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

#include "common.h"
#include <ctype.h>
#include <plumb.h>
#include <libsec.h>
#include <auth.h>
#include "dat.h"

#pragma varargck argpos imap4cmd 2
#pragma varargck	type	"Z"	char*

int	doublequote(Fmt*);
int	pipeline = 1;

static char Eio[] = "i/o error";

typedef struct Imap Imap;
struct Imap {
	char *freep;	// free this to free the strings below

	char *host;
	char *user;
	char *mbox;

	int mustssl;
	int refreshtime;
	int debug;

	ulong tag;
	ulong validity;
	int nmsg;
	int size;
	char *base;
	char *data;

	vlong *uid;
	int nuid;
	int muid;

	Thumbprint *thumb;

	// open network connection
	Biobuf bin;
	Biobuf bout;
	int fd;
};

static char*
removecr(char *s)
{
	char *r, *w;

	for(r=w=s; *r; r++)
		if(*r != '\r')
			*w++ = *r;
	*w = '\0';
	return s;
}

//
// send imap4 command
//
static void
imap4cmd(Imap *imap, char *fmt, ...)
{
	char buf[128], *p;
	va_list va;

	va_start(va, fmt);
	p = buf+sprint(buf, "9X%lud ", imap->tag);
	vseprint(p, buf+sizeof(buf), fmt, va);
	va_end(va);

	p = buf+strlen(buf);
	if(p > (buf+sizeof(buf)-3))
		sysfatal("imap4 command too long");

	if(imap->debug)
		fprint(2, "-> %s\n", buf);
	strcpy(p, "\r\n");
	Bwrite(&imap->bout, buf, strlen(buf));
	Bflush(&imap->bout);
}

enum {
	OK,
	NO,
	BAD,
	BYE,
	EXISTS,
	STATUS,
	FETCH,
	UNKNOWN,
};

static char *verblist[] = {
[OK]		"OK",
[NO]		"NO",
[BAD]	"BAD",
[BYE]	"BYE",
[EXISTS]	"EXISTS",
[STATUS]	"STATUS",
[FETCH]	"FETCH",
};

static int
verbcode(char *verb)
{
	int i;
	char *q;

	if(q = strchr(verb, ' '))
		*q = '\0';

	for(i=0; i<nelem(verblist); i++)
		if(verblist[i] && strcmp(verblist[i], verb)==0){
			if(q)
				*q = ' ';
			return i;
		}
	if(q)
		*q = ' ';
	return UNKNOWN;
}

static void
strupr(char *s)
{
	for(; *s; s++)
		if('a' <= *s && *s <= 'z')
			*s += 'A'-'a';
}

static void
imapgrow(Imap *imap, int n)
{
	int i;

	if(imap->data == nil){
		imap->base = emalloc(n+1);	
		imap->data = imap->base;
		imap->size = n+1;
	}
	if(n >= imap->size){
		// friggin microsoft - reallocate
		i = imap->data - imap->base;
		imap->base = erealloc(imap->base, i+n+1);
		imap->data = imap->base + i;
		imap->size = n+1;
	}
}


//
// get imap4 response line.  there might be various 
// data or other informational lines mixed in.
//
static char*
imap4resp(Imap *imap)
{
	char *line, *p, *ep, *op, *q, *r, *en, *verb;
	int i, n;
	static char error[256];

	while(p = Brdline(&imap->bin, '\n')){
		ep = p+Blinelen(&imap->bin);
		while(ep > p && (ep[-1]=='\n' || ep[-1]=='\r'))
			*--ep = '\0';
		
		if(imap->debug)
			fprint(2, "<- %s\n", p);
		strupr(p);

		switch(p[0]){
		case '+':
			if(imap->tag == 0)
				fprint(2, "unexpected: %s\n", p);
			break;

		// ``unsolicited'' information; everything happens here.
		case '*':
			if(p[1]!=' ')
				continue;
			p += 2;
			line = p;
			n = strtol(p, &p, 10);
			if(*p==' ')
				p++;
			verb = p;
			
			if(p = strchr(verb, ' '))
				p++;
			else
				p = verb+strlen(verb);

			switch(verbcode(verb)){
			case OK:
			case NO:
			case BAD:
				// human readable text at p;
				break;
			case BYE:
				// early disconnect
				// human readable text at p;
				break;

			// * 32 EXISTS
			case EXISTS:
				imap->nmsg = n;
				break;

			// * STATUS Inbox (MESSAGES 2 UIDVALIDITY 960164964)
			case STATUS:
				if(q = strstr(p, "MESSAGES"))
					imap->nmsg = atoi(q+8);
				if(q = strstr(p, "UIDVALIDITY"))
					imap->validity = strtoul(q+11, 0, 10);
				break;

			case FETCH:
				// * 1 FETCH (uid 8889 RFC822.SIZE 3031 body[] {3031}
				// <3031 bytes of data>
 				// )
				if(strstr(p, "RFC822.SIZE") && strstr(p, "BODY[]")){
					if((q = strchr(p, '{')) 
					&& (n=strtol(q+1, &en, 0), *en=='}')){
						if(imap->data == nil || n >= imap->size)
							imapgrow(imap, n);
						if((i = Bread(&imap->bin, imap->data, n)) != n){
							snprint(error, sizeof error,
								"short read %d != %d: %r\n",
								i, n);
							return error;
						}
						if(imap->debug)
							fprint(2, "<- read %d bytes\n", n);
						imap->data[n] = '\0';
						if(imap->debug)
							fprint(2, "<- %s\n", imap->data);
						imap->data += n;
						imap->size -= n;
						p = Brdline(&imap->bin, '\n');
						if(imap->debug)
							fprint(2, "<- ignoring %.*s\n",
								Blinelen(&imap->bin), p);
					}else if((q = strchr(p, '"')) && (r = strchr(q+1, '"'))){
						*r = '\0';
						q++;
						n = r-q;
						if(imap->data == nil || n >= imap->size)
							imapgrow(imap, n);
						memmove(imap->data, q, n);
						imap->data[n] = '\0';
						imap->data += n;
						imap->size -= n;
					}else
						return "confused about FETCH response";
					break;
				}

