src/qpack-dec.c - haproxy - Gitiles

 /*
  * QPACK decompressor
  *
  * Copyright 2021 HAProxy Technologies, Frederic Lecaille <flecaille@haproxy.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation, version 2.1
  * exclusively.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */

 #include <inttypes.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>

 #include <import/ist.h>
 #include <haproxy/buf.h>
 #include <haproxy/chunk.h>
 #include <haproxy/h3.h>
 #include <haproxy/mux_quic.h>
 #include <haproxy/qpack-t.h>
 #include <haproxy/qpack-dec.h>
 #include <haproxy/qpack-tbl.h>
 #include <haproxy/hpack-huff.h>
 #include <haproxy/hpack-tbl.h>
 #include <haproxy/http-hdr.h>
 #include <haproxy/tools.h>

 #if defined(DEBUG_QPACK)
 #define qpack_debug_printf fprintf
 #define qpack_debug_hexdump debug_hexdump
 #else
 #define qpack_debug_printf(...) do { } while (0)
 #define qpack_debug_hexdump(...) do { } while (0)
 #endif

 /* Encoded field line bitmask */
 #define QPACK_EFL_BITMASK  0xf0
 #define QPACK_LFL_WPBNM    0x00 // Literal field line with post-base name reference
 #define QPACK_IFL_WPBI     0x10 // Indexed field line with post-based index
 #define QPACK_LFL_WLN_BIT  0x20 // Literal field line with literal name
 #define QPACK_LFL_WNR_BIT  0x40 // Literal field line with name reference
 #define QPACK_IFL_BIT      0x80 // Indexed field line

 /* reads a varint from <raw>'s lowest <b> bits and <len> bytes max (raw included).
  * returns the 64-bit value on success after updating buf and len_in. Forces
  * len_in to (uint64_t)-1 on truncated input.
  * Note that this function is similar to the one used for HPACK (except that is supports
  * up to 62-bits integers).
  */
 static uint64_t qpack_get_varint(const unsigned char **buf, uint64_t *len_in, int b)
 {
 	uint64_t ret = 0;
 	int len = *len_in;
 	const uint8_t *raw = *buf;
 	uint8_t shift = 0;

 	len--;
 	ret = *raw++ & ((1ULL << b) - 1);
 	if (ret != (uint64_t)((1ULL << b) - 1))
 		goto end;

 	while (len && (*raw & 128)) {
 		ret += ((uint64_t)*raw++ & 127) << shift;
 		shift += 7;
 		len--;
 	}

 	/* last 7 bits */
 	if (!len)
 		goto too_short;

 	len--;
 	ret += ((uint64_t)*raw++ & 127) << shift;

  end:
 	*buf = raw;
 	*len_in = len;
 	return ret;

  too_short:
 	*len_in = (uint64_t)-1;
 	return 0;
 }

 /* Decode an encoder stream.
  *
  * Returns 0 on success else non-zero.
  */
 int qpack_decode_enc(struct buffer *buf, int fin, void *ctx)
 {
 	struct qcs *qcs = ctx;
 	size_t len;
 	unsigned char inst;

 	/* RFC 9204 4.2. Encoder and Decoder Streams
 	 *
 	 * The sender MUST NOT close either of these streams, and the receiver
 	 * MUST NOT request that the sender close either of these streams.
 	 * Closure of either unidirectional stream type MUST be treated as a
 	 * connection error of type H3_CLOSED_CRITICAL_STREAM.
 	 */
 	if (fin) {
 		qcc_emit_cc_app(qcs->qcc, H3_CLOSED_CRITICAL_STREAM, 1);
 		return -1;
 	}

 	len = b_data(buf);
 	qpack_debug_hexdump(stderr, "[QPACK-DEC-ENC] ", b_head(buf), 0, len);

 	if (!len) {
 		qpack_debug_printf(stderr, "[QPACK-DEC-ENC] empty stream\n");
 		return 0;
 	}

 	inst = (unsigned char)*b_head(buf) & QPACK_ENC_INST_BITMASK;
 	if (inst == QPACK_ENC_INST_DUP) {
 		/* Duplicate */
 	}
 	else if (inst & QPACK_ENC_INST_IWNR_BIT) {
 		/* Insert With Name Reference */
 	}
 	else if (inst & QPACK_ENC_INST_IWLN_BIT) {
 		/* Insert with literal name */
 	}
 	else if (inst & QPACK_ENC_INST_SDTC_BIT) {
 		/* Set dynamic table capacity */
 	}

 	return 0;
 }

 /* Decode an decoder stream.
  *
  * Returns 0 on success else non-zero.
  */
 int qpack_decode_dec(struct buffer *buf, int fin, void *ctx)
 {
 	struct qcs *qcs = ctx;
 	size_t len;
 	unsigned char inst;

