src/kauth/kkids.c

   1 /*
   2  * Copyright 2000, International Business Machines Corporation and others.
   3  * All Rights Reserved.
   4  *
   5  * This software has been released under the terms of the IBM Public
   6  * License.  For details, see the LICENSE file in the top-level source
   7  * directory or online at http://www.openafs.org/dl/license10.html
   8  */
   9
  10 /*
  11  * ALL RIGHTS RESERVED
  12  */
  13
  14 /* These two needed for rxgen output to work */
  15 #include <afsconfig.h>
  16 #include <afs/param.h>
  17 #include <afs/stds.h>
  18
  19 #include <roken.h>
  20
  21 #ifdef AFS_NT40_ENV
  22 #include <afs/fs_utils.h>
  23 #else
  24 #include <afs/venus.h>
  25 #endif
  26
  27 #include <rx/xdr.h>
  28 #include <afs/prs_fs.h>
  29 #include <afs/sys_prototypes.h>
  30 #include <afs/afs_consts.h>
  31
  32 #include "kkids.h"
  33
  34 #define MAXNAME 100
  35
  36 static int using_child = 0;
  37 static FILE *childin, *childout;        /* file pointers on pipe to kpwvalid */
  38
  39 /* this removes symlinks from the tail end of path names.
  40  * PRECONDITION: name must be either absolute ('/something') or
  41  * explictly relative to current directory ('./something')
  42  */
  43 static int
  44 simplify_name(char *orig_name, char *true_name)
  45 {
  46     struct stat statbuff;
  47
  48
  49 #ifdef AFS_NT40_ENV
  50     if (stat(orig_name, &statbuff) < 0) {
  51         *true_name = '\0';
  52         return 0;
  53     } else {
  54         strcpy(true_name, orig_name);
  55         return 1;
  56     }
  57 #else /* !NT40 */
  58     {
  59         int link_chars_read;
  60         char *last_component;
  61         if (lstat(orig_name, &statbuff) < 0) {
  62             /* if lstat fails, it's possible that it's transient, but
  63              * unlikely.  Let's hope it isn't, and continue... */
  64             *true_name = '\0';
  65             return 0;
  66         }
  67
  68         /*
  69          * The lstat succeeded.  If the given file is a symlink, substitute
  70          * the contents of the link for the file name.
  71          */
  72         if ((statbuff.st_mode & S_IFMT) == S_IFLNK) {
  73             link_chars_read = readlink(orig_name, true_name, 1024);
  74             if (link_chars_read <= 0) {
  75                 *true_name = '\0';
  76                 return 0;
  77             }
  78
  79             true_name[link_chars_read++] = '\0';
  80
  81             /*
  82              * If the symlink is an absolute pathname, we're fine.  Otherwise, we
  83              * have to create a full pathname using the original name and the
  84              * relative symlink name.  Find the rightmost slash in the original
  85              * name (we know there is one) and splice in the symlink contents.
  86              */
  87             if (true_name[0] != '/') {
  88                 last_component = (char *)strrchr(orig_name, '/');
  89                 strcpy(++last_component, true_name);
  90                 strcpy(true_name, orig_name);
  91             }
  92         } else
  93             strcpy(true_name, orig_name);
  94
  95         return 1;               /* found it */
  96     }
  97 #endif /* !NT40 */
  98 }
  99
 100
 101   /* We find our own location by:
 102    * 1. checking for an absolute or relative path name in argv[0]
 103    *         this is moderately system-dependant: argv[0] is just a convention.
 104    * 2. successively checking each component of PATH, and concatenating argv[0]
 105    *    onto it, then stating the result.
 106    * if it exists, it must be us, eh?
 107    * NB there may be possible security implications involving
 108    * symlinks; I think they are only relevant if the symlink points
 109    * directly at kpasswd, not when it points at kpasswd's parent directory.
 110    */
 111 static int
 112 find_me(char *arg, char *parent_dir)
 113 {
 114     char *bp;                   /* basename pointer */
 115     char *dp;                   /* dirname pointer */
 116     char *pathelt, orig_name[1024], truename[1022];
 117
 118 #define explicitname(a,b,c) \
 119         (  ((a) == '/') ||                                \
 120            (   ((a) == '.') &&                            \
 121                (   ((b) == '/') ||                        \
 122                    (   ((b) == '.') && ((c) == '/') )       \
 123                )                                        \
 124             )                                           \
 125          )
 126
 127     if (strlen(arg) > 510)      /* just give up */
 128         return 0;
 129
 130     *parent_dir = '\0';
 131     truename[0] = '\0';
 132
 133     if (explicitname(arg[0], arg[1], arg[2])) {
 134         strcpy(orig_name, arg);
 135         simplify_name(orig_name, truename);
 136     } else {
 137         bp = (char *)strrchr(arg, '/');
 138         if (bp) {
 139             orig_name[0] = '.';
 140             orig_name[1] = '/';
 141             strcpy(orig_name + 2, arg);
 142             simplify_name(orig_name, truename);
 143         }
 144     }
 145
 146     if (!truename[0]) {         /* didn't find it */
 147         char path[2046];
 148
 149         dp = getenv("PATH");
 150         if (!dp)
 151             return 0;
 152         strncpy(path, dp, 2045);
 153
 154         for (pathelt = strtok(path, ":"); pathelt;
 155              pathelt = strtok(NULL, ":")) {
 156             strncpy(orig_name, pathelt, 510);
 157
 158             bp = orig_name + strlen(orig_name);
 159             *bp = '/';          /* replace NUL with / */
 160             strncpy(bp + 1, arg, 510);
 161
 162             if (simplify_name(orig_name, truename))
 163                 break;
 164         }
 165     }
 166     if (!truename[0])           /* didn't find it */
 167         return 0;               /* give up */
 168
 169     /* DID FIND IT */
 170     /*
 171      * Find rightmost slash, if any.
