imapurl.c

/*
 * Copyright (c) 1994-2008 Carnegie Mellon University.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any legal
 *    details, please contact
 *      Carnegie Mellon University
 *      Center for Technology Transfer and Enterprise Creation
 *      4615 Forbes Avenue
 *      Suite 302
 *      Pittsburgh, PA  15213
 *      (412) 268-7393, fax: (412) 268-7395
 *      innovation@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * $Id: imapurl.c,v 1.18 2010/01/06 17:01:45 murch Exp $
 *
 * derived from chris newman's code
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <time.h>

#include "imapurl.h"
#include "xmalloc.h"
#include "times.h"
#include "util.h"

/* URL unsafe printable characters */
static const char urlunsafe[] = " \"#%&+:;<=>?@[\\]^`{|}";

/* UTF7 modified base64 alphabet */
static const char base64chars[] =
  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
#define UNDEFINED 64

/* UTF16 definitions */
#define UTF16MASK       0x03FFUL
#define UTF16SHIFT      10
#define UTF16BASE       0x10000UL
#define UTF16HIGHSTART  0xD800UL
#define UTF16HIGHEND    0xDBFFUL
#define UTF16LOSTART    0xDC00UL
#define UTF16LOEND      0xDFFFUL

/* Convert an IMAP mailbox to a URL path
 *  dst needs to have roughly 4 times the storage space of src
 *    Hex encoding can triple the size of the input
 *    UTF-7 can be slightly denser than UTF-8
 *     (worst case: 8 octets UTF-7 becomes 9 octets UTF-8)
 */
static void MailboxToURL(char *dst, const char *src)
{
    unsigned char c, i, bitcount;
    unsigned long ucs4, utf16, bitbuf;
    unsigned char base64[256], utf8[6];

    /* initialize modified base64 decoding table */
    memset(base64, UNDEFINED, sizeof (base64));
    for (i = 0; i < sizeof (base64chars); ++i) {
        base64[(int) base64chars[i]] = i;
    }

    /* loop until end of string */
    while (*src != '\0') {
        c = *src++;
        /* deal with literal characters and &- */
        if (c != '&' || *src == '-') {
            if (c < ' ' || c > '~' || strchr(urlunsafe, c) != NULL) {
                /* hex encode if necessary */
                *dst++ = '%';
		dst += bin_to_hex(&c, 1, dst, BH_UPPER);
            } else {
                /* encode literally */
                *dst++ = c;
            }
            /* skip over the '-' if this is an &- sequence */
            if (c == '&') ++src;
        } else {
        /* convert modified UTF-7 -> UTF-16 -> UCS-4 -> UTF-8 -> HEX */
            bitbuf = 0;
            bitcount = 0;
            ucs4 = 0;
            while ((c = base64[(unsigned char) *src]) != UNDEFINED) {
                ++src;
                bitbuf = (bitbuf << 6) | c;
                bitcount += 6;
                /* enough bits for a UTF-16 character? */
                if (bitcount >= 16) {
                    bitcount -= 16;
                    utf16 = (bitcount ? bitbuf >> bitcount
                             : bitbuf) & 0xffff;
                    /* convert UTF16 to UCS4 */
                    if
                    (utf16 >= UTF16HIGHSTART && utf16 <= UTF16HIGHEND) {
                        ucs4 = (utf16 - UTF16HIGHSTART) << UTF16SHIFT;
                        continue;
                    } else if
                    (utf16 >= UTF16LOSTART && utf16 <= UTF16LOEND) {
                        ucs4 += utf16 - UTF16LOSTART + UTF16BASE;
                    } else {
                        ucs4 = utf16;
                    }
                    /* convert UTF-16 range of UCS4 to UTF-8 */
                    if (ucs4 <= 0x7fUL) {
                        utf8[0] = ucs4;
                        i = 1;
                    } else if (ucs4 <= 0x7ffUL) {
                        utf8[0] = 0xc0 | (ucs4 >> 6);
                        utf8[1] = 0x80 | (ucs4 & 0x3f);
                        i = 2;
                    } else if (ucs4 <= 0xffffUL) {
                        utf8[0] = 0xe0 | (ucs4 >> 12);
                        utf8[1] = 0x80 | ((ucs4 >> 6) & 0x3f);
                        utf8[2] = 0x80 | (ucs4 & 0x3f);
                        i = 3;
                    } else {
                        utf8[0] = 0xf0 | (ucs4 >> 18);
                        utf8[1] = 0x80 | ((ucs4 >> 12) & 0x3f);
                        utf8[2] = 0x80 | ((ucs4 >> 6) & 0x3f);
                        utf8[3] = 0x80 | (ucs4 & 0x3f);
                        i = 4;
                    }
                    /* convert utf8 to hex.
		     * RFC3986 says: For consistency, URI producers and
		     * normalizers should use uppercase hexadecimal digits
		     * for all percent-encodings. */
		    *dst++ = '%';
		    dst += bin_to_hex(utf8, i, dst, BH_UPPER|BH_SEPARATOR('%'));
                }
            }
            /* skip over trailing '-' in modified UTF-7 encoding */
            if (*src == '-') ++src;
        }
    }
    /* terminate destination string */
    *dst = '\0';
}

