freebsd-nq/lib/libfetch/http.c

/*-
 * Copyright (c) 2000 Dag-Erling Coïdan Smørgrav
 * 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
 *    in this position and unchanged.
 * 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 of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

/*
 * The following copyright applies to the base64 code:
 *
 *-
 * Copyright 1997 Massachusetts Institute of Technology
 *
 * Permission to use, copy, modify, and distribute this software and
 * its documentation for any purpose and without fee is hereby
 * granted, provided that both the above copyright notice and this
 * permission notice appear in all copies, that both the above
 * copyright notice and this permission notice appear in all
 * supporting documentation, and that the name of M.I.T. not be used
 * in advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.  M.I.T. makes
 * no representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied
 * warranty.
 *
 * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''.  M.I.T. DISCLAIMS
 * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
 * SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/socket.h>

#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <locale.h>
#include <netdb.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include "fetch.h"
#include "common.h"
#include "httperr.h"

/* Maximum number of redirects to follow */
#define MAX_REDIRECT 5

/* Symbolic names for reply codes we care about */
#define HTTP_OK			200
#define HTTP_PARTIAL		206
#define HTTP_MOVED_PERM		301
#define HTTP_MOVED_TEMP		302
#define HTTP_SEE_OTHER		303
#define HTTP_NEED_AUTH		401
#define HTTP_NEED_PROXY_AUTH	407
#define HTTP_PROTOCOL_ERROR	999

#define HTTP_REDIRECT(xyz) ((xyz) == HTTP_MOVED_PERM \
			    || (xyz) == HTTP_MOVED_TEMP \
			    || (xyz) == HTTP_SEE_OTHER)

#define HTTP_ERROR(xyz) ((xyz) > 400 && (xyz) < 599)


/*****************************************************************************
 * I/O functions for decoding chunked streams
 */

struct cookie
{
	int		 fd;
	char		*buf;
	size_t		 b_size;
	ssize_t		 b_len;
	int		 b_pos;
	int		 eof;
	int		 error;
	size_t		 chunksize;
#ifndef NDEBUG
	size_t		 total;
#endif
};

/*
 * Get next chunk header
 */
static int
_http_new_chunk(struct cookie *c)
{
	char *p;

	if (_fetch_getln(c->fd, &c->buf, &c->b_size, &c->b_len) == -1)
		return (-1);

	if (c->b_len < 2 || !ishexnumber(*c->buf))
		return (-1);

	for (p = c->buf; !isspace(*p) && p < c->buf + c->b_len; ++p) {
		if (*p == ';')
			break;
		if (!ishexnumber(*p))
			return (-1);
		if (isdigit(*p)) {
			c->chunksize = c->chunksize * 16 +
			    *p - '0';
		} else {
			c->chunksize = c->chunksize * 16 +
			    10 + tolower(*p) - 'a';
		}
	}

#ifndef NDEBUG
	if (fetchDebug) {
		c->total += c->chunksize;
		if (c->chunksize == 0)
			fprintf(stderr, "_http_fillbuf(): "
			    "end of last chunk\n");
		else
			fprintf(stderr, "_http_fillbuf(): "
			    "new chunk: %lu (%lu)\n",
			    (unsigned long)c->chunksize, (unsigned long)c->total);
	}
#endif

	return (c->chunksize);
}

/*
 * Fill the input buffer, do chunk decoding on the fly
 */
static int
_http_fillbuf(struct cookie *c)
{
	if (c->error)
		return (-1);
	if (c->eof)
		return (0);

	if (c->chunksize == 0) {
		switch (_http_new_chunk(c)) {
		case -1:
			c->error = 1;
			return (-1);
		case 0:
			c->eof = 1;
			return (0);
		}
	}

	if (c->b_size < c->chunksize) {
		char *tmp;

		if ((tmp = realloc(c->buf, c->chunksize)) == NULL)
			return (-1);
		c->buf = tmp;
		c->b_size = c->chunksize;
	}

	if ((c->b_len = read(c->fd, c->buf, c->chunksize)) == -1)
		return (-1);
	c->chunksize -= c->b_len;

