seahag/haggis.c

/*                 _,.---._    .-._        .--.-. ,--.--------.
 *   _,..---._   ,-.' , -  `. /==/ \  .-._/==/  //==/,  -   , -\
 * /==/,   -  \ /==/_,  ,  - \|==|, \/ /, |==\ -\\==\.-.  - ,-./
 * |==|   _   _\==|   .=.     |==|-  \|  | \==\- \`--`\==\- \
 * |==|  .=.   |==|_ : ;=:  - |==| ,  | -|  `--`-'     \==\_ \
 * |==|,|   | -|==| , '='     |==| -   _ |             |==|- |
 * |==|  '='   /\==\ -    ,_ /|==|  /\ , |             |==|, |
 * |==|-,   _`/  '.='. -   .' /==/, | |- |             /==/ -/
 * `-.`.____.'     `--`--''   `--`./  `--`             `--`--`
 *                    _ __    ,---.      .-._         .=-.-.  _,.----.
 *                 .-`.' ,`..--.'  \    /==/ \  .-._ /==/_ /.' .' -   \
 *                /==/, -   \==\-/\ \   |==|, \/ /, /==|, |/==/  ,  ,-'
 *               |==| _ .=. /==/-|_\ |  |==|-  \|  ||==|  ||==|-   |  .
 *               |==| , '=',\==\,   - \ |==| ,  | -||==|- ||==|_   `-' \
 *               |==|-  '..'/==/ -   ,| |==| -   _ ||==| ,||==|   _  , |
 *               |==|,  |  /==/-  /\ - \|==|  /\ , ||==|- |\==\.       /
 *               /==/ - |  \==\ _.\=\.-'/==/, | |- |/==/. / `-.`.___.-'
 *               `--`---'   `--`        `--`./  `--``--`-`
 *
 *	@(#)Copyright (c) 2023, Nathan D. Fisher.
 *
 *      This is free software.  It comes with NO WARRANTY.
 *      Permission to use, modify and distribute this source code
 *      is granted subject to the following conditions.
 *      1/ that the above copyright notice and this notice
 *      are preserved in all copies and that due credit be given
 *      to the author.
 *      2/ that any changes to this code are clearly commented
 *      as such so that the author does not get blamed for bugs
 *      other than his own.
 */

#include "haggis.h"
#include "mq.h"

#include <assert.h>      // assert
#include <errno.h>       // errno
#include <libgen.h>      // dirname
#include <limits.h>      // PATH_MAX
#include <stddef.h>      // size_t
#include <stdint.h>      // uint<x>_t

#if defined(__FreeBSD__) || defined(__DragonFly__)
#include <sha.h>
#include <sha256.h>
#include <sys/types.h>     // dev_t, makedev, major, minor
#elif defined(__NetBSD__) || defined(__OpenBSD__)
#include <sha1.h>
#include <sha2.h>
#include <sys/types.h>     // dev_t, makedev, major, minor
#elif defined(__linux__)
#include <sha1.h>
#include <sha2.h>
#include <sys/sysmacros.h> // major, minor, dev_t
#endif                     /* if defined (__FreeBSD__) */
#include <md5.h>

#include <stdio.h>         // fopen, fread, fwrite, FILE
#include <stdlib.h>        // free, malloc, calloc
#include <string.h>        // memcpy, strnlen, strndup
#include <sys/stat.h>      // stat, lstat, mkdir, mknod
#include <unistd.h>        // access, dirname, geteuid, readlink

