keyfs.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 <authsrv.h>
#include <fcall.h>
#include <bio.h>
#include <mp.h>
#include <libsec.h>
#include "authcmdlib.h"

char authkey[8];

typedef struct Fid	Fid;
typedef struct User	User;

enum{
	Qroot,
	Quser,
	Qkey,
	Qsecret,
	Qlog,
	Qstatus,
	Qexpire,
	Qwarnings,
	Qmax,

	Nuser	= 512,
	MAXBAD	= 10,			/* max number of bad attempts before disabling the account */
	Namelen	= ANAMELEN,		/* file must be randomly addressible, so names have fixed length */
};

enum{
	Sok,
	Sdisabled,
	Smax,
};

struct Fid{
	int	fid;
	ulong	qtype;
	User	*user;
	int	busy;
	Fid	*next;
};

struct User{
	char	*name;
	char	key[DESKEYLEN];
	char	secret[SECRETLEN];
	ulong	expire;			/* 0 == never */
	uchar	status;
	ulong	bad;			/* number of consecutive bad authentication attempts */
	int	ref;
	char	removed;
	uchar	warnings;
	long	purgatory;		/* time purgatory ends */
	ulong	uniq;
	User	*link;
};

char	*qinfo[Qmax] = {
	[Qroot]		"keys",
	[Quser]		".",
	[Qkey]		"key",
	[Qsecret]	"secret",
	[Qlog]		"log",
	[Qexpire]	"expire",
	[Qstatus]	"status",
	[Qwarnings]	"warnings",
};

char	*status[Smax] = {
	[Sok]		"ok",
	[Sdisabled]	"disabled",
};

Fid	*fids;
User	*users[Nuser];
char	*userkeys;
int	nuser;
ulong	uniq = 1;
Fcall	rhdr,
	thdr;
int	usepass;
char	*warnarg;
uchar	mdata[8192 + IOHDRSZ];
int	messagesize = sizeof mdata;

int	readusers(void);
ulong	hash(char*);
Fid	*findfid(int);
User	*finduser(char*);
User	*installuser(char*);
int	removeuser(User*);
void	insertuser(User*);
void	writeusers(void);
void	io(int, int);
void	*emalloc(ulong);
Qid	mkqid(User*, ulong);
int	dostat(User*, ulong, void*, int);
int	newkeys(void);
void	warning(void);

char	*Auth(Fid*), *Attach(Fid*), *Version(Fid*),
	*Flush(Fid*), *Walk(Fid*),
	*Open(Fid*), *Create(Fid*),
	*Read(Fid *), *Write(Fid*), *Clunk(Fid*),
	*Remove(Fid *), *Stat(Fid*), *Wstat(Fid*);
char 	*(*fcalls[])(Fid*) = {
	[Tattach]	Attach,
	[Tauth]	Auth,
	[Tclunk]	Clunk,
	[Tcreate]	Create,
	[Tflush]	Flush,
	[Topen]		Open,
	[Tread]		Read,
	[Tremove]	Remove,
	[Tstat]		Stat,
	[Tversion]	Version,
	[Twalk]		Walk,
	[Twrite]	Write,
	[Twstat]	Wstat,
};

void
main(int argc, char *argv[])
{
	char *mntpt;
	int p[2];

	mntpt = "/mnt/keys";
	ARGBEGIN{
	case 'm':
		mntpt = ARGF();
		break;
	case 'w':
		warnarg = ARGF();
		break;
	case 'p':
		usepass = 1;
		break;
	}ARGEND
	argv0 = "keyfs";

	userkeys = "/adm/keys";
	if(argc > 0)
		userkeys = argv[0];

	if(pipe(p) < 0)
		error("can't make pipe: %r");

	if(usepass) {
		getpass(authkey, nil, 0, 0);
	} else {
		if(!getauthkey(authkey))
			print("keyfs: warning: can't read /dev/key\n");
	}

	switch(rfork(RFPROC|RFNAMEG|RFNOTEG|RFNOWAIT|RFENVG|RFFDG)){
	case 0:
		close(p[0]);
		io(p[1], p[1]);
		exits(0);
	case -1:
		error("fork");
	default:
		close(p[1]);
		if(mount(p[0], -1, mntpt, MREPL|MCREATE, "") < 0)
			error("can't mount: %r");
		exits(0);
	}
}

