/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "array.h"
#include "istream.h"
#include "iostream.h"
#include "istream-sized.h"
#include "http-parser.h"
#include "http-header.h"
#include "http-header-parser.h"
#include "http-date.h"
#include "http-transfer.h"
#include "http-message-parser.h"

#include <ctype.h>

void http_message_parser_init(struct http_message_parser *parser,
			      struct istream *input,
			      const struct http_header_limits *hdr_limits,
			      uoff_t max_payload_size,
			      enum http_message_parse_flags flags)
{
	i_zero(parser);
	parser->input = input;
	i_stream_ref(parser->input);
	if (hdr_limits != NULL)
		parser->header_limits = *hdr_limits;
	parser->max_payload_size = max_payload_size;
	parser->flags = flags;
}

void http_message_parser_deinit(struct http_message_parser *parser)
{
	if (parser->header_parser != NULL)
		http_header_parser_deinit(&parser->header_parser);
	pool_unref(&parser->msg.pool);
	i_stream_unref(&parser->payload);
	i_stream_unref(&parser->input);
}

void http_message_parser_restart(struct http_message_parser *parser,
				 pool_t pool)
{
	i_assert(parser->payload == NULL);

	if (parser->header_parser == NULL) {
		enum http_header_parse_flags hdr_flags = 0;

		if ((parser->flags & HTTP_MESSAGE_PARSE_FLAG_STRICT) != 0)
			hdr_flags |= HTTP_HEADER_PARSE_FLAG_STRICT;
		parser->header_parser = http_header_parser_init(
			parser->input, &parser->header_limits,	hdr_flags);
	} else {
		http_header_parser_reset(parser->header_parser);
	}

	pool_unref(&parser->msg.pool);
	i_zero(&parser->msg);
	if (pool != NULL) {
		parser->msg.pool = pool;
		pool_ref(pool);
	}
	parser->msg.date = (time_t)-1;
}

pool_t http_message_parser_get_pool(struct http_message_parser *parser)
{
	if (parser->msg.pool == NULL)
		parser->msg.pool = pool_alloconly_create("http_message", 4096);
	return parser->msg.pool;
}

int http_message_parse_version(struct http_message_parser *parser)
{
	const unsigned char *p = parser->cur;
	const size_t size = parser->end - parser->cur;

	parser->error_code = HTTP_MESSAGE_PARSE_ERROR_NONE;
	parser->error = NULL;

	/* RFC 7230, Section 2.6: Protocol Versioning

	   HTTP-version  = HTTP-name "/" DIGIT "." DIGIT
	   HTTP-name     = %x48.54.54.50 ; "HTTP", case-sensitive
	 */
	if (size < 8)
		return 0;
	if (memcmp(p, "HTTP/", 5) != 0 ||
	    !i_isdigit(p[5]) || p[6] != '.' || !i_isdigit(p[7])) {
		parser->error = "Bad HTTP version";
		parser->error_code = HTTP_MESSAGE_PARSE_ERROR_BROKEN_MESSAGE;
		return -1;
	}
	parser->msg.version_major = p[5] - '0';
	parser->msg.version_minor = p[7] - '0';
	parser->cur += 8;
	return 1;
}

static void
http_message_parse_finish_payload_error(struct http_message_parser *parser)
{
	if (parser->payload->stream_errno == EMSGSIZE) {
		parser->error_code = HTTP_MESSAGE_PARSE_ERROR_PAYLOAD_TOO_LARGE;
		parser->error = "Payload is too large";
	} else if (parser->payload->stream_errno == EIO) {
		parser->error_code = HTTP_MESSAGE_PARSE_ERROR_BROKEN_MESSAGE;
		parser->error = t_strdup_printf(
			"Invalid payload: %s",
			i_stream_get_error(parser->payload));
	} else {
		parser->error_code = HTTP_MESSAGE_PARSE_ERROR_BROKEN_STREAM;
		parser->error = t_strdup_printf(
			"Stream error while skipping payload: %s",
			i_stream_get_error(parser->payload));
	}
}

int http_message_parse_finish_payload(struct http_message_parser *parser)
{
	const unsigned char *data;
	size_t size;
	int ret;

	parser->error_code = HTTP_MESSAGE_PARSE_ERROR_NONE;
	parser->error = NULL;

	if (parser->payload == NULL)
		return 1;