	if (c->chunksize == 0) {
		char endl;
		if (read(c->fd, &endl, 1) == -1 ||
		    read(c->fd, &endl, 1) == -1)
			return (-1);
	}

	c->b_pos = 0;

	return (c->b_len);
}

/*
 * Read function
 */
static int
_http_readfn(void *v, char *buf, int len)
{
	struct cookie *c = (struct cookie *)v;
	int l, pos;

	if (c->error)
		return (-1);
	if (c->eof)
		return (0);

	for (pos = 0; len > 0; pos += l, len -= l) {
		/* empty buffer */
		if (!c->buf || c->b_pos == c->b_len)
			if (_http_fillbuf(c) < 1)
				break;
		l = c->b_len - c->b_pos;
		if (len < l)
			l = len;
		bcopy(c->buf + c->b_pos, buf + pos, l);
		c->b_pos += l;
	}

	if (!pos && c->error)
		return (-1);
	return (pos);
}

/*
 * Write function
 */
static int
_http_writefn(void *v, const char *buf, int len)
{
	struct cookie *c = (struct cookie *)v;

	return (write(c->fd, buf, len));
}

/*
 * Close function
 */
static int
_http_closefn(void *v)
{
	struct cookie *c = (struct cookie *)v;
	int r;

	r = close(c->fd);
	if (c->buf)
		free(c->buf);
	free(c);
	return (r);
}

/*
 * Wrap a file descriptor up
 */
static FILE *
_http_funopen(int fd)
{
	struct cookie *c;
	FILE *f;

	if ((c = calloc(1, sizeof *c)) == NULL) {
		_fetch_syserr();
		return (NULL);
	}
	c->fd = fd;
	f = funopen(c, _http_readfn, _http_writefn, NULL, _http_closefn);
	if (f == NULL) {
		_fetch_syserr();
		free(c);
		return (NULL);
	}
	return (f);
}


/*****************************************************************************
 * Helper functions for talking to the server and parsing its replies
 */

/* Header types */
typedef enum {
	hdr_syserror = -2,
	hdr_error = -1,
	hdr_end = 0,
	hdr_unknown = 1,
	hdr_content_length,
	hdr_content_range,
	hdr_last_modified,
	hdr_location,
	hdr_transfer_encoding,
	hdr_www_authenticate
} hdr_t;

/* Names of interesting headers */
static struct {
	hdr_t		 num;
	const char	*name;
} hdr_names[] = {
	{ hdr_content_length,		"Content-Length" },
	{ hdr_content_range,		"Content-Range" },
	{ hdr_last_modified,		"Last-Modified" },
	{ hdr_location,			"Location" },
	{ hdr_transfer_encoding,	"Transfer-Encoding" },
	{ hdr_www_authenticate,		"WWW-Authenticate" },
	{ hdr_unknown,			NULL },
};

static char		*reply_buf;
static size_t		 reply_size;
static size_t		 reply_length;

/*
 * Send a formatted line; optionally echo to terminal
 */
static int
_http_cmd(int fd, const char *fmt, ...)
{
	va_list ap;
	size_t len;
	char *msg;
	int r;

	va_start(ap, fmt);
	len = vasprintf(&msg, fmt, ap);
	va_end(ap);

	if (msg == NULL) {
		errno = ENOMEM;
		_fetch_syserr();
		return (-1);
	}

	r = _fetch_putln(fd, msg, len);
	free(msg);

	if (r == -1) {
		_fetch_syserr();
		return (-1);
	}

	return (0);
}

/*
 * Get and parse status line
 */
static int
_http_get_reply(int fd)
{
	char *p;

