httpread.c

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/**
 * httpread - Manage reading file(s) from HTTP/TCP socket
 * Author: Ted Merrill
 * Copyright 2008 Atheros Communications
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 *
 * The files are buffered via internal callbacks from eloop, then presented to
 * an application callback routine when completely read into memory. May also
 * be used if no file is expected but just to get the header, including HTTP
 * replies (e.g. HTTP/1.1 200 OK etc.).
 *
 * This does not attempt to be an optimally efficient implementation, but does
 * attempt to be of reasonably small size and memory consumption; assuming that
 * only small files are to be read. A maximum file size is provided by
 * application and enforced.
 *
 * It is assumed that the application does not expect any of the following:
 * -- transfer encoding other than chunked
 * -- trailer fields
 * It is assumed that, even if the other side requested that the connection be
 * kept open, that we will close it (thus HTTP messages sent by application
 * should have the connection closed field); this is allowed by HTTP/1.1 and
 * simplifies things for us.
 *
 * Other limitations:
 * -- HTTP header may not exceed a hard-coded size.
 *
 * Notes:
 * This code would be massively simpler without some of the new features of
 * HTTP/1.1, especially chunked data.
 */

#include "includes.h"

#include "common.h"
#include "eloop.h"
#include "httpread.h"


/* Tunable parameters */
#define HTTPREAD_READBUF_SIZE 1024      /* read in chunks of this size */
#define HTTPREAD_HEADER_MAX_SIZE 4096   /* max allowed for headers */
#define HTTPREAD_BODYBUF_DELTA 4096     /* increase allocation by this */

#if 0
/* httpread_debug -- set this global variable > 0 e.g. from debugger
 * to enable debugs (larger numbers for more debugs)
 * Make this a #define of 0 to eliminate the debugging code.
 */
int httpread_debug = 99;
#else
#define httpread_debug 0        /* eliminates even the debugging code */
#endif


/* control instance -- actual definition (opaque to application)
 */
struct httpread {
	/* information from creation */
	int sd;         /* descriptor of TCP socket to read from */
	void (*cb)(struct httpread *handle, void *cookie,
		    enum httpread_event e);  /* call on event */
	void *cookie;   /* pass to callback */
	int max_bytes;          /* maximum file size else abort it */
	int timeout_seconds;            /* 0 or total duration timeout period */

	/* dynamically used information follows */
	int sd_registered;      /* nonzero if we need to unregister socket */
	int to_registered;      /* nonzero if we need to unregister timeout */

	int got_hdr;            /* nonzero when header is finalized */
	char hdr[HTTPREAD_HEADER_MAX_SIZE+1];   /* headers stored here */
	int hdr_nbytes;

	enum httpread_hdr_type hdr_type;
	int version;            /* 1 if we've seen 1.1 */
	int reply_code;         /* for type REPLY, e.g. 200 for HTTP/1.1 200 OK */
	int got_content_length; /* true if we know content length for sure */
	int content_length;     /* body length,  iff got_content_length */
	int chunked;            /* nonzero for chunked data */
	char *uri;

	int got_body;           /* nonzero when body is finalized */
	char *body;
	int body_nbytes;
	int body_alloc_nbytes;  /* amount allocated */

	int got_file;           /* here when we are done */

	/* The following apply if data is chunked: */
	int in_chunk_data;      /* 0=in/at header, 1=in the data or tail*/
	int chunk_start;        /* offset in body of chunk hdr or data */
	int chunk_size;         /* data of chunk (not hdr or ending CRLF)*/
	int in_trailer;         /* in header fields after data (chunked only)*/
	enum trailer_state {
		trailer_line_begin = 0,
		trailer_empty_cr,       /* empty line + CR */
		trailer_nonempty,
		trailer_nonempty_cr,
	} trailer_state;
};


/* Check words for equality, where words consist of graphical characters
 * delimited by whitespace
 * Returns nonzero if "equal" doing case insensitive comparison.
 */
static int word_eq(char *s1, char *s2)
{
	int c1;
	int c2;
	int end1 = 0;
	int end2 = 0;
	for (;;) {
		c1 = *s1++;
		c2 = *s2++;
		if (isalpha(c1) && isupper(c1))
			c1 = tolower(c1);
		if (isalpha(c2) && isupper(c2))
			c2 = tolower(c2);
		end1 = !isgraph(c1);
		end2 = !isgraph(c2);
		if (end1 || end2 || c1 != c2)
			break;
	}
	return end1 && end2;  /* reached end of both words? */
}


/* convert hex to binary
 * Requires that c have been previously tested true with isxdigit().
 */
static int hex_value(int c)
{
	if (isdigit(c))
		return c - '0';
	if (islower(c))
		return 10 + c - 'a';
	return 10 + c - 'A';
}


static void httpread_timeout_handler(void *eloop_data, void *user_ctx);