#include "haggis_private.h"

static unsigned char header[7] = {0x89, 'h', 'a', 'g', 'g', 'i', 's'};

int haggis_store_header(FILE *stream) {
    if (fwrite(header, 1, 7, stream) < 7)
        return 1;
    return 0;
}

int haggis_check_header(FILE *stream) {
    unsigned char *buf[7];
    if (fread(buf, 1, 7, stream) < 7)
        return 1;
    if (memcmp(buf, header, 7))
        return 2;
    return 0;
}

void haggis_device_init(haggis_device *self, dev_t rdev) {
    self->major.val = (uint32_t)major(rdev);
    self->minor.val = (uint32_t)minor(rdev);
}

int haggis_store_device(haggis_device *self, FILE *stream) {
    if (fwrite(self->major.bytes, 1, 4, stream) != 4)
        return 1;
    if (fwrite(self->minor.bytes, 1, 4, stream) != 4)
        return 1;
    return 0;
}

int haggis_load_device(haggis_device *self, FILE *stream) {
    if (fread(self->major.bytes, 1, 4, stream) != 4)
        return 1;
    if (fread(self->minor.bytes, 1, 4, stream) != 4)
        return 1;
    return 0;
}

int haggis_store_cksum(haggis_checksum *self, FILE *stream) {
    u8 flag;

    switch (self->tag) {
    case md5:
        flag = 0;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        if (fwrite(self->md5, 1, 16, stream) != 16)
            return 1;
        break;
    case sha1:
        flag = 1;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        if (fwrite(self->sha1, 1, 20, stream) != 20)
            return 1;
        break;
    case sha256:
        flag = 2;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        if (fwrite(self->sha256, 1, 32, stream) != 32)
            return 1;
        break;
    case skip:
        flag = 3;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        break;
    }
    return 0;
}

int haggis_load_cksum(haggis_checksum *self, FILE *stream) {
    u8 flag;

    if (fread(&flag, 1, 1, stream) != 1)
        return 1;
    switch (flag) {
    case md5:
        self->tag = 0;
        if (fread(&self->md5, 1, 16, stream) != 16)
            return 1;
        break;
    case sha1:
        self->tag = 1;
        if (fread(&self->sha1, 1, 20, stream) != 20)
            return 1;
        break;
    case sha256:
        self->tag = 2;
        if (fread(&self->sha256, 1, 32, stream) != 32)
            return 1;
        break;
    case skip:
        self->tag = 3;
        break;
    }
    return 0;
}

void init_md5(haggis_file *f) {
    MD5_CTX ctx;

    f->cksum.tag = md5;
    MD5Init(&ctx);
    MD5Update(&ctx, f->data, (size_t)f->len.val);
    MD5Final(f->cksum.md5, &ctx);
}

int validate_md5(haggis_file *file) {
    MD5_CTX ctx;
    u8 digest[16];

    MD5Init(&ctx);
    MD5Update(&ctx, file->data, (size_t)file->len.val);
    MD5Final(digest, &ctx);
    if (memcmp(file->cksum.md5, digest, sizeof(digest)))
        return 2;
    return 0;
}

#if defined(__FreeBSD__) || defined(__DragonFly__)
void init_sha1(haggis_file *f) {
    SHA1_CTX ctx;

    f->cksum.tag = sha1;
    SHA1_Init(&ctx);
    SHA1_Update(&ctx, f->data, (size_t)f->len.val);
    SHA1_Final(f->cksum.sha1, &ctx);
}

int validate_sha1(haggis_file *file) {
    SHA1_CTX ctx;
    u8 digest[20];

    SHA1_Init(&ctx);
    SHA1_Update(&ctx, file->data, (size_t)file->len.val);
    SHA1_Final(digest, &ctx);
    if (memcmp(file->cksum.sha1, digest, sizeof(digest)))
        return 2;
    return 0;
}
#elif defined(__linux__) || defined(__NetBSD__) || defined(__OpenBSD__)
void init_sha1(haggis_file *f) {
    SHA1_CTX ctx;

    f->cksum.tag = sha1;
    SHA1Init(&ctx);
    SHA1Update(&ctx, f->data, (size_t)f->len.val);
    SHA1Final(f->cksum.sha1, &ctx);
}

int validate_sha1(haggis_file *file) {
    SHA1_CTX ctx;
    u8 digest[20];