	if (_fetch_getln(fd, &reply_buf, &reply_size, &reply_length) == -1)
		return (-1);
	/*
	 * A valid status line looks like "HTTP/m.n xyz reason" where m
	 * and n are the major and minor protocol version numbers and xyz
	 * is the reply code.
	 * Unfortunately, there are servers out there (NCSA 1.5.1, to name
	 * just one) that do not send a version number, so we can't rely
	 * on finding one, but if we do, insist on it being 1.0 or 1.1.
	 * We don't care about the reason phrase.
	 */
	if (strncmp(reply_buf, "HTTP", 4) != 0)
		return (HTTP_PROTOCOL_ERROR);
	p = reply_buf + 4;
	if (*p == '/') {
		if (p[1] != '1' || p[2] != '.' || (p[3] != '0' && p[3] != '1'))
			return (HTTP_PROTOCOL_ERROR);
		p += 4;
	}
	if (*p != ' ' || !isdigit(p[1]) || !isdigit(p[2]) || !isdigit(p[3]))
		return (HTTP_PROTOCOL_ERROR);

	return ((p[1] - '0') * 100 + (p[2] - '0') * 10 + (p[3] - '0'));
}

/*
 * Check a header; if the type matches the given string, return a pointer
 * to the beginning of the value.
 */
static const char *
_http_match(const char *str, const char *hdr)
{
	while (*str && *hdr && tolower(*str++) == tolower(*hdr++))
		/* nothing */;
	if (*str || *hdr != ':')
		return (NULL);
	while (*hdr && isspace(*++hdr))
		/* nothing */;
	return (hdr);
}

/*
 * Get the next header and return the appropriate symbolic code.
 */
static hdr_t
_http_next_header(int fd, const char **p)
{
	int i;

	if (_fetch_getln(fd, &reply_buf, &reply_size, &reply_length) == -1)
		return (hdr_syserror);
	while (reply_length && isspace(reply_buf[reply_length-1]))
		reply_length--;
	reply_buf[reply_length] = 0;
	if (reply_length == 0)
	return (hdr_end);
	/*
	 * We could check for malformed headers but we don't really care.
	 * A valid header starts with a token immediately followed by a
	 * colon; a token is any sequence of non-control, non-whitespace
	 * characters except "()<>@,;:\\\"{}".
	 */
	for (i = 0; hdr_names[i].num != hdr_unknown; i++)
		if ((*p = _http_match(hdr_names[i].name, reply_buf)) != NULL)
			return (hdr_names[i].num);
	return (hdr_unknown);
}

/*
 * Parse a last-modified header
 */
static int
_http_parse_mtime(const char *p, time_t *mtime)
{
	char locale[64], *r;
	struct tm tm;

	strncpy(locale, setlocale(LC_TIME, NULL), sizeof locale);
	setlocale(LC_TIME, "C");
	r = strptime(p, "%a, %d %b %Y %H:%M:%S GMT", &tm);
	/* XXX should add support for date-2 and date-3 */
	setlocale(LC_TIME, locale);
	if (r == NULL)
		return (-1);
	DEBUG(fprintf(stderr, "last modified: [%04d-%02d-%02d "
		  "%02d:%02d:%02d]\n",
		  tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
		  tm.tm_hour, tm.tm_min, tm.tm_sec));
	*mtime = timegm(&tm);
	return (0);
}

/*
 * Parse a content-length header
 */
static int
_http_parse_length(const char *p, off_t *length)
{
	off_t len;

	for (len = 0; *p && isdigit(*p); ++p)
		len = len * 10 + (*p - '0');
	if (*p)
		return (-1);
	DEBUG(fprintf(stderr, "content length: [%lld]\n",
	    (long long)len));
	*length = len;
	return (0);
}

/*
 * Parse a content-range header
 */
static int
_http_parse_range(const char *p, off_t *offset, off_t *length, off_t *size)
{
	off_t first, last, len;

	if (strncasecmp(p, "bytes ", 6) != 0)
		return (-1);
	for (first = 0, p += 6; *p && isdigit(*p); ++p)
		first = first * 10 + *p - '0';
	if (*p != '-')
		return (-1);
	for (last = 0, ++p; *p && isdigit(*p); ++p)
		last = last * 10 + *p - '0';
	if (first > last || *p != '/')
		return (-1);
	for (len = 0, ++p; *p && isdigit(*p); ++p)
		len = len * 10 + *p - '0';
	if (*p || len < last - first + 1)
		return (-1);
	DEBUG(fprintf(stderr, "content range: [%lld-%lld/%lld]\n",
	    (long long)first, (long long)last, (long long)len));
	*offset = first;
	*length = last - first + 1;
	*size = len;
	return (0);
}


