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/types.h> 17 #include <sys/param.h> 18 #include <ctype.h> 19 #include <errno.h> 20 #include <grp.h> 21 #include <netdb.h> 22 #include <pwd.h> 23 #include <stdio.h> 24 #include <stdlib.h> 25 #include <string.h> 26 #include <syslog.h> 27 #include <unistd.h> 28 29 #include "pam_login_access.h" 30 31 /* Constants to be used in assignments only, not in comparisons... */ 32 33 #define YES 1 34 #define NO 0 35 36 static int from_match(const char *, const char *, struct pam_login_access_options *); 37 static int list_match(char *, const char *, 38 int (*)(const char *, const char *, 39 struct pam_login_access_options *), 40 struct pam_login_access_options *); 41 static int netgroup_match(const char *, const char *, const char *); 42 static int string_match(const char *, const char *); 43 static int user_match(const char *, const char *, struct pam_login_access_options *); 44 static int group_match(const char *, const char *); 45 46 /* login_access - match username/group and host/tty with access control file */ 47 48 int 49 login_access(const char *user, const char *from, 50 struct pam_login_access_options *login_access_opts) 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 const char *fieldsep = login_access_opts->fieldsep; 61 62 /* 63 * Process the table one line at a time and stop at the first match. 64 * Blank lines and lines that begin with a '#' character are ignored. 65 * Non-comment lines are broken at the ':' character. All fields are 66 * mandatory. The first field should be a "+" or "-" character. A 67 * non-existing table means no access control. 68 */ 69 70 if ((fp = fopen(login_access_opts->accessfile, "r")) != NULL) { 71 while (!match && fgets(line, sizeof(line), fp)) { 72 lineno++; 73 if (line[end = strlen(line) - 1] != '\n') { 74 syslog(LOG_ERR, "%s: line %d: missing newline or line too long", 75 login_access_opts->accessfile, lineno); 76 continue; 77 } 78 if (line[0] == '#') 79 continue; /* comment line */ 80 while (end > 0 && isspace(line[end - 1])) 81 end--; 82 line[end] = 0; /* strip trailing whitespace */ 83 if (line[0] == 0) /* skip blank lines */ 84 continue; 85 if (!(perm = strtok(line, fieldsep)) 86 || !(users = strtok((char *) 0, fieldsep)) 87 || !(froms = strtok((char *) 0, fieldsep)) 88 || strtok((char *) 0, fieldsep)) { 89 syslog(LOG_ERR, "%s: line %d: bad field count", login_access_opts->accessfile, 90 lineno); 91 continue; 92 } 93 if (perm[0] != '+' && perm[0] != '-') { 94 syslog(LOG_ERR, "%s: line %d: bad first field", login_access_opts->accessfile, 95 lineno); 96 continue; 97 } 98 match = (list_match(froms, from, from_match, login_access_opts) 99 && list_match(users, user, user_match, login_access_opts)); 100 } 101 (void) fclose(fp); 102 } else if (errno != ENOENT) { 103 syslog(LOG_ERR, "cannot open %s: %m", login_access_opts->accessfile); 104 } 105 return (match == 0 || (line[0] == '+')); 106 } 107 108 /* list_match - match an item against a list of tokens with exceptions */ 109 110 static int 111 list_match(char *list, const char *item, 112 int (*match_fn)(const char *, const char *, struct pam_login_access_options *), 113 struct pam_login_access_options *login_access_opts) 114 { 115 char *tok; 116 int match = NO; 117 const char *listsep = login_access_opts->listsep; 118 119 /* 120 * Process tokens one at a time. We have exhausted all possible matches 121 * when we reach an "EXCEPT" token or the end of the list. If we do find 122 * a match, look for an "EXCEPT" list and recurse to determine whether 123 * the match is affected by any exceptions. 124 */ 125 126 for (tok = strtok(list, listsep); tok != NULL; tok = strtok((char *) 0, listsep)) { 127 if (strcmp(tok, "EXCEPT") == 0) /* EXCEPT: give up */ 128 break; 129 if ((match = (*match_fn)(tok, item, login_access_opts)) != 0) /* YES */ 130 break; 131 } 132 /* Process exceptions to matches. */ 133 134 if (match != NO) { 135 while ((tok = strtok((char *) 0, listsep)) && strcmp(tok, "EXCEPT")) { 136 /* VOID */ ; 137 } 138 if (tok == NULL || 139 list_match((char *) 0, item, match_fn, login_access_opts) == NO) { 140 return (match); 141 } 142 } 143 return (NO); 144 } 145 146 /* netgroup_match - match group against machine or user */ 147 148 static int 149 netgroup_match(const char *group, const char *machine, const char *user) 150 { 151 char domain[1024]; 152 unsigned int i; 153 154 if (getdomainname(domain, sizeof(domain)) != 0 || *domain == '\0') { 155 syslog(LOG_ERR, "NIS netgroup support disabled: no NIS domain"); 156 return (NO); 157 } 158 159 /* getdomainname() does not reliably terminate the string */ 160 for (i = 0; i < sizeof(domain); ++i) 161 if (domain[i] == '\0') 162 break; 163 if (i == sizeof(domain)) { 164 syslog(LOG_ERR, "NIS netgroup support disabled: invalid NIS domain"); 165 return (NO); 166 } 167 168 if (innetgr(group, machine, user, domain) == 1) 169 return (YES); 170 return (NO); 171 } 172 173 /* group_match - match a group against one token */ 174 175 int 176 group_match(const char *tok, const char *username) 177 { 178 struct group *group; 179 struct passwd *passwd; 180 gid_t *grouplist; 181 int i, ret, ngroups = NGROUPS; 182 183 if ((passwd = getpwnam(username)) == NULL) 184 return (NO); 185 errno = 0; 186 if ((group = getgrnam(tok)) == NULL) { 187 if (errno != 0) 188 syslog(LOG_ERR, "getgrnam() failed for %s: %s", username, strerror(errno)); 189 else 190 syslog(LOG_NOTICE, "group not found: %s", username); 191 return (NO); 192 } 193 if ((grouplist = calloc(ngroups, sizeof(gid_t))) == NULL) { 194 syslog(LOG_ERR, "cannot allocate memory for grouplist: %s", username); 195 return (NO); 196 } 197 ret = NO; 198 if (getgrouplist(username, passwd->pw_gid, grouplist, &ngroups) != 0) 199 syslog(LOG_ERR, "getgrouplist() failed for %s", username); 200 for (i = 0; i < ngroups; i++) 201 if (grouplist[i] == group->gr_gid) 202 ret = YES; 203 free(grouplist); 204 return (ret); 205 } 206 207 /* user_match - match a username against one token */ 208 209 static int 210 user_match(const char *tok, const char *string, 211 struct pam_login_access_options *login_access_opts) 212 { 213 size_t stringlen; 214 char *grpstr; 215 int rc; 216 217 /* 218 * If a token has the magic value "ALL" the match always succeeds. 219 * Otherwise, return YES if the token fully matches the username, or if 220 * the token is a group that contains the username. 221 */ 222 223 if (tok[0] == '@') { /* netgroup */ 224 return (netgroup_match(tok + 1, (char *) 0, string)); 225 } else if (tok[0] == '(' && tok[(stringlen = strlen(&tok[1]))] == ')') { /* group */ 226 if ((grpstr = strndup(&tok[1], stringlen - 1)) == NULL) { 227 syslog(LOG_ERR, "cannot allocate memory for %s", string); 228 return (NO); 229 } 230 rc = group_match(grpstr, string); 231 free(grpstr); 232 return (rc); 233 } else if (string_match(tok, string)) { /* ALL or exact match */ 234 return (YES); 235 } else if (login_access_opts->defgroup == true) {/* try group membership */ 236 return (group_match(tok, string)); 237 } 238 return (NO); 239 } 240 241 /* from_match - match a host or tty against a list of tokens */ 242 243 static int 244 from_match(const char *tok, const char *string, 245 struct pam_login_access_options *login_access_opts __unused) 246 { 247 int tok_len; 248 int str_len; 249 250 /* 251 * If a token has the magic value "ALL" the match always succeeds. Return 252 * YES if the token fully matches the string. If the token is a domain 253 * name, return YES if it matches the last fields of the string. If the 254 * token has the magic value "LOCAL", return YES if the string does not 255 * contain a "." character. If the token is a network number, return YES 256 * if it matches the head of the string. 257 */ 258 259 if (tok[0] == '@') { /* netgroup */ 260 return (netgroup_match(tok + 1, string, (char *) 0)); 261 } else if (string_match(tok, string)) { /* ALL or exact match */ 262 return (YES); 263 } else if (tok[0] == '.') { /* domain: match last fields */ 264 if ((str_len = strlen(string)) > (tok_len = strlen(tok)) 265 && strcasecmp(tok, string + str_len - tok_len) == 0) 266 return (YES); 267 } else if (strcmp(tok, "LOCAL") == 0) { /* local: no dots */ 268 if (strchr(string, '.') == NULL) 269 return (YES); 270 } else if (tok[(tok_len = strlen(tok)) - 1] == '.' /* network */ 271 && strncmp(tok, string, tok_len) == 0) { 272 return (YES); 273 } 274 return (NO); 275 } 276 277 /* string_match - match a string against one token */ 278 279 static int 280 string_match(const char *tok, const char *string) 281 { 282 283 /* 284 * If the token has the magic value "ALL" the match always succeeds. 285 * Otherwise, return YES if the token fully matches the string. 286 */ 287 288 if (strcmp(tok, "ALL") == 0) { /* all: always matches */ 289 return (YES); 290 } else if (strcasecmp(tok, string) == 0) { /* try exact match */ 291 return (YES); 292 } 293 return (NO); 294 } 295