 	/* RFC 9204 4.2. Encoder and Decoder Streams
 	 *
 	 * The sender MUST NOT close either of these streams, and the receiver
 	 * MUST NOT request that the sender close either of these streams.
 	 * Closure of either unidirectional stream type MUST be treated as a
 	 * connection error of type H3_CLOSED_CRITICAL_STREAM.
 	 */
 	if (fin) {
 		qcc_emit_cc_app(qcs->qcc, H3_CLOSED_CRITICAL_STREAM, 1);
 		return -1;
 	}

 	len = b_data(buf);
 	qpack_debug_hexdump(stderr, "[QPACK-DEC-DEC] ", b_head(buf), 0, len);

 	if (!len) {
 		qpack_debug_printf(stderr, "[QPACK-DEC-DEC] empty stream\n");
 		return 0;
 	}

 	inst = (unsigned char)*b_head(buf) & QPACK_DEC_INST_BITMASK;
 	if (inst == QPACK_DEC_INST_ICINC) {
 		/* Insert count increment */
 	}
 	else if (inst & QPACK_DEC_INST_SACK) {
 		/* Section Acknowledgment */
 	}
 	else if (inst & QPACK_DEC_INST_SCCL) {
 		/* Stream cancellation */
 	}

 	return 0;
 }

 /* Decode a field section prefix made of <enc_ric> and <db> two varints.
  * Also set the 'S' sign bit for <db>.
  * Return a negative error if failed, 0 if not.
  */
 static int qpack_decode_fs_pfx(uint64_t *enc_ric, uint64_t *db, int *sign_bit,
                                const unsigned char **raw, uint64_t *len)
 {
 	*enc_ric = qpack_get_varint(raw, len, 8);
 	if (*len == (uint64_t)-1)
 		return -QPACK_ERR_RIC;

 	*sign_bit = **raw & 0x8;
 	*db = qpack_get_varint(raw, len, 7);
 	if (*len == (uint64_t)-1)
 		return -QPACK_ERR_DB;

 	return 0;
 }

 /* Decode a field section from the <raw> buffer of <len> bytes. Each parsed
  * header is inserted into <list> of <list_size> entries max and uses <tmp> as
  * a storage for some elements pointing into it. An end marker is inserted at
  * the end of the list with empty strings as name/value.
  *
  * Returns the number of headers inserted into list excluding the end marker.
  * In case of error, a negative code QPACK_ERR_* is returned.
  */
 int qpack_decode_fs(const unsigned char *raw, uint64_t len, struct buffer *tmp,
                     struct http_hdr *list, int list_size)
 {
 	struct ist name, value;
 	uint64_t enc_ric, db;
 	int s;
 	unsigned int efl_type;
 	int ret;
 	int hdr_idx = 0;

 	qpack_debug_hexdump(stderr, "[QPACK-DEC-FS] ", (const char *)raw, 0, len);

 	/* parse field section prefix */
 	ret = qpack_decode_fs_pfx(&enc_ric, &db, &s, &raw, &len);
 	if (ret < 0) {
 		qpack_debug_printf(stderr, "##ERR@%d(%d)\n", __LINE__, ret);
 		goto out;
 	}

 	chunk_reset(tmp);
 	qpack_debug_printf(stderr, "enc_ric: %llu db: %llu s=%d\n",
 	                   (unsigned long long)enc_ric, (unsigned long long)db, !!s);
 	/* Decode field lines */
 	while (len) {
 		if (hdr_idx >= list_size) {
 			qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 			ret = -QPACK_ERR_TOO_LARGE;
 			goto out;
 		}

 		/* parse field line representation */
 		efl_type = *raw & QPACK_EFL_BITMASK;
 		qpack_debug_printf(stderr, "efl_type=0x%02x\n", efl_type);

 		if (efl_type == QPACK_LFL_WPBNM) {
 			/* Literal field line with post-base name reference
 			 * TODO adjust this when dynamic table support is implemented.
 			 */
 #if 0
 			uint64_t index __maybe_unused, length;
 			unsigned int n __maybe_unused, h __maybe_unused;

 			qpack_debug_printf(stderr, "literal field line with post-base name reference:");
 			n = *raw & 0x08;
 			index = qpack_get_varint(&raw, &len, 3);
 			if (len == (uint64_t)-1) {
 				qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 				ret = -QPACK_ERR_TRUNCATED;
 				goto out;
 			}