/* httpread_destroy -- if h is non-NULL, clean up
 * This must eventually be called by the application following
 * call of the application's callback and may be called
 * earlier if desired.
 */
void httpread_destroy(struct httpread *h)
{
	if (httpread_debug >= 10)
		wpa_printf(MSG_DEBUG, "ENTER httpread_destroy(%p)", h);
	if (!h)
		return;

	if (h->to_registered)
		eloop_cancel_timeout(httpread_timeout_handler, NULL, h);
	h->to_registered = 0;
	if (h->sd_registered)
		eloop_unregister_sock(h->sd, EVENT_TYPE_READ);
	h->sd_registered = 0;
	os_free(h->body);
	os_free(h->uri);
	os_memset(h, 0, sizeof(*h));  /* aid debugging */
	h->sd = -1;     /* aid debugging */
	os_free(h);
}


/* httpread_timeout_handler -- called on excessive total duration
 */
static void httpread_timeout_handler(void *eloop_data, void *user_ctx)
{
	struct httpread *h = user_ctx;
	wpa_printf(MSG_DEBUG, "httpread timeout (%p)", h);
	h->to_registered = 0;   /* is self-cancelling */
	(*h->cb)(h, h->cookie, HTTPREAD_EVENT_TIMEOUT);
}


/* Analyze options only so far as is needed to correctly obtain the file.
 * The application can look at the raw header to find other options.
 */
static int httpread_hdr_option_analyze(
	struct httpread *h,
	char *hbp       /* pointer to current line in header buffer */
	)
{
	if (word_eq(hbp, "CONTENT-LENGTH:")) {
		while (isgraph(*hbp))
			hbp++;
		while (*hbp == ' ' || *hbp == '\t')
			hbp++;
		if (!isdigit(*hbp))
			return -1;
		h->content_length = atol(hbp);
		h->got_content_length = 1;
		return 0;
	}
	if (word_eq(hbp, "TRANSFER_ENCODING:")) {
		while (isgraph(*hbp))
			hbp++;
		while (*hbp == ' ' || *hbp == '\t')
			hbp++;
		/* There should (?) be no encodings of interest
		 * other than chunked...
		 */
		if (os_strncmp(hbp, "CHUNKED", 7)) {
			h->chunked = 1;
			h->in_chunk_data = 0;
			/* ignore possible ;<parameters> */
		}
		return 0;
	}
	/* skip anything we don't know, which is a lot */
	return 0;
}


static int httpread_hdr_analyze(struct httpread *h)
{
	char *hbp = h->hdr;      /* pointer into h->hdr */
	int standard_first_line = 1;

	/* First line is special */
	h->hdr_type = HTTPREAD_HDR_TYPE_UNKNOWN;
	if (!isgraph(*hbp))
		goto bad;
	if (os_strncmp(hbp, "HTTP/", 5) == 0) {
		h->hdr_type = HTTPREAD_HDR_TYPE_REPLY;
		standard_first_line = 0;
		hbp += 5;
		if (hbp[0] == '1' && hbp[1] == '.' &&
		    isdigit(hbp[2]) && hbp[2] != '0')
			h->version = 1;
		while (isgraph(*hbp))
			hbp++;
		while (*hbp == ' ' || *hbp == '\t')
			hbp++;
		if (!isdigit(*hbp))
			goto bad;
		h->reply_code = atol(hbp);
	} else if (word_eq(hbp, "GET"))
		h->hdr_type = HTTPREAD_HDR_TYPE_GET;
	else if (word_eq(hbp, "HEAD"))
		h->hdr_type = HTTPREAD_HDR_TYPE_HEAD;
	else if (word_eq(hbp, "POST"))
		h->hdr_type = HTTPREAD_HDR_TYPE_POST;
	else if (word_eq(hbp, "PUT"))
		h->hdr_type = HTTPREAD_HDR_TYPE_PUT;
	else if (word_eq(hbp, "DELETE"))
		h->hdr_type = HTTPREAD_HDR_TYPE_DELETE;
	else if (word_eq(hbp, "TRACE"))
		h->hdr_type = HTTPREAD_HDR_TYPE_TRACE;
	else if (word_eq(hbp, "CONNECT"))
		h->hdr_type = HTTPREAD_HDR_TYPE_CONNECT;
	else if (word_eq(hbp, "NOTIFY"))
		h->hdr_type = HTTPREAD_HDR_TYPE_NOTIFY;
	else if (word_eq(hbp, "M-SEARCH"))
		h->hdr_type = HTTPREAD_HDR_TYPE_M_SEARCH;
	else if (word_eq(hbp, "M-POST"))
		h->hdr_type = HTTPREAD_HDR_TYPE_M_POST;
	else if (word_eq(hbp, "SUBSCRIBE"))
		h->hdr_type = HTTPREAD_HDR_TYPE_SUBSCRIBE;
	else if (word_eq(hbp, "UNSUBSCRIBE"))
		h->hdr_type = HTTPREAD_HDR_TYPE_UNSUBSCRIBE;
	else {
	}