/*****************************************************************************
 * Helper functions for authorization
 */

/*
 * Base64 encoding
 */
static char *
_http_base64(const char *src)
{
	static const char base64[] =
	    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
	    "abcdefghijklmnopqrstuvwxyz"
	    "0123456789+/";
	char *str, *dst;
	size_t l;
	int t, r;

	l = strlen(src);
	if ((str = malloc(((l + 2) / 3) * 4)) == NULL)
		return (NULL);
	dst = str;
	r = 0;

	while (l >= 3) {
		t = (src[0] << 16) | (src[1] << 8) | src[2];
		dst[0] = base64[(t >> 18) & 0x3f];
		dst[1] = base64[(t >> 12) & 0x3f];
		dst[2] = base64[(t >> 6) & 0x3f];
		dst[3] = base64[(t >> 0) & 0x3f];
		src += 3; l -= 3;
		dst += 4; r += 4;
	}

	switch (l) {
	case 2:
		t = (src[0] << 16) | (src[1] << 8);
		dst[0] = base64[(t >> 18) & 0x3f];
		dst[1] = base64[(t >> 12) & 0x3f];
		dst[2] = base64[(t >> 6) & 0x3f];
		dst[3] = '=';
		dst += 4;
		r += 4;
		break;
	case 1:
		t = src[0] << 16;
		dst[0] = base64[(t >> 18) & 0x3f];
		dst[1] = base64[(t >> 12) & 0x3f];
		dst[2] = dst[3] = '=';
		dst += 4;
		r += 4;
		break;
	case 0:
		break;
	}

	*dst = 0;
	return (str);
}

/*
 * Encode username and password
 */
static int
_http_basic_auth(int fd, const char *hdr, const char *usr, const char *pwd)
{
	char *upw, *auth;
	int r;

	DEBUG(fprintf(stderr, "usr: [%s]\n", usr));
	DEBUG(fprintf(stderr, "pwd: [%s]\n", pwd));
	if (asprintf(&upw, "%s:%s", usr, pwd) == -1)
		return (-1);
	auth = _http_base64(upw);
	free(upw);
	if (auth == NULL)
		return (-1);
	r = _http_cmd(fd, "%s: Basic %s", hdr, auth);
	free(auth);
	return (r);
}

/*
 * Send an authorization header
 */
static int
_http_authorize(int fd, const char *hdr, const char *p)
{
	/* basic authorization */
	if (strncasecmp(p, "basic:", 6) == 0) {
		char *user, *pwd, *str;
		int r;

		/* skip realm */
		for (p += 6; *p && *p != ':'; ++p)
			/* nothing */ ;
		if (!*p || strchr(++p, ':') == NULL)
			return (-1);
		if ((str = strdup(p)) == NULL)
			return (-1); /* XXX */
		user = str;
		pwd = strchr(str, ':');
		*pwd++ = '\0';
		r = _http_basic_auth(fd, hdr, user, pwd);
		free(str);
		return (r);
	}
	return (-1);
}


/*****************************************************************************
 * Helper functions for connecting to a server or proxy
 */

/*
 * Connect to the correct HTTP server or proxy.
 */
static int
_http_connect(struct url *URL, struct url *purl, const char *flags)
{
	int verbose;
	int af, fd;

#ifdef INET6
	af = AF_UNSPEC;
#else
	af = AF_INET;
#endif

	verbose = CHECK_FLAG('v');
	if (CHECK_FLAG('4'))
		af = AF_INET;
#ifdef INET6
	else if (CHECK_FLAG('6'))
		af = AF_INET6;
#endif

	if (purl) {
		URL = purl;
	} else if (strcasecmp(URL->scheme, SCHEME_FTP) == 0) {
		/* can't talk http to an ftp server */
		/* XXX should set an error code */
		return (-1);
	}

	if ((fd = _fetch_connect(URL->host, URL->port, af, verbose)) == -1)
		/* _fetch_connect() has already set an error code */
		return (-1);
	return (fd);
}