 			qpack_debug_printf(stderr, " n=%d index=%llu", !!n, (unsigned long long)index);
 			h = *raw & 0x80;
 			length = qpack_get_varint(&raw, &len, 7);
 			if (len == (uint64_t)-1) {
 				qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 				ret = -QPACK_ERR_TRUNCATED;
 				goto out;
 			}

 			qpack_debug_printf(stderr, " h=%d length=%llu", !!h, (unsigned long long)length);

 			if (len < length) {
 				qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 				ret = -QPACK_ERR_TRUNCATED;
 				goto out;
 			}

 			raw += length;
 			len -= length;
 #endif

 			/* RFC9204 2.2.3 Invalid References
 			 *
 			 * If the decoder encounters a reference in a field line representation
 			 * to a dynamic table entry that has already been evicted or that has an
 			 * absolute index greater than or equal to the declared Required Insert
 			 * Count (Section 4.5.1), it MUST treat this as a connection error of
 			 * type QPACK_DECOMPRESSION_FAILED.
 			 */
 			return -QPACK_DECOMPRESSION_FAILED;
 		}
 		else if (efl_type == QPACK_IFL_WPBI) {
 			/* Indexed field line with post-base index
 			 * TODO adjust this when dynamic table support is implemented.
 			 */
 #if 0
 			uint64_t index __maybe_unused;

 			qpack_debug_printf(stderr, "indexed field line with post-base index:");
 			index = qpack_get_varint(&raw, &len, 4);
 			if (len == (uint64_t)-1) {
 				qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 				ret = -QPACK_ERR_TRUNCATED;
 				goto out;
 			}

 			qpack_debug_printf(stderr, " index=%llu", (unsigned long long)index);
 #endif

 			/* RFC9204 2.2.3 Invalid References
 			 *
 			 * If the decoder encounters a reference in a field line representation
 			 * to a dynamic table entry that has already been evicted or that has an
 			 * absolute index greater than or equal to the declared Required Insert
 			 * Count (Section 4.5.1), it MUST treat this as a connection error of
 			 * type QPACK_DECOMPRESSION_FAILED.
 			 */
 			return -QPACK_DECOMPRESSION_FAILED;
 		}
 		else if (efl_type & QPACK_IFL_BIT) {
 			/* Indexed field line */
 			uint64_t index;
 			unsigned int static_tbl;

 			qpack_debug_printf(stderr, "indexed field line:");
 			static_tbl = efl_type & 0x40;
 			index = qpack_get_varint(&raw, &len, 6);
 			if (len == (uint64_t)-1) {
 				qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 				ret = -QPACK_ERR_TRUNCATED;
 				goto out;
 			}

 			if (static_tbl) {
 				name = qpack_sht[index].n;
 				value = qpack_sht[index].v;
 			}
 			else {
 				/* RFC9204 2.2.3 Invalid References
 				 *
 				 * If the decoder encounters a reference in a field line representation
 				 * to a dynamic table entry that has already been evicted or that has an
 				 * absolute index greater than or equal to the declared Required Insert
 				 * Count (Section 4.5.1), it MUST treat this as a connection error of
 				 * type QPACK_DECOMPRESSION_FAILED.
 				 *
 				 * TODO adjust this when dynamic table support is implemented.
 				 */
 				return -QPACK_DECOMPRESSION_FAILED;
 			}

 			qpack_debug_printf(stderr,  " t=%d index=%llu", !!static_tbl, (unsigned long long)index);
 		}
 		else if (efl_type & QPACK_LFL_WNR_BIT) {
 			/* Literal field line with name reference */
 			uint64_t index, length;
 			unsigned int static_tbl, n __maybe_unused, h;

 			qpack_debug_printf(stderr, "Literal field line with name reference:");
 			n = efl_type & 0x20;
 			static_tbl = efl_type & 0x10;
 			index = qpack_get_varint(&raw, &len, 4);
 			if (len == (uint64_t)-1) {
 				qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 				ret = -QPACK_ERR_TRUNCATED;
 				goto out;
 			}

 			if (static_tbl) {
 				name = qpack_sht[index].n;
 			}
 			else {
 				/* RFC9204 2.2.3 Invalid References
 				 *
 				 * If the decoder encounters a reference in a field line representation
 				 * to a dynamic table entry that has already been evicted or that has an
 				 * absolute index greater than or equal to the declared Required Insert
 				 * Count (Section 4.5.1), it MUST treat this as a connection error of
 				 * type QPACK_DECOMPRESSION_FAILED.
 				 *
 				 * TODO adjust this when dynamic table support is implemented.
 				 */
 				return -QPACK_DECOMPRESSION_FAILED;
 			}

