 for (i = 0; i < ngroups; i++) 204 if (grouplist[i] == group->gr_gid) 205 ret = YES; 206 free(grouplist); 207 return (ret); 208 } 209 210 /* user_match - match a username against one token */ 211 212 static int 213 user_match(const char *tok, const char *string, 214 struct pam_login_access_options *login_access_opts) 215 { 216 size_t stringlen; 217 char *grpstr; 218 int rc; 219 220 /* 221 * If a token has the magic value "ALL" the match always succeeds. 222 * Otherwise, return YES if the token fully matches the username, or if 223 * the token is a group that contains the username. 224 */ 225 226 if (tok[0] == '@') { /* netgroup */ 227 return (netgroup_match(tok + 1, (char *) 0, string)); 228 } else if (tok[0] == '(' && tok[(stringlen = strlen(&tok[1]))] == ')') { /* group */ 229 if ((grpstr = strndup(&tok[1], stringlen - 1)) == NULL) { 230 syslog(LOG_ERR, "cannot allocate memory for %s", string); 231 return (NO); 232 } 233 rc = group_match(grpstr, string); 234 free(grpstr); 235 return (rc); 236 } else if (string_match(tok, string)) { /* ALL or exact match */ 237 return (YES); 238 } else if (login_access_opts->defgroup == true) {/* try group membership */ 239 return (group_match(tok, string)); 240 } 241 return (NO); 242 } 243 244 /* from_match - match a host or tty against a list of tokens */ 245 246 static int 247 from_match(const char *tok, const char *string, 248 struct pam_login_access_options *login_access_opts __unused) 249 { 250 int tok_len; 251 int str_len; 252 253 /* 254 * If a token has the magic value "ALL" the match always succeeds. Return 255 * YES if the token fully matches the string. If the token is a domain 256 * name, return YES if it matches the last fields of the string. If the 257 * token has the magic value "LOCAL", return YES if the string does not 258 * contain a "." character. If the token is a network number, return YES 259 * if it matches the head of the string. 260 */ 261 262 if (tok[0] == '@') { /* netgroup */ 263 return (netgroup_match(tok + 1, string, (char *) 0)); 264 } else if (string_match(tok, string)) { /* ALL or exact match */ 265 return (YES); 266 } else if (tok[0] == '.') { /* domain: match last fields */ 267 if ((str_len = strlen(string)) > (tok_len = strlen(tok)) 268 && strcasecmp(tok, string + str_len - tok_len) == 0) 269 return (YES); 270 } else if (strcmp(tok, "LOCAL") == 0) { /* local: no dots */ 271 if (strchr(string, '.') == NULL) 272 return (YES); 273 } else if (tok[(tok_len = strlen(tok)) - 1] == '.' /* network */ 274 && strncmp(tok, string, tok_len) == 0) { 275 return (YES); 276 } 277 return (NO); 278 } 279 280 /* string_match - match a string against one token */ 281 282 static int 283 string_match(const char *tok, const char *string) 284 { 285 286 /* 287 * If the token has the magic value "ALL" the match always succeeds. 288 * Otherwise, return YES if the token fully matches the string. 289 */ 290 291 if (strcmp(tok, "ALL") == 0) { /* all: always matches */ 292 return (YES); 293 } else if (strcasecmp(tok, string) == 0) { /* try exact match */ 294 return (YES); 295 } 296 return (NO); 297 } 298