/* Convert hex coded UTF-8 URL path to modified UTF-7 IMAP mailbox
 *  dst should be about twice the length of src to deal with non-hex
 *  coded URLs
 */
int URLtoMailbox(char *dst, const char *src)
{
    unsigned char c;
    unsigned int utf8pos = 0, utf8total, utf7mode, bitstogo, utf16flag;
    unsigned long ucs4 = 0, bitbuf = 0;

    utf7mode = 0; /* is the output UTF7 currently in base64 mode? */
    utf8total = 0; /* how many octets is the current input UTF-8 char;
                      0 == between characters */
    bitstogo = 0; /* bits that need to be encoded into base64; if
                     bitstogo != 0 then utf7mode == 1 */
    while ((c = (unsigned char)*src) != '\0') {
        ++src;
        /* undo hex-encoding */
        if (c == '%' && src[0] != '\0' && src[1] != '\0') {
	    if (hex_to_bin(src, 2, &c) != 1)
		return -1;
            src += 2;
        }

        /* normal character? */
        if (c >= ' ' && c <= '~') {
            /* switch out of UTF-7 mode */
            if (utf7mode) {
                if (bitstogo) {
		    *dst++ = base64chars[(bitbuf << (6 - bitstogo)) & 0x3F];
                }
                *dst++ = '-';
                utf7mode = 0;
		bitstogo = bitbuf = 0;
            }
            *dst++ = c;
            /* encode '&' as '&-' */
            if (c == '&') {
                *dst++ = '-';
            }
            continue;
        }

        /* switch to UTF-7 mode */
        if (!utf7mode) {
            *dst++ = '&';
            utf7mode = 1;
        }

        /* Encode US-ASCII characters as themselves */
        if (c < 0x80) {
            ucs4 = c;
            utf8total = 1;
        } else if (utf8total) {
            /* this is a subsequent octet of a multi-octet character */

            /* save UTF8 bits into UCS4 */
            ucs4 = (ucs4 << 6) | (c & 0x3FUL);
            if (++utf8pos < utf8total) {
                continue;
            }
        } else {
            /* this is the first octet of a multi-octet character */

            utf8pos = 1;
            if (c < 0xE0) {
                utf8total = 2;
                ucs4 = c & 0x1F;
            } else if (c < 0xF0) {
                utf8total = 3;
                ucs4 = c & 0x0F;
            } else {
                /* NOTE: can't convert UTF8 sequences longer than 4 */
                utf8total = 4;
                ucs4 = c & 0x03;
            }
            continue;
        }

