thodg/got/lib/pack.c

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• Show log

  Commit

• Author : Stefan Sperling
  Date : 2018-11-11 15:05:43
  Hash : 96732e0b
  Message : fix error handling in got_pack_stop_privsep_child()

• lib/pack.c

• /*
   * Copyright (c) 2018 Stefan Sperling <stsp@openbsd.org>
   *
   * Permission to use, copy, modify, and distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <sys/queue.h>
  #include <sys/uio.h>
  #include <sys/mman.h>
  
  #include <fcntl.h>
  #include <errno.h>
  #include <stdio.h>
  #include <stdint.h>
  #include <stdlib.h>
  #include <string.h>
  #include <limits.h>
  #include <sha1.h>
  #include <endian.h>
  #include <zlib.h>
  #include <imsg.h>
  
  #include "got_error.h"
  #include "got_object.h"
  #include "got_opentemp.h"
  
  #include "got_lib_sha1.h"
  #include "got_lib_pack.h"
  #include "got_lib_path.h"
  #include "got_lib_delta.h"
  #include "got_lib_inflate.h"
  #include "got_lib_object.h"
  #include "got_lib_privsep.h"
  
  #ifndef nitems
  #define nitems(_a) (sizeof(_a) / sizeof((_a)[0]))
  #endif
  
  #ifndef MIN
  #define	MIN(_a,_b) ((_a) < (_b) ? (_a) : (_b))
  #endif
  
  static const struct got_error *
  verify_fanout_table(uint32_t *fanout_table)
  {
  	int i;
  
  	for (i = 0; i < 0xff - 1; i++) {
  		if (be32toh(fanout_table[i]) > be32toh(fanout_table[i + 1]))
  			return got_error(GOT_ERR_BAD_PACKIDX);
  	}
  
  	return NULL;
  }
  
  const struct got_error *
  got_pack_get_packfile_size(size_t *size, const char *path)
  {
  	struct stat sb;
  	char *dot;
  
  	*size = 0;
  
  	dot = strrchr(path, '.');
  	if (dot == NULL)
  		return got_error(GOT_ERR_BAD_PATH);
  
  	/* Path must point to a pack index or to a pack file. */
  	if (strcmp(dot, GOT_PACKIDX_SUFFIX) == 0) {
  		const struct got_error *err = NULL;
  		char *path_pack;
  		char base_path[PATH_MAX];
  
  		/* Convert pack index path to pack file path. */
  		if (strlcpy(base_path, path, PATH_MAX) > PATH_MAX)
  			return got_error(GOT_ERR_NO_SPACE);
  		dot = strrchr(base_path, '.');
  		if (dot == NULL)
  			return got_error(GOT_ERR_BAD_PATH);
  		*dot = '\0';
  		if (asprintf(&path_pack, "%s.pack", base_path) == -1)
  			return got_error_from_errno();
  
  		if (stat(path_pack, &sb) != 0)
  			err = got_error_from_errno();
  		free(path_pack);
  		if (err)
  			return err;
  	} else if (strcmp(dot, GOT_PACKFILE_SUFFIX) == 0) {
  		if (stat(path, &sb) != 0)
  			return got_error_from_errno();
  	} else
  		return got_error(GOT_ERR_BAD_PATH);
  
  	*size = sb.st_size;
  	return 0;
  }
  
  const struct got_error *
  got_packidx_init_hdr(struct got_packidx *p, int verify)
  {
  	const struct got_error *err = NULL;
  	struct got_packidx_v2_hdr *h;
  	SHA1_CTX ctx;
  	uint8_t sha1[SHA1_DIGEST_LENGTH];
  	size_t nobj, len_fanout, len_ids, offset, remain;
  	ssize_t n;
  
  	SHA1Init(&ctx);
  
  	h = &p->hdr;
  	offset = 0;
  	remain = p->len;
  
  	if (remain < sizeof(*h->magic)) {
  		err = got_error(GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  	if (p->map)
  		h->magic = (uint32_t *)(p->map + offset);
  	else {
  		h->magic = malloc(sizeof(*h->magic));
  		if (h->magic == NULL) {
  			err = got_error_from_errno();
  			goto done;
  		}
  		n = read(p->fd, h->magic, sizeof(*h->magic));
  		if (n < 0)
  			err = got_error_from_errno();
  		else if (n != sizeof(*h->magic)) {
  			err = got_error(GOT_ERR_BAD_PACKIDX);
  			goto done;
  		}
  	}
  	if (betoh32(*h->magic) != GOT_PACKIDX_V2_MAGIC) {
  		err = got_error(GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  	offset += sizeof(*h->magic);
  	remain -= sizeof(*h->magic);
  
  	if (verify)
  		SHA1Update(&ctx, (uint8_t *)h->magic, sizeof(*h->magic));
  
  	if (remain < sizeof(*h->version)) {
  		err = got_error(GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  	if (p->map)
  		h->version = (uint32_t *)(p->map + offset);
  	else {
  		h->version = malloc(sizeof(*h->version));
  		if (h->version == NULL) {
  			err = got_error_from_errno();
  			goto done;
  		}
  		n = read(p->fd, h->version, sizeof(*h->version));
  		if (n < 0)
  			err = got_error_from_errno();
  		else if (n != sizeof(*h->version)) {
  			err = got_error(GOT_ERR_BAD_PACKIDX);
  			goto done;
  		}
  	}
  	if (betoh32(*h->version) != GOT_PACKIDX_VERSION) {
  		err = got_error(GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  	offset += sizeof(*h->version);
  	remain -= sizeof(*h->version);
  
