archival/unzip.c

/* vi: set sw=4 ts=4: */
/*
 * Mini unzip implementation for busybox
 *
 * Copyright (C) 2004 by Ed Clark
 *
 * Loosely based on original busybox unzip applet by Laurence Anderson.
 * All options and features should work in this version.
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */
/* For reference see
 * http://www.pkware.com/company/standards/appnote/
 * http://www.info-zip.org/pub/infozip/doc/appnote-iz-latest.zip
 *
 * TODO
 * Zip64 + other methods
 */
//config:config UNZIP
//config:	bool "unzip (26 kb)"
//config:	default y
//config:	help
//config:	unzip will list or extract files from a ZIP archive,
//config:	commonly found on DOS/WIN systems. The default behavior
//config:	(with no options) is to extract the archive into the
//config:	current directory.
//config:
//config:config FEATURE_UNZIP_CDF
//config:	bool "Read and use Central Directory data"
//config:	default y
//config:	depends on UNZIP
//config:	help
//config:	If you know that you only need to deal with simple
//config:	ZIP files without deleted/updated files, SFX archives etc,
//config:	you can reduce code size by unselecting this option.
//config:	To support less trivial ZIPs, say Y.
//config:
//config:config FEATURE_UNZIP_BZIP2
//config:	bool "Support compression method 12 (bzip2)"
//config:	default y
//config:	depends on FEATURE_UNZIP_CDF && DESKTOP
// FEATURE_UNZIP_CDF is needed, otherwise we can't find start of next file
// DESKTOP is needed to get back uncompressed length
//config:
//config:config FEATURE_UNZIP_LZMA
//config:	bool "Support compression method 14 (lzma)"
//config:	default y
//config:	depends on FEATURE_UNZIP_CDF && DESKTOP
//config:
//config:config FEATURE_UNZIP_XZ
//config:	bool "Support compression method 95 (xz)"
//config:	default y
//config:	depends on FEATURE_UNZIP_CDF && DESKTOP

//applet:IF_UNZIP(APPLET(unzip, BB_DIR_USR_BIN, BB_SUID_DROP))
//kbuild:lib-$(CONFIG_UNZIP) += unzip.o

//usage:#define unzip_trivial_usage
//usage:       "[-lnojpq] FILE[.zip] [FILE]... [-x FILE...] [-d DIR]"
//usage:#define unzip_full_usage "\n\n"
//usage:       "Extract FILEs from ZIP archive\n"
//usage:     "\n	-l	List contents (with -q for short form)"
//usage:     "\n	-n	Never overwrite files (default: ask)"
//usage:     "\n	-o	Overwrite"
//usage:     "\n	-j	Do not restore paths"
//usage:     "\n	-p	Print to stdout"
//usage:     "\n	-q	Quiet"
//usage:     "\n	-x FILE	Exclude FILEs"
//usage:     "\n	-d DIR	Extract into DIR"

#include "libbb.h"
#include "bb_archive.h"

#if 0
# define dbg(...) bb_error_msg(__VA_ARGS__)
#else
# define dbg(...) ((void)0)
#endif

enum {
#if BB_BIG_ENDIAN
	ZIP_FILEHEADER_MAGIC = 0x504b0304,
	ZIP_CDF_MAGIC        = 0x504b0102, /* CDF item */
	ZIP_CDE_MAGIC        = 0x504b0506, /* End of CDF */
	ZIP_DD_MAGIC         = 0x504b0708,
#else
	ZIP_FILEHEADER_MAGIC = 0x04034b50,
	ZIP_CDF_MAGIC        = 0x02014b50,
	ZIP_CDE_MAGIC        = 0x06054b50,
	ZIP_DD_MAGIC         = 0x08074b50,
#endif
};

#define ZIP_HEADER_LEN 26

typedef union {
	uint8_t raw[ZIP_HEADER_LEN];
	struct {
		uint16_t version;               /* 0-1 */
		uint16_t zip_flags;             /* 2-3 */
		uint16_t method;                /* 4-5 */
		uint16_t modtime;               /* 6-7 */
		uint16_t moddate;               /* 8-9 */
		uint32_t crc32 PACKED;          /* 10-13 */
		uint32_t cmpsize PACKED;        /* 14-17 */
		uint32_t ucmpsize PACKED;       /* 18-21 */
		uint16_t filename_len;          /* 22-23 */
		uint16_t extra_len;             /* 24-25 */
		/* filename follows (not NUL terminated) */
		/* extra field follows */
		/* data follows */
	} fmt PACKED;
} zip_header_t; /* PACKED - gcc 4.2.1 doesn't like it (spews warning) */

#define FIX_ENDIANNESS_ZIP(zip) \
do { if (BB_BIG_ENDIAN) { \
	(zip).fmt.method        = SWAP_LE16((zip).fmt.method      ); \
	(zip).fmt.crc32         = SWAP_LE32((zip).fmt.crc32       ); \
	(zip).fmt.cmpsize       = SWAP_LE32((zip).fmt.cmpsize     ); \
	(zip).fmt.ucmpsize      = SWAP_LE32((zip).fmt.ucmpsize    ); \
	(zip).fmt.filename_len  = SWAP_LE16((zip).fmt.filename_len); \
	(zip).fmt.extra_len     = SWAP_LE16((zip).fmt.extra_len   ); \
}} while (0)