static struct url *
_http_get_proxy(void)
{
	struct url *purl;
	char *p;

	if (((p = getenv("HTTP_PROXY")) || (p = getenv("http_proxy"))) &&
	    (purl = fetchParseURL(p))) {
		if (!*purl->scheme)
			strcpy(purl->scheme, SCHEME_HTTP);
		if (!purl->port)
			purl->port = _fetch_default_proxy_port(purl->scheme);
		if (strcasecmp(purl->scheme, SCHEME_HTTP) == 0)
			return (purl);
		fetchFreeURL(purl);
	}
	return (NULL);
}

static void
_http_print_html(FILE *out, FILE *in)
{
	size_t len;
	char *line, *p, *q;
	int comment, tag;

	comment = tag = 0;
	while ((line = fgetln(in, &len)) != NULL) {
		while (len && isspace(line[len - 1]))
			--len;
		for (p = q = line; q < line + len; ++q) {
			if (comment && *q == '-') {
				if (q + 2 < line + len &&
				    strcmp(q, "-->") == 0) {
					tag = comment = 0;
					q += 2;
				}
			} else if (tag && !comment && *q == '>') {
				p = q + 1;
				tag = 0;
			} else if (!tag && *q == '<') {
				if (q > p)
					fwrite(p, q - p, 1, out);
				tag = 1;
				if (q + 3 < line + len &&
				    strcmp(q, "<!--") == 0) {
					comment = 1;
					q += 3;
				}
			}
		}
		if (!tag && q > p)
			fwrite(p, q - p, 1, out);
		fputc('\n', out);
	}
}


/*****************************************************************************
 * Core
 */

/*
 * Send a request and process the reply
 */
FILE *
_http_request(struct url *URL, const char *op, struct url_stat *us,
    struct url *purl, const char *flags)
{
	struct url *url, *new;
	int chunked, direct, need_auth, noredirect, verbose;
	int code, fd, i, n;
	off_t offset, clength, length, size;
	time_t mtime;
	const char *p;
	FILE *f;
	hdr_t h;
	char *host;
#ifdef INET6
	char hbuf[MAXHOSTNAMELEN + 1];
#endif

	direct = CHECK_FLAG('d');
	noredirect = CHECK_FLAG('A');
	verbose = CHECK_FLAG('v');

	if (direct && purl) {
		fetchFreeURL(purl);
		purl = NULL;
	}

	/* try the provided URL first */
	url = URL;

	/* if the A flag is set, we only get one try */
	n = noredirect ? 1 : MAX_REDIRECT;
	i = 0;

	need_auth = 0;
	do {
		new = NULL;
		chunked = 0;
		offset = 0;
		clength = -1;
		length = -1;
		size = -1;
		mtime = 0;

		/* check port */
		if (!url->port)
			url->port = _fetch_default_port(url->scheme);

		/* were we redirected to an FTP URL? */
		if (purl == NULL && strcmp(url->scheme, SCHEME_FTP) == 0) {
			if (strcmp(op, "GET") == 0)
				return (_ftp_request(url, "RETR", us, purl, flags));
			else if (strcmp(op, "HEAD") == 0)
				return (_ftp_request(url, "STAT", us, purl, flags));
		}

		/* connect to server or proxy */
		if ((fd = _http_connect(url, purl, flags)) == -1)
			goto ouch;

		host = url->host;
#ifdef INET6
		if (strchr(url->host, ':')) {
			snprintf(hbuf, sizeof(hbuf), "[%s]", url->host);
			host = hbuf;
		}
#endif

		/* send request */
		if (verbose)
			_fetch_info("requesting %s://%s:%d%s",
			    url->scheme, host, url->port, url->doc);
		if (purl) {
			_http_cmd(fd, "%s %s://%s:%d%s HTTP/1.1",
			    op, url->scheme, host, url->port, url->doc);
		} else {
			_http_cmd(fd, "%s %s HTTP/1.1",
			    op, url->doc);
		}