 172      */
 173     bp = (char *)strrchr(truename, '/');
 174     if (bp) {
 175         /*
 176          * Found it.  Designate everything before it as the parent directory,
 177          * everything after it as the final component.
 178          */
 179         strncpy(parent_dir, truename, bp - truename);
 180         parent_dir[bp - truename] = 0;
 181     } else {
 182         /*
 183          * No slash appears in the given file name.  Set parent_dir to the current
 184          * directory, and the last component as the given name.
 185          */
 186         strcpy(parent_dir, ".");
 187     }
 188
 189     return 1;                   /* found it */
 190 }
 191
 192 #define SkipLine(str) { while (*str !='\n') str++; str++; }
 193
 194 /* this function returns TRUE (1) if the file is in AFS, otherwise false (0) */
 195 static int
 196 InAFS(char *apath)
 197 {
 198     struct ViceIoctl blob;
 199     afs_int32 code;
 200     char space[AFS_PIOCTL_MAXSIZE];
 201
 202     blob.in_size = 0;
 203     blob.out_size = AFS_PIOCTL_MAXSIZE;
 204     blob.out = space;
 205
 206     code = pioctl(apath, VIOC_FILE_CELL_NAME, &blob, 1);
 207     if (code) {
 208         if ((errno == EINVAL) || (errno == ENOENT))
 209             return 0;
 210     }
 211     return 1;
 212 }
 213
 214 struct Acl {
 215     int nplus;
 216     int nminus;
 217     struct AclEntry *pluslist;
 218     struct AclEntry *minuslist;
 219 };
 220
 221 struct AclEntry {
 222     struct AclEntry *next;
 223     char name[MAXNAME];
 224     afs_int32 rights;
 225 };
 226
 227 static struct Acl *
 228 ParseAcl(char *astr)
 229 {
 230     int nplus, nminus, i, trights;
 231     char tname[MAXNAME];
 232     struct AclEntry *first, *last, *tl;
 233     struct Acl *ta;
 234     sscanf(astr, "%d", &nplus);
 235     SkipLine(astr);
 236     sscanf(astr, "%d", &nminus);
 237     SkipLine(astr);
 238
 239     ta = malloc(sizeof(struct Acl));
 240     ta->nplus = nplus;
 241
 242     last = 0;
 243     first = 0;
 244     for (i = 0; i < nplus; i++) {
 245         sscanf(astr, "%100s %d", tname, &trights);
 246         SkipLine(astr);
 247         tl = malloc(sizeof(struct AclEntry));
 248         if (!first)
 249             first = tl;
 250         strcpy(tl->name, tname);
 251         tl->rights = trights;
 252         tl->next = 0;
 253         if (last)
 254             last->next = tl;
 255         last = tl;
 256     }
 257     ta->pluslist = first;
 258
 259     return ta;
 260 }
 261
 262 static char *
 263 safestrtok(char *str, char *tok)
 264 {
 265     char *temp;
 266
 267     if (str)
 268         return (strtok(str, tok));
 269
 270     temp = strtok(NULL, tok);
 271     if (temp)
 272         *(temp - 1) = *tok;
 273
 274     return temp;
 275
 276 }
 277
 278
 279 /* If it exists, we do some fussing about whether or not this
 280  * is a reasonably secure path - not that it makes *much* difference, since
 281  * there's not much point in being more secure than the kpasswd executable.
 282  */
 283 /* 1.  is this directory in AFS?
 284  * 2.  Is every component of the pathname secure
 285  *     (ie, only system:administrators have w or a rights)?
 286  */
 287 static int
 288 is_secure(char *dir)
 289 {
 290     char *temp;
 291     struct ViceIoctl blob;
 292     struct AclEntry *te;
 293     char space[2046];
 294     afs_int32 code;
 295     struct Acl *ta;
 296
 297     if (!InAFS(dir))            /* final component *must* be in AFS */
 298         return 0;
 299
 300 #ifndef INSECURE
 301     for (temp = safestrtok(dir, "/"); temp; temp = safestrtok(NULL, "/")) {
 302         /* strtok keeps sticking NUL in place of /, so we can look at
 303          * ever-longer chunks of the path.