 			qpack_debug_printf(stderr, " n=%d t=%d index=%llu", !!n, !!static_tbl, (unsigned long long)index);
 			h = *raw & 0x80;
 			length = qpack_get_varint(&raw, &len, 7);
 			if (len == (uint64_t)-1) {
 				qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 				ret = -QPACK_ERR_TRUNCATED;
 				goto out;
 			}

 			qpack_debug_printf(stderr, " h=%d length=%llu", !!h, (unsigned long long)length);
 			if (h) {
 				char *trash;
 				int nlen;

 				trash = chunk_newstr(tmp);
 				if (!trash) {
 					qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 					ret = -QPACK_DECOMPRESSION_FAILED;
 					goto out;
 				}
 				nlen = huff_dec(raw, length, trash, tmp->size - tmp->data);
 				if (nlen == (uint32_t)-1) {
 					qpack_debug_printf(stderr, " can't decode huffman.\n");
 					ret = -QPACK_ERR_HUFFMAN;
 					goto out;
 				}

 				qpack_debug_printf(stderr, " [name huff %d->%d '%s']", (int)length, (int)nlen, trash);
 				/* makes an ist from tmp storage */
 				b_add(tmp, nlen);
 				value = ist2(trash, nlen);
 			}
 			else {
 				value = ist2(raw, length);
 			}

 			if (len < length) {
 				qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 				ret = -QPACK_ERR_TRUNCATED;
 				goto out;
 			}

 			raw += length;
 			len -= length;
 		}
 		else if (efl_type & QPACK_LFL_WLN_BIT) {
 			/* Literal field line with literal name */
 			unsigned int n __maybe_unused, hname, hvalue;
 			uint64_t name_len, value_len;

 			qpack_debug_printf(stderr, "Literal field line with literal name:");
 			n = *raw & 0x10;
 			hname = *raw & 0x08;
 			name_len = qpack_get_varint(&raw, &len, 3);
 			if (len == (uint64_t)-1) {
 				qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 				ret = -QPACK_ERR_TRUNCATED;
 				goto out;
 			}

 			qpack_debug_printf(stderr, " n=%d hname=%d name_len=%llu", !!n, !!hname, (unsigned long long)name_len);
 			/* Name string */

 			if (len < name_len) {
 				qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 				ret = -QPACK_ERR_TRUNCATED;
 				goto out;
 			}

 			if (hname) {
 				char *trash;
 				int nlen;

 				trash = chunk_newstr(tmp);
 				if (!trash) {
 					qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 					ret = -QPACK_DECOMPRESSION_FAILED;
 					goto out;
 				}
 				nlen = huff_dec(raw, name_len, trash, tmp->size - tmp->data);
 				if (nlen == (uint32_t)-1) {
 					qpack_debug_printf(stderr, " can't decode huffman.\n");
 					ret = -QPACK_ERR_HUFFMAN;
 					goto out;
 				}

 				qpack_debug_printf(stderr, " [name huff %d->%d '%s']", (int)name_len, (int)nlen, trash);
 				/* makes an ist from tmp storage */
 				b_add(tmp, nlen);
 				name = ist2(trash, nlen);
 			}
 			else {
 				name = ist2(raw, name_len);
 			}

 			raw += name_len;
 			len -= name_len;

 			hvalue = *raw & 0x80;
 			value_len = qpack_get_varint(&raw, &len, 7);
 			if (len == (uint64_t)-1) {
 				qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 				ret = -QPACK_ERR_TRUNCATED;
 				goto out;
 			}

 			qpack_debug_printf(stderr, " hvalue=%d value_len=%llu", !!hvalue, (unsigned long long)value_len);

 			if (len < value_len) {
 				qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 				ret = -QPACK_ERR_TRUNCATED;
 				goto out;
 			}

 			if (hvalue) {
 				char *trash;
 				int nlen;

 				trash = chunk_newstr(tmp);
 				if (!trash) {
 					qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 					ret = -QPACK_DECOMPRESSION_FAILED;
 					goto out;
 				}
 				nlen = huff_dec(raw, value_len, trash, tmp->size - tmp->data);
 				if (nlen == (uint32_t)-1) {
 					qpack_debug_printf(stderr, " can't decode huffman.\n");
 					ret = -QPACK_ERR_HUFFMAN;
 					goto out;
 				}

 				qpack_debug_printf(stderr, " [name huff %d->%d '%s']", (int)value_len, (int)nlen, trash);
 				/* makes an ist from tmp storage */
 				b_add(tmp, nlen);
 				value = ist2(trash, nlen);
 			}
 			else {
 				value = ist2(raw, value_len);
 			}

 			raw += value_len;
 			len -= value_len;
 		}

 		/* We must not accept empty header names (forbidden by the spec and used
 		 * as a list termination).
 		 */
 		if (!name.len) {
 			qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 			ret = -QPACK_DECOMPRESSION_FAILED;
 			goto out;
 		}

 		list[hdr_idx].n = name;
 		list[hdr_idx].v = value;
 		++hdr_idx;

 		qpack_debug_printf(stderr, "\n");
 	}

 	if (hdr_idx >= list_size) {
 		qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
 		ret = -QPACK_ERR_TOO_LARGE;
 		goto out;
 	}