#define CDF_HEADER_LEN 42

typedef union {
	uint8_t raw[CDF_HEADER_LEN];
	struct {
		/* uint32_t signature; 50 4b 01 02 */
		uint16_t version_made_by;       /* 0-1 */
		uint16_t version_needed;        /* 2-3 */
		uint16_t cdf_flags;             /* 4-5 */
		uint16_t method;                /* 6-7 */
		uint16_t modtime;               /* 8-9 */
		uint16_t moddate;               /* 10-11 */
		uint32_t crc32;                 /* 12-15 */
		uint32_t cmpsize;               /* 16-19 */
		uint32_t ucmpsize;              /* 20-23 */
		uint16_t filename_len;          /* 24-25 */
		uint16_t extra_len;             /* 26-27 */
		uint16_t file_comment_length;   /* 28-29 */
		uint16_t disk_number_start;     /* 30-31 */
		uint16_t internal_attributes;   /* 32-33 */
		uint32_t external_attributes PACKED; /* 34-37 */
		uint32_t relative_offset_of_local_header PACKED; /* 38-41 */
		/* filename follows (not NUL terminated) */
		/* extra field follows */
		/* file comment follows */
	} fmt PACKED;
} cdf_header_t;

#define FIX_ENDIANNESS_CDF(cdf) \
do { if (BB_BIG_ENDIAN) { \
	(cdf).fmt.version_made_by = SWAP_LE16((cdf).fmt.version_made_by); \
	(cdf).fmt.version_needed  = SWAP_LE16((cdf).fmt.version_needed ); \
	(cdf).fmt.method          = SWAP_LE16((cdf).fmt.method         ); \
	(cdf).fmt.modtime         = SWAP_LE16((cdf).fmt.modtime        ); \
	(cdf).fmt.moddate         = SWAP_LE16((cdf).fmt.moddate        ); \
	(cdf).fmt.crc32           = SWAP_LE32((cdf).fmt.crc32          ); \
	(cdf).fmt.cmpsize         = SWAP_LE32((cdf).fmt.cmpsize        ); \
	(cdf).fmt.ucmpsize        = SWAP_LE32((cdf).fmt.ucmpsize       ); \
	(cdf).fmt.filename_len    = SWAP_LE16((cdf).fmt.filename_len   ); \
	(cdf).fmt.extra_len       = SWAP_LE16((cdf).fmt.extra_len      ); \
	(cdf).fmt.file_comment_length = SWAP_LE16((cdf).fmt.file_comment_length); \
	(cdf).fmt.external_attributes = SWAP_LE32((cdf).fmt.external_attributes); \
}} while (0)

#define CDE_LEN 16

typedef union {
	uint8_t raw[CDE_LEN];
	struct {
		/* uint32_t signature; 50 4b 05 06 */
		uint16_t this_disk_no;
		uint16_t disk_with_cdf_no;
		uint16_t cdf_entries_on_this_disk;
		uint16_t cdf_entries_total;
		uint32_t cdf_size;
		uint32_t cdf_offset;
		/* uint16_t archive_comment_length; */
		/* archive comment follows */
	} fmt PACKED;
} cde_t;

#define FIX_ENDIANNESS_CDE(cde) \
do { if (BB_BIG_ENDIAN) { \
	(cde).fmt.cdf_offset = SWAP_LE32((cde).fmt.cdf_offset); \
}} while (0)

struct BUG {
	/* Check the offset of the last element, not the length.  This leniency
	 * allows for poor packing, whereby the overall struct may be too long,
	 * even though the elements are all in the right place.
	 */
	char BUG_zip_header_must_be_26_bytes[
		offsetof(zip_header_t, fmt.extra_len) + 2
			== ZIP_HEADER_LEN ? 1 : -1];
	char BUG_cdf_header_must_be_42_bytes[
		offsetof(cdf_header_t, fmt.relative_offset_of_local_header) + 4
			== CDF_HEADER_LEN ? 1 : -1];
	char BUG_cde_must_be_16_bytes[
		sizeof(cde_t) == CDE_LEN ? 1 : -1];
};


enum { zip_fd = 3 };


/* This value means that we failed to find CDF */
#define BAD_CDF_OFFSET ((uint32_t)0xffffffff)

