rcmd.c

ucLinux is a very good embeded sytem. Most of company use this as their development OS.

/* Extremely paranoid file open function. */
static FILE *
iruserfopen (char *file, uid_t okuser)
{
  struct stat st;
  char *cp = NULL;
  FILE *res = NULL;

  /* If not a regular file, if owned by someone other than user or
     root, if writeable by anyone but the owner, or if hardlinked
     anywhere, quit.  */
  cp = NULL;
  if (lstat (file, &st))
    cp = "lstat failed";
  else if (!S_ISREG (st.st_mode))
    cp = "not regular file";
  else
    {
      res = fopen (file, "r");
      if (!res)
	cp = "cannot open";
      else if (fstat (fileno (res), &st) < 0)
	cp = "fstat failed";
      else if (st.st_uid && st.st_uid != okuser)
	cp = "bad owner";
      else if (st.st_mode & (S_IWGRP|S_IWOTH))
	cp = "writeable by other than owner";
      else if (st.st_nlink > 1)
	cp = "hard linked somewhere";
    }

  /* If there were any problems, quit.  */
  if (cp != NULL)
    {
      __rcmd_errstr = cp;
      if (res)
	fclose (res);
      return NULL;
    }

  return res;
}


/*
 * New .rhosts strategy: We are passed an ip address. We spin through
 * hosts.equiv and .rhosts looking for a match. When the .rhosts only
 * has ip addresses, we don't have to trust a nameserver.  When it
 * contains hostnames, we spin through the list of addresses the nameserver
 * gives us and look for a match.
 *
 * Returns 0 if ok, -1 if not ok.
 */
static int
iruserok2 (raddr, superuser, ruser, luser, rhost)
     u_int32_t raddr;
     int superuser;
     const char *ruser, *luser, *rhost;
{
	FILE *hostf = NULL;
	int isbad = -1;

	if (!superuser)
		hostf = iruserfopen (_PATH_HEQUIV, 0);
	
	if (hostf) {
		isbad = __ivaliduser2 (hostf, raddr, luser, ruser, rhost);
		fclose (hostf);

		if (!isbad)
			return 0;
	}

	if (__check_rhosts_file || superuser) {
		char *pbuf;
		struct passwd *pwd;
		size_t dirlen;
		uid_t uid;

#ifdef __UCLIBC_HAS_THREADS__
		size_t buflen = sysconf (_SC_GETPW_R_SIZE_MAX);
		struct passwd pwdbuf;
#ifdef __ARCH_HAS_MMU__
		char *buffer = alloca (buflen);
#else
		char *buffer = malloc (buflen);
#endif

		if (getpwnam_r (luser, &pwdbuf, buffer, 
			    buflen, &pwd) != 0 || pwd == NULL)
		{
#ifndef __ARCH_HAS_MMU__
			free(buffer);
#endif
			return -1;
		}
#ifndef __ARCH_HAS_MMU__
		free(buffer);
#endif
#else
		if ((pwd = getpwnam(luser)) == NULL)
			return -1;
#endif

		dirlen = strlen (pwd->pw_dir);
		pbuf = malloc (dirlen + sizeof "/.rhosts");
		strcpy (pbuf, pwd->pw_dir);
		strcat (pbuf, "/.rhosts");

		/* Change effective uid while reading .rhosts.  If root and
		   reading an NFS mounted file system, can't read files that
		   are protected read/write owner only.  */
		uid = geteuid ();
		seteuid (pwd->pw_uid);
		hostf = iruserfopen (pbuf, pwd->pw_uid);
		free(pbuf);
		
		if (hostf != NULL) {
			isbad = __ivaliduser2 (hostf, raddr, luser, ruser, rhost);
			fclose (hostf);
		}
		
		seteuid (uid);
		return isbad;
	}
	return -1;
}

/* This is the exported version.  */
int iruserok (u_int32_t raddr, int superuser, const char * ruser, const char * luser)
{
	return iruserok2 (raddr, superuser, ruser, luser, "-");
}


/*
 * XXX
 * Don't make static, used by lpd(8).
 *
 * This function is not used anymore. It is only present because lpd(8)
 * calls it (!?!). We simply call __invaliduser2() with an illegal rhost
 * argument. This means that netgroups won't work in .rhost/hosts.equiv
 * files. If you want lpd to work with netgroups, fix lpd to use ruserok()
 * or PAM.
 * Returns 0 if ok, -1 if not ok.
 */
int
__ivaliduser(FILE *hostf, u_int32_t raddr, const char *luser, const char *ruser)
{
	return __ivaliduser2(hostf, raddr, luser, ruser, "-");
}


/* Returns 1 on positive match, 0 on no match, -1 on negative match.  */
static int
__icheckhost (u_int32_t raddr, char *lhost, const char *rhost)
{
	struct hostent *hp;
	u_int32_t laddr;
	int negate=1;    /* Multiply return with this to get -1 instead of 1 */
	char **pp;