 	/* put an end marker */
 	list[hdr_idx].n = list[hdr_idx].v = IST_NULL;
 	ret = hdr_idx;

  out:
 	qpack_debug_printf(stderr, "-- done: ret=%d\n", ret);
 	return ret;
 }
	/*
	* QPACK decompressor
	*
	* Copyright 2021 HAProxy Technologies, Frederic Lecaille <flecaille@haproxy.com>
	*
	* This library is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Lesser General Public
	* License as published by the Free Software Foundation, version 2.1
	* exclusively.
	*
	* This library is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Lesser General Public License for more details.
	*
	* You should have received a copy of the GNU Lesser General Public
	* License along with this library; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	*/

	#include <inttypes.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>

	#include <import/ist.h>
	#include <haproxy/buf.h>
	#include <haproxy/chunk.h>
	#include <haproxy/h3.h>
	#include <haproxy/mux_quic.h>
	#include <haproxy/qpack-t.h>
	#include <haproxy/qpack-dec.h>
	#include <haproxy/qpack-tbl.h>
	#include <haproxy/hpack-huff.h>
	#include <haproxy/hpack-tbl.h>
	#include <haproxy/http-hdr.h>
	#include <haproxy/tools.h>

	#if defined(DEBUG_QPACK)
	#define qpack_debug_printf fprintf
	#define qpack_debug_hexdump debug_hexdump
	#else
	#define qpack_debug_printf(...) do { } while (0)
	#define qpack_debug_hexdump(...) do { } while (0)
	#endif

	/* Encoded field line bitmask */
	#define QPACK_EFL_BITMASK 0xf0
	#define QPACK_LFL_WPBNM 0x00 // Literal field line with post-base name reference
	#define QPACK_IFL_WPBI 0x10 // Indexed field line with post-based index
	#define QPACK_LFL_WLN_BIT 0x20 // Literal field line with literal name
	#define QPACK_LFL_WNR_BIT 0x40 // Literal field line with name reference
	#define QPACK_IFL_BIT 0x80 // Indexed field line

	/* reads a varint from <raw>'s lowest <b> bits and <len> bytes max (raw included).
	* returns the 64-bit value on success after updating buf and len_in. Forces
	* len_in to (uint64_t)-1 on truncated input.
	* Note that this function is similar to the one used for HPACK (except that is supports
	* up to 62-bits integers).
	*/
	static uint64_t qpack_get_varint(const unsigned char *buf, uint64_t len_in, int b)
	{
	uint64_t ret = 0;
	int len = *len_in;
	const uint8_t raw = buf;
	uint8_t shift = 0;

	len--;
	ret = *raw++ & ((1ULL << b) - 1);
	if (ret != (uint64_t)((1ULL << b) - 1))
	goto end;

	while (len && (*raw & 128)) {
	ret += ((uint64_t)*raw++ & 127) << shift;
	shift += 7;
	len--;
	}

	/* last 7 bits */
	if (!len)
	goto too_short;

	len--;
	ret += ((uint64_t)*raw++ & 127) << shift;

	end:
	*buf = raw;
	*len_in = len;
	return ret;

	too_short:
	*len_in = (uint64_t)-1;
	return 0;
	}

	/* Decode an encoder stream.
	*
	* Returns 0 on success else non-zero.
	*/
	int qpack_decode_enc(struct buffer buf, int fin, void ctx)
	{
	struct qcs *qcs = ctx;
	size_t len;
	unsigned char inst;

	/* RFC 9204 4.2. Encoder and Decoder Streams
	*
	* The sender MUST NOT close either of these streams, and the receiver
	* MUST NOT request that the sender close either of these streams.
	* Closure of either unidirectional stream type MUST be treated as a
	* connection error of type H3_CLOSED_CRITICAL_STREAM.
	*/
	if (fin) {
	qcc_emit_cc_app(qcs->qcc, H3_CLOSED_CRITICAL_STREAM, 1);
	return -1;
	}

	len = b_data(buf);
	qpack_debug_hexdump(stderr, "[QPACK-DEC-ENC] ", b_head(buf), 0, len);

	if (!len) {
	qpack_debug_printf(stderr, "[QPACK-DEC-ENC] empty stream\n");
	return 0;
	}