#if !ENABLE_FEATURE_UNZIP_CDF

# define find_cdf_offset() BAD_CDF_OFFSET

#else
/* Seen in the wild:
 * Self-extracting PRO2K3XP_32.exe contains 19078464 byte zip archive,
 * where CDE was nearly 48 kbytes before EOF.
 * (Surprisingly, it also apparently has *another* CDE structure
 * closer to the end, with bogus cdf_offset).
 * To make extraction work, bumped PEEK_FROM_END from 16k to 64k.
 */
#define PEEK_FROM_END (64*1024)
/* NB: does not preserve file position! */
static uint32_t find_cdf_offset(void)
{
	cde_t cde;
	unsigned char *buf;
	unsigned char *p;
	off_t end;
	uint32_t found;

	end = lseek(zip_fd, 0, SEEK_END);
	if (end == (off_t) -1)
		return BAD_CDF_OFFSET;

	end -= PEEK_FROM_END;
	if (end < 0)
		end = 0;

	dbg("Looking for cdf_offset starting from 0x%"OFF_FMT"x", end);
	xlseek(zip_fd, end, SEEK_SET);
	buf = xzalloc(PEEK_FROM_END);
	full_read(zip_fd, buf, PEEK_FROM_END);

	found = BAD_CDF_OFFSET;
	p = buf;
	while (p <= buf + PEEK_FROM_END - CDE_LEN - 4) {
		if (*p != 'P') {
			p++;
			continue;
		}
		if (*++p != 'K')
			continue;
		if (*++p != 5)
			continue;
		if (*++p != 6)
			continue;
		/* we found CDE! */
		memcpy(cde.raw, p + 1, CDE_LEN);
		FIX_ENDIANNESS_CDE(cde);
		/*
		 * I've seen .ZIP files with seemingly valid CDEs
		 * where cdf_offset points past EOF - ??
		 * This check ignores such CDEs:
		 */
		if (cde.fmt.cdf_offset < end + (p - buf)) {
			found = cde.fmt.cdf_offset;
			dbg("Possible cdf_offset:0x%x at 0x%"OFF_FMT"x",
				(unsigned)found, end + (p-3 - buf));
			dbg("  cdf_offset+cdf_size:0x%x",
				(unsigned)(found + SWAP_LE32(cde.fmt.cdf_size)));
			/*
			 * We do not "break" here because only the last CDE is valid.
			 * I've seen a .zip archive which contained a .zip file,
			 * uncompressed, and taking the first CDE was using
			 * the CDE inside that file!
			 */
		}
	}
	free(buf);
	dbg("Found cdf_offset:0x%x", (unsigned)found);
	return found;
};

static uint32_t read_next_cdf(uint32_t cdf_offset, cdf_header_t *cdf)
{
	uint32_t magic;

	if (cdf_offset == BAD_CDF_OFFSET)
		return cdf_offset;

	dbg("Reading CDF at 0x%x", (unsigned)cdf_offset);
	xlseek(zip_fd, cdf_offset, SEEK_SET);
	xread(zip_fd, &magic, 4);
	/* Central Directory End? Assume CDF has ended.
	 * (more correct method is to use cde.cdf_entries_total counter)
	 */
	if (magic == ZIP_CDE_MAGIC) {
		dbg("got ZIP_CDE_MAGIC");
		return 0; /* EOF */
	}
	xread(zip_fd, cdf->raw, CDF_HEADER_LEN);

	FIX_ENDIANNESS_CDF(*cdf);
	dbg("  filename_len:%u extra_len:%u file_comment_length:%u",
		(unsigned)cdf->fmt.filename_len,
		(unsigned)cdf->fmt.extra_len,
		(unsigned)cdf->fmt.file_comment_length
	);
	cdf_offset += 4 + CDF_HEADER_LEN
		+ cdf->fmt.filename_len
		+ cdf->fmt.extra_len
		+ cdf->fmt.file_comment_length;

	return cdf_offset;
};
#endif

static void die_if_bad_fnamesize(unsigned sz)
{
	if (sz > 0xfff) /* more than 4k?! no funny business please */
		bb_simple_error_msg_and_die("bad archive");
}

static void unzip_skip(off_t skip)
{
	if (skip != 0)
		if (lseek(zip_fd, skip, SEEK_CUR) == (off_t)-1)
			bb_copyfd_exact_size(zip_fd, -1, skip);
}

static void unzip_create_leading_dirs(const char *fn)
{
	/* Create all leading directories */
	char *name = xstrdup(fn);

	/* mode of -1: set mode according to umask */
	if (bb_make_directory(dirname(name), -1, FILEUTILS_RECUR)) {
		xfunc_die(); /* bb_make_directory is noisy */
	}
	free(name);
}

#if ENABLE_FEATURE_UNZIP_CDF
static void unzip_extract_symlink(llist_t **symlink_placeholders,
		zip_header_t *zip,
		const char *dst_fn)
{
	char *target;

	die_if_bad_fnamesize(zip->fmt.ucmpsize);

	if (zip->fmt.method == 0) {
		/* Method 0 - stored (not compressed) */
		target = xzalloc(zip->fmt.ucmpsize + 1);
		xread(zip_fd, target, zip->fmt.ucmpsize);
	} else {
#if 1
		bb_simple_error_msg_and_die("compressed symlink is not supported");
#else
		transformer_state_t xstate;
		init_transformer_state(&xstate);
		xstate.mem_output_size_max = zip->fmt.ucmpsize;
		/* ...unpack... */
		if (!xstate.mem_output_buf)
			WTF();
		target = xstate.mem_output_buf;
		target = xrealloc(target, xstate.mem_output_size + 1);
		target[xstate.mem_output_size] = '\0';
#endif
	}
	create_or_remember_link(symlink_placeholders,
			target,
			dst_fn,
			0);
	free(target);
}
#endif

