ftpd.c

伯克利大学的一个ftp协议的实现源代码,包括客户端和服务器端.

	return (new);
}

/*
 * Save the result of a getpwnam.  Used for USER command, since
 * the data returned must not be clobbered by any other command
 * (e.g., globbing).
 */
static struct passwd *
sgetpwnam(name)
	const char *name;
{
	static struct passwd save;
	struct passwd *p;

	if ((p = getpwnam(name)) == NULL)
		return (p);
#ifdef USE_SHADOW
	if ((spw = getspnam(name)) != NULL)
		p->pw_passwd = spw->sp_pwdp;
	endspent();  /* ? */
#endif
	if (save.pw_name) {
		free(save.pw_name);
		memset(save.pw_passwd, 0, strlen(save.pw_passwd));
		free(save.pw_passwd);
		free(save.pw_gecos);
		free(save.pw_dir);
		free(save.pw_shell);
	}
	save = *p;
	save.pw_name = sgetsave(p->pw_name);
	save.pw_passwd = sgetsave(p->pw_passwd);
	save.pw_gecos = sgetsave(p->pw_gecos);
	save.pw_dir = sgetsave(p->pw_dir);
	save.pw_shell = sgetsave(p->pw_shell);
	return (&save);
}

static int login_attempts;	/* number of failed login attempts */
static int askpasswd;		/* had user command, ask for passwd */
static char curname[16];	/* current USER name */

/*
 * USER command.
 * Sets global passwd pointer pw if named account exists and is acceptable;
 * sets askpasswd if a PASS command is expected.  If logged in previously,
 * need to reset state.  If name is "ftp" or "anonymous", the name is not in
 * _PATH_FTPUSERS, and ftp account exists, set guest and pw, then just return.
 * If account doesn't exist, ask for passwd anyway.  Otherwise, check user
 * requesting login privileges.  Disallow anyone who does not have a standard
 * shell as returned by getusershell().  Disallow anyone mentioned in the file
 * _PATH_FTPUSERS to allow people such as root and uucp to be avoided.
 */
void
user(name)
	char *name;
{
	const char *cp, *shell;

	if (logged_in) {
		if (guest) {
			reply(530, "Can't change user from guest login.");
			return;
		} else if (dochroot) {
			reply(530, "Can't change user from chroot user.");
			return;
		}
		end_login();
	}

	guest = 0;
	if (strcmp(name, "ftp") == 0 || strcmp(name, "anonymous") == 0) {
		if (checkuser(_PATH_FTPUSERS, "ftp") ||
		    checkuser(_PATH_FTPUSERS, "anonymous"))
			reply(530, "User %s access denied.", name);
		else if ((pw = sgetpwnam("ftp")) != NULL) {
			guest = 1;
			askpasswd = 1;
			reply(331,
			    "Guest login ok, type your name as password.");
		} else
			reply(530, "User %s unknown.", name);
		if (!askpasswd && logging)
			syslog(LOG_NOTICE,
			    "ANONYMOUS FTP LOGIN REFUSED FROM %s", remotehost);
		return;
	}
	if (anon_only && !checkuser(_PATH_FTPCHROOT, name)) {
		reply(530, "Sorry, only anonymous ftp allowed.");
		return;
	}

	if ((pw = sgetpwnam(name))!=NULL) {
		if ((shell = pw->pw_shell) == NULL || *shell == 0)
			shell = _PATH_BSHELL;
		while ((cp = getusershell()) != NULL)
			if (strcmp(cp, shell) == 0)
				break;
		endusershell();

		if (cp == NULL || checkuser(_PATH_FTPUSERS, name)) {
			reply(530, "User %s access denied.", name);
			if (logging)
				syslog(LOG_NOTICE,
				    "FTP LOGIN REFUSED FROM %s, %s",
				    remotehost, name);
			pw = (struct passwd *) NULL;
			return;
		}
	}
	if (logging) {
		strncpy(curname, name, sizeof(curname)-1);
		curname[sizeof(curname)-1] = '\0';
	}
#ifdef SKEY
	if (!skey_haskey(name)) {
		char *myskey, *skey_keyinfo __P((char *name));

		myskey = skey_keyinfo(name);
		reply(331, "Password [ %s ] for %s required.",
		    myskey ? myskey : "error getting challenge", name);
	} else
#endif
		reply(331, "Password required for %s.", name);

	askpasswd = 1;
	/*
	 * Delay before reading passwd after first failed
	 * attempt to slow down passwd-guessing programs.
	 */
	if (login_attempts)
		sleep((unsigned) login_attempts);
}