	while ((ret = i_stream_read_more(parser->payload, &data, &size)) > 0)
		i_stream_skip(parser->payload, size);
	if (ret == 0 || parser->payload->stream_errno != 0) {
		if (ret < 0)
			http_message_parse_finish_payload_error(parser);
		return ret;
	}

	i_stream_destroy(&parser->payload);
	return 1;
}

static int
http_message_parse_hdr_connection(struct http_message_parser *parser,
				  const unsigned char *data, size_t size)
{
	pool_t pool = http_message_parser_get_pool(parser);
	struct http_parser hparser;
	const char **opt_idx;
	const char *option;
	unsigned int num_tokens = 0;

	/* RFC 7230, Section 6.1: Connection

	   Connection        = 1#connection-option
	   connection-option = token
	*/

	/* Multiple Connection headers are allowed and combined
	   into one */
	http_parser_init(&hparser, data, size);
	for (;;) {
		if (http_parse_token_list_next(&hparser, &option) <= 0)
			break;
		num_tokens++;
		if (strcasecmp(option, "close") == 0)
			parser->msg.connection_close = TRUE;
		if (!array_is_created(&parser->msg.connection_options))
			p_array_init(&parser->msg.connection_options, pool, 4);
		opt_idx = array_append_space(&parser->msg.connection_options);
		*opt_idx = p_strdup(pool, option);
	}

	if (hparser.cur < hparser.end || num_tokens == 0) {
		parser->error = "Invalid Connection header";
		parser->error_code = HTTP_MESSAGE_PARSE_ERROR_BROKEN_MESSAGE;
		return -1;
	}

	return 0;
}

static int
http_message_parse_hdr_content_length(struct http_message_parser *parser,
				      const struct http_header_field *hdr)
{
	if (parser->msg.have_content_length) {
		/* There is no acceptable way to allow duplicates for this
		   header. */
		parser->error = "Duplicate Content-Length header";
		parser->error_code = HTTP_MESSAGE_PARSE_ERROR_BROKEN_MESSAGE;
		return -1;
	}

	/* RFC 7230, Section 3.3.2: Content-Length

	   Content-Length = 1*DIGIT
	 */
	if (str_to_uoff(hdr->value, &parser->msg.content_length) < 0) {
		parser->error = "Invalid Content-Length header";
		parser->error_code = HTTP_MESSAGE_PARSE_ERROR_BROKEN_MESSAGE;
		return -1;
	}
	parser->msg.have_content_length = TRUE;
	return 0;
}

static int
http_message_parse_hdr_date(struct http_message_parser *parser,
			    const unsigned char *data, size_t size)
{
	if (parser->msg.date != (time_t)-1) {
		if ((parser->flags & HTTP_MESSAGE_PARSE_FLAG_STRICT) != 0) {
			parser->error = "Duplicate Date header";
			parser->error_code =
				HTTP_MESSAGE_PARSE_ERROR_BROKEN_MESSAGE;
			return -1;
		}
		/* Allow the duplicate; last instance is used */
	}

	/* RFC 7231, Section 7.1.1.2: Date

	   Date = HTTP-date
	 */
	if (!http_date_parse(data, size, &parser->msg.date) &&
	    (parser->flags & HTTP_MESSAGE_PARSE_FLAG_STRICT) != 0) {
		parser->error = "Invalid Date header";
		parser->error_code = HTTP_MESSAGE_PARSE_ERROR_BROKEN_MESSAGE;
		return -1;
	}
	return 0;
}

static int
http_message_parse_hdr_location(struct http_message_parser *parser,
				const struct http_header_field *hdr)
{
	/* RFC 7231, Section 7.1.2: Location

	   Location = URI-reference 

	   -> not parsed here
	 */
	/* FIXME: move this to response parser */
	parser->msg.location = hdr->value;
	return 0;

}

static int
http_message_parse_hdr_transfer_encoding(struct http_message_parser *parser,
					 const unsigned char *data, size_t size)
{
	pool_t pool = http_message_parser_get_pool(parser);
	struct http_parser hparser;
	const char *trenc = NULL;

	/* Multiple Transfer-Encoding headers are allowed and combined into one
	 */
	if (!array_is_created(&parser->msg.transfer_encoding))
		p_array_init(&parser->msg.transfer_encoding, pool, 4);