		/* virtual host */
		if (url->port == _fetch_default_port(url->scheme))
			_http_cmd(fd, "Host: %s", host);
		else
			_http_cmd(fd, "Host: %s:%d", host, url->port);

		/* proxy authorization */
		if (purl) {
			if (*purl->user || *purl->pwd)
				_http_basic_auth(fd, "Proxy-Authorization",
				    purl->user, purl->pwd);
			else if ((p = getenv("HTTP_PROXY_AUTH")) != NULL && *p != '\0')
				_http_authorize(fd, "Proxy-Authorization", p);
		}

		/* server authorization */
		if (need_auth || *url->user || *url->pwd) {
			if (*url->user || *url->pwd)
				_http_basic_auth(fd, "Authorization", url->user, url->pwd);
			else if ((p = getenv("HTTP_AUTH")) != NULL && *p != '\0')
				_http_authorize(fd, "Authorization", p);
			else if (fetchAuthMethod && fetchAuthMethod(url) == 0) {
				_http_basic_auth(fd, "Authorization", url->user, url->pwd);
			} else {
				_http_seterr(HTTP_NEED_AUTH);
				goto ouch;
			}
		}

		/* other headers */
		if ((p = getenv("HTTP_USER_AGENT")) != NULL && *p != '\0')
			_http_cmd(fd, "User-Agent: %s", p);
		else
			_http_cmd(fd, "User-Agent: %s " _LIBFETCH_VER, _getprogname());
		if (url->offset)
			_http_cmd(fd, "Range: bytes=%lld-", (long long)url->offset);
		_http_cmd(fd, "Connection: close");
		_http_cmd(fd, "");

		/* get reply */
		switch ((code = _http_get_reply(fd))) {
		case HTTP_OK:
		case HTTP_PARTIAL:
			/* fine */
			break;
		case HTTP_MOVED_PERM:
		case HTTP_MOVED_TEMP:
		case HTTP_SEE_OTHER:
			/*
			 * Not so fine, but we still have to read the headers to
			 * get the new location.
			 */
			break;
		case HTTP_NEED_AUTH:
			if (need_auth) {
				/*
				 * We already sent out authorization code, so there's
				 * nothing more we can do.
				 */
				_http_seterr(code);
				goto ouch;
			}
			/* try again, but send the password this time */
			if (verbose)
				_fetch_info("server requires authorization");
			break;
		case HTTP_NEED_PROXY_AUTH:
			/*
			 * If we're talking to a proxy, we already sent our proxy
			 * authorization code, so there's nothing more we can do.
			 */
			_http_seterr(code);
			goto ouch;
		case HTTP_PROTOCOL_ERROR:
			/* fall through */
		case -1:
			_fetch_syserr();
			goto ouch;
		default:
			_http_seterr(code);
			if (!verbose)
				goto ouch;
			/* fall through so we can get the full error message */
		}

		/* get headers */
		do {
			switch ((h = _http_next_header(fd, &p))) {
			case hdr_syserror:
				_fetch_syserr();
				goto ouch;
			case hdr_error:
				_http_seterr(HTTP_PROTOCOL_ERROR);
				goto ouch;
			case hdr_content_length:
				_http_parse_length(p, &clength);
				break;
			case hdr_content_range:
				_http_parse_range(p, &offset, &length, &size);
				break;
			case hdr_last_modified:
				_http_parse_mtime(p, &mtime);
				break;
			case hdr_location:
				if (!HTTP_REDIRECT(code))
					break;
				if (new)
					free(new);
				if (verbose)
					_fetch_info("%d redirect to %s", code, p);
				if (*p == '/')
					/* absolute path */
					new = fetchMakeURL(url->scheme, url->host, url->port, p,
					    url->user, url->pwd);
				else
					new = fetchParseURL(p);
				if (new == NULL) {
					/* XXX should set an error code */
					DEBUG(fprintf(stderr, "failed to parse new URL\n"));
					goto ouch;
				}
				if (!*new->user && !*new->pwd) {
					strcpy(new->user, url->user);
					strcpy(new->pwd, url->pwd);
				}
				new->offset = url->offset;
				new->length = url->length;
				break;
			case hdr_transfer_encoding:
				/* XXX weak test*/
				chunked = (strcasecmp(p, "chunked") == 0);
				break;
			case hdr_www_authenticate:
				if (code != HTTP_NEED_AUTH)
					break;
				/* if we were smarter, we'd check the method and realm */
				break;
			case hdr_end:
				/* fall through */
			case hdr_unknown:
				/* ignore */
				break;
			}
		} while (h > hdr_end);