/*
 * Check if a user is in the file "fname"
 */
static int
checkuser(fname, name)
	const char *fname;
	const char *name;
{
	FILE *fd;
	int found = 0;
	char *p, line[BUFSIZ];

	if ((fd = fopen(fname, "r")) != NULL) {
		while (fgets(line, sizeof(line), fd) != NULL)
			if ((p = strchr(line, '\n')) != NULL) {
				*p = '\0';
				if (line[0] == '#')
					continue;
				if (strcmp(line, name) == 0) {
					found = 1;
					break;
				}
			}
		(void) fclose(fd);
	}
	return (found);
}

/*
 * Terminate login as previous user, if any, resetting state;
 * used when USER command is given or login fails.
 */
static void
end_login()
{
	sigset_t allsigs;
	sigfillset (&allsigs);
	sigprocmask (SIG_BLOCK, &allsigs, NULL);
	(void) seteuid((uid_t)0);
	if (logged_in) {
		logwtmp(ttyline, "", "");
		if (doutmp)
			logout(utmp.ut_line);
	}
	pw = NULL;
	logged_in = 0;
	guest = 0;
	dochroot = 0;
}

void
pass(passwd)
	char *passwd;
{
	int rval;
	FILE *fd;
	static char homedir[MAXPATHLEN];
	char rootdir[MAXPATHLEN];
	sigset_t allsigs;

	if (logged_in || askpasswd == 0) {
		reply(503, "Login with USER first.");
		return;
	}
	askpasswd = 0;
	if (!guest) {		/* "ftp" is only account allowed no password */
		if (pw == NULL) {
			rval = 1;	/* failure below */
			goto skip;
		}
#if defined(KERBEROS)
		rval = klogin(pw, "", hostname, passwd);
		if (rval == 0)
			goto skip;
#endif
#ifdef SKEY
		if (skey_haskey(pw->pw_name) == 0 &&
		   (skey_passcheck(pw->pw_name, passwd) != -1)) {
			rval = 0;
			goto skip;
		}
#endif
		/* the strcmp does not catch null passwords! */
		if (pw == NULL || *pw->pw_passwd == '\0' ||
		    strcmp(crypt(passwd, (pw ? pw->pw_passwd : "xx")), pw->pw_passwd)) {
			rval = 1;	 /* failure */
			goto skip;
		}
		rval = 0;

skip:
		/*
		 * If rval == 1, the user failed the authentication check
		 * above.  If rval == 0, either Kerberos or local authentication
		 * succeeded.
		 */
		if (rval) {
			reply(530, "Login incorrect.");
			if (logging)
				syslog(LOG_NOTICE,
				    "FTP LOGIN FAILED FROM %s, %s",
				    remotehost, curname);
			pw = NULL;
			if (login_attempts++ >= 5) {
				syslog(LOG_NOTICE,
				    "repeated login failures from %s",
				    remotehost);
				exit(0);
			}
			return;
		}
	} else {
		/* Save anonymous' password. */
		guestpw = strdup(passwd);
		if (guestpw == (char *)NULL)
			fatal("Out of memory");
	}
	login_attempts = 0;		/* this time successful */
#ifdef USE_SHADOW
	switch (isexpired(spw)) {
	  case 0: /* success */
		break;
	  case 1:
		syslog(LOG_NOTICE, "expired password from %s, %s",
		       remotehost, pw->pw_name);
		reply(530, "Please change your password and try again.");
		return;
	  case 2:
       		syslog(LOG_NOTICE, "inactive login from %s, %s",
		       remotehost, pw->pw_name);
		reply(530, "Login inactive -- contact administrator.");
		return;
	  case 3:
		syslog(LOG_NOTICE, "expired login from %s, %s",
		       remotehost, pw->pw_name);
		reply(530, "Account expired -- contact administrator.");
		return;
	}
#endif
	if (setegid((gid_t)pw->pw_gid) < 0) {
		reply(550, "Can't set gid.");
		return;
	}
	(void) initgroups(pw->pw_name, pw->pw_gid);

