/*- 
 * Copyright (c) 2007-2014, Juniper Networks, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "stand.h"

#include <sys/stat.h>
#include <sys/stdint.h>
#include <string.h>
#include <zlib.h>

static int   pkg_open(const char *, struct open_file *);
static int   pkg_close(struct open_file *);
static int   pkg_read(struct open_file *, void *, size_t, size_t *);
static off_t pkg_seek(struct open_file *, off_t, int);
static int   pkg_stat(struct open_file *, struct stat *);
static int   pkg_readdir(struct open_file *, struct dirent *);
static off_t pkg_atol(const char *, unsigned);

struct fs_ops pkgfs_fsops = {
        .fs_name = "pkg",
        .fs_flags = FS_OPS_NO_DEVOPEN,
        .fo_open = pkg_open,
        .fo_close = pkg_close,
        .fo_read = pkg_read,
        .fo_write = null_write,
        .fo_seek = pkg_seek,
        .fo_stat = pkg_stat,
        .fo_readdir = pkg_readdir,
};

#define PKG_BUFSIZE     512
#define PKG_MAXCACHESZ  (512 * 1024)

#define PKG_FILEEXT     ".tgz"

/*
 * Layout of POSIX 'ustar' header.
 */
struct ustar_hdr {
        char    ut_name[100];
        char    ut_mode[8];
        char    ut_uid[8];
        char    ut_gid[8];
        char    ut_size[12];
        char    ut_mtime[12];
        char    ut_checksum[8];
        char    ut_typeflag[1];
        char    ut_linkname[100];
        char    ut_magic[6];            /* For POSIX: "ustar\0" */
        char    ut_version[2];          /* For POSIX: "00" */
        char    ut_uname[32];
        char    ut_gname[32];
        char    ut_rdevmajor[8];
        char    ut_rdevminor[8];
        union {
                struct {
                        char    prefix[155];
                } posix;
                struct {
                        char    atime[12];
                        char    ctime[12];
                        char    offset[12];
                        char    longnames[4];
                        char    unused[1];
                        struct gnu_sparse {
                                char    offset[12];
                                char    numbytes[12];
                        } sparse[4];
                        char    isextended[1];
                        char    realsize[12];
                } gnu;
        } u;
        u_char __padding[12];
};

struct package;

struct tarfile
{
        struct package *tf_pkg;
        struct tarfile *tf_next;
        struct ustar_hdr tf_hdr;
        off_t   tf_ofs;
        off_t   tf_size;
        off_t   tf_fp;
        size_t  tf_cachesz;
        void    *tf_cache;
};

struct package
{
        struct package *pkg_chain;
        int     pkg_fd;
        off_t   pkg_ofs;
        z_stream pkg_zs;
        struct tarfile *pkg_first;
        struct tarfile *pkg_last;
        u_char  pkg_buf[PKG_BUFSIZE];
};

static struct package *package = NULL;

static int new_package(int, struct package **);
static int cache_data(struct tarfile *tf, int);

void
pkgfs_cleanup(void)
{
        struct package *chain;
        struct tarfile *tf, *tfn;

        while (package != NULL) {
                inflateEnd(&package->pkg_zs);
                close(package->pkg_fd);

                tf = package->pkg_first;
                while (tf != NULL) {
                        tfn = tf->tf_next;
                        if (tf->tf_cachesz > 0)
                                free(tf->tf_cache);
                        free(tf);
                        tf = tfn;
                }

                chain = package->pkg_chain;
                free(package);
                package = chain;
        }
}

int
pkgfs_init(const char *pkgname, struct fs_ops *proto)
{
        struct package *pkg;
        int error, fd;

        pkg = NULL;
        if (proto != &pkgfs_fsops)
                pkgfs_cleanup();

        exclusive_file_system = proto;

        fd = open(pkgname, O_RDONLY);

        exclusive_file_system = NULL;