 304          */
 305         if (!InAFS(dir))
 306             continue;
 307
 308         blob.out_size = AFS_PIOCTL_MAXSIZE;
 309         blob.in_size = 0;
 310         blob.out = space;
 311         code = pioctl(dir, VIOCGETAL, &blob, 1);
 312         if (code) {
 313             continue;
 314         }
 315         ta = ParseAcl(space);
 316         if (ta->nplus <= 0)
 317             continue;
 318
 319         for (te = ta->pluslist; te; te = te->next) {
 320             if (((te->rights & PRSFS_INSERT) && (te->rights & PRSFS_DELETE))
 321                 || (te->rights & (PRSFS_WRITE | PRSFS_ADMINISTER)))
 322                 if (strcmp(te->name, "system:administrators"))
 323                     return 0;   /* somebody who we can't trust has got power */
 324         }
 325     }
 326 #endif /* INSECURE */
 327
 328     return 1;
 329 }
 330
 331 /* Then, once we've found our own location, we look for a program named
 332  * kpwvalid.
 333  */
 334
 335 /* look for a password-checking program named kpwvalid.
 336  * It has to be in a secure place (same place as this executable)
 337  */
 338 static int
 339 kpwvalid_is(char *dir)
 340 {
 341     struct stat statbuff;
 342     int len;
 343
 344     len = (int)strlen(dir);
 345     strcpy(dir + len, "/kpwvalid");
 346
 347     if (stat(dir, &statbuff) < 0) {
 348         /* if lstat fails, it's possible that it's transient, but
 349          * unlikely.  Let's hope it isn't, and continue... */
 350         *(dir + len) = '\0';
 351         return 0;
 352     }
 353
 354     *(dir + len) = '\0';
 355     return 1;
 356 }
 357
 358 #ifdef AFS_NT40_ENV
 359 /* We don't allow the use of kpwvalid executable scripts to set policy
 360  * for passwd changes.
 361  */
 362 int
 363 init_child(char *myname)
 364 {
 365
 366     using_child = 0;
 367     return using_child;
 368
 369 }
 370 #else /* !NT40 */
 371 int
 372 init_child(char *myname)
 373 {
 374     int pipe1[2], pipe2[2];
 375     pid_t pid;
 376     char dirpath[1024];
 377     char *argv[2];
 378
 379     if (!(find_me(myname, dirpath) && is_secure(dirpath)
 380           && kpwvalid_is(dirpath))) {
 381         using_child = 0;
 382         return 0;
 383     }
 384
 385     /* make a couple of pipes, one for the child's stdin, and the other
 386      * for the child's stdout.  The parent writes to the former, and
 387      * reads from the latter, the child reads from the former, and
 388      * writes to the latter.
 389      */
 390     if (pipe(pipe1) || pipe(pipe2)) {
 391         using_child = 0;
 392         return 0;
 393     }
 394
 395     /* fork a child */
 396     pid = fork();
 397     if (pid == -1) {
 398         using_child = 0;
 399         perror("kpasswd: can't fork because ");
 400         return (using_child);
 401     }
 402     if (pid == 0) {             /* in child process */
 403         /* tie stdin and stdout to these pipes */
 404         /* if dup2 doesn't exist everywhere, close and then dup, but make */
 405         /* sure that you really get stdin or stdout from the dup. */
 406         if ((-1 == dup2(pipe1[0], 0)) || (-1 == dup2(pipe2[1], 1))) {
 407             perror("kpasswd: can't exec kpwvalid because ");
 408             exit(-1);
 409         }
 410
 411         strcat(dirpath, "/kpwvalid");
 412         argv[1] = NULL;
 413         argv[0] = dirpath;
 414         execv(dirpath, argv);
 415         return 0;
 416     } else {
 417         using_child = pid;      /* save it for later */
 418         childin = fdopen(pipe1[1], "w");
 419         childout = fdopen(pipe2[0], "r");
 420         return (using_child);
 421     }
 422 }
 423 #endif /* not NT40 */
 424
 425 int
 426 password_bad(char *pw)
 427 {
 428     int rc;
 429     rc = 0;
 430
 431     if (using_child) {
 432         fprintf(childin, "%s\n", pw);
 433         fflush(childin);
 434         if (fscanf(childout, "%d", &rc) < 1)
 435             rc = -1;
 436     }
 437
 438     return (rc);
 439 }
 440
 441 /* this is originally only used to give the child the old password, so she
 442  * can compare putative new passwords against it.
 443  */
 444 int
 445 give_to_child(char *pw)
 446 {
 447     int rc;
 448     rc = 0;
 449
 450     if (using_child) {
 451         fprintf(childin, "%s\n", pw);
 452         fflush(childin);
 453     }
 454
 455     return (rc);
 456 }
 457
 458 /* quickly and painlessly
 459  */
 460 int
 461 terminate_child(void)
 462 {
 463     int rc;
 464     rc = 0;
 465
 466 #ifndef AFS_NT40_ENV
 467     if (using_child) {
 468         rc = kill(using_child, SIGKILL);
 469     }
 470 #endif
 471     return (rc);
 472 }