        /* finished with UTF-8 character. make sure it isn't an
           overlong sequence. if it is, drop that character */
        if ((ucs4 < 0x80 && utf8total > 1) || 
            (ucs4 < 0x0800 && utf8total > 2) ||
            (ucs4 < 0x00010000 && utf8total > 3) ||
            (ucs4 < 0x00200000 && utf8total > 4) ||
            (ucs4 < 0x04000000 && utf8total > 5) ||
            (ucs4 < 0x80000000 && utf8total > 6)) {
            utf8total = 0;
            continue;
        }
        utf8total = 0;

        /* loop to split ucs4 into two utf16 chars if necessary */
        do {
            if (ucs4 >= UTF16BASE) {
                ucs4 -= UTF16BASE;
                bitbuf = (bitbuf << 16) | ((ucs4 >> UTF16SHIFT)
                                           + UTF16HIGHSTART);
                ucs4 = (ucs4 & UTF16MASK) + UTF16LOSTART;
                utf16flag = 1;
            } else {
                bitbuf = (bitbuf << 16) | ucs4;
                utf16flag = 0;
            }
            bitstogo += 16;
            /* spew out base64 */
            while (bitstogo >= 6) {
                bitstogo -= 6;
                *dst++ = base64chars[(bitstogo ? (bitbuf >> bitstogo)
                               : bitbuf)
                                     & 0x3F];
            }
        } while (utf16flag);
    }

    /* if in UTF-7 mode, finish in ASCII */
    if (utf7mode) {
        if (bitstogo) {
            *dst++ = base64chars[(bitbuf << (6 - bitstogo)) & 0x3F];
        }
        *dst++ = '-';
    }

    /* tie off string */
    *dst = '\0';

    return 0;
}

/* Decode hex coded url
 *  dst can be the same location as src,
 *  since the decoded length will be shorter than the encoded length
 */
static int decode_url(char *dst, char *src)
{
    unsigned char c;
    
    while ((c = (unsigned char)*src) != '\0') {
        ++src;
        /* undo hex-encoding */
        if (c == '%' && src[0] != '\0' && src[1] != '\0') {
	    if (hex_to_bin(src, 2, &c) != 1)
		return -1;
            src += 2;
        }
        *dst++ = (char) c;
    }

    /* tie off string */
    *dst = '\0';

    return 0;
}

int imapurl_fromURL(struct imapurl *url, const char *s)
{
    char *src;
    int step = 0;  /* used to force correct ordering of url parts */

    memset(url, 0, sizeof(struct imapurl));
    url->freeme = xmalloc(6 * strlen(s) + 3); /* space for copy of URL +
						 decoded mailbox */
    src = strcpy(url->freeme, s);

    if (src[0] == '{') {	/* c-client style */
	char *se;

	src++;
	se = strchr(src, '}');
	if (se == NULL) return -1;
	*se = '\0';
	url->server = src;
	url->mailbox = se + 1;
    } else { /* IMAP URL */
	int r;
	char *se;
	char *at;
	char *mbox = NULL;
	
	if (!strncmp(src, "imap://", 7)) { /* absolute URL */
	    src += 7; /* skip imap:// */
	    se = strchr(src, '/');
	    if (se == NULL) return -1;
	    at = strchr(src, '@');
	
	    if (at) {
		*at = '\0';
		url->user = src;
		r = decode_url((char *) url->user, (char *) url->user);
		if (r) return r;
		src = at + 1; 
	    }
	    *se = '\0';
	    url->server = src;
	    src = mbox = ++se;
	}
	else { /* relative URL */
	    if (*src == '/') src++;
	    mbox = src;
	}

