/* * Copyright (c) 1998-2000 Sendmail, Inc. and its suppliers. * All rights reserved. * Copyright (c) 1983, 1995-1997 Eric P. Allman. All rights reserved. * Copyright (c) 1988, 1993 * The Regents of the University of California. All rights reserved. * * By using this file, you agree to the terms and conditions set * forth in the LICENSE file which can be found at the top level of * the sendmail distribution. * */ #ifndef lint static char id[] = "@(#)Id: safefile.c,v 8.81.4.5 2000/07/17 22:33:37 ca Exp"; #endif /* ! lint */ #include /* ** SAFEFILE -- return 0 if a file exists and is safe for a user. ** ** Parameters: ** fn -- filename to check. ** uid -- user id to compare against. ** gid -- group id to compare against. ** user -- user name to compare against (used for group ** sets). ** flags -- modifiers: ** SFF_MUSTOWN -- "uid" must own this file. ** SFF_NOSLINK -- file cannot be a symbolic link. ** mode -- mode bits that must match. ** st -- if set, points to a stat structure that will ** get the stat info for the file. ** ** Returns: ** 0 if fn exists, is owned by uid, and matches mode. ** An errno otherwise. The actual errno is cleared. ** ** Side Effects: ** none. */ int safefile(fn, uid, gid, user, flags, mode, st) char *fn; UID_T uid; GID_T gid; char *user; long flags; int mode; struct stat *st; { register char *p; register struct group *gr = NULL; int file_errno = 0; bool checkpath; struct stat stbuf; struct stat fstbuf; char fbuf[MAXPATHLEN + 1]; if (tTd(44, 4)) dprintf("safefile(%s, uid=%d, gid=%d, flags=%lx, mode=%o):\n", fn, (int) uid, (int) gid, flags, mode); errno = 0; if (st == NULL) st = &fstbuf; if (strlcpy(fbuf, fn, sizeof fbuf) >= sizeof fbuf) { if (tTd(44, 4)) dprintf("\tpathname too long\n"); return ENAMETOOLONG; } fn = fbuf; /* ignore SFF_SAFEDIRPATH if we are debugging */ if (RealUid != 0 && RunAsUid == RealUid) flags &= ~SFF_SAFEDIRPATH; /* first check to see if the file exists at all */ # if HASLSTAT if ((bitset(SFF_NOSLINK, flags) ? lstat(fn, st) : stat(fn, st)) < 0) # else /* HASLSTAT */ if (stat(fn, st) < 0) # endif /* HASLSTAT */ { file_errno = errno; } else if (bitset(SFF_SETUIDOK, flags) && !bitset(S_IXUSR|S_IXGRP|S_IXOTH, st->st_mode) && S_ISREG(st->st_mode)) { /* ** If final file is setuid, run as the owner of that ** file. Gotta be careful not to reveal anything too ** soon here! */ # ifdef SUID_ROOT_FILES_OK if (bitset(S_ISUID, st->st_mode)) # else /* SUID_ROOT_FILES_OK */ if (bitset(S_ISUID, st->st_mode) && st->st_uid != 0 && st->st_uid != TrustedUid) # endif /* SUID_ROOT_FILES_OK */ { uid = st->st_uid; user = NULL; } # ifdef SUID_ROOT_FILES_OK if (bitset(S_ISGID, st->st_mode)) # else /* SUID_ROOT_FILES_OK */ if (bitset(S_ISGID, st->st_mode) && st->st_gid != 0) # endif /* SUID_ROOT_FILES_OK */ gid = st->st_gid; } checkpath = !bitset(SFF_NOPATHCHECK, flags) || (uid == 0 && !bitset(SFF_ROOTOK|SFF_OPENASROOT, flags)); if (bitset(SFF_NOWLINK, flags) && !bitset(SFF_SAFEDIRPATH, flags)) { int ret; /* check the directory */ p = strrchr(fn, '/'); if (p == NULL) { ret = safedirpath(".", uid, gid, user, flags|SFF_SAFEDIRPATH, 0, 0); } else { *p = '\0'; ret = safedirpath(fn, uid, gid, user, flags|SFF_SAFEDIRPATH, 0, 0); *p = '/'; } if (ret == 0) { /* directory is safe */ checkpath = FALSE; } else { # if HASLSTAT /* Need lstat() information if called stat() before */ if (!bitset(SFF_NOSLINK, flags) && lstat(fn, st) < 0) { ret = errno; if (tTd(44, 4)) dprintf("\t%s\n", errstring(ret)); return ret; } # endif /* HASLSTAT */ /* directory is writable: disallow links */ flags |= SFF_NOLINK; } } if (checkpath) { int ret; p = strrchr(fn, '/'); if (p == NULL) { ret = safedirpath(".", uid, gid, user, flags, 0, 0); } else { *p = '\0'; ret = safedirpath(fn, uid, gid, user, flags, 0, 0); *p = '/'; } if (ret != 0) return ret; } /* ** If the target file doesn't exist, check the directory to ** ensure that it is writable by this user. */ if (file_errno != 0) { int ret = file_errno; char *dir = fn; if (tTd(44, 4)) dprintf("\t%s\n", errstring(ret)); errno = 0; if (!bitset(SFF_CREAT, flags) || file_errno != ENOENT) return ret; /* check to see if legal to create the file */ p = strrchr(dir, '/'); if (p == NULL) dir = "."; else if (p == dir) dir = "/"; else *p = '\0'; if (stat(dir, &stbuf) >= 0) { int md = S_IWRITE|S_IEXEC; if (stbuf.st_uid == uid) /* EMPTY */ ; else if (uid == 0 && stbuf.st_uid == TrustedUid) /* EMPTY */ ; else { md >>= 3; if (stbuf.st_gid == gid) /* EMPTY */ ; # ifndef NO_GROUP_SET else if (user != NULL && !DontInitGroups && ((gr != NULL && gr->gr_gid == stbuf.st_gid) || (gr = getgrgid(stbuf.st_gid)) != NULL)) { register char **gp; for (gp = gr->gr_mem; *gp != NULL; gp++) if (strcmp(*gp, user) == 0) break; if (*gp == NULL) md >>= 3; } # endif /* ! NO_GROUP_SET */ else md >>= 3; } if ((stbuf.st_mode & md) != md) errno = EACCES; } ret = errno; if (tTd(44, 4)) dprintf("\t[final dir %s uid %d mode %lo] %s\n", dir, (int) stbuf.st_uid, (u_long) stbuf.st_mode, errstring(ret)); if (p != NULL) *p = '/'; st->st_mode = ST_MODE_NOFILE; return ret; } # ifdef S_ISLNK if (bitset(SFF_NOSLINK, flags) && S_ISLNK(st->st_mode)) { if (tTd(44, 4)) dprintf("\t[slink mode %lo]\tE_SM_NOSLINK\n", (u_long) st->st_mode); return E_SM_NOSLINK; } # endif /* S_ISLNK */ if (bitset(SFF_REGONLY, flags) && !S_ISREG(st->st_mode)) { if (tTd(44, 4)) dprintf("\t[non-reg mode %lo]\tE_SM_REGONLY\n", (u_long) st->st_mode); return E_SM_REGONLY; } if (bitset(SFF_NOGWFILES, flags) && bitset(S_IWGRP, st->st_mode)) { if (tTd(44, 4)) dprintf("\t[write bits %lo]\tE_SM_GWFILE\n", (u_long) st->st_mode); return E_SM_GWFILE; } if (bitset(SFF_NOWWFILES, flags) && bitset(S_IWOTH, st->st_mode)) { if (tTd(44, 4)) dprintf("\t[write bits %lo]\tE_SM_WWFILE\n", (u_long) st->st_mode); return E_SM_WWFILE; } if (bitset(SFF_NOGRFILES, flags) && bitset(S_IRGRP, st->st_mode)) { if (tTd(44, 4)) dprintf("\t[read bits %lo]\tE_SM_GRFILE\n", (u_long) st->st_mode); return E_SM_GRFILE; } if (bitset(SFF_NOWRFILES, flags) && bitset(S_IROTH, st->st_mode)) { if (tTd(44, 4)) dprintf("\t[read bits %lo]\tE_SM_WRFILE\n", (u_long) st->st_mode); return E_SM_WRFILE; } if (!bitset(SFF_EXECOK, flags) && bitset(S_IWUSR|S_IWGRP|S_IWOTH, mode) && bitset(S_IXUSR|S_IXGRP|S_IXOTH, st->st_mode)) { if (tTd(44, 4)) dprintf("\t[exec bits %lo]\tE_SM_ISEXEC]\n", (u_long) st->st_mode); return E_SM_ISEXEC; } if (bitset(SFF_NOHLINK, flags) && st->st_nlink != 1) { if (tTd(44, 4)) dprintf("\t[link count %d]\tE_SM_NOHLINK\n", (int) st->st_nlink); return E_SM_NOHLINK; } if (uid == 0 && bitset(SFF_OPENASROOT, flags)) /* EMPTY */ ; else if (uid == 0 && !bitset(SFF_ROOTOK, flags)) mode >>= 6; else if (st->st_uid == uid) /* EMPTY */ ; else if (uid == 0 && st->st_uid == TrustedUid) /* EMPTY */ ; else { mode >>= 3; if (st->st_gid == gid) /* EMPTY */ ; # ifndef NO_GROUP_SET else if (user != NULL && !DontInitGroups && ((gr != NULL && gr->gr_gid == st->st_gid) || (gr = getgrgid(st->st_gid)) != NULL)) { register char **gp; for (gp = gr->gr_mem; *gp != NULL; gp++) if (strcmp(*gp, user) == 0) break; if (*gp == NULL) mode >>= 3; } # endif /* ! NO_GROUP_SET */ else mode >>= 3; } if (tTd(44, 4)) dprintf("\t[uid %d, nlink %d, stat %lo, mode %lo] ", (int) st->st_uid, (int) st->st_nlink, (u_long) st->st_mode, (u_long) mode); if ((st->st_uid == uid || st->st_uid == 0 || st->st_uid == TrustedUid || !bitset(SFF_MUSTOWN, flags)) && (st->st_mode & mode) == mode) { if (tTd(44, 4)) dprintf("\tOK\n"); return 0; } if (tTd(44, 4)) dprintf("\tEACCES\n"); return EACCES; } /* ** SAFEDIRPATH -- check to make sure a path to a directory is safe ** ** Safe means not writable and owned by the right folks. ** ** Parameters: ** fn -- filename to check. ** uid -- user id to compare against. ** gid -- group id to compare against. ** user -- user name to compare against (used for group ** sets). ** flags -- modifiers: ** SFF_ROOTOK -- ok to use root permissions to open. ** SFF_SAFEDIRPATH -- writable directories are considered ** to be fatal errors. ** level -- symlink recursive level. ** offset -- offset into fn to start checking from. ** ** Returns: ** 0 -- if the directory path is "safe". ** else -- an error number associated with the path. */ int safedirpath(fn, uid, gid, user, flags, level, offset) char *fn; UID_T uid; GID_T gid; char *user; long flags; int level; int offset; { int ret = 0; int mode = S_IWOTH; char save = '\0'; char *saveptr = NULL; char *p, *enddir; register struct group *gr = NULL; char s[MAXLINKPATHLEN + 1]; struct stat stbuf; /* make sure we aren't in a symlink loop */ if (level > MAXSYMLINKS) return ELOOP; /* special case root directory */ if (*fn == '\0') fn = "/"; if (tTd(44, 4)) dprintf("safedirpath(%s, uid=%ld, gid=%ld, flags=%lx, level=%d, offset=%d):\n", fn, (long) uid, (long) gid, flags, level, offset); if (!bitnset(DBS_GROUPWRITABLEDIRPATHSAFE, DontBlameSendmail)) mode |= S_IWGRP; /* Make a modifiable copy of the filename */ if (strlcpy(s, fn, sizeof s) >= sizeof s) return EINVAL; p = s + offset; while (p != NULL) { /* put back character */ if (saveptr != NULL) { *saveptr = save; saveptr = NULL; p++; } if (*p == '\0') break; p = strchr(p, '/'); /* Special case for root directory */ if (p == s) { save = *(p + 1); saveptr = p + 1; *(p + 1) = '\0'; } else if (p != NULL) { save = *p; saveptr = p; *p = '\0'; } /* Heuristic: . and .. have already been checked */ enddir = strrchr(s, '/'); if (enddir != NULL && (strcmp(enddir, "/..") == 0 || strcmp(enddir, "/.") == 0)) continue; if (tTd(44, 20)) dprintf("\t[dir %s]\n", s); # if HASLSTAT ret = lstat(s, &stbuf); # else /* HASLSTAT */ ret = stat(s, &stbuf); # endif /* HASLSTAT */ if (ret < 0) { ret = errno; break; } # ifdef S_ISLNK /* Follow symlinks */ if (S_ISLNK(stbuf.st_mode)) { char *target; char buf[MAXPATHLEN + 1]; memset(buf, '\0', sizeof buf); if (readlink(s, buf, sizeof buf) < 0) { ret = errno; break; } offset = 0; if (*buf == '/') { target = buf; /* If path is the same, avoid rechecks */ while (s[offset] == buf[offset] && s[offset] != '\0') offset++; if (s[offset] == '\0' && buf[offset] == '\0') { /* strings match, symlink loop */ return ELOOP; } /* back off from the mismatch */ if (offset > 0) offset--; /* Make sure we are at a directory break */ if (offset > 0 && s[offset] != '/' && s[offset] != '\0') { while (buf[offset] != '/' && offset > 0) offset--; } if (offset > 0 && s[offset] == '/' && buf[offset] == '/') { /* Include the trailing slash */ offset++; } } else { char *sptr; char fullbuf[MAXLINKPATHLEN + 1]; sptr = strrchr(s, '/'); if (sptr != NULL) { *sptr = '\0'; offset = sptr + 1 - s; if ((strlen(s) + 1 + strlen(buf) + 1) > sizeof fullbuf) { ret = EINVAL; break; } snprintf(fullbuf, sizeof fullbuf, "%s/%s", s, buf); *sptr = '/'; } else { if (strlen(buf) + 1 > sizeof fullbuf) { ret = EINVAL; break; } (void) strlcpy(fullbuf, buf, sizeof fullbuf); } target = fullbuf; } ret = safedirpath(target, uid, gid, user, flags, level + 1, offset); if (ret != 0) break; /* Don't check permissions on the link file itself */ continue; } #endif /* S_ISLNK */ if ((uid == 0 || bitset(SFF_SAFEDIRPATH, flags)) && #ifdef S_ISVTX !(bitnset(DBS_TRUSTSTICKYBIT, DontBlameSendmail) && bitset(S_ISVTX, stbuf.st_mode)) && #endif /* S_ISVTX */ bitset(mode, stbuf.st_mode)) { if (tTd(44, 4)) dprintf("\t[dir %s] mode %lo ", s, (u_long) stbuf.st_mode); if (bitset(SFF_SAFEDIRPATH, flags)) { if (bitset(S_IWOTH, stbuf.st_mode)) ret = E_SM_WWDIR; else ret = E_SM_GWDIR; if (tTd(44, 4)) dprintf("FATAL\n"); break; } if (tTd(44, 4)) dprintf("WARNING\n"); if (Verbose > 1) message("051 WARNING: %s writable directory %s", bitset(S_IWOTH, stbuf.st_mode) ? "World" : "Group", s); } if (uid == 0 && !bitset(SFF_ROOTOK|SFF_OPENASROOT, flags)) { if (bitset(S_IXOTH, stbuf.st_mode)) continue; ret = EACCES; break; } /* ** Let OS determine access to file if we are not ** running as a privileged user. This allows ACLs ** to work. Also, if opening as root, assume we can ** scan the directory. */ if (geteuid() != 0 || bitset(SFF_OPENASROOT, flags)) continue; if (stbuf.st_uid == uid && bitset(S_IXUSR, stbuf.st_mode)) continue; if (stbuf.st_gid == gid && bitset(S_IXGRP, stbuf.st_mode)) continue; # ifndef