    SHA1Init(&ctx);
    SHA1Update(&ctx, file->data, (size_t)file->len.val);
    SHA1Final(digest, &ctx);
    if (memcmp(file->cksum.sha1, digest, sizeof(digest)))
        return 2;
    return 0;
}
#endif /* if defined (__FreeBSD__) */

#if defined(__FreeBSD__) || defined(__DragonFly) || defined(__NetBSD__)
void init_sha256(haggis_file *f) {
    SHA256_CTX ctx;

    f->cksum.tag = sha256;
    SHA256_Init(&ctx);
    SHA256_Update(&ctx, f->data, (size_t)f->len.val);
    SHA256_Final(f->cksum.sha256, &ctx);
}

int validate_sha256(haggis_file *file) {
    SHA256_CTX ctx;
    u8 digest[32];

    SHA256_Init(&ctx);
    SHA256_Update(&ctx, file->data, (size_t)file->len.val);
    SHA256_Final(digest, &ctx);
    if (memcmp(file->cksum.sha256, digest, sizeof(digest)))
        return 2;
    return 0;
}
#elif defined(__linux__) || defined(__OpenBSD__)
void init_sha256(haggis_file *f) {
    SHA2_CTX ctx;

    f->cksum.tag = sha256;
    SHA256Init(&ctx);
    SHA256Update(&ctx, f->data, (size_t)f->len.val);
    SHA256Final(f->cksum.sha256, &ctx);
}

int validate_sha256(haggis_file *file) {
    SHA2_CTX ctx;
    u8 digest[32];

    SHA256Init(&ctx);
    SHA256Update(&ctx, file->data, (size_t)file->len.val);
    SHA256Final(digest, &ctx);
    if (memcmp(file->cksum.sha256, digest, sizeof(digest)))
        return 2;
    return 0;
}
#endif /* if defined (__FreeBSD__) */

void haggis_init_cksum(haggis_file *f, haggis_algorithm a) {
    switch (a) {
    case md5:
        init_md5(f);
        break;
    case sha1:
        init_sha1(f);
        break;
    case sha256:
        init_sha256(f);
        break;
    case skip:
        break;
    }
}

int haggis_validate_cksum(haggis_file *file) {
    switch (file->cksum.tag) {
    case md5:
        return validate_md5(file);
    case sha1:
        return validate_sha1(file);
    case sha256:
        return validate_sha256(file);
    case skip:
        return 0;
    }
    return 0;
}

int haggis_file_init(haggis_file *self, char *path, haggis_algorithm a) {
    FILE *f;
    long len;

    f = fopen(path, "r");
    if (f == NULL)
        return 2;
    if (fseek(f, 0, SEEK_END) == -1) {
        fclose(f);
        return 2;
    }
    len = ftell(f);
    if (len == -1) {
        fclose(f);
        return 2;
    }
    self->len.val = (uint64_t)len;
    rewind(f);
    self->data = calloc(1, (size_t)len);
    if (fread(self->data, 1, (size_t)len, f) != (size_t)len) {
        free(self->data);
        fclose(f);
        return 1;
    }
    fclose(f);
    haggis_init_cksum(self, a);
    return 0;
}

void haggis_file_deinit(haggis_file *f) {
    if (f->data != NULL)
        free(f->data);
}

int haggis_store_file(haggis_file *self, FILE *stream) {
    if (store_u64(stream, &self->len) != 8)
        return 1;
    if (haggis_store_cksum(&self->cksum, stream) != 0)
        return 1;
    int res = fwrite(self->data, 1, (size_t)self->len.val, stream);
    if (res != (size_t)self->len.val)
        return 1;
    return 0;
}

int haggis_load_file(haggis_file *self, FILE *stream) {
    if (load_u64(stream, &self->len) != 8)
        return 1;
    if (haggis_load_cksum(&self->cksum, stream) != 0)
        return 1;
    self->data = calloc(1, (size_t)self->len.val);
    if (self->data == NULL)
        return -1;
    int res = fread(self->data, 1, (size_t)self->len.val, stream);
    if (res != (size_t)self->len.val) {
        free(self->data);
        return 1;
    }
    if (haggis_validate_cksum(self)) {
        free(self->data);
        return 1;
    }
    return 0;
}

