imap4.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

	if(imap->mustssl){
		memset(&conn, 0, sizeof conn);
		sfd = tlsClient(imap->fd, &conn);
		if(sfd < 0)
			sysfatal("tlsClient: %r");
		if(conn.cert==nil || conn.certlen <= 0)
			sysfatal("server did not provide TLS certificate");
		sha1(conn.cert, conn.certlen, digest, nil);
		if(!imap->thumb || !okThumbprint(digest, imap->thumb)){
			fmtinstall('H', encodefmt);
			sysfatal("server certificate %.*H not recognized", SHA1dlen, digest);
		}
		free(conn.cert);
		close(imap->fd);
		imap->fd = sfd;

		if(imap->debug){
			char fn[128];
			int fd;

			snprint(fn, sizeof fn, "%s/ctl", conn.dir);
			fd = open(fn, ORDWR);
			if(fd < 0)
				fprint(2, "opening ctl: %r\n");
			if(fprint(fd, "debug") < 0)
				fprint(2, "writing ctl: %r\n");
			close(fd);
		}
	}
	Binit(&imap->bin, imap->fd, OREAD);
	Binit(&imap->bout, imap->fd, OWRITE);

	if(err = imap4login(imap)) {
		close(imap->fd);
		return err;
	}

	return nil;
}

//
// close connection
//
static void
imap4hangup(Imap *imap)
{
	imap4cmd(imap, "LOGOUT");
	imap4resp(imap);
	close(imap->fd);
}

//
// download a single message
//
static char*
imap4fetch(Mailbox *mb, Message *m)
{
	int i;
	char *p, *s, sdigest[2*SHA1dlen+1];
	Imap *imap;

	imap = mb->aux;

	imap->size = 0;

	if(!isokay(s = imap4resp(imap)))
		return s;

	p = imap->base;
	if(p == nil)
		return "did not get message body";

	removecr(p);
	free(m->start);
	m->start = p;
	m->end = p+strlen(p);
	m->bend = m->rbend = m->end;
	m->header = m->start;

	imap->base = nil;
	imap->data = nil;

	parse(m, 0, mb, 1);

	// digest headers
	sha1((uchar*)m->start, m->end - m->start, m->digest, nil);
	for(i = 0; i < SHA1dlen; i++)
		sprint(sdigest+2*i, "%2.2ux", m->digest[i]);
	m->sdigest = s_copy(sdigest);

	return nil;
}

//
// check for new messages on imap4 server
// download new messages, mark deleted messages
//
static char*
imap4read(Imap *imap, Mailbox *mb, int doplumb)
{
	char *s;
	int i, ignore, nnew, t;
	Message *m, *next, **l;

	imap4cmd(imap, "STATUS %Z (MESSAGES UIDVALIDITY)", imap->mbox);
	if(!isokay(s = imap4resp(imap)))
		return s;

	imap->nuid = 0;
	imap->uid = erealloc(imap->uid, imap->nmsg*sizeof(imap->uid[0]));
	imap->muid = imap->nmsg;

	if(imap->nmsg > 0){
		imap4cmd(imap, "UID FETCH 1:* UID");
		if(!isokay(s = imap4resp(imap)))
			return s;
	}

	l = &mb->root->part;
	for(i=0; i<imap->nuid; i++){
		ignore = 0;
		while(*l != nil){
			if((*l)->imapuid == imap->uid[i]){
				ignore = 1;
				l = &(*l)->next;
				break;
			}else{
				// old mail, we don't have it anymore
				if(doplumb)
					mailplumb(mb, *l, 1);
				(*l)->inmbox = 0;
				(*l)->deleted = 1;
				l = &(*l)->next;
			}
		}
		if(ignore)
			continue;

		// new message
		m = newmessage(mb->root);
		m->mallocd = 1;
		m->inmbox = 1;
		m->imapuid = imap->uid[i];

		// add to chain, will download soon
		*l = m;
		l = &m->next;
	}

	// whatever is left at the end of the chain is gone
	while(*l != nil){
		if(doplumb)
			mailplumb(mb, *l, 1);
		(*l)->inmbox = 0;
		(*l)->deleted = 1;
		l = &(*l)->next;
	}

	// download new messages
	t = imap->tag;
	if(pipeline)
	switch(rfork(RFPROC|RFMEM)){
	case -1:
		sysfatal("rfork: %r");
	default:
		break;
	case 0:
		for(m = mb->root->part; m != nil; m = m->next){
			if(m->start != nil)
				continue;
			if(imap->debug)
				fprint(2, "9X%d UID FETCH %lud (UID RFC822.SIZE BODY[])\r\n",
					t, (ulong)m->imapuid);
			Bprint(&imap->bout, "9X%d UID FETCH %lud (UID RFC822.SIZE BODY[])\r\n",
				t++, (ulong)m->imapuid);
		}
		Bflush(&imap->bout);
		_exits(nil);
	}

	nnew = 0;
	for(m=mb->root->part; m!=nil; m=next){
		next = m->next;
		if(m->start != nil)
			continue;

		if(!pipeline){
			Bprint(&imap->bout, "9X%lud UID FETCH %lud (UID RFC822.SIZE BODY[])\r\n",
				(ulong)imap->tag, (ulong)m->imapuid);
			Bflush(&imap->bout);
		}

		if(s = imap4fetch(mb, m)){
			// message disappeared?  unchain
			fprint(2, "download %lud: %s\n", (ulong)m->imapuid, s);
			delmessage(mb, m);
			mb->root->subname--;
			continue;
		}
		nnew++;
		if(doplumb)
			mailplumb(mb, m, 0);
	}
	if(pipeline)
		waitpid();

	if(nnew || mb->vers == 0){
		mb->vers++;
		henter(PATH(0, Qtop), mb->name,
			(Qid){PATH(mb->id, Qmbox), mb->vers, QTDIR}, nil, mb);
	}
	return nil;
}

