include/common/h2.h

/*
 * include/common/h2.h
 * This file contains types and macros used for the HTTP/2 protocol
 *
 * Copyright (C) 2000-2017 Willy Tarreau - w@1wt.eu
 * Copyright (C) 2017 HAProxy Technologies
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

#ifndef _COMMON_H2_H
#define _COMMON_H2_H

#include <common/config.h>
#include <common/http-hdr.h>
#include <common/htx.h>
#include <common/ist.h>


/* indexes of most important pseudo headers can be simplified to an almost
 * linear array by dividing the index by 2 for all values from 1 to 9, and
 * caping to 4 for values up to 14 ; thus it fits in a single 24-bit array
 * shifted by 3 times the index value/2, or a 32-bit array shifted by 4x.
 * Don't change these values, they are assumed by hpack_idx_to_phdr(). There
 * is an entry for the Host header field which is not a pseudo-header but
 * needs to be tracked as we should only use :authority if it's absent.
 */
enum {
	H2_PHDR_IDX_NONE = 0,
	H2_PHDR_IDX_AUTH = 1, /* :authority = 1     */
	H2_PHDR_IDX_METH = 2, /* :method    = 2..3  */
	H2_PHDR_IDX_PATH = 3, /* :path      = 4..5  */
	H2_PHDR_IDX_SCHM = 4, /* :scheme    = 6..7  */
	H2_PHDR_IDX_STAT = 5, /* :status    = 8..14 */
	H2_PHDR_IDX_HOST = 6, /* Host, never returned, just a place-holder */
	H2_PHDR_NUM_ENTRIES   /* must be last */
};

/* bit fields indicating the pseudo-headers found. It also covers the HOST
 * header field as well as any non-pseudo-header field (NONE).
 */
enum {
	H2_PHDR_FND_NONE = 1 << H2_PHDR_IDX_NONE, /* found a regular header */
	H2_PHDR_FND_AUTH = 1 << H2_PHDR_IDX_AUTH,
	H2_PHDR_FND_METH = 1 << H2_PHDR_IDX_METH,
	H2_PHDR_FND_PATH = 1 << H2_PHDR_IDX_PATH,
	H2_PHDR_FND_SCHM = 1 << H2_PHDR_IDX_SCHM,
	H2_PHDR_FND_STAT = 1 << H2_PHDR_IDX_STAT,
	H2_PHDR_FND_HOST = 1 << H2_PHDR_IDX_HOST,
};

/* frame types, from the standard */
enum h2_ft {
	H2_FT_DATA            = 0x00,     // RFC7540 #6.1
	H2_FT_HEADERS         = 0x01,     // RFC7540 #6.2
	H2_FT_PRIORITY        = 0x02,     // RFC7540 #6.3
	H2_FT_RST_STREAM      = 0x03,     // RFC7540 #6.4
	H2_FT_SETTINGS        = 0x04,     // RFC7540 #6.5
	H2_FT_PUSH_PROMISE    = 0x05,     // RFC7540 #6.6
	H2_FT_PING            = 0x06,     // RFC7540 #6.7
	H2_FT_GOAWAY          = 0x07,     // RFC7540 #6.8
	H2_FT_WINDOW_UPDATE   = 0x08,     // RFC7540 #6.9
	H2_FT_CONTINUATION    = 0x09,     // RFC7540 #6.10
	H2_FT_ENTRIES /* must be last */
} __attribute__((packed));

/* frame types, turned to bits or bit fields */
enum {
	/* one bit per frame type */
	H2_FT_DATA_BIT          = 1U << H2_FT_DATA,
	H2_FT_HEADERS_BIT       = 1U << H2_FT_HEADERS,
	H2_FT_PRIORITY_BIT      = 1U << H2_FT_PRIORITY,
	H2_FT_RST_STREAM_BIT    = 1U << H2_FT_RST_STREAM,
	H2_FT_SETTINGS_BIT      = 1U << H2_FT_SETTINGS,
	H2_FT_PUSH_PROMISE_BIT  = 1U << H2_FT_PUSH_PROMISE,
	H2_FT_PING_BIT          = 1U << H2_FT_PING,
	H2_FT_GOAWAY_BIT        = 1U << H2_FT_GOAWAY,
	H2_FT_WINDOW_UPDATE_BIT = 1U << H2_FT_WINDOW_UPDATE,
	H2_FT_CONTINUATION_BIT  = 1U << H2_FT_CONTINUATION,
	/* padded frames */
	H2_FT_PADDED_MASK       = H2_FT_DATA_BIT | H2_FT_HEADERS_BIT | H2_FT_PUSH_PROMISE_BIT,
	/* flow controlled frames */
	H2_FT_FC_MASK           = H2_FT_DATA_BIT,
	/* header frames */
	H2_FT_HDR_MASK          = H2_FT_HEADERS_BIT | H2_FT_PUSH_PROMISE_BIT | H2_FT_CONTINUATION_BIT,
	/* frames allowed to arrive late on a stream */
	H2_FT_LATE_MASK         = H2_FT_WINDOW_UPDATE_BIT | H2_FT_RST_STREAM_BIT | H2_FT_PRIORITY_BIT,
};


