ftpd.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include <u.h>
#include <libc.h>
#include <bio.h>
#include <auth.h>
#include <ip.h>
#include <libsec.h>
#include <String.h>

#include "glob.h"

enum
{
	/* telnet control character */
	Iac=		255,
	
	/* representation types */
	Tascii=		0,
	Timage=		1,

	/* transmission modes */
	Mstream=	0,
	Mblock=		1,
	Mpage=		2,

	/* file structure */
	Sfile=		0,
	Sblock=		1,
	Scompressed=	2,

	/* read/write buffer size */
	Nbuf=		4096,

	/* maximum ms we'll wait for a command */
	Maxwait=	1000*60*30,		/* inactive for 30 minutes, we hang up */

	Maxerr=		128,
	Maxpath=	512,
};

int	abortcmd(char*);
int	appendcmd(char*);
int	cdupcmd(char*);
int	cwdcmd(char*);
int	delcmd(char*);
int	helpcmd(char*);
int	listcmd(char*);
int	mdtmcmd(char*);
int	mkdircmd(char*);
int	modecmd(char*);
int	namelistcmd(char*);
int	nopcmd(char*);
int	passcmd(char*);
int	pasvcmd(char*);
int	portcmd(char*);
int	pwdcmd(char*);
int	quitcmd(char*);
int	rnfrcmd(char*);
int	rntocmd(char*);
int	reply(char*, ...);
int	restartcmd(char*);
int	retrievecmd(char*);
int	sizecmd(char*);
int	storecmd(char*);
int	storeucmd(char*);
int	structcmd(char*);
int	systemcmd(char*);
int	typecmd(char*);
int	usercmd(char*);

int	dialdata(void);
char*	abspath(char*);
int	crlfwrite(int, char*, int);
int	sodoff(void);
int	accessok(char*);

typedef struct Cmd	Cmd;
struct Cmd
{
	char	*name;
	int	(*f)(char*);
	int	needlogin;
};

Cmd cmdtab[] =
{
	{ "abor",	abortcmd,	0, },
	{ "appe",	appendcmd,	1, },
	{ "cdup",	cdupcmd,	1, },
	{ "cwd",	cwdcmd,		1, },
	{ "dele",	delcmd,		1, },
	{ "help",	helpcmd,	0, },
	{ "list",	listcmd,	1, },
	{ "mdtm",	mdtmcmd,	1, },
	{ "mkd",	mkdircmd,	1, },
	{ "mode",	modecmd,	0, },
	{ "nlst",	namelistcmd,	1, },
	{ "noop",	nopcmd,		0, },
	{ "pass",	passcmd,	0, },
	{ "pasv",	pasvcmd,	1, },
	{ "pwd",	pwdcmd,		0, },
	{ "port", 	portcmd,	1, },
	{ "quit",	quitcmd,	0, },
	{ "rest",	restartcmd,	1, },
	{ "retr",	retrievecmd,	1, },
	{ "rmd",	delcmd,		1, },
	{ "rnfr",	rnfrcmd,	1, },
	{ "rnto",	rntocmd,	1, },
	{ "size", 	sizecmd,	1, },
	{ "stor", 	storecmd,	1, },
	{ "stou", 	storeucmd,	1, },
	{ "stru",	structcmd,	1, },
	{ "syst",	systemcmd,	0, },
	{ "type", 	typecmd,	0, },
	{ "user",	usercmd,	0, },
	{ 0, 0, 0 },
};

#define NONENS "/lib/namespace.ftp"	/* default ns for none */

char	user[Maxpath];		/* logged in user */
char	curdir[Maxpath];	/* current directory path */
Chalstate	*ch;
int	loggedin;
int	type;			/* transmission type */
int	mode;			/* transmission mode */
int	structure;		/* file structure */
char	data[64];		/* data address */
int	pid;			/* transfer process */
int	encryption;		/* encryption state */
int	isnone, anon_ok, anon_only, anon_everybody;
char	cputype[Maxpath];	/* the environment variable of the same name */
char	bindir[Maxpath];	/* bin directory for this architecture */
char	mailaddr[Maxpath];
char	*namespace = NONENS;
int	debug;
NetConnInfo	*nci;
int	createperm = 0660;
int	isnoworld;
vlong	offset;			/* from restart command */

ulong id;

typedef struct Passive Passive;
struct Passive
{
	int	inuse;
	char	adir[40];
	int	afd;
	int	port;
	uchar	ipaddr[IPaddrlen];
} passive;