	inst = (unsigned char)*b_head(buf) & QPACK_ENC_INST_BITMASK;
	if (inst == QPACK_ENC_INST_DUP) {
	/* Duplicate */
	}
	else if (inst & QPACK_ENC_INST_IWNR_BIT) {
	/* Insert With Name Reference */
	}
	else if (inst & QPACK_ENC_INST_IWLN_BIT) {
	/* Insert with literal name */
	}
	else if (inst & QPACK_ENC_INST_SDTC_BIT) {
	/* Set dynamic table capacity */
	}

	return 0;
	}

	/* Decode an decoder stream.
	*
	* Returns 0 on success else non-zero.
	*/
	int qpack_decode_dec(struct buffer buf, int fin, void ctx)
	{
	struct qcs *qcs = ctx;
	size_t len;
	unsigned char inst;

	/* RFC 9204 4.2. Encoder and Decoder Streams
	*
	* The sender MUST NOT close either of these streams, and the receiver
	* MUST NOT request that the sender close either of these streams.
	* Closure of either unidirectional stream type MUST be treated as a
	* connection error of type H3_CLOSED_CRITICAL_STREAM.
	*/
	if (fin) {
	qcc_emit_cc_app(qcs->qcc, H3_CLOSED_CRITICAL_STREAM, 1);
	return -1;
	}

	len = b_data(buf);
	qpack_debug_hexdump(stderr, "[QPACK-DEC-DEC] ", b_head(buf), 0, len);

	if (!len) {
	qpack_debug_printf(stderr, "[QPACK-DEC-DEC] empty stream\n");
	return 0;
	}

	inst = (unsigned char)*b_head(buf) & QPACK_DEC_INST_BITMASK;
	if (inst == QPACK_DEC_INST_ICINC) {
	/* Insert count increment */
	}
	else if (inst & QPACK_DEC_INST_SACK) {
	/* Section Acknowledgment */
	}
	else if (inst & QPACK_DEC_INST_SCCL) {
	/* Stream cancellation */
	}

	return 0;
	}

	/* Decode a field section prefix made of <enc_ric> and <db> two varints.
	* Also set the 'S' sign bit for <db>.
	* Return a negative error if failed, 0 if not.
	*/
	static int qpack_decode_fs_pfx(uint64_t enc_ric, uint64_t db, int *sign_bit,
	const unsigned char *raw, uint64_t len)
	{
	*enc_ric = qpack_get_varint(raw, len, 8);
	if (*len == (uint64_t)-1)
	return -QPACK_ERR_RIC;

	sign_bit = *raw & 0x8;
	*db = qpack_get_varint(raw, len, 7);
	if (*len == (uint64_t)-1)
	return -QPACK_ERR_DB;

	return 0;
	}

	/* Decode a field section from the <raw> buffer of <len> bytes. Each parsed
	* header is inserted into <list> of <list_size> entries max and uses <tmp> as
	* a storage for some elements pointing into it. An end marker is inserted at
	* the end of the list with empty strings as name/value.
	*
	* Returns the number of headers inserted into list excluding the end marker.
	* In case of error, a negative code QPACK_ERR_* is returned.
	*/
	int qpack_decode_fs(const unsigned char raw, uint64_t len, struct buffer tmp,
	struct http_hdr *list, int list_size)
	{
	struct ist name, value;
	uint64_t enc_ric, db;
	int s;
	unsigned int efl_type;
	int ret;
	int hdr_idx = 0;

	qpack_debug_hexdump(stderr, "[QPACK-DEC-FS] ", (const char *)raw, 0, len);

	/* parse field section prefix */
	ret = qpack_decode_fs_pfx(&enc_ric, &db, &s, &raw, &len);
	if (ret < 0) {
	qpack_debug_printf(stderr, "##ERR@%d(%d)\n", __LINE__, ret);
	goto out;
	}

	chunk_reset(tmp);
	qpack_debug_printf(stderr, "enc_ric: %llu db: %llu s=%d\n",
	(unsigned long long)enc_ric, (unsigned long long)db, !!s);
	/* Decode field lines */
	while (len) {
	if (hdr_idx >= list_size) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_ERR_TOO_LARGE;
	goto out;
	}