  	if (verify)
  		SHA1Update(&ctx, (uint8_t *)h->version, sizeof(*h->version));
  
  	len_fanout =
  	    sizeof(*h->fanout_table) * GOT_PACKIDX_V2_FANOUT_TABLE_ITEMS;
  	if (remain < len_fanout) {
  		err = got_error(GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  	if (p->map)
  		h->fanout_table = (uint32_t *)(p->map + offset);
  	else {
  		h->fanout_table = malloc(len_fanout);
  		if (h->fanout_table == NULL) {
  			err = got_error_from_errno();
  			goto done;
  		}
  		n = read(p->fd, h->fanout_table, len_fanout);
  		if (n < 0)
  			err = got_error_from_errno();
  		else if (n != len_fanout) {
  			err = got_error(GOT_ERR_BAD_PACKIDX);
  			goto done;
  		}
  	}
  	err = verify_fanout_table(h->fanout_table);
  	if (err)
  		goto done;
  	if (verify)
  		SHA1Update(&ctx, (uint8_t *)h->fanout_table, len_fanout);
  	offset += len_fanout;
  	remain -= len_fanout;
  
  	nobj = betoh32(h->fanout_table[0xff]);
  	len_ids = nobj * sizeof(*h->sorted_ids);
  	if (len_ids <= nobj || len_ids > remain) {
  		err = got_error(GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  	if (p->map)
  		h->sorted_ids =
  		    (struct got_packidx_object_id *)((uint8_t*)(p->map + offset));
  	else {
  		h->sorted_ids = malloc(len_ids);
  		if (h->sorted_ids == NULL) {
  			err = got_error(GOT_ERR_BAD_PACKIDX);
  			goto done;
  		}
  		n = read(p->fd, h->sorted_ids, len_ids);
  		if (n < 0)
  			err = got_error_from_errno();
  		else if (n != len_ids) {
  			err = got_error(GOT_ERR_BAD_PACKIDX);
  			goto done;
  		}
  	}
  	if (verify)
  		SHA1Update(&ctx, (uint8_t *)h->sorted_ids, len_ids);
  	offset += len_ids;
  	remain -= len_ids;
  
  	if (remain < nobj * sizeof(*h->crc32)) {
  		err = got_error(GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  	if (p->map)
  		h->crc32 = (uint32_t *)((uint8_t*)(p->map + offset));
  	else {
  		h->crc32 = malloc(nobj * sizeof(*h->crc32));
  		if (h->crc32 == NULL) {
  			err = got_error_from_errno();
  			goto done;
  		}
  		n = read(p->fd, h->crc32, nobj * sizeof(*h->crc32));
  		if (n < 0)
  			err = got_error_from_errno();
  		else if (n != nobj * sizeof(*h->crc32)) {
  			err = got_error(GOT_ERR_BAD_PACKIDX);
  			goto done;
  		}
  	}
  	if (verify)
  		SHA1Update(&ctx, (uint8_t *)h->crc32, nobj * sizeof(*h->crc32));
  	remain -= nobj * sizeof(*h->crc32);
  	offset += nobj * sizeof(*h->crc32);
  
  	if (remain < nobj * sizeof(*h->offsets)) {
  		err = got_error(GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  	if (p->map)
  		h->offsets = (uint32_t *)((uint8_t*)(p->map + offset));
  	else {
  		h->offsets = malloc(nobj * sizeof(*h->offsets));
  		if (h->offsets == NULL) {
  			err = got_error_from_errno();
  			goto done;
  		}
  		n = read(p->fd, h->offsets, nobj * sizeof(*h->offsets));
  		if (n < 0)
  			err = got_error_from_errno();
  		else if (n != nobj * sizeof(*h->offsets)) {
  			err = got_error(GOT_ERR_BAD_PACKIDX);
  			goto done;
  		}
  	}
  	if (verify)
  		SHA1Update(&ctx, (uint8_t *)h->offsets,
  		    nobj * sizeof(*h->offsets));
  	remain -= nobj * sizeof(*h->offsets);
  	offset += nobj * sizeof(*h->offsets);
  
  	/* Large file offsets are contained only in files > 2GB. */
  	if (p->len <= 0x80000000)
  		goto checksum;
  
  	if (remain < nobj * sizeof(*h->large_offsets)) {
  		err = got_error(GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  	if (p->map)
  		h->large_offsets = (uint64_t *)((uint8_t*)(p->map + offset));
  	else {
  		h->offsets = malloc(nobj * sizeof(*h->large_offsets));
  		if (h->offsets == NULL) {
  			err = got_error_from_errno();
  			goto done;
  		}
  		n = read(p->fd, h->large_offsets,
  		    nobj * sizeof(*h->large_offsets));
  		if (n < 0)
  			err = got_error_from_errno();
  		else if (n != nobj * sizeof(*h->large_offsets)) {
  			err = got_error(GOT_ERR_BAD_PACKIDX);
  			goto done;
  		}
  	}
  	if (verify)
  		SHA1Update(&ctx, (uint8_t*)h->large_offsets,
  		    nobj * sizeof(*h->large_offsets));
  	remain -= nobj * sizeof(*h->large_offsets);
  	offset += nobj * sizeof(*h->large_offsets);
  