void haggis_filename_init(char *target, haggis_filename *fname) {
    size_t len;

    len = strlen(target);
    fname->len.val = (uint16_t)len;
    fname->name = target;
}

void haggis_filename_deinit(haggis_filename *fname) {
    if (fname->name != NULL)
        free(fname->name);
}

int haggis_load_filename(FILE *stream, haggis_filename *n) {
    u16 len;
    char *name;

    len.val = 0;
    if (fread(len.bytes, 1, 2, stream) != 2)
        return 2;
    n->len = len;
    name = calloc(1, (size_t)len.val);
    if (name == NULL)
        return -1;
    if (fread(name, 1, (size_t)len.val, stream) != (size_t)len.val) {
        free(name);
        return 2;
    }
    n->name = name;
    return 0;
}

int haggis_store_filename(FILE *stream, haggis_filename *n) {
    if (fwrite(n->len.bytes, 1, 2, stream) != 2)
        return 2;
    if (fwrite(n->name, 1, (size_t)n->len.val, stream) != (size_t)n->len.val)
        return 2;
    return 0;
}

int haggis_load_filetype(
    FILE *stream,
    haggis_typeflag tag,
    haggis_filetype *file
) {
    switch (tag) {
    case normal:
        file->tag = 0;
        return haggis_load_file(&file->file, stream);
    case hardlink:
        return haggis_load_filename(stream, &file->target);
        file->tag = 1;
    case softlink:
        return haggis_load_filename(stream, &file->target);
        file->tag = 2;
    case directory:
        file->tag = 3;
        break;
    case character:
        file->tag = 4;
        return haggis_load_device(&file->dev, stream);
    case block:
        file->tag = 5;
        return haggis_load_device(&file->dev, stream);
    case fifo:
        file->tag = 6;
        break;
    case eof:
        file->tag = 7;
        break;
    }
    return 0;
}

int haggis_store_filetype(FILE *stream, haggis_filetype *filetype) {
    u8 flag;

    switch (filetype->tag) {
    case normal:
        flag = 0;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        if (haggis_store_file(&filetype->file, stream) != 0)
            return 1;
        break;
    case hardlink:
        flag = 1;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        return haggis_store_filename(stream, &filetype->target);
    case softlink:
        flag = 2;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        return haggis_store_filename(stream, &filetype->target);
    case directory:
        flag = 3;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        break;
    case character:
        flag = 4;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        if (haggis_store_device(&filetype->dev, stream) != 0)
            return 1;
        break;
    case block:
        flag = 5;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        if (haggis_store_device(&filetype->dev, stream) != 0)
            return 1;
        break;
    case fifo:
        flag = 6;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        break;
    case eof:
        flag = 7;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        break;
    };
    return 0;
}

haggis_typeflag haggis_filetype_from_mode(u16 mode) {
    u8 mask = 07 << 5;
    int filetype = (int)((mode.bytes[0] & mask) >> 5);
    return filetype;
}

u16 haggis_derive_mode(u16 raw, haggis_filetype *ft) {
    u16 mode;
    mode.val = ((uint16_t)ft->tag << 5) & raw.val;
    return mode;
}

void haggis_node_deinit(haggis_node *node) {
    if (node == NULL)
        return;
    if (node->name.name != NULL)
        haggis_filename_deinit(&node->name);
    switch (node->filetype.tag) {
    case normal:
        if (node->filetype.file.data != NULL) {
            free(node->filetype.file.data);
        }
        break;
    case hardlink:
    case softlink:
        if (node->filetype.target.name != NULL) {
            haggis_filename_deinit(&node->filetype.target);
        }
        break;
    case character:
    case block:
    case directory:
    case fifo:
    case eof:
        break;
    };
    free(node);
}