#define FTPLOG "ftp"

void
logit(char *fmt, ...)
{
	char buf[8192];
	va_list arg;
	char errstr[128];

	rerrstr(errstr, sizeof errstr);
	va_start(arg, fmt);
	vseprint(buf, buf+sizeof(buf), fmt, arg);
	va_end(arg);
	syslog(0, FTPLOG, "%s.%s %s", nci->rsys, nci->rserv, buf);
	werrstr(errstr, sizeof errstr);
}

/*
 *  read commands from the control stream and dispatch
 */
void
main(int argc, char **argv)
{
	char *cmd;
	char *arg;
	char *p;
	Cmd *t;
	Biobuf in;
	int i;

	ARGBEGIN{
	case 'd':
		debug++;
		break;
	case 'a':		/* anonymous OK */
		anon_ok = 1;
		break;
	case 'A':
		anon_ok = 1;
		anon_only = 1;
		break;
	case 'e':
		anon_ok = 1;
		anon_everybody = 1;
		break;
	case 'n':
		namespace = ARGF();
		break;
	}ARGEND

	/* open log file before doing a newns */
	syslog(0, FTPLOG, nil);

	/* find out who is calling */
	if(argc < 1)
		nci = getnetconninfo(nil, 0);
	else
		nci = getnetconninfo(argv[argc-1], 0);
	if(nci == nil)
		sysfatal("ftpd needs a network address");

	strcpy(mailaddr, "?");
	id = getpid();

	/* figure out which binaries to bind in later */
	arg = getenv("cputype");
	if(arg)
		strecpy(cputype, cputype+sizeof cputype, arg);
	else
		strcpy(cputype, "mips");
	snprint(bindir, sizeof(bindir), "/bin/%s/bin", cputype);

	Binit(&in, 0, OREAD);
	reply("220 Plan 9 FTP server ready");
	alarm(Maxwait);
	while(cmd = Brdline(&in, '\n')){
		alarm(0);

		/*
		 *  strip out trailing cr's & lf and delimit with null
		 */
		i = Blinelen(&in)-1;
		cmd[i] = 0;
		if(debug)
			logit("%s", cmd);
		while(i > 0 && cmd[i-1] == '\r')
			cmd[--i] = 0;

		/*
		 *  hack for GatorFTP+, look for a 0x10 used as a delimiter
		 */
		p = strchr(cmd, 0x10);
		if(p)
			*p = 0;

		/*
		 *  get rid of telnet control sequences (we don't need them)
		 */
		while(*cmd && (uchar)*cmd == Iac){
			cmd++;
			if(*cmd)
				cmd++;
		}

		/*
		 *  parse the message (command arg)
		 */
		arg = strchr(cmd, ' ');
		if(arg){
			*arg++ = 0;
			while(*arg == ' ')
				arg++;
		}

		/*
		 *  ignore blank commands
		 */
		if(*cmd == 0)
			continue;

		/*
		 *  lookup the command and do it
		 */
		for(p = cmd; *p; p++)
			*p = tolower(*p);
		for(t = cmdtab; t->name; t++)
			if(strcmp(cmd, t->name) == 0){
				if(t->needlogin && !loggedin)
					sodoff();
				else if((*t->f)(arg) < 0)
					exits(0);
				break;
			}
		if(t->f != restartcmd){
			/*
			 *  the file offset is set to zero following
			 *  all commands except the restart command
			 */
			offset = 0;
		}
		if(t->name == 0){
			/*
			 *  the OOB bytes preceding an abort from UCB machines
			 *  comes out as something unrecognizable instead of
			 *  IAC's.  Certainly a Plan 9 bug but I can't find it.
			 *  This is a major hack to avoid the problem. -- presotto
			 */ 
			i = strlen(cmd);
			if(i > 4 && strcmp(cmd+i-4, "abor") == 0){
				abortcmd(0);	
			} else{
				logit("%s (%s) command not implemented", cmd, arg?arg:"");
				reply("502 %s command not implemented", cmd);
			}
		}
		alarm(Maxwait);
	}
	if(pid)
		postnote(PNPROC, pid, "kill");
}