	/* RFC 7230, Section 3.3.1: Transfer-Encoding

	   Transfer-Encoding  = 1#transfer-coding 

	   RFC 7230, Section 4: Transfer Codings

	   transfer-coding    = "chunked"  ; RFC 7230, Section 4.1
			      / "compress" ; RFC 7230, Section 4.2.1
			      / "deflate"  ; RFC 7230, Section 4.2.2
			      / "gzip"     ; RFC 7230, Section 4.2.3
			      / transfer-extension
	   transfer-extension = token *( OWS ";" OWS transfer-parameter )
	   transfer-parameter = token BWS "=" BWS ( token / quoted-string )
	 */
	http_parser_init(&hparser, data, size);
	for (;;) {
		/* transfer-coding */
		if (http_parse_token(&hparser, &trenc) > 0) {
			struct http_transfer_coding *coding;
			bool parse_error;

			coding = array_append_space(
				&parser->msg.transfer_encoding);
			coding->name = p_strdup(pool, trenc);

			/* *( OWS ";" OWS transfer-parameter ) */
			parse_error = FALSE;
			for (;;) {
				struct http_transfer_param *param;
				const char *attribute, *value;

				/* OWS ";" OWS */
				http_parse_ows(&hparser);
				if (hparser.cur >= hparser.end ||
				    *hparser.cur != ';')
					break;
				hparser.cur++;
				http_parse_ows(&hparser);

				/* attribute */
				if (http_parse_token(&hparser,
						     &attribute) <= 0) {
					parse_error = TRUE;
					break;
				}

				/* BWS "=" BWS */
				http_parse_ows(&hparser);
				if (hparser.cur >= hparser.end ||
				    *hparser.cur != '=') {
					parse_error = TRUE;
					break;
				}
				hparser.cur++;
				http_parse_ows(&hparser);

				/* token / quoted-string */
				if (http_parse_token_or_qstring(&hparser,
								&value) <= 0) {
					parse_error = TRUE;
					break;
				}

				if (!array_is_created(&coding->parameters)) {
					p_array_init(&coding->parameters,
						     pool, 2);
				}
				param = array_append_space(&coding->parameters);
				param->attribute = p_strdup(pool, attribute);
				param->value = p_strdup(pool, value);
			}
			if (parse_error)
				break;
			
		} else {
			/* RFC 7230, Section 7: ABNF List Extension: #rule

			   For compatibility with legacy list rules, a recipient
			   MUST parse and ignore a reasonable number of empty
			   list elements: enough to handle common mistakes by
			   senders that merge values, but not so much that they
			   could be used as a denial-of-service mechanism.
			 */
			// FIXME: limit allowed number of empty list elements
			// FIXME: handle invalid transfer encoding
		}
		http_parse_ows(&hparser);
		if (hparser.cur >= hparser.end || *hparser.cur != ',')
			break;
		hparser.cur++;
		http_parse_ows(&hparser);
	}

	if (hparser.cur < hparser.end ||
		array_count(&parser->msg.transfer_encoding) == 0) {
		parser->error = "Invalid Transfer-Encoding header";
		parser->error_code = HTTP_MESSAGE_PARSE_ERROR_BROKEN_MESSAGE;
		return -1;
	}
	return 0;
}

static int
http_message_parse_header(struct http_message_parser *parser,
			  const char *name, const unsigned char *data,
			  size_t size)
{
	const struct http_header_field *hdr;
	pool_t pool;

	pool = http_message_parser_get_pool(parser);
	if (parser->msg.header == NULL)
		parser->msg.header = http_header_create(pool, 32);
	hdr = http_header_field_add(parser->msg.header, name, data, size);

	/* RFC 7230, Section 3.2.2: Field Order

	   A sender MUST NOT generate multiple header fields with the same field
	   name in a message unless either the entire field value for that
	   header field is defined as a comma-separated list [i.e., #(values)]
	   or the header field is a well-known exception.
	 */