				// * 1 FETCH (UID 1 RFC822.SIZE 511)
				if(q=strstr(p, "RFC822.SIZE")){
					imap->size = atoi(q+11);
					break;
				}

				// * 1 FETCH (UID 1 RFC822.HEADER {496}
				// <496 bytes of data>
 				// )
				// * 1 FETCH (UID 1 RFC822.HEADER "data")
				if(strstr(p, "RFC822.HEADER") || strstr(p, "RFC822.TEXT")){
					if((q = strchr(p, '{')) 
					&& (n=strtol(q+1, &en, 0), *en=='}')){
						if(imap->data == nil || n >= imap->size)
							imapgrow(imap, n);
						if((i = Bread(&imap->bin, imap->data, n)) != n){
							snprint(error, sizeof error,
								"short read %d != %d: %r\n",
								i, n);
							return error;
						}
						if(imap->debug)
							fprint(2, "<- read %d bytes\n", n);
						imap->data[n] = '\0';
						if(imap->debug)
							fprint(2, "<- %s\n", imap->data);
						imap->data += n;
						imap->size -= n;
						p = Brdline(&imap->bin, '\n');
						if(imap->debug)
							fprint(2, "<- ignoring %.*s\n",
								Blinelen(&imap->bin), p);
					}else if((q = strchr(p, '"')) && (r = strchr(q+1, '"'))){
						*r = '\0';
						q++;
						n = r-q;
						if(imap->data == nil || n >= imap->size)
							imapgrow(imap, n);
						memmove(imap->data, q, n);
						imap->data[n] = '\0';
						imap->data += n;
						imap->size -= n;
					}else
						return "confused about FETCH response";
					break;
				}

				// * 1 FETCH (UID 1)
				// * 2 FETCH (UID 6)
				if(q = strstr(p, "UID")){
					if(imap->nuid < imap->muid)
						imap->uid[imap->nuid++] = ((vlong)imap->validity<<32)|strtoul(q+3, nil, 10);
					break;
				}
			}

			if(imap->tag == 0)
				return line;
			break;

		case '9':		// response to our message
			op = p;
			if(p[1]=='X' && strtoul(p+2, &p, 10)==imap->tag){
				while(*p==' ')
					p++;
				imap->tag++;
				return p;
			}
			fprint(2, "expected %lud; got %s\n", imap->tag, op);
			break;

		default:
			if(imap->debug || *p)
				fprint(2, "unexpected line: %s\n", p);
		}
	}
	snprint(error, sizeof error, "i/o error: %r\n");
	return error;
}

static int
isokay(char *resp)
{
	return strncmp(resp, "OK", 2)==0;
}

//
// log in to IMAP4 server, select mailbox, no SSL at the moment
//
static char*
imap4login(Imap *imap)
{
	char *s;
	UserPasswd *up;

	imap->tag = 0;
	s = imap4resp(imap);
	if(!isokay(s))
		return "error in initial IMAP handshake";

	if(imap->user != nil)
		up = auth_getuserpasswd(auth_getkey, "proto=pass service=imap server=%q user=%q", imap->host, imap->user);
	else
		up = auth_getuserpasswd(auth_getkey, "proto=pass service=imap server=%q", imap->host);
	if(up == nil)
		return "cannot find IMAP password";

	imap->tag = 1;
	imap4cmd(imap, "LOGIN %Z %Z", up->user, up->passwd);
	free(up);
	if(!isokay(s = imap4resp(imap)))
		return s;

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

	return nil;
}

//
// push tls onto a connection
//
int
mypushtls(int fd)
{
	int p[2];
	char buf[10];

	if(pipe(p) < 0)
		return -1;

	switch(fork()){
	case -1:
		close(p[0]);
		close(p[1]);
		return -1;
	case 0:
		close(p[1]);
		dup(p[0], 0);
		dup(p[0], 1);
		sprint(buf, "/fd/%d", fd);
		execl("/bin/tlsrelay", "tlsrelay", "-f", buf, nil);
		_exits(nil);
	default:
		break;
	}
	close(fd);
	close(p[0]);
	return p[1];
}

//
// dial and handshake with the imap server
//
static char*
imap4dial(Imap *imap)
{
	char *err, *port;
	uchar digest[SHA1dlen];
	int sfd;
	TLSconn conn;

	if(imap->fd >= 0){
		imap4cmd(imap, "noop");
		if(isokay(imap4resp(imap)))
			return nil;
		close(imap->fd);
		imap->fd = -1;
	}

	if(imap->mustssl)
		port = "imaps";
	else
		port = "imap";

	if((imap->fd = dial(netmkaddr(imap->host, "net", port), 0, 0, 0)) < 0)
		return geterrstr();