/* flags defined for each frame type */

// RFC7540 #6.1
#define H2_F_DATA_END_STREAM 0x01
#define H2_F_DATA_PADDED     0x08

// RFC7540 #6.2
#define H2_F_HEADERS_END_STREAM  0x01
#define H2_F_HEADERS_END_HEADERS 0x04
#define H2_F_HEADERS_PADDED      0x08
#define H2_F_HEADERS_PRIORITY    0x20

// RFC7540 #6.3 : PRIORITY defines no flags
// RFC7540 #6.4 : RST_STREAM defines no flags

// RFC7540 #6.5
#define H2_F_SETTINGS_ACK   0x01

// RFC7540 #6.6
#define H2_F_PUSH_PROMISE_END_HEADERS 0x04
#define H2_F_PUSH_PROMISE_PADDED      0x08

// RFC7540 #6.7
#define H2_F_PING_ACK   0x01

// RFC7540 #6.8 : GOAWAY defines no flags
// RFC7540 #6.9 : WINDOW_UPDATE defines no flags

// PADDED is the exact same among DATA, HEADERS and PUSH_PROMISE (8)
#define H2_F_PADDED              0x08

/* HTTP/2 error codes - RFC7540 #7 */
enum h2_err {
	H2_ERR_NO_ERROR            = 0x0,
	H2_ERR_PROTOCOL_ERROR      = 0x1,
	H2_ERR_INTERNAL_ERROR      = 0x2,
	H2_ERR_FLOW_CONTROL_ERROR  = 0x3,
	H2_ERR_SETTINGS_TIMEOUT    = 0x4,
	H2_ERR_STREAM_CLOSED       = 0x5,
	H2_ERR_FRAME_SIZE_ERROR    = 0x6,
	H2_ERR_REFUSED_STREAM      = 0x7,
	H2_ERR_CANCEL              = 0x8,
	H2_ERR_COMPRESSION_ERROR   = 0x9,
	H2_ERR_CONNECT_ERROR       = 0xa,
	H2_ERR_ENHANCE_YOUR_CALM   = 0xb,
	H2_ERR_INADEQUATE_SECURITY = 0xc,
	H2_ERR_HTTP_1_1_REQUIRED   = 0xd,
} __attribute__((packed));

// RFC7540 #11.3 : Settings Registry
#define H2_SETTINGS_HEADER_TABLE_SIZE      0x0001
#define H2_SETTINGS_ENABLE_PUSH            0x0002
#define H2_SETTINGS_MAX_CONCURRENT_STREAMS 0x0003
#define H2_SETTINGS_INITIAL_WINDOW_SIZE    0x0004
#define H2_SETTINGS_MAX_FRAME_SIZE         0x0005
#define H2_SETTINGS_MAX_HEADER_LIST_SIZE   0x0006


/* some protocol constants */

// PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n
#define H2_CONN_PREFACE                     \
	"\x50\x52\x49\x20\x2a\x20\x48\x54"  \
	"\x54\x50\x2f\x32\x2e\x30\x0d\x0a"  \
	"\x0d\x0a\x53\x4d\x0d\x0a\x0d\x0a"


/* some flags related to protocol parsing */
#define H2_MSGF_BODY           0x0001    // a body is present
#define H2_MSGF_BODY_CL        0x0002    // content-length is present
#define H2_MSGF_BODY_TUNNEL    0x0004    // a tunnel is in use (CONNECT)
#define H2_MSGF_RSP_1XX        0x0010    // a 1xx ( != 101) HEADERS frame was received

#define H2_MAX_STREAM_ID       ((1U << 31) - 1)
#define H2_MAX_FRAME_LEN       ((1U << 24) - 1)
#define H2_DIR_REQ             1
#define H2_DIR_RES             2
#define H2_DIR_BOTH            3

/* constraints imposed by the protocol on each frame type, in terms of stream
 * ID values, frame sizes, and direction so that most connection-level checks
 * can be centralized regardless of the frame's acceptance.
 */
struct h2_frame_definition {
	int32_t dir;     /* 0=none, 1=request, 2=response, 3=both */
	int32_t min_id;  /* minimum allowed stream ID */
	int32_t max_id;  /* maximum allowed stream ID */
	int32_t min_len; /* minimum frame length */
	int32_t max_len; /* maximum frame length */
};

extern struct h2_frame_definition h2_frame_definition[H2_FT_ENTRIES];

