9user.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 "stdinc.h"

#include "9.h"

enum {
	NUserHash	= 1009,
};

typedef struct Ubox Ubox;
typedef struct User User;

typedef struct User {
	char*	uid;
	char*	uname;
	char*	leader;
	char**	group;
	int	ngroup;

	User*	next;			/* */
	User*	ihash;			/* lookup by .uid */
	User*	nhash;			/* lookup by .uname */
} User;

#pragma varargck type "U"   User*

typedef struct Ubox {
	User*	head;
	User*	tail;
	int	nuser;
	int	len;

	User*	ihash[NUserHash];	/* lookup by .uid */
	User*	nhash[NUserHash];	/* lookup by .uname */
} Ubox;

static struct {
	VtLock*	lock;

	Ubox*	box;
} ubox;

static char usersDefault[] = {
	"adm:adm:adm:sys\n"
	"none:none::\n"
	"noworld:noworld::\n"
	"sys:sys::glenda\n"
	"glenda:glenda:glenda:\n"
};

static char* usersMandatory[] = {
	"adm",
	"none",
	"noworld",
	"sys",
	nil,
};

char* uidadm = "adm";
char* unamenone = "none";
char* uidnoworld = "noworld";

static u32int
userHash(char* s)
{
	uchar *p;
	u32int hash;

	hash = 0;
	for(p = (uchar*)s; *p != '\0'; p++)
		hash = hash*7 + *p;

	return hash % NUserHash;
}

static User*
_userByUid(Ubox* box, char* uid)
{
	User *u;

	if(box != nil){
		for(u = box->ihash[userHash(uid)]; u != nil; u = u->ihash){
			if(strcmp(u->uid, uid) == 0)
				return u;
		}
	}
	vtSetError("uname: uid '%s' not found", uid);
	return nil;
}

char*
unameByUid(char* uid)
{
	User *u;
	char *uname;

	vtRLock(ubox.lock);
	if((u = _userByUid(ubox.box, uid)) == nil){
		vtRUnlock(ubox.lock);
		return nil;
	}
	uname = vtStrDup(u->uname);
	vtRUnlock(ubox.lock);

	return uname;
}

static User*
_userByUname(Ubox* box, char* uname)
{
	User *u;

	if(box != nil){
		for(u = box->nhash[userHash(uname)]; u != nil; u = u->nhash){
			if(strcmp(u->uname, uname) == 0)
				return u;
		}
	}
	vtSetError("uname: uname '%s' not found", uname);
	return nil;
}

char*
uidByUname(char* uname)
{
	User *u;
	char *uid;

	vtRLock(ubox.lock);
	if((u = _userByUname(ubox.box, uname)) == nil){
		vtRUnlock(ubox.lock);
		return nil;
	}
	uid = vtStrDup(u->uid);
	vtRUnlock(ubox.lock);

	return uid;
}

static int
_groupMember(Ubox* box, char* group, char* member, int whenNoGroup)
{
	int i;
	User *g, *m;

	/*
	 * Is 'member' a member of 'group'?
	 * Note that 'group' is a 'uid' and not a 'uname'.
	 * A 'member' is automatically in their own group.
	 */
	if((g = _userByUid(box, group)) == nil)
		return whenNoGroup;
	if((m = _userByUname(box, member)) == nil)
		return 0;
	if(m == g)
		return 1;
	for(i = 0; i < g->ngroup; i++){
		if(strcmp(g->group[i], member) == 0)
			return 1;
	}
	return 0;
}

int
groupWriteMember(char* uname)
{
	int ret;

	/*
	 * If there is a ``write'' group, then only its members can write
	 * to the file system, no matter what the permission bits say.
	 *
	 * To users not in the ``write'' group, the file system appears
	 * read only.  This is used to serve sources.cs.bell-labs.com
	 * to the world.
	 *
	 * Note that if there is no ``write'' group, then this routine
	 * makes it look like everyone is a member -- the opposite
	 * of what groupMember does.
	 *
	 * We use this for sources.cs.bell-labs.com.
	 * If this slows things down too much on systems that don't
	 * use this functionality, we could cache the write group lookup.
	 */

	vtRLock(ubox.lock);
	ret = _groupMember(ubox.box, "write", uname, 1);
	vtRUnlock(ubox.lock);
	return ret;
}

static int
_groupRemMember(Ubox* box, User* g, char* member)
{
	int i;

	if(_userByUname(box, member) == nil)
		return 0;

	for(i = 0; i < g->ngroup; i++){
		if(strcmp(g->group[i], member) == 0)
			break;
	}
	if(i >= g->ngroup){
		if(strcmp(g->uname, member) == 0)
			vtSetError("uname: '%s' always in own group", member);
		else
			vtSetError("uname: '%s' not in group '%s'",
				member, g->uname);
		return 0;
	}

	vtMemFree(g->group[i]);

	box->len -= strlen(member);
	if(g->ngroup > 1)
		box->len--;
	g->ngroup--;
	switch(g->ngroup){
	case 0:
		vtMemFree(g->group);
		g->group = nil;
		break;
	default:
		while(i < g->ngroup){
			g->group[i] = g->group[i+1];
			i++;
		}
		/*FALLTHROUGH*/
	case 1:
		g->group = vtMemRealloc(g->group, (g->ngroup)*sizeof(char*));
		break;
	}

	return 1;
}

static int
_groupAddMember(Ubox* box, User* g, char* member)
{
	User *u;

	if((u = _userByUname(box, member)) == nil)
		return 0;
	if(_groupMember(box, g->uid, u->uname, 0)){
		if(strcmp(g->uname, member) == 0)
			vtSetError("uname: '%s' always in own group", member);
		else
			vtSetError("uname: '%s' already in group '%s'",
				member, g->uname);
		return 0;
	}

	g->group = vtMemRealloc(g->group, (g->ngroup+1)*sizeof(char*));
	g->group[g->ngroup] = vtStrDup(member);
	box->len += strlen(member);
	g->ngroup++;
	if(g->ngroup > 1)
		box->len++;

	return 1;
}

int
groupMember(char* group, char* member)
{
	int r;

	if(group == nil)
		return 0;

	vtRLock(ubox.lock);
	r = _groupMember(ubox.box, group, member, 0);
	vtRUnlock(ubox.lock);

	return r;
}

int
groupLeader(char* group, char* member)
{
	int r;
	User *g;