static void unzip_extract(zip_header_t *zip, int dst_fd)
{
	transformer_state_t xstate;

	if (zip->fmt.method == 0) {
		/* Method 0 - stored (not compressed) */
		off_t size = zip->fmt.ucmpsize;
		if (size)
			bb_copyfd_exact_size(zip_fd, dst_fd, size);
		return;
	}

	init_transformer_state(&xstate);
	xstate.bytes_in = zip->fmt.cmpsize;
	xstate.src_fd = zip_fd;
	xstate.dst_fd = dst_fd;
	if (zip->fmt.method == 8) {
		/* Method 8 - inflate */
		if (inflate_unzip(&xstate) < 0)
			bb_simple_error_msg_and_die("inflate error");
		/* Validate decompression - crc */
		if (zip->fmt.crc32 != (xstate.crc32 ^ 0xffffffffL)) {
			bb_simple_error_msg_and_die("crc error");
		}
	}
#if ENABLE_FEATURE_UNZIP_BZIP2
	else if (zip->fmt.method == 12) {
		/* Tested. Unpacker reads too much, but we use CDF
		 * and will seek to the correct beginning of next file.
		 */
		xstate.bytes_out = unpack_bz2_stream(&xstate);
		if (xstate.bytes_out < 0)
			bb_simple_error_msg_and_die("inflate error");
	}
#endif
#if ENABLE_FEATURE_UNZIP_LZMA
	else if (zip->fmt.method == 14) {
		/* Not tested yet */
		xstate.bytes_out = unpack_lzma_stream(&xstate);
		if (xstate.bytes_out < 0)
			bb_simple_error_msg_and_die("inflate error");
	}
#endif
#if ENABLE_FEATURE_UNZIP_XZ
	else if (zip->fmt.method == 95) {
		/* Not tested yet */
		xstate.bytes_out = unpack_xz_stream(&xstate);
		if (xstate.bytes_out < 0)
			bb_simple_error_msg_and_die("inflate error");
	}
#endif
	else {
		bb_error_msg_and_die("unsupported method %u", zip->fmt.method);
	}

	/* Validate decompression - size */
	if (zip->fmt.ucmpsize != xstate.bytes_out) {
		/* Don't die. Who knows, maybe len calculation
		 * was botched somewhere. After all, crc matched! */
		bb_simple_error_msg("bad length");
	}
}

static void my_fgets80(char *buf80)
{
	fflush_all();
	if (!fgets(buf80, 80, stdin)) {
		bb_simple_perror_msg_and_die("can't read standard input");
	}
}

static int get_lstat_mode(const char *dst_fn)
{
	struct stat stat_buf;
	if (lstat(dst_fn, &stat_buf) == -1) {
		if (errno != ENOENT) {
			bb_perror_msg_and_die("can't stat '%s'",
				dst_fn
			);
		}
		/* File does not exist */
		return -1;
	}
	return stat_buf.st_mode;
}

int unzip_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int unzip_main(int argc, char **argv)
{
	enum {
		OPT_l = (1 << 0),
		OPT_x = (1 << 1),
		OPT_j = (1 << 2),
	};
	unsigned opts;
	smallint quiet = 0;
	IF_NOT_FEATURE_UNZIP_CDF(const) smallint verbose = 0;
	enum { O_PROMPT, O_NEVER, O_ALWAYS };
	smallint overwrite = O_PROMPT;
	uint32_t cdf_offset;
	unsigned long total_usize;
	unsigned long total_size;
	unsigned total_entries;
	int dst_fd = -1;
	char *src_fn = NULL;
	char *dst_fn = NULL;
	llist_t *zaccept = NULL;
	llist_t *zreject = NULL;
	char *base_dir = NULL;
#if ENABLE_FEATURE_UNZIP_CDF
	llist_t *symlink_placeholders = NULL;
#endif
	int i;
	char key_buf[80]; /* must match size used by my_fgets80 */