	/* open wtmp before chroot */
	logwtmp(ttyline, pw->pw_name, remotehost);

	/* open utmp before chroot */
	if (doutmp) {
		memset((void *)&utmp, 0, sizeof(utmp));
		(void)time(&utmp.ut_time);
		(void)strncpy(utmp.ut_name, pw->pw_name, sizeof(utmp.ut_name));
		(void)strncpy(utmp.ut_host, remotehost, sizeof(utmp.ut_host));
		(void)strncpy(utmp.ut_line, ttyline, sizeof(utmp.ut_line));
		login(&utmp);
	}

	/* open stats file before chroot */
	if (guest && (stats == 1) && (statfd < 0))
		if ((statfd = open(_PATH_FTPDSTATFILE, O_WRONLY|O_APPEND)) < 0)
			stats = 0;

	logged_in = 1;

	dochroot = checkuser(_PATH_FTPCHROOT, pw->pw_name);
	if (guest || dochroot) {
		if (multihome) {
			struct stat ts;

			/* Compute root directory. */
			snprintf (rootdir, sizeof(rootdir), "%s/%s",
				  pw->pw_dir, dhostname);
			if (stat(rootdir, &ts) < 0) {
				snprintf (rootdir, sizeof(rootdir), "%s/%s",
					  pw->pw_dir, hostname);
			}
		} else
			strcpy (rootdir, pw->pw_dir);
	}
	if (guest) {
		/*
		 * We MUST do a chdir() after the chroot. Otherwise
		 * the old current directory will be accessible as "."
		 * outside the new root!
		 */
		if (chroot(rootdir) < 0 || chdir("/") < 0) {
			reply(550, "Can't set guest privileges.");
			goto bad;
		}
		strcpy(pw->pw_dir, "/");
		setenv("HOME", "/", 1);
	} else if (dochroot) {
		if (chroot(rootdir) < 0 || chdir("/") < 0) {
			reply(550, "Can't change root.");
			goto bad;
		}
		strcpy(pw->pw_dir, "/");
		setenv("HOME", "/", 1);
	} else if (chdir(pw->pw_dir) < 0) {
		if (chdir("/") < 0) {
			reply(530, "User %s: can't change directory to %s.",
			    pw->pw_name, pw->pw_dir);
			goto bad;
		} else
			lreply(230, "No directory! Logging in with home=/");
	}
	if (seteuid((uid_t)pw->pw_uid) < 0) {
		reply(550, "Can't set uid.");
		goto bad;
	}
	sigfillset(&allsigs);
	sigprocmask(SIG_UNBLOCK,&allsigs,NULL);

	/*
	 * Set home directory so that use of ~ (tilde) works correctly.
	 */
	if (getcwd(homedir, MAXPATHLEN) != NULL)
		setenv("HOME", homedir, 1);

	/*
	 * Display a login message, if it exists.
	 * N.B. reply(230,) must follow the message.
	 */
	if ((fd = fopen(_PATH_FTPLOGINMESG, "r")) != NULL) {
		char *cp, line[LINE_MAX];

		while (fgets(line, sizeof(line), fd) != NULL) {
			if ((cp = strchr(line, '\n')) != NULL)
				*cp = '\0';
			lreply(230, "%s", line);
		}
		(void) fflush(stdout);
		(void) fclose(fd);
	}
	if (guest) {
		if (ident != NULL)
			free(ident);
		ident = strdup(passwd);
		if (ident == (char *)NULL)
			fatal("Ran out of memory.");
		reply(230, "Guest login ok, access restrictions apply.");
#ifdef HASSETPROCTITLE
		snprintf(proctitle, sizeof(proctitle),
		    "%s: anonymous/%.*s", remotehost,
		    sizeof(proctitle) - sizeof(remotehost) -
		    sizeof(": anonymous/"), passwd);
		setproctitle(proctitle);
#endif /* HASSETPROCTITLE */
		if (logging)
			syslog(LOG_INFO, "ANONYMOUS FTP LOGIN FROM %s, %s",
			    remotehost, passwd);
	} else {
		reply(230, "User %s logged in.", pw->pw_name);
#ifdef HASSETPROCTITLE
		snprintf(proctitle, sizeof(proctitle),
		    "%s: %s", remotehost, pw->pw_name);
		setproctitle(proctitle);
#endif /* HASSETPROCTITLE */
		if (logging)
			syslog(LOG_INFO, "FTP LOGIN FROM %s as %s",
			    remotehost, pw->pw_name);
	}
	(void) umask(defumask);
	return;
bad:
	/* Forget all about it... */
	end_login();
}