  checksum:
  	if (remain < sizeof(*h->trailer)) {
  		err = got_error(GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  	if (p->map)
  		h->trailer =
  		    (struct got_packidx_trailer *)((uint8_t*)(p->map + offset));
  	else {
  		h->trailer = malloc(sizeof(*h->trailer));
  		if (h->trailer == NULL) {
  			err = got_error_from_errno();
  			goto done;
  		}
  		n = read(p->fd, h->trailer, sizeof(*h->trailer));
  		if (n < 0)
  			err = got_error_from_errno();
  		else if (n != sizeof(*h->trailer)) {
  			err = got_error(GOT_ERR_BAD_PACKIDX);
  			goto done;
  		}
  	}
  	if (verify) {
  		SHA1Update(&ctx, h->trailer->packfile_sha1, SHA1_DIGEST_LENGTH);
  		SHA1Final(sha1, &ctx);
  		if (memcmp(h->trailer->packidx_sha1, sha1,
  		    SHA1_DIGEST_LENGTH) != 0)
  			err = got_error(GOT_ERR_PACKIDX_CSUM);
  	}
  done:
  	return err;
  }
  
  const struct got_error *
  got_packidx_open(struct got_packidx **packidx, const char *path, int verify)
  {
  	const struct got_error *err = NULL;
  	struct got_packidx *p;
  
  	*packidx = NULL;
  
  	p = calloc(1, sizeof(*p));
  	if (p == NULL)
  		return got_error_from_errno();
  
  	p->fd = open(path, O_RDONLY | O_NOFOLLOW, GOT_DEFAULT_FILE_MODE);
  	if (p->fd == -1)
  		return got_error_from_errno();
  
  	err = got_pack_get_packfile_size(&p->len, path);
  	if (err) {
  		close(p->fd);
  		free(p);
  		return err;
  	}
  	if (p->len < sizeof(p->hdr)) {
  		err = got_error(GOT_ERR_BAD_PACKIDX);
  		close(p->fd);
  		free(p);
  		return err;
  	}
  
  	p->path_packidx = strdup(path);
  	if (p->path_packidx == NULL) {
  		err = got_error_from_errno();
  		goto done;
  	}
  
  #ifndef GOT_PACK_NO_MMAP
  	p->map = mmap(NULL, p->len, PROT_READ, MAP_PRIVATE, p->fd, 0);
  	if (p->map == MAP_FAILED)
  		p->map = NULL; /* fall back to read(2) */
  #endif
  
  	err = got_packidx_init_hdr(p, verify);
  done:
  	if (err)
  		got_packidx_close(p);
  	else
  		*packidx = p;
  
  	return err;
  }
  
  const struct got_error *
  got_packidx_close(struct got_packidx *packidx)
  {
  	const struct got_error *err = NULL;
  
  	free(packidx->path_packidx);
  	if (packidx->map) {
  		if (munmap(packidx->map, packidx->len) == -1)
  			err = got_error_from_errno();
  	} else {
  		free(packidx->hdr.magic);
  		free(packidx->hdr.version);
  		free(packidx->hdr.fanout_table);
  		free(packidx->hdr.sorted_ids);
  		free(packidx->hdr.crc32);
  		free(packidx->hdr.offsets);
  		free(packidx->hdr.large_offsets);
  		free(packidx->hdr.trailer);
  	}
  	close(packidx->fd);
  	free(packidx);
  
  	return err;
  }
  
  static off_t
  get_object_offset(struct got_packidx *packidx, int idx)
  {
  	uint32_t totobj = betoh32(packidx->hdr.fanout_table[0xff]);
  	uint32_t offset = betoh32(packidx->hdr.offsets[idx]);
  	if (offset & GOT_PACKIDX_OFFSET_VAL_IS_LARGE_IDX) {
  		uint64_t loffset;
  		idx = offset & GOT_PACKIDX_OFFSET_VAL_MASK;
  		if (idx < 0 || idx > totobj ||
  		    packidx->hdr.large_offsets == NULL)
  			return -1;
  		loffset = betoh64(packidx->hdr.large_offsets[idx]);
  		return (loffset > INT64_MAX ? -1 : (off_t)loffset);
  	}
  	return (off_t)(offset & GOT_PACKIDX_OFFSET_VAL_MASK);
  }
  
  int
  got_packidx_get_object_idx(struct got_packidx *packidx, struct got_object_id *id)
  {
  	u_int8_t id0 = id->sha1[0];
  	uint32_t totobj = betoh32(packidx->hdr.fanout_table[0xff]);
  	int left = 0, right = totobj - 1;
  
  	if (id0 > 0)
  		left = betoh32(packidx->hdr.fanout_table[id0 - 1]);
  
  	while (left <= right) {
  		struct got_packidx_object_id *oid;
  		int i, cmp;
  
  		i = ((left + right) / 2);
  		oid = &packidx->hdr.sorted_ids[i];
  		cmp = memcmp(id->sha1, oid->sha1, SHA1_DIGEST_LENGTH);
  		if (cmp == 0)
  			return i;
  		else if (cmp > 0)
  			left = i + 1;
  		else if (cmp < 0)
  			right = i - 1;
  	}
  
  	return -1;
  }
  
  const struct got_error *
  got_pack_stop_privsep_child(struct got_pack *pack)
  {
  	const struct got_error *err = NULL;
  
  	if (pack->privsep_child == NULL)
  		return NULL;
  
  	err = got_privsep_send_stop(pack->privsep_child->imsg_fd);
  	if (err)
  		return err;
  	err = got_privsep_wait_for_child(pack->privsep_child->pid);
  	free(pack->privsep_child);
  	pack->privsep_child = NULL;
  	return err;
  }
  
  const struct got_error *
  got_pack_close(struct got_pack *pack)
  {
  	const struct got_error *err = NULL;
  
  	err = got_pack_stop_privsep_child(pack);
  	if (pack->map && munmap(pack->map, pack->filesize) == -1 && !err)
  		err = got_error_from_errno();
  	close(pack->fd);
  	pack->fd = -1;
  	free(pack->path_packfile);
  	pack->path_packfile = NULL;
  	pack->filesize = 0;
  
  	return err;
  }
  
  static const struct got_error *
  parse_object_type_and_size(uint8_t *type, uint64_t *size, size_t *len,
      struct got_pack *pack, off_t offset)
  {
  	uint8_t t = 0;
  	uint64_t s = 0;
  	uint8_t sizeN;
  	size_t mapoff = 0;
  	int i = 0;
  