/* -q, -l and -v: UnZip 5.52 of 28 February 2005, by Info-ZIP:
 *
 * # /usr/bin/unzip -qq -v decompress_unlzma.i.zip
 *   204372  Defl:N    35278  83%  09-06-09 14:23  0d056252  decompress_unlzma.i
 * # /usr/bin/unzip -q -v decompress_unlzma.i.zip
 *  Length   Method    Size  Ratio   Date   Time   CRC-32    Name
 * --------  ------  ------- -----   ----   ----   ------    ----
 *   204372  Defl:N    35278  83%  09-06-09 14:23  0d056252  decompress_unlzma.i
 * --------          -------  ---                            -------
 *   204372            35278  83%                            1 file
 * # /usr/bin/unzip -v decompress_unlzma.i.zip
 * Archive:  decompress_unlzma.i.zip
 *  Length   Method    Size  Ratio   Date   Time   CRC-32    Name
 * --------  ------  ------- -----   ----   ----   ------    ----
 *   204372  Defl:N    35278  83%  09-06-09 14:23  0d056252  decompress_unlzma.i
 * --------          -------  ---                            -------
 *   204372            35278  83%                            1 file
 * # unzip -v decompress_unlzma.i.zip
 * Archive:  decompress_unlzma.i.zip
 *   Length     Date   Time    Name
 *  --------    ----   ----    ----
 *    204372  09-06-09 14:23   decompress_unlzma.i
 *  --------                   -------
 *    204372                   1 files
 * # /usr/bin/unzip -l -qq decompress_unlzma.i.zip
 *    204372  09-06-09 14:23   decompress_unlzma.i
 * # /usr/bin/unzip -l -q decompress_unlzma.i.zip
 *   Length     Date   Time    Name
 *  --------    ----   ----    ----
 *    204372  09-06-09 14:23   decompress_unlzma.i
 *  --------                   -------
 *    204372                   1 file
 * # /usr/bin/unzip -l decompress_unlzma.i.zip
 * Archive:  decompress_unlzma.i.zip
 *   Length     Date   Time    Name
 *  --------    ----   ----    ----
 *    204372  09-06-09 14:23   decompress_unlzma.i
 *  --------                   -------
 *    204372                   1 file
 */

	opts = 0;
	/* '-' makes getopt return 1 for non-options */
	while ((i = getopt(argc, argv, "-d:lnopqxjv")) != -1) {
		switch (i) {
		case 'd':  /* Extract to base directory */
			base_dir = optarg;
			break;

		case 'l': /* List */
			opts |= OPT_l;
			break;

		case 'n': /* Never overwrite existing files */
			overwrite = O_NEVER;
			break;

		case 'o': /* Always overwrite existing files */
			overwrite = O_ALWAYS;
			break;

		case 'p': /* Extract files to stdout and fall through to set verbosity */
			dst_fd = STDOUT_FILENO;

		case 'q': /* Be quiet */
			quiet++;
			break;

		case 'v': /* Verbose list */
			IF_FEATURE_UNZIP_CDF(verbose++;)
			opts |= OPT_l;
			break;

		case 'x':
			opts |= OPT_x;
			break;

		case 'j':
			opts |= OPT_j;
			break;

		case 1:
			if (!src_fn) {
				/* The zip file */
				/* +5: space for ".zip" and NUL */
				src_fn = xmalloc(strlen(optarg) + 5);
				strcpy(src_fn, optarg);
			} else if (!(opts & OPT_x)) {
				/* Include files */
				llist_add_to(&zaccept, optarg);
			} else {
				/* Exclude files */
				llist_add_to(&zreject, optarg);
			}
			break;

		default:
			bb_show_usage();
		}
	}

#ifndef __GLIBC__
	/*
	 * This code is needed for non-GNU getopt
	 * which doesn't understand "-" in option string.
	 * The -x option won't work properly in this case:
	 * "unzip a.zip q -x w e" will be interpreted as
	 * "unzip a.zip q w e -x" = "unzip a.zip q w e"
	 */
	argv += optind;
	if (argv[0]) {
		/* +5: space for ".zip" and NUL */
		src_fn = xmalloc(strlen(argv[0]) + 5);
		strcpy(src_fn, argv[0]);
		while (*++argv)
			llist_add_to(&zaccept, *argv);
	}
#endif

	if (!src_fn) {
		bb_show_usage();
	}

	/* Open input file */
	if (LONE_DASH(src_fn)) {
		xdup2(STDIN_FILENO, zip_fd);
		/* Cannot use prompt mode since zip data is arriving on STDIN */
		if (overwrite == O_PROMPT)
			overwrite = O_NEVER;
	} else {
		static const char extn[][5] ALIGN1 = { ".zip", ".ZIP" };
		char *ext = src_fn + strlen(src_fn);
		int src_fd;

		i = 0;
		for (;;) {
			src_fd = open(src_fn, O_RDONLY);
			if (src_fd >= 0)
				break;
			if (++i > 2) {
				*ext = '\0';
				bb_error_msg_and_die("can't open %s[.zip]",
					src_fn
				);
			}
			strcpy(ext, extn[i - 1]);
		}
		xmove_fd(src_fd, zip_fd);
	}

	/* Change dir if necessary */
	if (base_dir)
		xchdir(base_dir);

	if (quiet <= 1) { /* not -qq */
		if (quiet == 0) {
			printf("Archive:  %s\n",
				printable_string(src_fn)
			);
		}
		if (opts & OPT_l) {
			puts(verbose ?
				" Length   Method    Size  Cmpr    Date    Time   CRC-32   Name\n"
				"--------  ------  ------- ---- ---------- ----- --------  ----"
				:
				"  Length      Date    Time    Name\n"
				"---------  ---------- -----   ----"
				);
		}
	}