char *
Flush(Fid *f)
{
	USED(f);
	return 0;
}

char *
Auth(Fid *)
{
	return "keyfs: authentication not required";
}

char *
Attach(Fid *f)
{
	if(f->busy)
		Clunk(f);
	f->user = 0;
	f->qtype = Qroot;
	f->busy = 1;
	thdr.qid = mkqid(f->user, f->qtype);
	return 0;
}

char*
Version(Fid*)
{
	Fid *f;

	for(f = fids; f; f = f->next)
		if(f->busy)
			Clunk(f);
	if(rhdr.msize > sizeof mdata)
		thdr.msize = sizeof mdata;
	else
		thdr.msize = rhdr.msize;
	messagesize = thdr.msize;
	if(strncmp(rhdr.version, "9P2000", 6) != 0)
		return "bad 9P version";
	thdr.version = "9P2000";
	return 0;
}

char *
Walk(Fid *f)
{
	char *name, *err;
	int i, j, max;
	Fid *nf;
	ulong qtype;
	User *user;

	if(!f->busy)
		return "walk of unused fid";
	nf = nil;
	qtype = f->qtype;
	user = f->user;
	if(rhdr.fid != rhdr.newfid){
		nf = findfid(rhdr.newfid);
		if(nf->busy)
			return "fid in use";
		f = nf;	/* walk f */
	}

	err = nil;
	i = 0;
	if(rhdr.nwname > 0){
		for(; i<rhdr.nwname; i++){
			if(i >= MAXWELEM){
				err = "too many path name elements";
				break;
			}
			name = rhdr.wname[i];
			switch(qtype){
			case Qroot:
				if(strcmp(name, "..") == 0)
					goto Accept;
				user = finduser(name);
				if(!user)
					goto Out;
				qtype = Quser;

			Accept:
				thdr.wqid[i] = mkqid(user, qtype);
				break;

			case Quser:
				if(strcmp(name, "..") == 0) {
					qtype = Qroot;
					user = 0;
					goto Accept;
				}
				max = Qmax;
				for(j = Quser + 1; j < Qmax; j++)
					if(strcmp(name, qinfo[j]) == 0){
						qtype = j;
						break;
					}
				if(j < max)
					goto Accept;
				goto Out;

			default:
				err = "file is not a directory";
				goto Out;
			}
		}
	    Out:
		if(i < rhdr.nwname && err == nil)
			err = "file not found";
	}

	if(err != nil){
		return err;
	}

	/* if we cloned and then completed the walk, update new fid */
	if(rhdr.fid != rhdr.newfid && i == rhdr.nwname){
		nf->busy = 1;
		nf->qtype = qtype;
		if(nf->user = user)
			nf->user->ref++;
	}else if(nf == nil && rhdr.nwname > 0){	/* walk without clone (rare) */
		Clunk(f);
		f->busy = 1;
		f->qtype = qtype;
		if(f->user = user)
			f->user->ref++;
	}

	thdr.nwqid = i;
	return 0;
}

char *
Clunk(Fid *f)
{
	f->busy = 0;
	if(f->user && --f->user->ref == 0 && f->user->removed) {
		free(f->user->name);
		free(f->user);
	}
	f->user = 0;
	return 0;
}

char *
Open(Fid *f)
{
	int mode;

	if(!f->busy)
		return "open of unused fid";
	mode = rhdr.mode;
	if(f->qtype == Quser && (mode & (OWRITE|OTRUNC)))
		return "user already exists";
	thdr.qid = mkqid(f->user, f->qtype);
	thdr.iounit = messagesize - IOHDRSZ;
	return 0;
}

char *
Create(Fid *f)
{
	char *name;
	long perm;

	if(!f->busy)
		return "create of unused fid";
	name = rhdr.name;
	if(f->user){
		return "permission denied";
	}else{
		perm = rhdr.perm;
		if(!(perm & DMDIR))
			return "permission denied";
		if(strcmp(name, "") == 0)
			return "empty file name";
		if(strlen(name) >= Namelen)
			return "file name too long";
		if(finduser(name))
			return "user already exists";
		f->user = installuser(name);
		f->user->ref++;
		f->qtype = Quser;
	}
	thdr.qid = mkqid(f->user, f->qtype);
	thdr.iounit = messagesize - IOHDRSZ;
	writeusers();
	return 0;
}