  	*len = 0;
  
  	if (offset >= pack->filesize)
  		return got_error(GOT_ERR_PACK_OFFSET);
  
  	if (pack->map) {
  		mapoff = (size_t)offset;
  	} else {
  		if (lseek(pack->fd, offset, SEEK_SET) == -1)
  			return got_error_from_errno();
  	}
  
  	do {
  		/* We do not support size values which don't fit in 64 bit. */
  		if (i > 9)
  			return got_error(GOT_ERR_NO_SPACE);
  
  		if (pack->map) {
  			sizeN = *(pack->map + mapoff);
  			mapoff += sizeof(sizeN);
  		} else {
  			ssize_t n = read(pack->fd, &sizeN, sizeof(sizeN));
  			if (n < 0)
  				return got_error_from_errno();
  			if (n != sizeof(sizeN))
  				return got_error(GOT_ERR_BAD_PACKFILE);
  		}
  		*len += sizeof(sizeN);
  
  		if (i == 0) {
  			t = (sizeN & GOT_PACK_OBJ_SIZE0_TYPE_MASK) >>
  			    GOT_PACK_OBJ_SIZE0_TYPE_MASK_SHIFT;
  			s = (sizeN & GOT_PACK_OBJ_SIZE0_VAL_MASK);
  		} else {
  			size_t shift = 4 + 7 * (i - 1);
  			s |= ((sizeN & GOT_PACK_OBJ_SIZE_VAL_MASK) << shift);
  		}
  		i++;
  	} while (sizeN & GOT_PACK_OBJ_SIZE_MORE);
  
  	*type = t;
  	*size = s;
  	return NULL;
  }
  
  static const struct got_error *
  open_plain_object(struct got_object **obj, const char *path_packfile,
      struct got_object_id *id, uint8_t type, off_t offset, size_t size, int idx)
  {
  	*obj = calloc(1, sizeof(**obj));
  	if (*obj == NULL)
  		return got_error_from_errno();
  
  	(*obj)->path_packfile = strdup(path_packfile);
  	if ((*obj)->path_packfile == NULL) {
  		const struct got_error *err = got_error_from_errno();
  		free(*obj);
  		*obj = NULL;
  		return err;
  	}
  
  	(*obj)->type = type;
  	(*obj)->flags = GOT_OBJ_FLAG_PACKED;
  	(*obj)->pack_idx = idx;
  	(*obj)->hdrlen = 0;
  	(*obj)->size = size;
  	memcpy(&(*obj)->id, id, sizeof((*obj)->id));
  	(*obj)->pack_offset = offset;
  
  	return NULL;
  }
  
  static const struct got_error *
  parse_negative_offset(int64_t *offset, size_t *len, struct got_pack *pack,
      off_t delta_offset)
  {
  	int64_t o = 0;
  	uint8_t offN;
  	int i = 0;
  
  	*len = 0;
  
  	do {
  		/* We do not support offset values which don't fit in 64 bit. */
  		if (i > 8)
  			return got_error(GOT_ERR_NO_SPACE);
  
  		if (pack->map) {
  			size_t mapoff;
  			if (delta_offset >= pack->filesize)
  				return got_error(GOT_ERR_PACK_OFFSET);
  			mapoff = (size_t)delta_offset + *len;
  			offN = *(pack->map + mapoff);
  		} else {
  			ssize_t n;
  			n = read(pack->fd, &offN, sizeof(offN));
  			if (n < 0)
  				return got_error_from_errno();
  			if (n != sizeof(offN))
  				return got_error(GOT_ERR_BAD_PACKFILE);
  		}
  		*len += sizeof(offN);
  
  		if (i == 0)
  			o = (offN & GOT_PACK_OBJ_DELTA_OFF_VAL_MASK);
  		else {
  			o++;
  			o <<= 7;
  			o += (offN & GOT_PACK_OBJ_DELTA_OFF_VAL_MASK);
  		}
  		i++;
  	} while (offN & GOT_PACK_OBJ_DELTA_OFF_MORE);
  
  	*offset = o;
  	return NULL;
  }
  
  static const struct got_error *
  parse_offset_delta(off_t *base_offset, size_t *len, struct got_pack *pack,
      off_t offset, int tslen)
  {
  	const struct got_error *err;
  	int64_t negoffset;
  	size_t negofflen;
  
  	*len = 0;
  
  	err = parse_negative_offset(&negoffset, &negofflen, pack,
  	    offset + tslen);
  	if (err)
  		return err;
  
  	/* Compute the base object's offset (must be in the same pack file). */
  	*base_offset = (offset - negoffset);
  	if (*base_offset <= 0)
  		return got_error(GOT_ERR_BAD_PACKFILE);
  