	switch (name[0]) {
	case 'C': case 'c':
		/* Connection: */
		if (strcasecmp(name, "Connection") == 0) {
			return http_message_parse_hdr_connection(
				parser, data, size);
		}
		/* Content-Length: */
		if (strcasecmp(name, "Content-Length") == 0)
			return http_message_parse_hdr_content_length(
				parser, hdr);
		break;
	case 'D': case 'd':
		/* Date: */
		if (strcasecmp(name, "Date") == 0)
			return http_message_parse_hdr_date(parser, data, size);
		break;
	case 'L': case 'l':
		/* Location: */
		if (strcasecmp(name, "Location") == 0)
			return http_message_parse_hdr_location(parser, hdr);
		break;
	case 'T': case 't':
		/* Transfer-Encoding: */
		if (strcasecmp(name, "Transfer-Encoding") == 0) {
			return http_message_parse_hdr_transfer_encoding(
				parser, data, size);
		}
		break;
	default:
		break;
	}
	return 0;
}

static int http_message_parse_eoh(struct http_message_parser *parser)
{
	struct http_message *msg = &parser->msg;
	pool_t pool;

	/* EOH */

	/* Create empty header if there is none */
	pool = http_message_parser_get_pool(parser);
	if (msg->header == NULL)
		msg->header = http_header_create(pool, 1);

	/* handle HTTP/1.0 persistence */
	if (msg->version_major == 1 && msg->version_minor == 0 &&
	    !msg->connection_close) {
		const char *option;

		msg->connection_close = TRUE;
		if (array_is_created(&msg->connection_options)) {
			array_foreach_elem(&msg->connection_options, option) {
				if (strcasecmp(option, "Keep-Alive") == 0) {
					msg->connection_close = FALSE;
					break;
				}
			}
		}
	}
	return 1;
}

int http_message_parse_headers(struct http_message_parser *parser)
{
	const unsigned char *field_data;
	const char *field_name, *error;
	size_t field_size;
	int ret;

	parser->error_code = HTTP_MESSAGE_PARSE_ERROR_NONE;
	parser->error = NULL;

	/* *( header-field CRLF ) CRLF */
	while ((ret = http_header_parse_next_field(
		parser->header_parser,  &field_name, &field_data, &field_size,
		&error)) > 0) {
		if (field_name == NULL)
			return http_message_parse_eoh(parser);

		if (http_message_parse_header(parser,
			field_name, field_data, field_size) < 0)
			return -1;
	}

	if (ret < 0) {
		if (parser->input->eof || parser->input->stream_errno != 0)  {			
			parser->error_code =
				HTTP_MESSAGE_PARSE_ERROR_BROKEN_STREAM;
			parser->error = "Broken stream";
		} else {
			parser->error_code =
				HTTP_MESSAGE_PARSE_ERROR_BROKEN_MESSAGE;
			parser->error = t_strdup_printf(
				"Failed to parse header: %s", error);
		}
	
	}
	return ret;
}

static const char *
http_istream_error_callback(const struct istream_sized_error_data *data,
			    struct istream *input)
{
	i_assert(data->eof);
	i_assert(data->v_offset + data->new_bytes < data->wanted_size);

	return t_strdup_printf(
		"Disconnected while reading message payload at offset %"PRIuUOFF_T
		" (wanted %"PRIuUOFF_T"): %s", data->v_offset + data->new_bytes,
		data->wanted_size, io_stream_get_disconnect_reason(input, NULL));
}

static int
http_message_parse_body_coding(struct http_message_parser *parser,
			       const struct http_transfer_coding *coding,
			       bool *seen_chunked)
{
	if (strcasecmp(coding->name, "chunked") == 0) {
		*seen_chunked = TRUE;

		if ((parser->error_code == HTTP_MESSAGE_PARSE_ERROR_NONE)
			&& array_is_created(&coding->parameters)
			&& array_count(&coding->parameters) > 0) {
			const struct http_transfer_param *param =
				array_front(&coding->parameters);

			parser->error_code = HTTP_MESSAGE_PARSE_ERROR_BAD_MESSAGE;
			parser->error = t_strdup_printf(
				"Unexpected parameter `%s' specified"
				"for the `%s' transfer coding",
				param->attribute, coding->name);
			/* recoverable */
		}
	} else if (*seen_chunked) {
		parser->error_code = HTTP_MESSAGE_PARSE_ERROR_BROKEN_MESSAGE;
		parser->error = "Chunked Transfer-Encoding must be last";
		return -1;
	} else if (parser->error_code == HTTP_MESSAGE_PARSE_ERROR_NONE) {
		parser->error_code = HTTP_MESSAGE_PARSE_ERROR_NOT_IMPLEMENTED;
		parser->error = t_strdup_printf(
		"Unknown transfer coding `%s'", coding->name);
		/* recoverable */
	}
	return 0;
}

static int
http_message_parse_body_encoded(struct http_message_parser *parser,
				bool request)
{
	const struct http_transfer_coding *coding;
	bool seen_chunked = FALSE;

	array_foreach(&parser->msg.transfer_encoding, coding) {
		if (http_message_parse_body_coding(parser, coding,
						   &seen_chunked) < 0)
			return -1;
	}

	if (seen_chunked) {	
		parser->payload = http_transfer_chunked_istream_create(
			parser->input, parser->max_payload_size);
	} else if (!request) {
		/* RFC 7230, Section 3.3.3: Message Body Length