	/* parse field line representation */
	efl_type = *raw & QPACK_EFL_BITMASK;
	qpack_debug_printf(stderr, "efl_type=0x%02x\n", efl_type);

	if (efl_type == QPACK_LFL_WPBNM) {
	/* Literal field line with post-base name reference
	* TODO adjust this when dynamic table support is implemented.
	*/
	#if 0
	uint64_t index __maybe_unused, length;
	unsigned int n __maybe_unused, h __maybe_unused;

	qpack_debug_printf(stderr, "literal field line with post-base name reference:");
	n = *raw & 0x08;
	index = qpack_get_varint(&raw, &len, 3);
	if (len == (uint64_t)-1) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_ERR_TRUNCATED;
	goto out;
	}

	qpack_debug_printf(stderr, " n=%d index=%llu", !!n, (unsigned long long)index);
	h = *raw & 0x80;
	length = qpack_get_varint(&raw, &len, 7);
	if (len == (uint64_t)-1) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_ERR_TRUNCATED;
	goto out;
	}

	qpack_debug_printf(stderr, " h=%d length=%llu", !!h, (unsigned long long)length);

	if (len < length) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_ERR_TRUNCATED;
	goto out;
	}

	raw += length;
	len -= length;
	#endif

	/* RFC9204 2.2.3 Invalid References
	*
	* If the decoder encounters a reference in a field line representation
	* to a dynamic table entry that has already been evicted or that has an
	* absolute index greater than or equal to the declared Required Insert
	* Count (Section 4.5.1), it MUST treat this as a connection error of
	* type QPACK_DECOMPRESSION_FAILED.
	*/
	return -QPACK_DECOMPRESSION_FAILED;
	}
	else if (efl_type == QPACK_IFL_WPBI) {
	/* Indexed field line with post-base index
	* TODO adjust this when dynamic table support is implemented.
	*/
	#if 0
	uint64_t index __maybe_unused;

	qpack_debug_printf(stderr, "indexed field line with post-base index:");
	index = qpack_get_varint(&raw, &len, 4);
	if (len == (uint64_t)-1) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_ERR_TRUNCATED;
	goto out;
	}

	qpack_debug_printf(stderr, " index=%llu", (unsigned long long)index);
	#endif

	/* RFC9204 2.2.3 Invalid References
	*
	* If the decoder encounters a reference in a field line representation
	* to a dynamic table entry that has already been evicted or that has an
	* absolute index greater than or equal to the declared Required Insert
	* Count (Section 4.5.1), it MUST treat this as a connection error of
	* type QPACK_DECOMPRESSION_FAILED.
	*/
	return -QPACK_DECOMPRESSION_FAILED;
	}
	else if (efl_type & QPACK_IFL_BIT) {
	/* Indexed field line */
	uint64_t index;
	unsigned int static_tbl;

	qpack_debug_printf(stderr, "indexed field line:");
	static_tbl = efl_type & 0x40;
	index = qpack_get_varint(&raw, &len, 6);
	if (len == (uint64_t)-1) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_ERR_TRUNCATED;
	goto out;
	}

	if (static_tbl) {
	name = qpack_sht[index].n;
	value = qpack_sht[index].v;
	}
	else {
	/* RFC9204 2.2.3 Invalid References
	*
	* If the decoder encounters a reference in a field line representation
	* to a dynamic table entry that has already been evicted or that has an
	* absolute index greater than or equal to the declared Required Insert
	* Count (Section 4.5.1), it MUST treat this as a connection error of
	* type QPACK_DECOMPRESSION_FAILED.
	*
	* TODO adjust this when dynamic table support is implemented.
	*/
	return -QPACK_DECOMPRESSION_FAILED;
	}

	qpack_debug_printf(stderr, " t=%d index=%llu", !!static_tbl, (unsigned long long)index);
	}
	else if (efl_type & QPACK_LFL_WNR_BIT) {
	/* Literal field line with name reference */
	uint64_t index, length;
	unsigned int static_tbl, n __maybe_unused, h;

	qpack_debug_printf(stderr, "Literal field line with name reference:");
	n = efl_type & 0x20;
	static_tbl = efl_type & 0x10;
	index = qpack_get_varint(&raw, &len, 4);
	if (len == (uint64_t)-1) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_ERR_TRUNCATED;
	goto out;
	}

	if (static_tbl) {
	name = qpack_sht[index].n;
	}
	else {
	/* RFC9204 2.2.3 Invalid References
	*
	* If the decoder encounters a reference in a field line representation
	* to a dynamic table entry that has already been evicted or that has an
	* absolute index greater than or equal to the declared Required Insert
	* Count (Section 4.5.1), it MUST treat this as a connection error of
	* type QPACK_DECOMPRESSION_FAILED.
	*
	* TODO adjust this when dynamic table support is implemented.
	*/
	return -QPACK_DECOMPRESSION_FAILED;
	}

	qpack_debug_printf(stderr, " n=%d t=%d index=%llu", !!n, !!static_tbl, (unsigned long long)index);
	h = *raw & 0x80;
	length = qpack_get_varint(&raw, &len, 7);
	if (len == (uint64_t)-1) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_ERR_TRUNCATED;
	goto out;
	}