char *
Read(Fid *f)
{
	User *u;
	char *data;
	ulong off, n, m;
	int i, j, max;

	if(!f->busy)
		return "read of unused fid";
	n = rhdr.count;
	off = rhdr.offset;
	thdr.count = 0;
	data = thdr.data;
	switch(f->qtype){
	case Qroot:
		j = 0;
		for(i = 0; i < Nuser; i++)
			for(u = users[i]; u; j += m, u = u->link){
				m = dostat(u, Quser, data, n);
				if(m <= BIT16SZ)
					break;
				if(j < off)
					continue;
				data += m;
				n -= m;
			}
		thdr.count = data - thdr.data;
		return 0;
	case Quser:
		max = Qmax;
		max -= Quser + 1;
		j = 0;
		for(i = 0; i < max; j += m, i++){
			m = dostat(f->user, i + Quser + 1, data, n);
			if(m <= BIT16SZ)
				break;
			if(j < off)
				continue;
			data += m;
			n -= m;
		}
		thdr.count = data - thdr.data;
		return 0;
	case Qkey:
		if(f->user->status != Sok)
			return "user disabled";
		if(f->user->purgatory > time(0))
			return "user in purgatory";
		if(f->user->expire != 0 && f->user->expire < time(0))
			return "user expired";
		if(off != 0)
			return 0;
		if(n > DESKEYLEN)
			n = DESKEYLEN;
		memmove(thdr.data, f->user->key, n);
		thdr.count = n;
		return 0;
	case Qsecret:
		if(f->user->status != Sok)
			return "user disabled";
		if(f->user->purgatory > time(0))
			return "user in purgatory";
		if(f->user->expire != 0 && f->user->expire < time(0))
			return "user expired";
		if(off != 0)
			return 0;
		if(n > strlen(f->user->secret))
			n = strlen(f->user->secret);
		memmove(thdr.data, f->user->secret, n);
		thdr.count = n;
		return 0;
	case Qstatus:
		if(off != 0){
			thdr.count = 0;
			return 0;
		}
		if(f->user->status == Sok && f->user->expire && f->user->expire < time(0))
			sprint(thdr.data, "expired\n");
		else
			sprint(thdr.data, "%s\n", status[f->user->status]);
		thdr.count = strlen(thdr.data);
		return 0;
	case Qexpire:
		if(off != 0){
			thdr.count = 0;
			return 0;
		}
		if(!f->user->expire)
			strcpy(data, "never\n");
		else
			sprint(data, "%lud\n", f->user->expire);
		if(n > strlen(data))
			n = strlen(data);
		thdr.count = n;
		return 0;
	case Qlog:
		if(off != 0){
			thdr.count = 0;
			return 0;
		}
		sprint(data, "%lud\n", f->user->bad);
		if(n > strlen(data))
			n = strlen(data);
		thdr.count = n;
		return 0;
	case Qwarnings:
		if(off != 0){
			thdr.count = 0;
			return 0;
		}
		sprint(data, "%ud\n", f->user->warnings);
		if(n > strlen(data))
			n = strlen(data);
		thdr.count = n;
		return 0;
	default:
		return "permission denied: unknown qid";
	}
}

char *
Write(Fid *f)
{
	char *data, *p;
	ulong n, expire;
	int i;

	if(!f->busy)
		return "permission denied";
	n = rhdr.count;
	data = rhdr.data;
	switch(f->qtype){
	case Qkey:
		if(n != DESKEYLEN)
			return "garbled write data";
		memmove(f->user->key, data, DESKEYLEN);
		thdr.count = DESKEYLEN;
		break;
	case Qsecret:
		if(n >= SECRETLEN)
			return "garbled write data";
		memmove(f->user->secret, data, n);
		f->user->secret[n] = 0;
		thdr.count = n;
		break;
	case Qstatus:
		data[n] = '\0';
		if(p = strchr(data, '\n'))
			*p = '\0';
		for(i = 0; i < Smax; i++)