  	*len = negofflen;
  	return NULL;
  }
  
  static const struct got_error *
  resolve_delta_chain(struct got_delta_chain *, struct got_packidx *,
      struct got_pack *, off_t, size_t, int, size_t, unsigned int);
  
  static const struct got_error *
  add_delta(struct got_delta_chain *deltas, off_t delta_offset, size_t tslen,
      int delta_type, size_t delta_size, size_t delta_data_offset,
      uint8_t *delta_buf, size_t delta_len)
  {
  	struct got_delta *delta;
  
  	delta = got_delta_open(delta_offset, tslen, delta_type, delta_size,
  	    delta_data_offset, delta_buf,
  	    delta_len);
  	if (delta == NULL)
  		return got_error_from_errno();
  	/* delta is freed in got_object_close() */
  	deltas->nentries++;
  	SIMPLEQ_INSERT_HEAD(&deltas->entries, delta, entry);
  	return NULL;
  }
  
  static const struct got_error *
  resolve_offset_delta(struct got_delta_chain *deltas,
      struct got_packidx *packidx, struct got_pack *pack, off_t delta_offset,
      size_t tslen, int delta_type, size_t delta_size, unsigned int recursion)
  
  {
  	const struct got_error *err;
  	off_t base_offset;
  	uint8_t base_type;
  	uint64_t base_size;
  	size_t base_tslen;
  	off_t delta_data_offset;
  	uint8_t *delta_buf;
  	size_t delta_len, consumed;
  
  	err = parse_offset_delta(&base_offset, &consumed, pack,
  	    delta_offset, tslen);
  	if (err)
  		return err;
  
  	delta_data_offset = delta_offset + tslen + consumed;
  	if (delta_data_offset >= pack->filesize)
  		return got_error(GOT_ERR_PACK_OFFSET);
  
  	if (pack->map == NULL) {
  		delta_data_offset = lseek(pack->fd, 0, SEEK_CUR);
  		if (delta_data_offset == -1)
  			return got_error_from_errno();
  	}
  
  	if (pack->map) {
  		size_t mapoff = (size_t)delta_data_offset;
  		err = got_inflate_to_mem_mmap(&delta_buf, &delta_len, pack->map,
  		    mapoff, pack->filesize - mapoff);
  		if (err)
  			return err;
  	} else {
  
  		err = got_inflate_to_mem_fd(&delta_buf, &delta_len, pack->fd);
  		if (err)
  			return err;
  	}
  
  	err = add_delta(deltas, delta_offset, tslen, delta_type, delta_size,
  	    delta_data_offset, delta_buf, delta_len);
  	if (err)
  		goto done;
  
  	/* An offset delta must be in the same packfile. */
  	if (base_offset >= pack->filesize) {
  		err = got_error(GOT_ERR_PACK_OFFSET);
  		goto done;
  	}
  
  	err = parse_object_type_and_size(&base_type, &base_size, &base_tslen,
  	    pack, base_offset);
  	if (err)
  		goto done;
  
  	err = resolve_delta_chain(deltas, packidx, pack, base_offset,
  	    base_tslen, base_type, base_size, recursion - 1);
  done:
  	if (err)
  		free(delta_buf);
  	return err;
  }
  
  static const struct got_error *
  resolve_ref_delta(struct got_delta_chain *deltas, struct got_packidx *packidx,
      struct got_pack *pack, off_t delta_offset, size_t tslen, int delta_type,
      size_t delta_size, unsigned int recursion)
  {
  	const struct got_error *err;
  	struct got_object_id id;
  	int idx;
  	off_t base_offset;
  	uint8_t base_type;
  	uint64_t base_size;
  	size_t base_tslen;
  	off_t delta_data_offset;
  	uint8_t *delta_buf = NULL;
  	size_t delta_len;
  
  	if (delta_offset >= pack->filesize)
  		return got_error(GOT_ERR_PACK_OFFSET);
  	delta_data_offset = delta_offset + tslen;
  	if (delta_data_offset >= pack->filesize)
  		return got_error(GOT_ERR_PACK_OFFSET);
  
  	if (pack->map == NULL) {
  		delta_data_offset = lseek(pack->fd, 0, SEEK_CUR);
  		if (delta_data_offset == -1)
  			return got_error_from_errno();
  	}
  
  
  	if (pack->map) {
  		size_t mapoff = (size_t)delta_data_offset;
  		memcpy(&id, pack->map + mapoff, sizeof(id));
  		mapoff += sizeof(id);
  		err = got_inflate_to_mem_mmap(&delta_buf, &delta_len, pack->map,
  		    mapoff, pack->filesize - mapoff);
  		if (err)
  			goto done;
  	} else {
  		ssize_t n = read(pack->fd, &id, sizeof(id));
  		if (n < 0)
  			return got_error_from_errno();
  		if (n != sizeof(id))
  			return got_error(GOT_ERR_BAD_PACKFILE);
  		err = got_inflate_to_mem_fd(&delta_buf, &delta_len, pack->fd);
  		if (err)
  			goto done;
  	}
  
  	err = add_delta(deltas, delta_offset, tslen, delta_type, delta_size,
  	    delta_data_offset, delta_buf, delta_len);
  	if (err)
  		goto done;
  