	qpack_debug_printf(stderr, " h=%d length=%llu", !!h, (unsigned long long)length);
	if (h) {
	char *trash;
	int nlen;

	trash = chunk_newstr(tmp);
	if (!trash) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_DECOMPRESSION_FAILED;
	goto out;
	}
	nlen = huff_dec(raw, length, trash, tmp->size - tmp->data);
	if (nlen == (uint32_t)-1) {
	qpack_debug_printf(stderr, " can't decode huffman.\n");
	ret = -QPACK_ERR_HUFFMAN;
	goto out;
	}

	qpack_debug_printf(stderr, " [name huff %d->%d '%s']", (int)length, (int)nlen, trash);
	/* makes an ist from tmp storage */
	b_add(tmp, nlen);
	value = ist2(trash, nlen);
	}
	else {
	value = ist2(raw, length);
	}

	if (len < length) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_ERR_TRUNCATED;
	goto out;
	}

	raw += length;
	len -= length;
	}
	else if (efl_type & QPACK_LFL_WLN_BIT) {
	/* Literal field line with literal name */
	unsigned int n __maybe_unused, hname, hvalue;
	uint64_t name_len, value_len;

	qpack_debug_printf(stderr, "Literal field line with literal name:");
	n = *raw & 0x10;
	hname = *raw & 0x08;
	name_len = qpack_get_varint(&raw, &len, 3);
	if (len == (uint64_t)-1) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_ERR_TRUNCATED;
	goto out;
	}

	qpack_debug_printf(stderr, " n=%d hname=%d name_len=%llu", !!n, !!hname, (unsigned long long)name_len);
	/* Name string */

	if (len < name_len) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_ERR_TRUNCATED;
	goto out;
	}

	if (hname) {
	char *trash;
	int nlen;

	trash = chunk_newstr(tmp);
	if (!trash) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_DECOMPRESSION_FAILED;
	goto out;
	}
	nlen = huff_dec(raw, name_len, trash, tmp->size - tmp->data);
	if (nlen == (uint32_t)-1) {
	qpack_debug_printf(stderr, " can't decode huffman.\n");
	ret = -QPACK_ERR_HUFFMAN;
	goto out;
	}

	qpack_debug_printf(stderr, " [name huff %d->%d '%s']", (int)name_len, (int)nlen, trash);
	/* makes an ist from tmp storage */
	b_add(tmp, nlen);
	name = ist2(trash, nlen);
	}
	else {
	name = ist2(raw, name_len);
	}

	raw += name_len;
	len -= name_len;

	hvalue = *raw & 0x80;
	value_len = qpack_get_varint(&raw, &len, 7);
	if (len == (uint64_t)-1) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_ERR_TRUNCATED;
	goto out;
	}

	qpack_debug_printf(stderr, " hvalue=%d value_len=%llu", !!hvalue, (unsigned long long)value_len);

	if (len < value_len) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_ERR_TRUNCATED;
	goto out;
	}

	if (hvalue) {
	char *trash;
	int nlen;

	trash = chunk_newstr(tmp);
	if (!trash) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_DECOMPRESSION_FAILED;
	goto out;
	}
	nlen = huff_dec(raw, value_len, trash, tmp->size - tmp->data);
	if (nlen == (uint32_t)-1) {
	qpack_debug_printf(stderr, " can't decode huffman.\n");
	ret = -QPACK_ERR_HUFFMAN;
	goto out;
	}

	qpack_debug_printf(stderr, " [name huff %d->%d '%s']", (int)value_len, (int)nlen, trash);
	/* makes an ist from tmp storage */
	b_add(tmp, nlen);
	value = ist2(trash, nlen);
	}
	else {
	value = ist2(raw, value_len);
	}

	raw += value_len;
	len -= value_len;
	}

	/* We must not accept empty header names (forbidden by the spec and used
	* as a list termination).
	*/
	if (!name.len) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_DECOMPRESSION_FAILED;
	goto out;
	}

	list[hdr_idx].n = name;
	list[hdr_idx].v = value;
	++hdr_idx;

	qpack_debug_printf(stderr, "\n");
	}

	if (hdr_idx >= list_size) {
	qpack_debug_printf(stderr, "##ERR@%d\n", __LINE__);
	ret = -QPACK_ERR_TOO_LARGE;
	goto out;
	}

	/* put an end marker */
	list[hdr_idx].n = list[hdr_idx].v = IST_NULL;
	ret = hdr_idx;

	out:
	qpack_debug_printf(stderr, "-- done: ret=%d\n", ret);
	return ret;
	}