NO_GROUP_SET if (user != NULL && !DontInitGroups && ((gr != NULL && gr->gr_gid == stbuf.st_gid) || (gr = getgrgid(stbuf.st_gid)) != NULL)) { register char **gp; for (gp = gr->gr_mem; gp != NULL && *gp != NULL; gp++) if (strcmp(*gp, user) == 0) break; if (gp != NULL && *gp != NULL && bitset(S_IXGRP, stbuf.st_mode)) continue; } # endif /* ! NO_GROUP_SET */ if (!bitset(S_IXOTH, stbuf.st_mode)) { ret = EACCES; break; } } if (tTd(44, 4)) dprintf("\t[dir %s] %s\n", fn, ret == 0 ? "OK" : errstring(ret)); return ret; } /* ** SAFEOPEN -- do a file open with extra checking ** ** Parameters: ** fn -- the file name to open. ** omode -- the open-style mode flags. ** cmode -- the create-style mode flags. ** sff -- safefile flags. ** ** Returns: ** Same as open. */ #ifndef O_ACCMODE # define O_ACCMODE (O_RDONLY|O_WRONLY|O_RDWR) #endif /* ! O_ACCMODE */ int safeopen(fn, omode, cmode, sff) char *fn; int omode; int cmode; long sff; { int rval; int fd; int smode; struct stat stb; if (tTd(44, 10)) printf("safeopen: fn=%s, omode=%x, cmode=%x, sff=%lx\n", fn, omode, cmode, sff); if (bitset(O_CREAT, omode)) sff |= SFF_CREAT; omode &= ~O_CREAT; smode = 0; switch (omode & O_ACCMODE) { case O_RDONLY: smode = S_IREAD; break; case O_WRONLY: smode = S_IWRITE; break; case O_RDWR: smode = S_IREAD|S_IWRITE; break; default: smode = 0; break; } if (bitset(SFF_OPENASROOT, sff)) rval = safefile(fn, RunAsUid, RunAsGid, RunAsUserName, sff, smode, &stb); else rval = safefile(fn, RealUid, RealGid, RealUserName, sff, smode, &stb); if (rval != 0) { errno = rval; return -1; } if (stb.st_mode == ST_MODE_NOFILE && bitset(SFF_CREAT, sff)) omode |= O_CREAT | (bitset(SFF_NOTEXCL, sff) ? 0 : O_EXCL); else if (bitset(SFF_CREAT, sff) && bitset(O_EXCL, omode)) { /* The file exists so an exclusive create would fail */ errno = EEXIST; return -1; } fd = dfopen(fn, omode, cmode, sff); if (fd < 0) return fd; if (filechanged(fn, fd, &stb)) { syserr("554 5.3.0 cannot open: file %s changed after open", fn); (void) close(fd); errno = E_SM_FILECHANGE; return -1; } return fd; } /* ** SAFEFOPEN -- do a file open with extra checking ** ** Parameters: ** fn -- the file name to open. ** omode -- the open-style mode flags. ** cmode -- the create-style mode flags. ** sff -- safefile flags. ** ** Returns: ** Same as fopen. */ FILE * safefopen(fn, omode, cmode, sff) char *fn; int omode; int cmode; long sff; { int fd; int save_errno; FILE *fp; char *fmode; switch (omode & O_ACCMODE) { case O_RDONLY: fmode = "r"; break; case O_WRONLY: if (bitset(O_APPEND, omode)) fmode = "a"; else fmode = "w"; break; case O_RDWR: if (bitset(O_TRUNC, omode)) fmode = "w+"; else if (bitset(O_APPEND, omode)) fmode = "a+"; else fmode = "r+"; break; default: syserr("554 5.3.5 safefopen: unknown omode %o", omode); fmode = "x"; } fd = safeopen(fn, omode, cmode, sff); if (fd < 0) { save_errno = errno; if (tTd(44, 10)) dprintf("safefopen: safeopen failed: %s\n", errstring(errno)); errno = save_errno; return NULL; } fp = fdopen(fd, fmode); if (fp != NULL) return fp; save_errno = errno; if (tTd(44, 10)) { dprintf("safefopen: fdopen(%s, %s) failed: omode=%x, sff=%lx, err=%s\n", fn, fmode, omode, sff, errstring(errno)); } (void) close(fd); errno = save_errno; return NULL; } /* ** FILECHANGED -- check to see if file changed after being opened ** ** Parameters: ** fn -- pathname of file to check. ** fd -- file descriptor to check. ** stb -- stat structure from before open. ** ** Returns: ** TRUE -- if a problem was detected. ** FALSE -- if this file is still the same. */ bool filechanged(fn, fd, stb) char *fn; int fd; struct stat *stb; { struct stat sta; if (stb->st_mode == ST_MODE_NOFILE) { # if HASLSTAT && BOGUS_O_EXCL /* only necessary if exclusive open follows symbolic links */ if (lstat(fn, stb) < 0 || stb->st_nlink != 1) return TRUE; # else /* HASLSTAT && BOGUS_O_EXCL */ return FALSE; # endif /* HASLSTAT && BOGUS_O_EXCL */ } if (fstat(fd, &sta) < 0) return TRUE; if (sta.st_nlink != stb->st_nlink || sta.st_dev != stb->st_dev || sta.st_ino != stb->st_ino || # if HAS_ST_GEN && 0 /* AFS returns garbage in st_gen */ sta.st_gen != stb->st_gen || # endif /* HAS_ST_GEN && 0 */ sta.st_uid != stb->st_uid || sta.st_gid != stb->st_gid) { if (tTd(44, 8)) { dprintf("File changed after opening:\n"); dprintf(" nlink = %ld/%ld\n", (long) stb->st_nlink, (long) sta.st_nlink); dprintf(" dev = %ld/%ld\n", (long) stb->st_dev, (long) sta.st_dev); if (sizeof sta.st_ino > sizeof (long)) { dprintf(" ino = %s/", quad_to_string(stb->st_ino)); dprintf("%s\n", quad_to_string(sta.st_ino)); } else dprintf(" ino = %lu/%lu\n", (unsigned long) stb->st_ino, (unsigned long) sta.st_ino); # if HAS_ST_GEN dprintf(" gen = %ld/%ld\n", (long) stb->st_gen, (long) sta.st_gen); # endif /* HAS_ST_GEN */ dprintf(" uid = %ld/%ld\n", (long) stb->st_uid, (long) sta.st_uid); dprintf(" gid = %ld/%ld\n", (long) stb->st_gid, (long) sta.st_gid); } return TRUE; } return FALSE; } /* ** DFOPEN -- determined file open ** ** This routine has the semantics of open, except that it will ** keep trying a few times to make this happen. The idea is that ** on very loaded systems, we may run out of resources (inodes, ** whatever), so this tries to get around it. */ int dfopen(filename, omode, cmode, sff) char *filename; int omode; int cmode; long sff; { register int tries; int fd = -1; struct stat st; for (tries = 0; tries < 10; tries++) { (void) sleep((unsigned) (10 * tries)); errno = 0; fd = open(filename, omode, cmode); if (fd >= 0) break; switch (errno) { case ENFILE: /* system file table full */ case EINTR: /* interrupted syscall */ #ifdef ETXTBSY case ETXTBSY: /* Apollo: net file locked */ #endif /* ETXTBSY */ continue; } break; } if (!bitset(SFF_NOLOCK, sff) && fd >= 0 && fstat(fd, &st) >= 0 && S_ISREG(st.st_mode)) { int locktype; /* lock the file to avoid accidental conflicts */ if ((omode & O_ACCMODE) != O_RDONLY) locktype = LOCK_EX; else locktype = LOCK_SH; if (!lockfile(fd, filename, NULL, locktype)) { int save_errno = errno; (void) close(fd); fd = -1; errno = save_errno; } else errno = 0; } return fd; }