void
retrieve(cmd, name)
	const char *cmd, *name;
{
	FILE *fin, *dout;
	struct stat st;
	int (*closefunc) __P((FILE *));
	time_t start;

	if (cmd == 0) {
		fin = fopen(name, "r"), closefunc = fclose;
		st.st_size = 0;
	} else {
		char line[BUFSIZ];

		(void) snprintf(line, sizeof(line), cmd, name);
		name = line;
		fin = ftpd_popen(line, "r"), closefunc = ftpd_pclose;
		st.st_size = -1;
		st.st_blksize = BUFSIZ;
	}
	if (fin == NULL) {
		if (errno != 0) {
			perror_reply(550, name);
			if (cmd == 0) {
				LOGCMD("get", name);
			}
		}
		return;
	}
	byte_count = -1;
	if (cmd == 0 && (fstat(fileno(fin), &st) < 0 || !S_ISREG(st.st_mode))) {
		reply(550, "%s: not a plain file.", name);
		goto done;
	}
	if (restart_point) {
		if (type == TYPE_A) {
			off_t i, n;
			int c;

			n = restart_point;
			i = 0;
			while (i++ < n) {
				if ((c=getc(fin)) == EOF) {
					perror_reply(550, name);
					goto done;
				}
				if (c == '\n')
					i++;
			}
		} else if (lseek(fileno(fin), restart_point, L_SET) < 0) {
			perror_reply(550, name);
			goto done;
		}
	}
	dout = dataconn(name, st.st_size, "w");
	if (dout == NULL)
		goto done;
	time(&start);
	send_data(fin, dout, st.st_blksize, st.st_size,
		  (restart_point == 0 && cmd == 0 && S_ISREG(st.st_mode)));
	if ((cmd == 0) && stats)
		logxfer(name, st.st_size, start);
	(void) fclose(dout);
	data = -1;
	pdata = -1;
done:
	if (cmd == 0)
		LOGBYTES("get", name, byte_count);
	(*closefunc)(fin);
}

void
store(name, mode, unique)
	const char *name, *mode;
	int unique;
{
	FILE *fout, *din;
	int (*closefunc) __P((FILE *));
	struct stat st;
	int fd;

	if (unique && stat(name, &st) == 0) {
		char *nam;

		fd = guniquefd(name, &nam);
		if (fd == -1) {
			LOGCMD(*mode == 'w' ? "put" : "append", name);
			return;
		}
		name = nam;
		if (restart_point)
			mode = "r+";
		fout = fdopen(fd, mode);
	} else
		fout = fopen(name, mode);

	closefunc = fclose;
	if (fout == NULL) {
		perror_reply(553, name);
		LOGCMD(*mode == 'w' ? "put" : "append", name);
		return;
	}
	byte_count = -1;
	if (restart_point) {
		if (type == TYPE_A) {
			off_t i, n;
			int c;

			n = restart_point;
			i = 0;
			while (i++ < n) {
				if ((c=getc(fout)) == EOF) {
					perror_reply(550, name);
					goto done;
				}
				if (c == '\n')
					i++;
			}
			/*
			 * We must do this seek to "current" position
			 * because we are changing from reading to
			 * writing.
			 */
			if (fseek(fout, 0L, L_INCR) < 0) {
				perror_reply(550, name);
				goto done;
			}
		} else if (lseek(fileno(fout), restart_point, L_SET) < 0) {
			perror_reply(550, name);
			goto done;
		}
	}
	din = dataconn(name, (off_t)-1, "r");
	if (din == NULL)
		goto done;
	if (receive_data(din, fout) == 0) {
		if (unique)
			reply(226, "Transfer complete (unique file name:%s).",
			    name);
		else
			reply(226, "Transfer complete.");