	if (standard_first_line) {
		char *rawuri;
		char *uri;
		/* skip type */
		while (isgraph(*hbp))
			hbp++;
		while (*hbp == ' ' || *hbp == '\t')
			hbp++;
		/* parse uri.
		 * Find length, allocate memory for translated
		 * copy, then translate by changing %<hex><hex>
		 * into represented value.
		 */
		rawuri = hbp;
		while (isgraph(*hbp))
			hbp++;
		h->uri = os_malloc((hbp - rawuri) + 1);
		if (h->uri == NULL)
			goto bad;
		uri = h->uri;
		while (rawuri < hbp) {
			int c = *rawuri;
			if (c == '%' &&
			    isxdigit(rawuri[1]) && isxdigit(rawuri[2])) {
				*uri++ = (hex_value(rawuri[1]) << 4) |
					hex_value(rawuri[2]);
				rawuri += 3;
			} else {
				*uri++ = c;
				rawuri++;
			}
		}
		*uri = 0;       /* null terminate */
		while (isgraph(*hbp))
			hbp++;
		while (*hbp == ' ' || *hbp == '\t')
			hbp++;
		/* get version */
		if (0 == strncmp(hbp, "HTTP/", 5)) {
			hbp += 5;
			if (hbp[0] == '1' && hbp[1] == '.' &&
			    isdigit(hbp[2]) && hbp[2] != '0')
				h->version = 1;
		}
	}
	/* skip rest of line */
	while (*hbp)
		if (*hbp++ == '\n')
			break;

	/* Remainder of lines are options, in any order;
	 * or empty line to terminate
	 */
	for (;;) {
		/* Empty line to terminate */
		if (hbp[0] == '\n' ||
		    (hbp[0] == '\r' && hbp[1] == '\n'))
			break;
		if (!isgraph(*hbp))
			goto bad;
		if (httpread_hdr_option_analyze(h, hbp))
			goto bad;
		/* skip line */
		while (*hbp)
			if (*hbp++ == '\n')
				break;
	}

	/* chunked overrides content-length always */
	if (h->chunked)
		h->got_content_length = 0;

	/* For some types, we should not try to read a body
	 * This is in addition to the application determining
	 * that we should not read a body.
	 */
	switch (h->hdr_type) {
	case HTTPREAD_HDR_TYPE_REPLY:
		/* Some codes can have a body and some not.
		 * For now, just assume that any other than 200
		 * do not...
		 */
		if (h->reply_code != 200)
			h->max_bytes = 0;
		break;
	case HTTPREAD_HDR_TYPE_GET:
	case HTTPREAD_HDR_TYPE_HEAD:
		/* in practice it appears that it is assumed
		 * that GETs have a body length of 0... ?
		 */
		if (h->chunked == 0 && h->got_content_length == 0)
			h->max_bytes = 0;
		break;
	case HTTPREAD_HDR_TYPE_POST:
	case HTTPREAD_HDR_TYPE_PUT:
	case HTTPREAD_HDR_TYPE_DELETE:
	case HTTPREAD_HDR_TYPE_TRACE:
	case HTTPREAD_HDR_TYPE_CONNECT:
	case HTTPREAD_HDR_TYPE_NOTIFY:
	case HTTPREAD_HDR_TYPE_M_SEARCH:
	case HTTPREAD_HDR_TYPE_M_POST:
	case HTTPREAD_HDR_TYPE_SUBSCRIBE:
	case HTTPREAD_HDR_TYPE_UNSUBSCRIBE:
	default:
		break;
	}

	return 0;

bad:
	/* Error */
	return -1;
}


/* httpread_read_handler -- called when socket ready to read
 *
 * Note: any extra data we read past end of transmitted file is ignored;
 * if we were to support keeping connections open for multiple files then
 * this would have to be addressed.
 */
static void httpread_read_handler(int sd, void *eloop_ctx, void *sock_ctx)
{
	struct httpread *h = sock_ctx;
	int nread;
	char *rbp;      /* pointer into read buffer */
	char *hbp;      /* pointer into header buffer */
	char *bbp;      /* pointer into body buffer */
	char readbuf[HTTPREAD_READBUF_SIZE];  /* temp use to read into */

	if (httpread_debug >= 20)
		wpa_printf(MSG_DEBUG, "ENTER httpread_read_handler(%p)", h);

	/* read some at a time, then search for the interal
	 * boundaries between header and data and etc.
	 */
	nread = read(h->sd, readbuf, sizeof(readbuf));
	if (nread < 0)
		goto bad;
	if (nread == 0) {
		/* end of transmission... this may be normal
		 * or may be an error... in some cases we can't
		 * tell which so we must assume it is normal then.
		 */
		if (!h->got_hdr) {
			/* Must at least have completed header */
			wpa_printf(MSG_DEBUG, "httpread premature eof(%p)", h);
			goto bad;
		}
		if (h->chunked || h->got_content_length) {
			/* Premature EOF; e.g. dropped connection */
			wpa_printf(MSG_DEBUG,