		/* we have a hit or an error */
		if (code == HTTP_OK || code == HTTP_PARTIAL || HTTP_ERROR(code))
			break;

		/* we need to provide authentication */
		if (code == HTTP_NEED_AUTH) {
			need_auth = 1;
			close(fd);
			fd = -1;
			continue;
		}

		/* all other cases: we got a redirect */
		need_auth = 0;
		close(fd);
		fd = -1;
		if (!new) {
			DEBUG(fprintf(stderr, "redirect with no new location\n"));
			break;
		}
		if (url != URL)
			fetchFreeURL(url);
		url = new;
	} while (++i < n);

	/* we failed, or ran out of retries */
	if (fd == -1) {
		_http_seterr(code);
		goto ouch;
	}

	DEBUG(fprintf(stderr, "offset %lld, length %lld,"
		  " size %lld, clength %lld\n",
		  (long long)offset, (long long)length,
		  (long long)size, (long long)clength));

	/* check for inconsistencies */
	if (clength != -1 && length != -1 && clength != length) {
		_http_seterr(HTTP_PROTOCOL_ERROR);
		goto ouch;
	}
	if (clength == -1)
		clength = length;
	if (clength != -1)
		length = offset + clength;
	if (length != -1 && size != -1 && length != size) {
		_http_seterr(HTTP_PROTOCOL_ERROR);
		goto ouch;
	}
	if (size == -1)
		size = length;

	/* fill in stats */
	if (us) {
		us->size = size;
		us->atime = us->mtime = mtime;
	}

	/* too far? */
	if (offset > URL->offset) {
		_http_seterr(HTTP_PROTOCOL_ERROR);
		goto ouch;
	}

	/* report back real offset and size */
	URL->offset = offset;
	URL->length = clength;

	/* wrap it up in a FILE */
	if ((f = chunked ? _http_funopen(fd) : fdopen(fd, "r")) == NULL) {
		_fetch_syserr();
		goto ouch;
	}

	if (url != URL)
		fetchFreeURL(url);
	if (purl)
		fetchFreeURL(purl);

	if (HTTP_ERROR(code)) {
		_http_print_html(stderr, f);
		fclose(f);
		f = NULL;
	}

	return (f);

ouch:
	if (url != URL)
		fetchFreeURL(url);
	if (purl)
		fetchFreeURL(purl);
	if (fd != -1)
		close(fd);
	return (NULL);
}


/*****************************************************************************
 * Entry points
 */

/*
 * Retrieve and stat a file by HTTP
 */
FILE *
fetchXGetHTTP(struct url *URL, struct url_stat *us, const char *flags)
{
	return (_http_request(URL, "GET", us, _http_get_proxy(), flags));
}

/*
 * Retrieve a file by HTTP
 */
FILE *
fetchGetHTTP(struct url *URL, const char *flags)
{
	return (fetchXGetHTTP(URL, NULL, flags));
}

/*
 * Store a file by HTTP
 */
FILE *
fetchPutHTTP(struct url *URL __unused, const char *flags __unused)
{
	warnx("fetchPutHTTP(): not implemented");
	return (NULL);
}

/*
 * Get an HTTP document's metadata
 */
int
fetchStatHTTP(struct url *URL, struct url_stat *us, const char *flags)
{
	FILE *f;

	if ((f = _http_request(URL, "HEAD", us, _http_get_proxy(), flags)) == NULL)
		return (-1);
	fclose(f);
	return (0);
}

/*
 * List a directory
 */
struct url_ent *
fetchListHTTP(struct url *url __unused, const char *flags __unused)
{
	warnx("fetchListHTTP(): not implemented");
	return (NULL);
}