        DEBUG_PRINTF(0, ("%s(%s: '%s') -> %d (error=%d)\n", __func__,
                proto->fs_name, pkgname, fd, errno));

        if (fd == -1)
                return (errno);

        error = new_package(fd, &pkg);
        if (error) {
                close(fd);
                return (error);
        }

        if (pkg == NULL)
                return (EDOOFUS);

        pkg->pkg_chain = package;
        package = pkg;
        exclusive_file_system = &pkgfs_fsops;
        return (0);
}

static int get_mode(struct tarfile *);
static int get_zipped(struct package *, void *, size_t);
static int new_package(int, struct package **);
static struct tarfile *scan_tarfile(struct package *, struct tarfile *);

static int
pkg_open_follow(const char *fn, struct open_file *f, int lnks)
{
        struct tarfile *tf;

        if (fn == NULL || f == NULL)
                return (EINVAL);

        if (package == NULL)
                return (ENXIO);

        /*
         * We can only read from a package, so reject request to open
         * for write-only or read-write.
         */
        if (f->f_flags != F_READ)
                return (EPERM);

        /*
         * Scan the file headers for the named file. We stop scanning
         * at the first filename that has the .pkg extension. This is
         * a package within a package. We assume we have all the files
         * we need up-front and without having to dig within nested
         * packages.
         *
         * Note that we preserve streaming properties as much as possible.
         */
        while (*fn == '/')
                fn++;

        /*
         * Allow opening of the root directory for use by readdir()
         * to support listing files in the package.
         */
        if (*fn == '\0') {
                f->f_fsdata = NULL;
                return (0);
        }

        tf = scan_tarfile(package, NULL);
        while (tf != NULL) {
                if (strcmp(fn, tf->tf_hdr.ut_name) == 0) {
                        f->f_fsdata = tf;
                        tf->tf_fp = 0;  /* Reset the file pointer. */
                        DEBUG_PRINTF(1, ("%s: found %s type %c\n", __func__,
                             fn, tf->tf_hdr.ut_typeflag[0]));
                        if (tf->tf_hdr.ut_typeflag[0] == '2') {
                            /* we have a symlink
                             * Note: ut_linkname is only 100 chars!
                             */
                            if (lnks++ >= 8)
                                return (EMLINK);
                            return pkg_open_follow(tf->tf_hdr.ut_linkname,
                                f, lnks);
                        }
                        return (0);
                }
                tf = scan_tarfile(package, tf);
        }
        return (errno);
}

static int
pkg_open(const char *fn, struct open_file *f)
{
    return pkg_open_follow(fn, f, 0);
}

static int
pkg_close(struct open_file *f)
{
        struct tarfile *tf;

        tf = (struct tarfile *)f->f_fsdata;
        if (tf == NULL)
                return (0);

        /*
         * Free up the cache if we read all of the file.
         */
        DEBUG_PRINTF(1, ("%s(%s)\n", __func__, tf->tf_hdr.ut_name));
        if (tf->tf_fp == tf->tf_size && tf->tf_cachesz > 0) {
                free(tf->tf_cache);
                tf->tf_cachesz = 0;
        }
        return (0);
}

static int
pkg_read(struct open_file *f, void *buf, size_t size, size_t *res)
{
        struct tarfile *tf;
        char *p;
        off_t fp;
        size_t sz;

        tf = (struct tarfile *)f->f_fsdata;
        if (tf == NULL) {
                if (res != NULL)
                        *res = size;
                return (EBADF);
        }