/* Example of an archive with one 0-byte long file named 'z'
 * created by Zip 2.31 on Unix:
 * 0000 [50 4b]03 04 0a 00 00 00 00 00 42 1a b8 3c 00 00 |PK........B..<..|
 *       sig........ vneed flags compr mtime mdate crc32>
 * 0010  00 00 00 00 00 00 00 00 00 00 01 00 15 00 7a 55 |..............zU|
 *      >..... csize...... usize...... fnlen exlen fn ex>
 * 0020  54 09 00 03 cc d3 f9 4b cc d3 f9 4b 55 78 04 00 |T......K...KUx..|
 *      >tra_field......................................
 * 0030  00 00 00 00[50 4b]01 02 17 03 0a 00 00 00 00 00 |....PK..........|
 *       ........... sig........ vmade vneed flags compr
 * 0040  42 1a b8 3c 00 00 00 00 00 00 00 00 00 00 00 00 |B..<............|
 *       mtime mdate crc32...... csize...... usize......
 * 0050  01 00 0d 00 00 00 00 00 00 00 00 00 a4 81 00 00 |................|
 *       fnlen exlen clen. dnum. iattr eattr...... relofs> (eattr = rw-r--r--)
 * 0060  00 00 7a 55 54 05 00 03 cc d3 f9 4b 55 78 00 00 |..zUT......KUx..|
 *      >..... fn extra_field...........................
 * 0070 [50 4b]05 06 00 00 00 00 01 00 01 00 3c 00 00 00 |PK..........<...|
 * 0080  34 00 00 00 00 00                               |4.....|
 */
	total_usize = 0;
	total_size = 0;
	total_entries = 0;
	cdf_offset = find_cdf_offset();	/* try to seek to the end, find CDE and CDF start */
	while (1) {
		zip_header_t zip;
		mode_t dir_mode = 0777;
#if ENABLE_FEATURE_UNZIP_CDF
		mode_t file_mode = 0666;
#endif

		if (!ENABLE_FEATURE_UNZIP_CDF || cdf_offset == BAD_CDF_OFFSET) {
			/* Normally happens when input is unseekable.
			 *
			 * Valid ZIP file has Central Directory at the end
			 * with central directory file headers (CDFs).
			 * After it, there is a Central Directory End structure.
			 * CDFs identify what files are in the ZIP and where
			 * they are located. This allows ZIP readers to load
			 * the list of files without reading the entire ZIP archive.
			 * ZIP files may be appended to, only files specified in
			 * the CD are valid. Scanning for local file headers is
			 * not a correct algorithm.
			 *
			 * We try to do the above, and resort to "linear" reading
			 * of ZIP file only if seek failed or CDE wasn't found.
			 */
			uint32_t magic;

			/* Check magic number */
			xread(zip_fd, &magic, 4);
			/* CDF item? Assume there are no more files, exit */
			if (magic == ZIP_CDF_MAGIC) {
				dbg("got ZIP_CDF_MAGIC");
				break;
			}
			/* Data descriptor? It was a streaming file, go on */
			if (magic == ZIP_DD_MAGIC) {
				dbg("got ZIP_DD_MAGIC");
				/* skip over duplicate crc32, cmpsize and ucmpsize */
				unzip_skip(3 * 4);
				continue;
			}
			if (magic != ZIP_FILEHEADER_MAGIC)
				bb_error_msg_and_die("invalid zip magic %08X", (int)magic);
			dbg("got ZIP_FILEHEADER_MAGIC");

			xread(zip_fd, zip.raw, ZIP_HEADER_LEN);
			FIX_ENDIANNESS_ZIP(zip);
			if (zip.fmt.zip_flags & SWAP_LE16(0x0008)) {
				bb_error_msg_and_die("zip flag %s is not supported",
					"8 (streaming)");
			}
		}
#if ENABLE_FEATURE_UNZIP_CDF
		else {
			/* cdf_offset is valid (and we know the file is seekable) */
			cdf_header_t cdf;
			cdf_offset = read_next_cdf(cdf_offset, &cdf);
			if (cdf_offset == 0) /* EOF? */
				break;
# if 1
			xlseek(zip_fd,
				SWAP_LE32(cdf.fmt.relative_offset_of_local_header) + 4,
				SEEK_SET);
			xread(zip_fd, zip.raw, ZIP_HEADER_LEN);
			FIX_ENDIANNESS_ZIP(zip);
			if (zip.fmt.zip_flags & SWAP_LE16(0x0008)) {
				/* 0x0008 - streaming. [u]cmpsize can be reliably gotten
				 * only from Central Directory.
				 */
				zip.fmt.crc32    = cdf.fmt.crc32;
				zip.fmt.cmpsize  = cdf.fmt.cmpsize;
				zip.fmt.ucmpsize = cdf.fmt.ucmpsize;
			}
// Seen in some zipfiles: central directory 9 byte extra field contains
// a subfield with ID 0x5455 and 5 data bytes, which is a Unix-style UTC mtime.
// Local header version:
//  u16 0x5455 ("UT")
//  u16 size (1 + 4 * n)
//  u8  flags: bit 0:mtime is present, bit 1:atime is present, bit 2:ctime is present
//  u32 mtime
//  u32 atime
//  u32 ctime
// Central header version:
//  u16 0x5455 ("UT")
//  u16 size (5 (or 1?))
//  u8  flags: bit 0:mtime is present, bit 1:atime is present, bit 2:ctime is present
//  u32 mtime (CDF does not store atime/ctime)
# else
			/* CDF has the same data as local header, no need to read the latter...
			 * ...not really. An archive was seen with cdf.extra_len == 6 but
			 * zip.extra_len == 0.
			 */
			memcpy(&zip.fmt.version,
				&cdf.fmt.version_needed, ZIP_HEADER_LEN);
			xlseek(zip_fd,
				SWAP_LE32(cdf.fmt.relative_offset_of_local_header) + 4 + ZIP_HEADER_LEN,
				SEEK_SET);
# endif
			if ((cdf.fmt.version_made_by >> 8) == 3) {
				/* This archive is created on Unix */
				dir_mode = file_mode = (cdf.fmt.external_attributes >> 16);
			}
		}
#endif