/*
 *  reply to a command
 */
int
reply(char *fmt, ...)
{
	va_list arg;
	char buf[8192], *s;

	va_start(arg, fmt);
	s = vseprint(buf, buf+sizeof(buf)-3, fmt, arg);
	va_end(arg);
	if(debug){
		*s = 0;
		logit("%s", buf);
	}
	*s++ = '\r';
	*s++ = '\n';
	write(1, buf, s - buf);
	return 0;
}

int
sodoff(void)
{
	return reply("530 Sod off, service requires login");
}

/*
 *  run a command in a separate process
 */
int
asproc(void (*f)(char*, int), char *arg, int arg2)
{
	int i;

	if(pid){
		/* wait for previous command to finish */
		for(;;){
			i = waitpid();
			if(i == pid || i < 0)
				break;
		}
	}

	switch(pid = rfork(RFFDG|RFPROC|RFNOTEG)){
	case -1:
		return reply("450 Out of processes: %r");
	case 0:
		(*f)(arg, arg2);
		exits(0);
	default:
		break;
	}
	return 0;
}

/*
 * run a command to filter a tail
 */
int
transfer(char *cmd, char *a1, char *a2, char *a3, int image)
{
	int n, dfd, fd, bytes, eofs, pid;
	int pfd[2];
	char buf[Nbuf], *p;
	Waitmsg *w;

	reply("150 Opening data connection for %s (%s)", cmd, data);
	dfd = dialdata();
	if(dfd < 0)
		return reply("425 Error opening data connection: %r");

	if(pipe(pfd) < 0)
		return reply("520 Internal Error: %r");

	bytes = 0;
	switch(pid = rfork(RFFDG|RFPROC|RFNAMEG)){
	case -1:
		return reply("450 Out of processes: %r");
	case 0:
		logit("running %s %s %s %s pid %d",
			cmd, a1?a1:"", a2?a2:"" , a3?a3:"",getpid());
		close(pfd[1]);
		close(dfd);
		dup(pfd[0], 1);
		dup(pfd[0], 2);
		if(isnone){
			fd = open("#s/boot", ORDWR);
			if(fd < 0
			|| bind("#/", "/", MAFTER) < 0
			|| amount(fd, "/bin", MREPL, "") < 0
			|| bind("#c", "/dev", MAFTER) < 0
			|| bind(bindir, "/bin", MREPL) < 0)
				exits("building name space");
			close(fd);
		}
		execl(cmd, cmd, a1, a2, a3, nil);
		exits(cmd);
	default:
		close(pfd[0]);
		eofs = 0;
		while((n = read(pfd[1], buf, sizeof buf)) >= 0){
			if(n == 0){
				if(eofs++ > 5)
					break;
				else
					continue;
			}
			eofs = 0;
			p = buf;
			if(offset > 0){
				if(n > offset){
					p = buf+offset;
					n -= offset;
					offset = 0;
				} else {
					offset -= n;
					continue;
				}
			}
			if(!image)
				n = crlfwrite(dfd, p, n);
			else
				n = write(dfd, p, n);
			if(n < 0){
				postnote(PNPROC, pid, "kill");
				bytes = -1;
				break;
			}
			bytes += n;
		}
		close(pfd[1]);
		close(dfd);
		break;
	}

	/* wait for this command to finish */
	for(;;){
		w = wait();
		if(w == nil || w->pid == pid)
			break;
		free(w);
	}
	if(w != nil && w->msg != nil && w->msg[0] != 0){
		bytes = -1;
		logit("%s", w->msg);
		logit("%s %s %s %s failed %s", cmd, a1?a1:"", a2?a2:"" , a3?a3:"", w->msg);
	}
	free(w);
	reply("226 Transfer complete");
	return bytes;
}