        DEBUG_PRINTF(4, ("%s(%s,%zd)\n", __func__, tf->tf_hdr.ut_name, size));

        if (tf->tf_cachesz == 0)
                cache_data(tf, 1);

        fp = tf->tf_fp;
        p = buf;
        sz = 0;
        while (size > 0) {
                sz = tf->tf_size - fp;
                if (fp < tf->tf_cachesz && tf->tf_cachesz < tf->tf_size)
                        sz = tf->tf_cachesz - fp;
                if (size < sz)
                        sz = size;
                if (sz == 0)
                        break;

                if (fp < tf->tf_cachesz) {
                        /* Satisfy the request from cache. */
                        memcpy(p, tf->tf_cache + fp, sz);
                        fp += sz;
                        p += sz;
                        size -= sz;
                        continue;
                }

                if (get_zipped(tf->tf_pkg, p, sz) == -1) {
                        sz = -1;
                        break;
                }

                fp += sz;
                p += sz;
                size -= sz;
        }

        tf->tf_fp = fp;
        if (res != NULL)
                *res = size;
        DEBUG_PRINTF(4, ("%s(%s) res=%zd\n", __func__, tf->tf_hdr.ut_name,
             (ssize_t)(tf->tf_size - tf->tf_fp)));
        return ((sz == -1) ? errno : 0);
}

static off_t
pkg_seek(struct open_file *f, off_t ofs, int whence)
{
        char buf[512];
        struct tarfile *tf;
        off_t delta;
        off_t nofs;
        size_t sz, res;
        int error;

        tf = (struct tarfile *)f->f_fsdata;
        if (tf == NULL) {
                errno = EBADF;
                return (-1);
        }

        switch (whence) {
        case SEEK_SET:
                delta = ofs - tf->tf_fp;
                break;
        case SEEK_CUR:
                delta = ofs;
                break;
        case SEEK_END:
                delta = tf->tf_size - tf->tf_fp + ofs;
                break;
        default:
                errno = EINVAL;
                return (-1);
        }

        if (delta < 0) {
                /* seeking backwards - ok if within cache */
                if (tf->tf_cachesz > 0 && tf->tf_fp <= tf->tf_cachesz) {
                        nofs = tf->tf_fp + delta;
                        if (nofs >= 0) {
                                tf->tf_fp = nofs;
                                return (tf->tf_fp);
                        }
                }
                DEBUG_PRINTF(3, ("%s: negative file seek (%jd)\n", __func__,
                    (intmax_t)delta));
                errno = ESPIPE;
                return (-1);
        }

        while (delta > 0 && tf->tf_fp < tf->tf_size) {
                sz = (delta > sizeof(buf)) ? sizeof(buf) : delta;
                error = pkg_read(f, buf, sz, &res);
                if (error != 0) {
                        errno = error;
                        return (-1);
                }
                delta -= sz - res;
        }

        return (tf->tf_fp);
}

static int
pkg_stat(struct open_file *f, struct stat *sb)
{
        struct tarfile *tf;

        tf = (struct tarfile *)f->f_fsdata;
        if (tf == NULL)
                return (EBADF);
        memset(sb, 0, sizeof(*sb));
        sb->st_mode = get_mode(tf);
        if ((sb->st_mode & S_IFMT) == 0) {
                /* tar file bug - assume regular file */
                sb->st_mode |= S_IFREG;
        }
        sb->st_size = tf->tf_size;
        sb->st_blocks = (tf->tf_size + 511) / 512;
        sb->st_mtime = pkg_atol(tf->tf_hdr.ut_mtime, 12);
        sb->st_dev = (off_t)((uintptr_t)tf->tf_pkg);
        sb->st_ino = tf->tf_ofs;        /* unique per tf_pkg */
        return (0);
}

static int
pkg_readdir(struct open_file *f, struct dirent *d)
{
        struct tarfile *tf;

        tf = (struct tarfile *)f->f_fsdata;
        if (tf != NULL)
                return (EBADF);

        tf = scan_tarfile(package, NULL);
        if (tf == NULL)
                return (ENOENT);

        d->d_fileno = 0;
        d->d_reclen = sizeof(*d);
        d->d_type = DT_REG;
        memcpy(d->d_name, tf->tf_hdr.ut_name, sizeof(d->d_name));
        return (0);
}