/* various protocol processing functions */

int h2_parse_cont_len_header(unsigned int *msgf, struct ist *value, unsigned long long *body_len);
int h2_make_htx_request(struct http_hdr *list, struct htx *htx, unsigned int *msgf, unsigned long long *body_len);
int h2_make_htx_response(struct http_hdr *list, struct htx *htx, unsigned int *msgf, unsigned long long *body_len);
int h2_make_htx_trailers(struct http_hdr *list, struct htx *htx);

/*
 * Some helpful debugging functions.
 */

/* returns a bit corresponding to the frame type */
static inline unsigned int h2_ft_bit(enum h2_ft ft)
{
	return 1U << ft;
}

/* returns the frame type as a string */
static inline const char *h2_ft_str(int type)
{
	switch (type) {
	case H2_FT_DATA          : return "DATA";
	case H2_FT_HEADERS       : return "HEADERS";
	case H2_FT_PRIORITY      : return "PRIORITY";
	case H2_FT_RST_STREAM    : return "RST_STREAM";
	case H2_FT_SETTINGS      : return "SETTINGS";
	case H2_FT_PUSH_PROMISE  : return "PUSH_PROMISE";
	case H2_FT_PING          : return "PING";
	case H2_FT_GOAWAY        : return "GOAWAY";
	case H2_FT_WINDOW_UPDATE : return "WINDOW_UPDATE";
	default                  : return "_UNKNOWN_";
	}
}

/* Returns an error code if the frame is valid protocol-wise, otherwise 0. <ft>
 * is the frame type (H2_FT_*), <dir> is the direction (1=req, 2=res), <id> is
 * the stream ID from the frame header, <len> is the frame length from the
 * header. The purpose is to be able to quickly return a PROTOCOL_ERROR or
 * FRAME_SIZE_ERROR connection error even for situations where the frame will
 * be ignored. <mfs> must be the max frame size currently in place for the
 * protocol.
 */
static inline int h2_frame_check(enum h2_ft ft, int dir, int32_t id, int32_t len, int32_t mfs)
{
	struct h2_frame_definition *fd;

	if (ft >= H2_FT_ENTRIES)
		return H2_ERR_NO_ERROR; // ignore unhandled frame types

	fd = &h2_frame_definition[ft];

	if (!(dir & fd->dir))
		return H2_ERR_PROTOCOL_ERROR;

	if (id < fd->min_id || id > fd->max_id)
		return H2_ERR_PROTOCOL_ERROR;

	if (len < fd->min_len || len > fd->max_len)
		return H2_ERR_FRAME_SIZE_ERROR;

	if (len > mfs)
		return H2_ERR_FRAME_SIZE_ERROR;

	if (ft == H2_FT_SETTINGS && (len % 6) != 0)
		return H2_ERR_FRAME_SIZE_ERROR; // RFC7540#6.5

	return H2_ERR_NO_ERROR;
}

/* returns the pseudo-header <str> corresponds to among H2_PHDR_IDX_*, 0 if not a
 * pseudo-header, or -1 if not a valid pseudo-header.
 */
static inline int h2_str_to_phdr(const struct ist str)
{
	if (*str.ptr == ':') {
		if (isteq(str, ist(":path")))           return H2_PHDR_IDX_PATH;
		else if (isteq(str, ist(":method")))    return H2_PHDR_IDX_METH;
		else if (isteq(str, ist(":scheme")))    return H2_PHDR_IDX_SCHM;
		else if (isteq(str, ist(":status")))    return H2_PHDR_IDX_STAT;
		else if (isteq(str, ist(":authority"))) return H2_PHDR_IDX_AUTH;

		/* all other names starting with ':' */
		return -1;
	}

	/* not a pseudo header */
	return 0;
}

/* returns the pseudo-header name <num> as a string, or ":UNKNOWN" if unknown */
static inline const char *h2_phdr_to_str(int phdr)
{
	switch (phdr) {
	case H2_PHDR_IDX_NONE: return ":NONE";
	case H2_PHDR_IDX_AUTH: return ":authority";
	case H2_PHDR_IDX_METH: return ":method";
	case H2_PHDR_IDX_PATH: return ":path";
	case H2_PHDR_IDX_SCHM: return ":scheme";
	case H2_PHDR_IDX_STAT: return ":status";
	case H2_PHDR_IDX_HOST: return "Host";
	default:               return ":UNKNOWN";
	}
}

#endif /* _COMMON_H2_H */

/*
 * Local variables:
 *  c-indent-level: 8
 *  c-basic-offset: 8
 * End:
 */