		if (zip.fmt.zip_flags & SWAP_LE16(0x0001)) {
			/* 0x0001 - encrypted */
			bb_error_msg_and_die("zip flag %s is not supported",
					"1 (encryption)");
		}
		dbg("File cmpsize:0x%x extra_len:0x%x ucmpsize:0x%x",
			(unsigned)zip.fmt.cmpsize,
			(unsigned)zip.fmt.extra_len,
			(unsigned)zip.fmt.ucmpsize
		);

		/* Read filename */
		free(dst_fn);
		die_if_bad_fnamesize(zip.fmt.filename_len);
		dst_fn = xzalloc(zip.fmt.filename_len + 1);
		xread(zip_fd, dst_fn, zip.fmt.filename_len);
		/* Skip extra header bytes */
		unzip_skip(zip.fmt.extra_len);

		/* Guard against "/abspath", "/../" and similar attacks */
		overlapping_strcpy(dst_fn, strip_unsafe_prefix(dst_fn));

		/* Filter zip entries */
		if (find_list_entry(zreject, dst_fn)
		 || (zaccept && !find_list_entry(zaccept, dst_fn))
		) { /* Skip entry */
			goto skip_cmpsize;
		}

		if (opts & OPT_l) {
			/* List entry */
			char dtbuf[sizeof("mm-dd-yyyy hh:mm")];
			sprintf(dtbuf, "%02u-%02u-%04u %02u:%02u",
				(zip.fmt.moddate >> 5) & 0xf,  // mm: 0x01e0
				(zip.fmt.moddate)      & 0x1f, // dd: 0x001f
				(zip.fmt.moddate >> 9) + 1980, // yy: 0xfe00
				(zip.fmt.modtime >> 11),       // hh: 0xf800
				(zip.fmt.modtime >> 5) & 0x3f  // mm: 0x07e0
				// seconds/2 not shown, encoded in -- 0x001f
			);
			if (!verbose) {
				//      "  Length      Date    Time    Name\n"
				//      "---------  ---------- -----   ----"
				printf(       "%9u  " "%s   "         "%s\n",
					(unsigned)zip.fmt.ucmpsize,
					dtbuf,
					printable_string(dst_fn)
				);
			} else {
				char method6[7];
				unsigned long percents;

				sprintf(method6, "%6u", zip.fmt.method);
				if (zip.fmt.method == 0) {
					strcpy(method6, "Stored");
				}
				if (zip.fmt.method == 8) {
					strcpy(method6, "Defl:N");
					/* normal, maximum, fast, superfast */
					IF_DESKTOP(method6[5] = "NXFS"[(zip.fmt.zip_flags >> 1) & 3];)
				}
				percents = zip.fmt.ucmpsize - zip.fmt.cmpsize;
				if ((int32_t)percents < 0)
					percents = 0; /* happens if ucmpsize < cmpsize */
				percents = percents * 100;
				if (zip.fmt.ucmpsize)
					percents /= zip.fmt.ucmpsize;
				//      " Length   Method    Size  Cmpr    Date    Time   CRC-32   Name\n"
				//      "--------  ------  ------- ---- ---------- ----- --------  ----"
				printf(      "%8u  %s"        "%9u%4u%% " "%s "         "%08x  "  "%s\n",
					(unsigned)zip.fmt.ucmpsize,
					method6,
					(unsigned)zip.fmt.cmpsize,
					(unsigned)percents,
					dtbuf,
					zip.fmt.crc32,
					printable_string(dst_fn)
				);
				total_size += zip.fmt.cmpsize;
			}
			total_usize += zip.fmt.ucmpsize;
			goto skip_cmpsize;
		}

		if (dst_fd == STDOUT_FILENO) {
			/* Extracting to STDOUT */
			goto do_extract;
		}