  	/* Delta base must be in the same pack file. */
  	idx = got_packidx_get_object_idx(packidx, &id);
  	if (idx == -1) {
  		err = got_error(GOT_ERR_BAD_PACKFILE);
  		goto done;
  	}
  
  	base_offset = get_object_offset(packidx, idx);
  	if (base_offset == (uint64_t)-1) {
  		err = got_error(GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  
  	if (base_offset >= pack->filesize) {
  		err = got_error(GOT_ERR_PACK_OFFSET);
  		goto done;
  	}
  
  	err = parse_object_type_and_size(&base_type, &base_size, &base_tslen,
  	    pack, base_offset);
  	if (err)
  		goto done;
  
  	err = resolve_delta_chain(deltas, packidx, pack, base_offset,
  	    base_tslen, base_type, base_size, recursion - 1);
  done:
  	if (err)
  		free(delta_buf);
  	return err;
  }
  
  static const struct got_error *
  resolve_delta_chain(struct got_delta_chain *deltas, struct got_packidx *packidx,
      struct got_pack *pack, off_t delta_offset, size_t tslen, int delta_type,
      size_t delta_size, unsigned int recursion)
  {
  	const struct got_error *err = NULL;
  
  	if (--recursion == 0)
  		return got_error(GOT_ERR_RECURSION);
  
  	switch (delta_type) {
  	case GOT_OBJ_TYPE_COMMIT:
  	case GOT_OBJ_TYPE_TREE:
  	case GOT_OBJ_TYPE_BLOB:
  	case GOT_OBJ_TYPE_TAG:
  		/* Plain types are the final delta base. Recursion ends. */
  		err = add_delta(deltas, delta_offset, tslen, delta_type,
  		    delta_size, 0, NULL, 0);
  		break;
  	case GOT_OBJ_TYPE_OFFSET_DELTA:
  		err = resolve_offset_delta(deltas, packidx, pack,
  		    delta_offset, tslen, delta_type, delta_size, recursion - 1);
  		break;
  	case GOT_OBJ_TYPE_REF_DELTA:
  		err = resolve_ref_delta(deltas, packidx, pack,
  		    delta_offset, tslen, delta_type, delta_size, recursion - 1);
  		break;
  	default:
  		return got_error(GOT_ERR_OBJ_TYPE);
  	}
  
  	return err;
  }
  
  static const struct got_error *
  open_delta_object(struct got_object **obj, struct got_packidx *packidx,
      struct got_pack *pack, struct got_object_id *id, off_t offset,
      size_t tslen, int delta_type, size_t delta_size, int idx)
  {
  	const struct got_error *err = NULL;
  	int resolved_type;
  
  	*obj = calloc(1, sizeof(**obj));
  	if (*obj == NULL)
  		return got_error_from_errno();
  
  	(*obj)->flags = 0;
  	(*obj)->hdrlen = 0;
  	(*obj)->size = 0; /* Not known because deltas aren't applied yet. */
  	memcpy(&(*obj)->id, id, sizeof((*obj)->id));
  	(*obj)->pack_offset = offset + tslen;
  
  	(*obj)->path_packfile = strdup(pack->path_packfile);
  	if ((*obj)->path_packfile == NULL) {
  		err = got_error_from_errno();
  		goto done;
  	}
  	(*obj)->flags |= GOT_OBJ_FLAG_PACKED;
  	(*obj)->pack_idx = idx;
  
  	SIMPLEQ_INIT(&(*obj)->deltas.entries);
  	(*obj)->flags |= GOT_OBJ_FLAG_DELTIFIED;
  
  	err = resolve_delta_chain(&(*obj)->deltas, packidx, pack, offset,
  	    tslen, delta_type, delta_size, GOT_DELTA_CHAIN_RECURSION_MAX);
  	if (err)
  		goto done;
  
  	err = got_delta_chain_get_base_type(&resolved_type, &(*obj)->deltas);
  	if (err)
  		goto done;
  	(*obj)->type = resolved_type;
  done:
  	if (err) {
  		got_object_close(*obj);
  		*obj = NULL;
  	}
  	return err;
  }
  
  const struct got_error *
  got_packfile_open_object(struct got_object **obj, struct got_pack *pack,
      struct got_packidx *packidx, int idx, struct got_object_id *id)
  {
  	const struct got_error *err = NULL;
  	off_t offset;
  	uint8_t type;
  	uint64_t size;
  	size_t tslen;
  
  	*obj = NULL;
  
  	offset = get_object_offset(packidx, idx);
  	if (offset == (uint64_t)-1)
  		return got_error(GOT_ERR_BAD_PACKIDX);
  
  	err = parse_object_type_and_size(&type, &size, &tslen, pack, offset);
  	if (err)
  		return err;
  
  	switch (type) {
  	case GOT_OBJ_TYPE_COMMIT:
  	case GOT_OBJ_TYPE_TREE:
  	case GOT_OBJ_TYPE_BLOB:
  	case GOT_OBJ_TYPE_TAG:
  		err = open_plain_object(obj, pack->path_packfile, id, type,
  		    offset + tslen, size, idx);
  		break;
  	case GOT_OBJ_TYPE_OFFSET_DELTA:
  	case GOT_OBJ_TYPE_REF_DELTA:
  		err = open_delta_object(obj, packidx, pack, id, offset,
  		    tslen, type, size, idx);
  		break;
  	default:
  		err = got_error(GOT_ERR_OBJ_TYPE);
  		break;
  	}
  
  	return err;
  }
  
  static const struct got_error *
  get_delta_chain_max_size(uint64_t *max_size, struct got_delta_chain *deltas)
  {
  	struct got_delta *delta;
  	uint64_t base_size = 0, result_size = 0;
  