/*
 *  just reply OK
 */
int
nopcmd(char *arg)
{
	USED(arg);
	reply("510 Plan 9 FTP daemon still alive");
	return 0;
}

/*
 *  login as user
 */
int
loginuser(char *user, char *nsfile, int gotoslash)
{
	logit("login %s %s %s %s", user, mailaddr, nci->rsys, nsfile);
	if(nsfile != nil && newns(user, nsfile) < 0){
		logit("namespace file %s does not exist", nsfile);
		return reply("530 Not logged in: login out of service");
	}
	getwd(curdir, sizeof(curdir));
	if(gotoslash){
		chdir("/");
		strcpy(curdir, "/");
	}
	putenv("service", "ftp");
	loggedin = 1;
	if(debug == 0)
		reply("230- If you have problems, send mail to 'postmaster'.");
	return reply("230 Logged in");
}

/*
 *  get a user id, reply with a challenge.  The users 'anonymous'
 *  and 'ftp' are equivalent to 'none'.  The user 'none' requires
 *  no challenge.
 */
int
usercmd(char *name)
{
	logit("user %s %s", name, nci->rsys);
	if(loggedin)
		return reply("530 Already logged in as %s", user);
	if(name == 0 || *name == 0)
		return reply("530 user command needs user name");
	isnoworld = 0;
	if(*name == ':'){
		debug = 1;
		name++;
	}
	strncpy(user, name, sizeof(user));
	if(debug)
		logit("debugging");
	user[sizeof(user)-1] = 0;
	if(strcmp(user, "anonymous") == 0 || strcmp(user, "ftp") == 0)
		strcpy(user, "none");
	else if(anon_everybody)
		strcpy(user,"none");
	if(strcmp(user, "*none") == 0){
		if(!anon_ok)
			return reply("530 Not logged in: anonymous disallowed");
		return loginuser("none", namespace, 1);
	}
	if(strcmp(user, "none") == 0){
		if(!anon_ok)
			return reply("530 Not logged in: anonymous disallowed");
		return reply("331 Send email address as password");
	}
	if(anon_only)
		return reply("530 Not logged in: anonymous access only");
	isnoworld = noworld(name);
	if(isnoworld)
		return reply("331 OK");
	if(ch)
		auth_freechal(ch);
	if((ch = auth_challenge("proto=p9cr role=server user=%q", user)) == nil)
		return reply("421 %r");
	return reply("331 encrypt challenge, %s, as a password", ch->chal);
}

/*
 *  get a password, set up user if it works.
 */
int
passcmd(char *response)
{
	char namefile[128];
	AuthInfo *ai;

	if(response == nil)
		response = "";

	if(strcmp(user, "none") == 0 || strcmp(user, "*none") == 0){
		/* for none, accept anything as a password */
		isnone = 1;
		strncpy(mailaddr, response, sizeof(mailaddr)-1);
		return loginuser("none", namespace, 1);
	}

	if(isnoworld){
		/* noworld gets a password in the clear */
		if(login(user, response, "/lib/namespace.noworld") < 0)
			return reply("530 Not logged in");
		createperm = 0664;
		/* login has already setup the namespace */
		return loginuser(user, nil, 0);
	} else {
		/* for everyone else, do challenge response */
		if(ch == nil)
			return reply("531 Send user id before encrypted challenge");
		ch->resp = response;
		ch->nresp = strlen(response);
		ai = auth_response(ch);
		if(ai == nil)
			return reply("530 Not logged in: %r");
		if(auth_chuid(ai, nil) < 0)
			return reply("530 Not logged in: %r");
		auth_freechal(ch);
		ch = nil;

		/* if the user has specified a namespace for ftp, use it */
		snprint(namefile, sizeof(namefile), "/usr/%s/lib/namespace.ftp", user);
		strcpy(mailaddr, user);
		createperm = 0660;
		if(access(namefile, 0) == 0)
			return loginuser(user, namefile, 0);
		else
			return loginuser(user, "/lib/namespace", 0);
	}
}

/*
 *  print working directory
 */
int
pwdcmd(char *arg)
{
	if(arg)
		return reply("550 Pwd takes no argument");
	return reply("257 \"%s\" is the current directory", curdir);
}