		/* Strip paths (after -l: unzip -lj a.zip lists full names) */
		if (opts & OPT_j)
			overlapping_strcpy(dst_fn, bb_basename(dst_fn));
		/* Did this strip everything ("DIR/" case)? Then skip */
		if (!dst_fn[0])
			goto skip_cmpsize;

		if (last_char_is(dst_fn, '/')) {
			int mode;

			/* Extract directory */
			mode = get_lstat_mode(dst_fn);
			if (mode == -1) { /* ENOENT */
				if (!quiet) {
					printf("   creating: %s\n", printable_string(dst_fn));
				}
				unzip_create_leading_dirs(dst_fn);
				if (bb_make_directory(dst_fn, dir_mode, FILEUTILS_IGNORE_CHMOD_ERR)) {
					xfunc_die();
				}
			} else {
				if (!S_ISDIR(mode)) {
					bb_error_msg_and_die("'%s' exists but is not a %s",
						printable_string(dst_fn),
						"directory"
					);
				}
			}
			goto skip_cmpsize;
		}
 check_file:
		/* Does target file already exist? */
		{
			int mode = get_lstat_mode(dst_fn);
			if (mode == -1) {
				/* ENOENT: does not exist */
				goto do_open_and_extract;
			}
			if (overwrite == O_NEVER) {
				goto skip_cmpsize;
			}
			if (!S_ISREG(mode)) {
 fishy:
				bb_error_msg_and_die("'%s' exists but is not a %s",
					printable_string(dst_fn),
					"regular file"
				);
			}
			if (overwrite == O_ALWAYS) {
				goto do_open_and_extract;
			}
			printf("replace %s? [y]es, [n]o, [A]ll, [N]one, [r]ename: ",
				printable_string(dst_fn)
			);
			my_fgets80(key_buf);
			/* User input could take a long time. Is it still a regular file? */
			mode = get_lstat_mode(dst_fn);
			if (!S_ISREG(mode))
				goto fishy;
		}

		/* Extract (or skip) it */
		switch (key_buf[0]) {
		case 'A':
			overwrite = O_ALWAYS;
		case 'y': /* Open file and fall into unzip */
 do_open_and_extract:
			unzip_create_leading_dirs(dst_fn);
#if ENABLE_FEATURE_UNZIP_CDF
			dst_fd = -1;
			if (!S_ISLNK(file_mode)) {
				dst_fd = xopen3(dst_fn,
					O_WRONLY | O_CREAT | O_TRUNC | O_NOFOLLOW,
					file_mode);
			}
#else
			/* O_NOFOLLOW defends against symlink attacks */
			dst_fd = xopen(dst_fn, O_WRONLY | O_CREAT | O_TRUNC | O_NOFOLLOW);
#endif
 do_extract:
			if (!quiet) {
				printf(/* zip.fmt.method == 0
					? " extracting: %s\n"
					: */ "  inflating: %s\n",
					printable_string(dst_fn)
				);
			}
#if ENABLE_FEATURE_UNZIP_CDF
			if (S_ISLNK(file_mode)) {
				if (dst_fd != STDOUT_FILENO) /* not -p? */
					unzip_extract_symlink(&symlink_placeholders, &zip, dst_fn);
			} else
#endif
			{
				unzip_extract(&zip, dst_fd);
				if (dst_fd != STDOUT_FILENO) {
					/* closing STDOUT is potentially bad for future business */
					close(dst_fd);
				}
			}
			break;

		case 'N':
			overwrite = O_NEVER;
		case 'n': /* Skip entry data */
 skip_cmpsize:
			unzip_skip(zip.fmt.cmpsize);
			break;

		case 'r':
			/* Prompt for new name */
			printf("new name: ");
			my_fgets80(key_buf);
			free(dst_fn);
			dst_fn = xstrdup(key_buf);
			chomp(dst_fn);
			goto check_file;

		default:
			printf("error: invalid response [%c]\n", (char)key_buf[0]);
			goto check_file;
		}

		total_entries++;
	}

#if ENABLE_FEATURE_UNZIP_CDF
	create_links_from_list(symlink_placeholders);
#endif

	if ((opts & OPT_l) && quiet <= 1) {
		if (!verbose) {
			//	"  Length      Date    Time    Name\n"
			//	"---------  ---------- -----   ----"
			printf( " --------%21s"               "-------\n"
				     "%9lu%21s"               "%u files\n",
				"",
				total_usize, "", total_entries);
		} else {
			unsigned long percents = total_usize - total_size;
			if ((long)percents < 0)
				percents = 0; /* happens if usize < size */
			percents = percents * 100;
			if (total_usize)
				percents /= total_usize;
			//	" Length   Method    Size  Cmpr    Date    Time   CRC-32   Name\n"
			//	"--------  ------  ------- ---- ---------- ----- --------  ----"
			printf( "--------          ------- ----%28s"                      "----\n"
				"%8lu"              "%17lu%4u%%%28s"                      "%u files\n",
				"",
				total_usize, total_size, (unsigned)percents, "",
				total_entries);
		}
	}

	return 0;
}