  	*max_size = 0;
  	SIMPLEQ_FOREACH(delta, &deltas->entries, entry) {
  		/* Plain object types are the delta base. */
  		if (delta->type != GOT_OBJ_TYPE_COMMIT &&
  		    delta->type != GOT_OBJ_TYPE_TREE &&
  		    delta->type != GOT_OBJ_TYPE_BLOB &&
  		    delta->type != GOT_OBJ_TYPE_TAG) {
  			const struct got_error *err;
  			err = got_delta_get_sizes(&base_size, &result_size,
  			    delta->delta_buf, delta->delta_len);
  			if (err)
  				return err;
  		} else
  			base_size = delta->size;
  		if (base_size > *max_size)
  			*max_size = base_size;
  		if (result_size > *max_size)
  			*max_size = result_size;
  	}
  
  	return NULL;
  }
  
  static const struct got_error *
  dump_delta_chain_to_file(size_t *result_size, struct got_delta_chain *deltas,
      struct got_pack *pack, FILE *outfile, FILE *base_file, FILE *accum_file)
  {
  	const struct got_error *err = NULL;
  	struct got_delta *delta;
  	uint8_t *base_buf = NULL, *accum_buf = NULL;
  	size_t base_bufsz = 0, accum_size = 0;
  	uint64_t max_size;
  	int n = 0;
  
  	*result_size = 0;
  
  	if (SIMPLEQ_EMPTY(&deltas->entries))
  		return got_error(GOT_ERR_BAD_DELTA_CHAIN);
  
  	/* We process small enough files entirely in memory for speed. */
  	err = get_delta_chain_max_size(&max_size, deltas);
  	if (err)
  		return err;
  	if (max_size < GOT_DELTA_RESULT_SIZE_CACHED_MAX) {
  		accum_buf = malloc(max_size);
  		if (accum_buf == NULL)
  			return got_error_from_errno();
  		base_file = NULL;
  		accum_file = NULL;
  	}
  
  	/* Deltas are ordered in ascending order. */
  	SIMPLEQ_FOREACH(delta, &deltas->entries, entry) {
  		if (n == 0) {
  			size_t mapoff;
  			off_t delta_data_offset;
  
  			/* Plain object types are the delta base. */
  			if (delta->type != GOT_OBJ_TYPE_COMMIT &&
  			    delta->type != GOT_OBJ_TYPE_TREE &&
  			    delta->type != GOT_OBJ_TYPE_BLOB &&
  			    delta->type != GOT_OBJ_TYPE_TAG) {
  				err = got_error(GOT_ERR_BAD_DELTA_CHAIN);
  				goto done;
  			}
  
  			delta_data_offset = delta->offset + delta->tslen;
  			if (delta_data_offset >= pack->filesize) {
  				err = got_error(GOT_ERR_PACK_OFFSET);
  				goto done;
  			}
  			if (pack->map == NULL) {
  				if (lseek(pack->fd, delta_data_offset, SEEK_SET)
  				    == -1) {
  					err = got_error_from_errno();
  					goto done;
  				}
  			}
  			if (base_file) {
  				if (pack->map) {
  					mapoff = (size_t)delta_data_offset;
  					err = got_inflate_to_file_mmap(
  					    &base_bufsz, pack->map, mapoff,
  					    pack->filesize - mapoff, base_file);
  				} else
  					err = got_inflate_to_file_fd(
  					    &base_bufsz, pack->fd, base_file);
  			} else {
  				if (pack->map) {
  					mapoff = (size_t)delta_data_offset;
  					err = got_inflate_to_mem_mmap(&base_buf,
  					    &base_bufsz, pack->map, mapoff,
  					    pack->filesize - mapoff);
  				} else
  					err = got_inflate_to_mem_fd(&base_buf,
  					    &base_bufsz, pack->fd);
  			}
  			if (err)
  				goto done;
  			n++;
  			if (base_file)
  				rewind(base_file);
  			continue;
  		}
  
  		if (base_buf) {
  			err = got_delta_apply_in_mem(base_buf, base_bufsz,
  			    delta->delta_buf, delta->delta_len, accum_buf,
  			    &accum_size, max_size);
  			n++;
  		} else {
  			err = got_delta_apply(base_file, delta->delta_buf,
  			    delta->delta_len,
  			    /* Final delta application writes to output file. */
  			    ++n < deltas->nentries ? accum_file : outfile,
  			    &accum_size);
  		}
  		if (err)
  			goto done;
  
  		if (n < deltas->nentries) {
  			/* Accumulated delta becomes the new base. */
  			if (base_buf) {
  				uint8_t *tmp = accum_buf;
  				/*
  				 * Base buffer switches roles with accumulation
  				 * buffer. Ensure it can hold the largest
  				 * result in the delta chain. The initial
  				 * allocation might have been smaller.
  				 */
  				if (base_bufsz < max_size) {
  					uint8_t *p;
  					p = reallocarray(base_buf, 1, max_size);
  					if (p == NULL) {
  						err = got_error_from_errno();
  						goto done;
  					}
  					base_buf = p;
  					base_bufsz = max_size;
  				}
  				accum_buf = base_buf;
  				base_buf = tmp;
  			} else {
  				FILE *tmp = accum_file;
  				accum_file = base_file;
  				base_file = tmp;
  				rewind(base_file);
  				rewind(accum_file);
  			}
  		}
  	}
  
  done:
  	free(base_buf);
  	if (accum_buf) {
  		size_t len = fwrite(accum_buf, 1, accum_size, outfile);
  		free(accum_buf);
  		if (len != accum_size)
  			err = got_ferror(outfile, GOT_ERR_IO);
  	}
  	if (base_file)
  		fclose(base_file);
  	if (accum_file)
  		fclose(accum_file);
  	rewind(outfile);
  	if (err == NULL)
  		*result_size = accum_size;
  	return err;
  }
  
  static const struct got_error *
  dump_delta_chain_to_mem(uint8_t **outbuf, size_t *outlen,
      struct got_delta_chain *deltas, struct got_pack *pack)
  {
  	const struct got_error *err = NULL;
  	struct got_delta *delta;
  	uint8_t *base_buf = NULL, *accum_buf = NULL;
  	size_t base_bufsz = 0, accum_size = 0;
  	uint64_t max_size;
  	int n = 0;
  