/*
 * Low-level support functions.
 */

static int
get_byte(struct package *pkg, off_t *op)
{
        int c;

        if (pkg->pkg_zs.avail_in == 0) {
                c = read(pkg->pkg_fd, pkg->pkg_buf, PKG_BUFSIZE);
                if (c <= 0)
                        return (-1);
                pkg->pkg_zs.avail_in = c;
                pkg->pkg_zs.next_in = pkg->pkg_buf;
        }

        c = *pkg->pkg_zs.next_in;
        pkg->pkg_zs.next_in++;
        pkg->pkg_zs.avail_in--;
        (*op)++;
        return (c);
}

static int
get_zipped(struct package *pkg, void *buf, size_t bufsz)
{
        int c;

        pkg->pkg_zs.next_out = buf;
        pkg->pkg_zs.avail_out = bufsz;

        while (pkg->pkg_zs.avail_out) {
                if (pkg->pkg_zs.avail_in == 0) {
                        c = read(pkg->pkg_fd, pkg->pkg_buf, PKG_BUFSIZE);
                        if (c <= 0) {
                                errno = EIO;
                                return (-1);
                        }
                        pkg->pkg_zs.avail_in = c;
                        pkg->pkg_zs.next_in = pkg->pkg_buf;
                }

                c = inflate(&pkg->pkg_zs, Z_SYNC_FLUSH);
                if (c != Z_OK && c != Z_STREAM_END) {
                        errno = EIO;
                        return (-1);
                }
        }

        pkg->pkg_ofs += bufsz;
        return (0);
}

/**
 * @brief
 * cache data of a tarfile
 *
 * @param[in] tf
 *      tarfile pointer
 *
 * @param[in] force
 *      If file size > PKG_MAXCACHESZ, cache that much
 *
 * @return 0, -1 (errno set to error value)
 */
static int
cache_data(struct tarfile *tf, int force)
{
        struct package *pkg;
        size_t sz;

        if (tf == NULL) {
                DEBUG_PRINTF(5, ("%s: no file to cache data for?\n",
                        __func__));
                errno = EINVAL;
                return (-1);
        }

        pkg = tf->tf_pkg;
        if (pkg == NULL) {
                DEBUG_PRINTF(5, ("%s: no package associated with file?\n",
                        __func__));
                errno = EINVAL;
                return (-1);
        }

        if (tf->tf_cachesz > 0) {
                DEBUG_PRINTF(5, ("%s: data already cached\n", __func__));
                errno = EINVAL;
                return (-1);
        }

        if (tf->tf_ofs != pkg->pkg_ofs) {
                DEBUG_PRINTF(5, ("%s: caching after force read of file %s?\n",
                    __func__, tf->tf_hdr.ut_name));
                errno = EINVAL;
                return (-1);
        }

        /* We don't cache everything... */
        if (tf->tf_size > PKG_MAXCACHESZ && !force)  {
                errno = ENOBUFS;
                return (-1);
        }

        sz = tf->tf_size < PKG_MAXCACHESZ ? tf->tf_size : PKG_MAXCACHESZ;
        /* All files are padded to a multiple of 512 bytes. */
        sz = (sz + 0x1ff) & ~0x1ff;

        tf->tf_cache = malloc(sz);
        if (tf->tf_cache == NULL) {
                DEBUG_PRINTF(5, ("%s: could not allocate %d bytes\n",
                        __func__, (int)sz));
                errno = ENOMEM;
                return (-1);
        }

        tf->tf_cachesz = sz;
        return (get_zipped(pkg, tf->tf_cache, sz));
}

/*
 * Note that this implementation does not (and should not!) obey
 * locale settings; you cannot simply substitute strtol here, since
 * it does obey locale.
 */
static off_t
pkg_atol8(const char *p, unsigned char_cnt)
{
        int64_t l, limit, last_digit_limit;
        int digit, sign, base;

        base = 8;
        limit = INT64_MAX / base;
        last_digit_limit = INT64_MAX % base;

        while (*p == ' ' || *p == '\t')
                p++;
        if (*p == '-') {
                sign = -1;
                p++;
        } else
                sign = 1;

        l = 0;
        digit = *p - '0';
        while (digit >= 0 && digit < base  && char_cnt-- > 0) {
                if (l>limit || (l == limit && digit > last_digit_limit)) {
                        l = UINT64_MAX; /* Truncate on overflow. */
                        break;
                }
                l = (l * base) + digit;
                digit = *++p - '0';
        }
        return (sign < 0) ? -l : l;
}