	/* parse options */
	errno = 0;
	while (src && (src = strchr(src, ';'))) {
	    unsigned long ul;
	    char *endp;

	    if (src[-1] == '/') src[-1] = '\0'; /* trim mailbox at /; */
	    *src++ = '\0'; /* break url at ; */
	    if (step == 0 && !strncasecmp(src, "uidvalidity=", 12)) {
		src += 12; /* skip uidvalidity= */
		ul = strtoul(src, &endp, 10);  /* ends at '/' or '\0' */
		if (errno || endp == src) return -1;
		url->uidvalidity = ul;
		step = 1;
	    }
	    else if (step <= 1 && !strncasecmp(src, "uid=", 4)) {
		src += 4; /* skip uid= */
		ul = strtoul(src, &endp, 10);  /* ends at '/' or '\0' */
		if (errno || endp == src) return -1;
		url->uid = ul;
		step = 2;
	    }
	    else if (step == 2 && !strncasecmp(src, "section=", 8)) {
		src += 8; /* skip section= */
		url->section = src;  /* ends at ';' (next pass) or '\0' */
		step = 3;
	    }
	    else if (step >= 2 && step <= 3 && !strncasecmp(src, "partial=", 8)) {
		src += 8; /* skip partial= */
		ul = strtoul(src, &endp, 10);  /* ends at '.', '/' or '\0' */
		if (errno || endp == src) return -1;
		url->start_octet = ul;
		if (*endp == '.') {
		    src = endp+1; /* skip . */
		    ul = strtoul(src, &endp, 10);  /* ends at '/' or '\0' */
		    if (errno || endp == src) return -1;
		    url->octet_count = ul;
		}
		step = 4;
	    }
	    else if (step >= 2 && step < 5 && !strncasecmp(src, "expire=", 7)) {
		int n;

		src += 7; /* skip expire= */
		n = time_from_iso8601(src, &url->urlauth.expire);
		if (n < 0)
		    return -1;
		src += n;
		step = 5;
	    }
	    else if (step >= 2 && step < 6 && !strncasecmp(src, "urlauth=", 8)) {
		char *u;

		src += 8; /* skip urlauth= */
		url->urlauth.access = src;
		if ((u = strchr(src, ':'))) {
		    url->urlauth.rump_len = (u - url->freeme);

		    *u++ = '\0'; /* break urlauth at : */
		    url->urlauth.mech = u;
		    if ((u = strchr(u, ':'))) {
			*u++ = '\0'; /* break urlauth at : */
			url->urlauth.token = u;
		    }
		    src = u;
		}
		else {
		    url->urlauth.rump_len = strlen(s);
		}
		step = 6;
	    }
	    else {
		return -1;
	    }
	}

	if (mbox && *mbox) {
	    url->mailbox = url->freeme + strlen(s) + 1;
	    return URLtoMailbox((char *)url->mailbox, mbox);
	}
    }
    return 0;
}

void imapurl_toURL(char *dst, struct imapurl *url)
{
    if (url->mailbox) {
	if (url->server) {
	    dst += sprintf(dst, "imap://");
	    if (url->auth) dst += sprintf(dst, ";AUTH=%s@", url->auth);
	    dst += sprintf(dst, "%s", url->server);
	}
	*dst++ = '/';
	MailboxToURL(dst, url->mailbox);
	dst += strlen(dst);
    }
    if (url->uidvalidity)
	dst += sprintf(dst, ";UIDVALIDITY=%lu", url->uidvalidity);
    if (url->uid) {
	dst += sprintf(dst, "/;UID=%lu", url->uid);
	if (url->section) dst += sprintf(dst, "/;SECTION=%s", url->section);
	if (url->start_octet || url->octet_count) {
	    dst += sprintf(dst, "/;PARTIAL=%lu", url->start_octet);
	    if (url->octet_count) dst += sprintf(dst, ".%lu", url->octet_count);
	}
    }
    if (url->urlauth.access) {
	if (url->urlauth.expire) {
	    strcpy(dst, ";EXPIRE=");
	    dst += strlen(dst);
	    dst += time_to_iso8601(url->urlauth.expire, dst, INT_MAX);
	}
	dst += sprintf(dst, ";URLAUTH=%s", url->urlauth.access);
	if (url->urlauth.mech) {
	    dst += sprintf(dst, ":%s", url->urlauth.mech);
	    if (url->urlauth.token) dst += sprintf(dst, ":%s", url->urlauth.token);
	}
    }
}