  	*outbuf = NULL;
  	*outlen = 0;
  
  	if (SIMPLEQ_EMPTY(&deltas->entries))
  		return got_error(GOT_ERR_BAD_DELTA_CHAIN);
  
  	err = get_delta_chain_max_size(&max_size, deltas);
  	if (err)
  		return err;
  	accum_buf = malloc(max_size);
  	if (accum_buf == NULL)
  		return got_error_from_errno();
  
  	/* Deltas are ordered in ascending order. */
  	SIMPLEQ_FOREACH(delta, &deltas->entries, entry) {
  		if (n == 0) {
  			size_t delta_data_offset;
  
  			/* Plain object types are the delta base. */
  			if (delta->type != GOT_OBJ_TYPE_COMMIT &&
  			    delta->type != GOT_OBJ_TYPE_TREE &&
  			    delta->type != GOT_OBJ_TYPE_BLOB &&
  			    delta->type != GOT_OBJ_TYPE_TAG) {
  				err = got_error(GOT_ERR_BAD_DELTA_CHAIN);
  				goto done;
  			}
  
  			delta_data_offset = delta->offset + delta->tslen;
  			if (delta_data_offset >= pack->filesize) {
  				err = got_error(GOT_ERR_PACK_OFFSET);
  				goto done;
  			}
  			if (pack->map) {
  				size_t mapoff = (size_t)delta_data_offset;
  				err = got_inflate_to_mem_mmap(&base_buf,
  				    &base_bufsz, pack->map, mapoff,
  				    pack->filesize - mapoff);
  			} else {
  				if (lseek(pack->fd, delta_data_offset, SEEK_SET)
  				    == -1) {
  					err = got_error_from_errno();
  					goto done;
  				}
  				err = got_inflate_to_mem_fd(&base_buf,
  				    &base_bufsz, pack->fd);
  			}
  			if (err)
  				goto done;
  			n++;
  			continue;
  		}
  
  		err = got_delta_apply_in_mem(base_buf, base_bufsz,
  		    delta->delta_buf, delta->delta_len, accum_buf,
  		    &accum_size, max_size);
  		n++;
  		if (err)
  			goto done;
  
  		if (n < deltas->nentries) {
  			/* Accumulated delta becomes the new base. */
  			uint8_t *tmp = accum_buf;
  			/*
  			 * Base buffer switches roles with accumulation buffer.
  			 * Ensure it can hold the largest result in the delta
  			 * chain. Initial allocation might have been smaller.
  			 */
  			if (base_bufsz < max_size) {
  				uint8_t *p;
  				p = reallocarray(base_buf, 1, max_size);
  				if (p == NULL) {
  					err = got_error_from_errno();
  					goto done;
  				}
  				base_buf = p;
  				base_bufsz = max_size;
  			}
  			accum_buf = base_buf;
  			base_buf = tmp;
  		}
  	}
  
  done:
  	free(base_buf);
  	if (err) {
  		free(accum_buf);
  		*outbuf = NULL;
  		*outlen = 0;
  	} else {
  		*outbuf = accum_buf;
  		*outlen = accum_size;
  	}
  	return err;
  }
  
  const struct got_error *
  got_packfile_extract_object(struct got_pack *pack, struct got_object *obj,
      FILE *outfile, FILE *base_file, FILE *accum_file)
  {
  	const struct got_error *err = NULL;
  
  	if ((obj->flags & GOT_OBJ_FLAG_PACKED) == 0)
  		return got_error(GOT_ERR_OBJ_NOT_PACKED);
  
  	if ((obj->flags & GOT_OBJ_FLAG_DELTIFIED) == 0) {
  		if (obj->pack_offset >= pack->filesize)
  			return got_error(GOT_ERR_PACK_OFFSET);
  
  		if (pack->map) {
  			size_t mapoff = (size_t)obj->pack_offset;
  			err = got_inflate_to_file_mmap(&obj->size, pack->map,
  			    mapoff, pack->filesize - mapoff, outfile);
  		} else {
  			if (lseek(pack->fd, obj->pack_offset, SEEK_SET) == -1)
  				return got_error_from_errno();
  			err = got_inflate_to_file_fd(&obj->size, pack->fd,
  			    outfile);
  		}
  	} else
  		err = dump_delta_chain_to_file(&obj->size, &obj->deltas, pack,
  		    outfile, base_file, accum_file);
  
  	return err;
  }
  
  const struct got_error *
  got_packfile_extract_object_to_mem(uint8_t **buf, size_t *len,
      struct got_object *obj, struct got_pack *pack)
  {
  	const struct got_error *err = NULL;
  
  	if ((obj->flags & GOT_OBJ_FLAG_PACKED) == 0)
  		return got_error(GOT_ERR_OBJ_NOT_PACKED);
  
  	if ((obj->flags & GOT_OBJ_FLAG_DELTIFIED) == 0) {
  		if (obj->pack_offset >= pack->filesize)
  			return got_error(GOT_ERR_PACK_OFFSET);
  		if (pack->map) {
  			size_t mapoff = (size_t)obj->pack_offset;
  			err = got_inflate_to_mem_mmap(buf, len, pack->map,
  			    mapoff, pack->filesize - mapoff);
  		} else {
  			if (lseek(pack->fd, obj->pack_offset, SEEK_SET) == -1)
  				return got_error_from_errno();
  			err = got_inflate_to_mem_fd(buf, len, pack->fd);
  		}
  	} else
  		err = dump_delta_chain_to_mem(buf, len, &obj->deltas, pack);
  
  	return err;
  }