/*
 * Parse a base-256 integer.  This is just a straight signed binary
 * value in big-endian order, except that the high-order bit is
 * ignored.  Remember that "int64_t" may or may not be exactly 64
 * bits; the implementation here tries to avoid making any assumptions
 * about the actual size of an int64_t.  It does assume we're using
 * twos-complement arithmetic, though.
 */
static int64_t
pkg_atol256(const char *_p, unsigned char_cnt)
{
        int64_t l, upper_limit, lower_limit;
        const unsigned char *p = (const unsigned char *)_p;

        upper_limit = INT64_MAX / 256;
        lower_limit = INT64_MIN / 256;

        /* Pad with 1 or 0 bits, depending on sign. */
        if ((0x40 & *p) == 0x40)
                l = (int64_t)-1;
        else
                l = 0;
        l = (l << 6) | (0x3f & *p++);
        while (--char_cnt > 0) {
                if (l > upper_limit) {
                        l = INT64_MAX; /* Truncate on overflow */
                        break;
                } else if (l < lower_limit) {
                        l = INT64_MIN;
                        break;
                }
                l = (l << 8) | (0xff & (int64_t)*p++);
        }
        return (l);
}

static off_t
pkg_atol(const char *p, unsigned char_cnt)
{
        /*
         * Technically, GNU pkg considers a field to be in base-256
         * only if the first byte is 0xff or 0x80.
         */
        if (*p & 0x80)
                return (pkg_atol256(p, char_cnt));
        return (pkg_atol8(p, char_cnt));
}

static int
get_mode(struct tarfile *tf)
{
        return (pkg_atol(tf->tf_hdr.ut_mode, sizeof(tf->tf_hdr.ut_mode)));
}

/* GZip flag byte */
#define ASCII_FLAG      0x01 /* bit 0 set: file probably ascii text */
#define HEAD_CRC        0x02 /* bit 1 set: header CRC present */
#define EXTRA_FIELD     0x04 /* bit 2 set: extra field present */
#define ORIG_NAME       0x08 /* bit 3 set: original file name present */
#define COMMENT         0x10 /* bit 4 set: file comment present */
#define RESERVED        0xE0 /* bits 5..7: reserved */

static int
new_package(int fd, struct package **pp)
{
        struct package *pkg;
        off_t ofs;
        int flags, i, error;

        pkg = malloc(sizeof(*pkg));
        if (pkg == NULL)
                return (ENOMEM);

        bzero(pkg, sizeof(*pkg));
        pkg->pkg_fd = fd;

        /*
         * Parse the header.
         */
        error = EFTYPE;
        ofs = 0;

        /* Check megic. */
        if (get_byte(pkg, &ofs) != 0x1f || get_byte(pkg, &ofs) != 0x8b)
                goto fail;
        /* Check method. */
        if (get_byte(pkg, &ofs) != Z_DEFLATED)
                goto fail;
        /* Check flags. */
        flags = get_byte(pkg, &ofs);
        if (flags & RESERVED)
                goto fail;

        /* Skip time, xflags and OS code. */
        for (i = 0; i < 6; i++) {
                if (get_byte(pkg, &ofs) == -1)
                        goto fail;
        }

        /* Skip extra field. */
        if (flags & EXTRA_FIELD) {
                i = (get_byte(pkg, &ofs) & 0xff) |
                    ((get_byte(pkg, &ofs) << 8) & 0xff);
                while (i-- > 0) {
                        if (get_byte(pkg, &ofs) == -1)
                                goto fail;
                }
        }