	/*
	 * Is 'member' the leader of 'group'?
	 * Note that 'group' is a 'uid' and not a 'uname'.
	 * Uname 'none' cannot be a group leader.
	 */
	if(strcmp(member, unamenone) == 0 || group == nil)
		return 0;

	vtRLock(ubox.lock);
	if((g = _userByUid(ubox.box, group)) == nil){
		vtRUnlock(ubox.lock);
		return 0;
	}
	if(g->leader != nil){
		if(strcmp(g->leader, member) == 0){
			vtRUnlock(ubox.lock);
			return 1;
		}
		r = 0;
	}
	else
		r = _groupMember(ubox.box, group, member, 0);
	vtRUnlock(ubox.lock);

	return r;
}

static void
userFree(User* u)
{
	int i;

	vtMemFree(u->uid);
	vtMemFree(u->uname);
	if(u->leader != nil)
		vtMemFree(u->leader);
	if(u->ngroup){
		for(i = 0; i < u->ngroup; i++)
			vtMemFree(u->group[i]);
		vtMemFree(u->group);
	}
	vtMemFree(u);
}

static User*
userAlloc(char* uid, char* uname)
{
	User *u;

	u = vtMemAllocZ(sizeof(User));
	u->uid = vtStrDup(uid);
	u->uname = vtStrDup(uname);

	return u;
}

int
validUserName(char* name)
{
	Rune *r;
	static Rune invalid[] = L"#:,()";

	for(r = invalid; *r != '\0'; r++){
		if(utfrune(name, *r))
			return 0;
	}
	return 1;
}

static int
userFmt(Fmt* fmt)
{
	User *u;
	int i, r;

	u = va_arg(fmt->args, User*);

	r = fmtprint(fmt, "%s:%s:", u->uid, u->uname);
	if(u->leader != nil)
		r += fmtprint(fmt, u->leader);
	r += fmtprint(fmt, ":");
	if(u->ngroup){
		r += fmtprint(fmt, u->group[0]);
		for(i = 1; i < u->ngroup; i++)
			r += fmtprint(fmt, ",%s", u->group[i]);
	}

	return r;
}

static int
usersFileWrite(Ubox* box)
{
	Fs *fs;
	User *u;
	int i, r;
	Fsys *fsys;
	char *p, *q, *s;
	File *dir, *file;

	if((fsys = fsysGet("main")) == nil)
		return 0;
	fsysFsRlock(fsys);
	fs = fsysGetFs(fsys);

	/*
	 * BUG:
	 * 	the owner/group/permissions need to be thought out.
	 */
	r = 0;
	if((dir = fileOpen(fs, "/active")) == nil)
		goto tidy0;
	if((file = fileWalk(dir, uidadm)) == nil)
		file = fileCreate(dir, uidadm, ModeDir|0775, uidadm);
	fileDecRef(dir);
	if(file == nil)
		goto tidy;
	dir = file;
	if((file = fileWalk(dir, "users")) == nil)
		file = fileCreate(dir, "users", 0664, uidadm);
	fileDecRef(dir);
	if(file == nil)
		goto tidy;
	if(!fileTruncate(file, uidadm))
		goto tidy;

	p = s = vtMemAlloc(box->len+1);
	q = p + box->len+1;
	for(u = box->head; u != nil; u = u->next){
		p += snprint(p, q-p, "%s:%s:", u->uid, u->uname);
		if(u->leader != nil)
			p+= snprint(p, q-p, u->leader);
		p += snprint(p, q-p, ":");
		if(u->ngroup){
			p += snprint(p, q-p, u->group[0]);
			for(i = 1; i < u->ngroup; i++)
				p += snprint(p, q-p, ",%s", u->group[i]);
		}
		p += snprint(p, q-p, "\n");
	}
	r = fileWrite(file, s, box->len, 0, uidadm);
	vtMemFree(s);

tidy:
	if(file != nil)
		fileDecRef(file);
tidy0:
	fsysFsRUnlock(fsys);
	fsysPut(fsys);

	return r;
}

static void
uboxRemUser(Ubox* box, User *u)
{
	User **h, *up;

	h = &box->ihash[userHash(u->uid)];
	for(up = *h; up != nil && up != u; up = up->ihash)
		h = &up->ihash;
	assert(up == u);
	*h = up->ihash;
	box->len -= strlen(u->uid);

	h = &box->nhash[userHash(u->uname)];
	for(up = *h; up != nil && up != u; up = up->nhash)
		h = &up->nhash;
	assert(up == u);
	*h = up->nhash;
	box->len -= strlen(u->uname);

	h = &box->head;
	for(up = *h; up != nil && strcmp(up->uid, u->uid) != 0; up = up->next)
		h = &up->next;
	assert(up == u);
	*h = u->next;
	u->next = nil;

	box->len -= 4;
	box->nuser--;
}

static void
uboxAddUser(Ubox* box, User* u)
{
	User **h, *up;

	h = &box->ihash[userHash(u->uid)];
	u->ihash = *h;
	*h = u;
	box->len += strlen(u->uid);