//
// sync mailbox
//
static void
imap4purge(Imap *imap, Mailbox *mb)
{
	int ndel;
	Message *m, *next;

	ndel = 0;
	for(m=mb->root->part; m!=nil; m=next){
		next = m->next;
		if(m->deleted && m->refs==0){
			if(m->inmbox && (ulong)(m->imapuid>>32)==imap->validity){
				imap4cmd(imap, "UID STORE %lud +FLAGS (\\Deleted)", (ulong)m->imapuid);
				if(isokay(imap4resp(imap))){
					ndel++;
					delmessage(mb, m);
				}
			}else
				delmessage(mb, m);
		}
	}

	if(ndel){
		imap4cmd(imap, "EXPUNGE");
		imap4resp(imap);
	}
}

//
// connect to imap4 server, sync mailbox
//
static char*
imap4sync(Mailbox *mb, int doplumb)
{
	char *err;
	Imap *imap;

	imap = mb->aux;

	if(err = imap4dial(imap)){
		mb->waketime = time(0) + imap->refreshtime;
		return err;
	}

	if((err = imap4read(imap, mb, doplumb)) == nil){
		imap4purge(imap, mb);
		mb->d->atime = mb->d->mtime = time(0);
	}
	/*
	 * don't hang up; leave connection open for next time.
	 */
	// imap4hangup(imap);
	mb->waketime = time(0) + imap->refreshtime;
	return err;
}

static char Eimap4ctl[] = "bad imap4 control message";

static char*
imap4ctl(Mailbox *mb, int argc, char **argv)
{
	int n;
	Imap *imap;

	imap = mb->aux;
	if(argc < 1)
		return Eimap4ctl;

	if(argc==1 && strcmp(argv[0], "debug")==0){
		imap->debug = 1;
		return nil;
	}

	if(argc==1 && strcmp(argv[0], "nodebug")==0){
		imap->debug = 0;
		return nil;
	}

	if(argc==1 && strcmp(argv[0], "thumbprint")==0){
		if(imap->thumb)
			freeThumbprints(imap->thumb);
		imap->thumb = initThumbprints("/sys/lib/tls/mail", "/sys/lib/tls/mail.exclude");
	}
	if(strcmp(argv[0], "refresh")==0){
		if(argc==1){
			imap->refreshtime = 60;
			return nil;
		}
		if(argc==2){
			n = atoi(argv[1]);
			if(n < 15)
				return Eimap4ctl;
			imap->refreshtime = n;
			return nil;
		}
	}

	return Eimap4ctl;
}

//
// free extra memory associated with mb
//
static void
imap4close(Mailbox *mb)
{
	Imap *imap;

	imap = mb->aux;
	free(imap->freep);
	free(imap->base);
	free(imap->uid);
	if(imap->fd >= 0)
		close(imap->fd);
	free(imap);
}

//
// open mailboxes of the form /imap/host/user
//
char*
imap4mbox(Mailbox *mb, char *path)
{
	char *f[10];
	int mustssl, nf;
	Imap *imap;

	quotefmtinstall();
	fmtinstall('Z', doublequote);
	if(strncmp(path, "/imap/", 6) != 0 && strncmp(path, "/imaps/", 7) != 0)
		return Enotme;
	mustssl = (strncmp(path, "/imaps/", 7) == 0);

	path = strdup(path);
	if(path == nil)
		return "out of memory";

	nf = getfields(path, f, 5, 0, "/");
	if(nf < 3){
		free(path);
		return "bad imap path syntax /imap[s]/system[/user[/mailbox]]";
	}

	imap = emalloc(sizeof(*imap));
	imap->fd = -1;
	imap->debug = debug;
	imap->freep = path;
	imap->mustssl = mustssl;
	imap->host = f[2];
	if(nf < 4)
		imap->user = nil;
	else
		imap->user = f[3];
	if(nf < 5)
		imap->mbox = "Inbox";
	else
		imap->mbox = f[4];
	imap->thumb = initThumbprints("/sys/lib/tls/mail", "/sys/lib/tls/mail.exclude");

	mb->aux = imap;
	mb->sync = imap4sync;
	mb->close = imap4close;
	mb->ctl = imap4ctl;
	mb->d = emalloc(sizeof(*mb->d));
	//mb->fetch = imap4fetch;

	return nil;
}

//
// Formatter for %"
// Use double quotes to protect white space, frogs, \ and "
//
enum
{
	Qok = 0,
	Qquote,
	Qbackslash,
};

static int
needtoquote(Rune r)
{
	if(r >= Runeself)
		return Qquote;
	if(r <= ' ')
		return Qquote;
	if(r=='\\' || r=='"')
		return Qbackslash;
	return Qok;
}

int
doublequote(Fmt *f)
{
	char *s, *t;
	int w, quotes;
	Rune r;

	s = va_arg(f->args, char*);
	if(s == nil || *s == '\0')
		return fmtstrcpy(f, "\"\"");

	quotes = 0;
	for(t=s; *t; t+=w){
		w = chartorune(&r, t);
		quotes |= needtoquote(r);
	}
	if(quotes == 0)
		return fmtstrcpy(f, s);

	fmtrune(f, '"');
	for(t=s; *t; t+=w){
		w = chartorune(&r, t);
		if(needtoquote(r) == Qbackslash)
			fmtrune(f, '\\');
		fmtrune(f, r);
	}
	return fmtrune(f, '"');
}