#ifdef __UCLIBC_HAS_THREADS__
	int save_errno;
	size_t buflen;
	char *buffer;
	struct hostent hostbuf;
	int herr;
#endif

#ifdef HAVE_NETGROUP
	/* Check nis netgroup.  */
	if (strncmp ("+@", lhost, 2) == 0)
		return innetgr (&lhost[2], rhost, NULL, NULL);

	if (strncmp ("-@", lhost, 2) == 0)
		return -innetgr (&lhost[2], rhost, NULL, NULL);
#endif /* HAVE_NETGROUP */

	/* -host */
	if (strncmp ("-", lhost,1) == 0) {
		negate = -1;
		lhost++;
	} else if (strcmp ("+",lhost) == 0) {
		return 1;                    /* asking for trouble, but ok.. */
	}

	/* Try for raw ip address first. */
	if (isdigit (*lhost) && (laddr = inet_addr (lhost)) != INADDR_NONE)
		return negate * (! (raddr ^ laddr));

	/* Better be a hostname. */
#ifdef __UCLIBC_HAS_THREADS__
	buflen = 1024;
	buffer = malloc(buflen);
	save_errno = errno;

	while (gethostbyname_r (lhost, &hostbuf, buffer, buflen, &hp, &herr)
	       != 0) {
	    free(buffer);
	    return (0);
	}
	free(buffer);
	__set_errno (save_errno);
#else
	hp = gethostbyname(lhost);
#endif /* __UCLIBC_HAS_THREADS__ */

	if (hp == NULL)
		return 0;

	/* Spin through ip addresses. */
	for (pp = hp->h_addr_list; *pp; ++pp)
		if (!memcmp (&raddr, *pp, sizeof (u_int32_t)))
			return negate;

	/* No match. */
	return (0);
}

/* Returns 1 on positive match, 0 on no match, -1 on negative match.  */
static int
__icheckuser (const char *luser, const char *ruser)
{

    /*
      luser is user entry from .rhosts/hosts.equiv file
      ruser is user id on remote host
      */

#ifdef HAVE_NETGROUP
    /* [-+]@netgroup */
    if (strncmp ("+@", luser, 2) == 0)
	return innetgr (&luser[2], NULL, ruser, NULL);

    if (strncmp ("-@", luser,2) == 0)
	return -innetgr (&luser[2], NULL, ruser, NULL);
#endif /* HAVE_NETGROUP */

    /* -user */
    if (strncmp ("-", luser, 1) == 0)
	return -(strcmp (&luser[1], ruser) == 0);

    /* + */
    if (strcmp ("+", luser) == 0)
	return 1;

    /* simple string match */
    return strcmp (ruser, luser) == 0;
}

/*
 * Returns 1 for blank lines (or only comment lines) and 0 otherwise
 */
static int
__isempty(char *p)
{
    while (*p && isspace (*p)) {
	++p;
    }

    return (*p == '\0' || *p == '#') ? 1 : 0 ;
}

/*
 * Returns 0 if positive match, -1 if _not_ ok.
 */
static int
__ivaliduser2(hostf, raddr, luser, ruser, rhost)
	FILE *hostf;
	u_int32_t raddr;
	const char *luser, *ruser, *rhost;
{
    register const char *user;
    register char *p;
    int hcheck, ucheck;
    char *buf = NULL;
    size_t bufsize = 0;
    int retval = -1;

    while (getline (&buf, &bufsize, hostf) > 0) {
	buf[bufsize - 1] = '\0'; /* Make sure it's terminated.  */
        p = buf;

	/* Skip empty or comment lines */
	if (__isempty (p)) {
	    continue;
	}

	/* Skip lines that are too long. */
	if (strchr (p, '\n') == NULL) {
	    int ch = getc_unlocked (hostf);

	    while (ch != '\n' && ch != EOF)
	      ch = getc_unlocked (hostf);
	    continue;
	}

	for (;*p && !isspace(*p); ++p) {
	    *p = tolower (*p);
	}

	/* Next we want to find the permitted name for the remote user.  */
	if (*p == ' ' || *p == '\t') {
	    /* <nul> terminate hostname and skip spaces */
	    for (*p++='\0'; *p && isspace (*p); ++p);

	    user = p;                   /* this is the user's name */
	    while (*p && !isspace (*p))
		++p;                    /* find end of user's name */
	} else
	    user = p;

	*p = '\0';              /* <nul> terminate username (+host?) */

	/* buf -> host(?) ; user -> username(?) */

	/* First check host part */
	hcheck = __icheckhost (raddr, buf, rhost);

	if (hcheck < 0)
	    break;

	if (hcheck) {
	    /* Then check user part */
	    if (! (*user))
		user = luser;

	    ucheck = __icheckuser (user, ruser);

	    /* Positive 'host user' match? */
	    if (ucheck > 0) {
		retval = 0;
		break;
	    }

	    /* Negative 'host -user' match? */
	    if (ucheck < 0)
		break;

	    /* Neither, go on looking for match */
	}
    }

    if (buf != NULL)
      free (buf);

    return retval;
}