		   If a Transfer-Encoding header field is present in a response
		   and the chunked transfer coding is not the final encoding,
		   the message body length is determined by reading the
		   connection until it is closed by the server. 
		 */
		/* FIXME: enforce max payload size (relevant to http-client
		   only) */
		parser->payload =
			i_stream_create_limit(parser->input, SIZE_MAX);
	} else {
		/* RFC 7230, Section 3.3.3: Message Body Length

		   If a Transfer-Encoding header field is present in a request
		   and the chunked transfer coding is not the final encoding,
		   the message body length cannot be determined reliably; the
		   server MUST respond with the 400 (Bad Request) status code
		   and then close the connection.
		 */
		parser->error_code = HTTP_MESSAGE_PARSE_ERROR_BROKEN_MESSAGE;
		parser->error =
			"Final Transfer-Encoding in request is not chunked";
		return -1;
	}

	/* RFC 7230, Section 3.3.3: Message Body Length

	   If a message is received with both a Transfer-Encoding and a
	   Content-Length header field, the Transfer-Encoding overrides the
	   Content-Length. Such a message might indicate an attempt to perform
	   request smuggling (Section 9.5 of [RFC7230]) or response splitting
	   (Section 9.4 of [RFC7230]) and ought to be handled as an error. A
	   sender MUST remove the received Content-Length field prior to
	   forwarding such a message downstream.
	 */
	// FIXME: make this an error?
	if (parser->msg.have_content_length)
		http_header_field_delete(parser->msg.header, "Content-Length");

	return 0;
}

static int http_message_parse_body_sized(struct http_message_parser *parser)
{
	struct istream *input;

	if (parser->max_payload_size > 0
		&& parser->msg.content_length > parser->max_payload_size) {
		parser->error_code = HTTP_MESSAGE_PARSE_ERROR_PAYLOAD_TOO_LARGE;
		parser->error = "Payload is too large";
		return -1;
	}

	/* Got explicit message size from Content-Length: header */
	input = i_stream_create_limit(parser->input,
				      parser->msg.content_length);
	/* Make sure we return failure if HTTP connection closes before we've
	   finished reading the full input. */
	parser->payload = i_stream_create_sized_with_callback(input,
				parser->msg.content_length,
				http_istream_error_callback, input);
	i_stream_unref(&input);
	return 0;
}

static int http_message_parse_body_closed(struct http_message_parser *parser)
{
	/* RFC 7230, Section 3.3.3: Message Body Length

	   6.  If this is a request message and none of the above are true, then
	       the message body length is zero (no message body is present).

	   7.  Otherwise, this is a response message without a declared message
	       body length, so the message body length is determined by the
	       number of octets received prior to the server closing the
	       connection
	 */
	// FIXME: enforce max payload size (relevant to http-client only)
	// FIXME: handle request case correctly.
	parser->payload = i_stream_create_limit(parser->input, SIZE_MAX);
	return 0;
}

int http_message_parse_body(struct http_message_parser *parser, bool request)
{
	i_assert(parser->payload == NULL);

	parser->error_code = HTTP_MESSAGE_PARSE_ERROR_NONE;
	parser->error = NULL;
 
	if (array_is_created(&parser->msg.transfer_encoding)) {
		if (http_message_parse_body_encoded(parser, request) < 0)
			return -1;
	} else if (parser->msg.content_length > 0) {
		if (http_message_parse_body_sized(parser) < 0)
			return -1;
	} else if (!parser->msg.have_content_length && !request) {
		if (http_message_parse_body_closed(parser) < 0)
			return -1;
	}
	if (parser->error_code != HTTP_MESSAGE_PARSE_ERROR_NONE)
		return -1;
	return 0;
}