        /* Skip original file name. */
        if (flags & ORIG_NAME) {
                do {
                        i = get_byte(pkg, &ofs);
                } while (i != 0 && i != -1);
                if (i == -1)
                        goto fail;
        }

        /* Print the comment if it's there. */
        if (flags & COMMENT) {
                while (1) {
                        i = get_byte(pkg, &ofs);
                        if (i == -1)
                                goto fail;
                        if (i == 0)
                                break;
                        putchar(i);
                }
        }

        /* Skip the CRC. */
        if (flags & HEAD_CRC) {
                if (get_byte(pkg, &ofs) == -1)
                        goto fail;
                if (get_byte(pkg, &ofs) == -1)
                        goto fail;
        }

        /*
         * Done parsing the ZIP header. Start the inflation engine.
         */
        error = inflateInit2(&pkg->pkg_zs, -15);
        if (error != Z_OK)
                goto fail;

        *pp = pkg;
        return (0);

 fail:
        free(pkg);
        return (error);
}

static struct tarfile *
scan_tarfile(struct package *pkg, struct tarfile *last)
{
        char buf[512];
        struct tarfile *cur;
        off_t ofs;
        size_t sz;

        cur = (last != NULL) ? last->tf_next : pkg->pkg_first;
        if (cur == NULL) {
                ofs = (last != NULL) ? last->tf_ofs + last->tf_size :
                    pkg->pkg_ofs;
                ofs = (ofs + 0x1ff) & ~0x1ff;

                /* Check if we've reached EOF. */
                if (ofs < pkg->pkg_ofs) {
                        errno = ENOSPC;
                        return (NULL);
                }

                if (ofs != pkg->pkg_ofs) {
                        if (last != NULL && pkg->pkg_ofs == last->tf_ofs) {
                                if (cache_data(last, 0) == -1)
                                        return (NULL);
                        } else {
                                sz = ofs - pkg->pkg_ofs;
                                while (sz != 0) {
                                        if (sz > sizeof(buf))
                                                sz = sizeof(buf);
                                        if (get_zipped(pkg, buf, sz) == -1)
                                                return (NULL);
                                        sz = ofs - pkg->pkg_ofs;
                                }
                        }
                }

                cur = malloc(sizeof(*cur));
                if (cur == NULL)
                        return (NULL);
                memset(cur, 0, sizeof(*cur));
                cur->tf_pkg = pkg;

                while (1) {
                        if (get_zipped(pkg, &cur->tf_hdr,
                            sizeof(cur->tf_hdr)) == -1) {
                                free(cur);
                                return (NULL);
                        }

                        /*
                         * There are always 2 empty blocks appended to
                         * a PKG. It marks the end of the archive.
                         */
                        if (strncmp(cur->tf_hdr.ut_magic, "ustar", 5) != 0) {
                                free(cur);
                                errno = ENOSPC;
                                return (NULL);
                        }

                        cur->tf_ofs = pkg->pkg_ofs;
                        cur->tf_size = pkg_atol(cur->tf_hdr.ut_size,
                            sizeof(cur->tf_hdr.ut_size));

                        if (cur->tf_hdr.ut_name[0] != '+')
                                break;

                        /*
                         * Skip package meta-files.
                         */
                        ofs = cur->tf_ofs + cur->tf_size;
                        ofs = (ofs + 0x1ff) & ~0x1ff;
                        while (pkg->pkg_ofs < ofs) {
                                if (get_zipped(pkg, buf, sizeof(buf)) == -1) {
                                        free(cur);
                                        return (NULL);
                                }
                        }
                }

                if (last != NULL)
                        last->tf_next = cur;
                else
                        pkg->pkg_first = cur;
                pkg->pkg_last = cur;
        }

        return (cur);
}