int haggis_init_hardlink_node(
    haggis_node *node,
    char *target,
    haggis_linkmap *map,
    haggis_mq *mq
) {
    haggis_message_body body;
    haggis_msg *msg;

    node->filetype.tag = hardlink;
    haggis_filename_init(target, &node->filetype.target);
    body.f_name = strndup(node->name.name, PATH_MAX);
    msg = haggis_msg_init(NodeCreated, body);
    if (msg == NULL)
        return 1;
    haggis_mq_push(mq, msg);
    return 0;
}

int haggis_init_file_node(
    haggis_node *node,
    struct stat *st,
    haggis_algorithm a,
    haggis_linkmap *map,
    haggis_mq *mq
) {
    haggis_message_body body;
    haggis_msg *msg;
    char *target;
    int res;

    if (st->st_nlink > 1) {
        target = haggis_linkmap_get_or_add(map, st->st_ino, node->name.name);
        if (target != NULL) {
            haggis_init_hardlink_node(node, target, map, mq);
            return 0;
        }
    }
    node->filetype.tag = normal;
    res = haggis_file_init(&node->filetype.file, node->name.name, a);
    if (res != 0) {
        haggis_node_deinit(node);
        return 1;
    }
    body.f_name = strndup(node->name.name, PATH_MAX);
    msg = haggis_msg_init(NodeCreated, body);
    haggis_mq_push(mq, msg);
    return 0;
}

int haggis_init_dev_node(haggis_node *node, struct stat *st,
                         haggis_linkmap *map, haggis_mq *mq) {
    haggis_message_body body;
    haggis_msg *msg;
    char *target;

    if (st->st_nlink > 1) {
        target = haggis_linkmap_get_or_add(map, st->st_ino, node->name.name);
        if (target != NULL) {
            haggis_init_hardlink_node(node, target, map, mq);
            return 0;
        }
    }
    haggis_device_init(&node->filetype.dev, st->st_rdev);
    body.f_name = strndup(node->name.name, PATH_MAX);
    msg = haggis_msg_init(NodeCreated, body);
    haggis_mq_push(mq, msg);
    return 0;
}

haggis_node *haggis_create_node(
    char *file,
    haggis_algorithm a,
    haggis_linkmap *map,
    haggis_mq *mq
) {
    u16 mode;
    char *target;
    char pathbuf[PATH_MAX];
    int res;
    size_t namlen;
    haggis_node *node;
    haggis_message_body body;
    haggis_msg *msg;
    struct stat st;

    node = calloc(1, sizeof(haggis_node));
    if (node == NULL)
        return NULL;
    if (lstat(file, &st) != 0) {
        free(node);
        return NULL;
    }
    errno = 0;
    if (file[0] == '/') {
        namlen = strnlen(file, PATH_MAX - 1);
        node->name.name = strndup(&file[1], namlen);
    } else {
        namlen = strnlen(file, PATH_MAX) + 1;
        node->name.name = strndup(file, namlen);
    }
    if (errno == ENOMEM) {
        haggis_node_deinit(node);
        return NULL;
    }
    node->name.len.val = (uint16_t)namlen;
    node->uid.val = (uint32_t)st.st_uid;
    node->gid.val = (uint32_t)st.st_gid;
    node->mtime.val = (uint64_t)st.st_mtim.tv_sec;
    mode.val = (uint16_t)(st.st_mode & 07777);
    node->mode = mode;
    if (S_ISBLK(st.st_mode)) {
        node->filetype.tag = block;
        res = haggis_init_dev_node(node, &st, map, mq);
        if (res != 0)
            return NULL;
    } else if (S_ISCHR(st.st_mode)) {
        node->filetype.tag = character;
        res = haggis_init_dev_node(node, &st, map, mq);
        if (res != 0)
            return NULL;
    } else if (S_ISDIR(st.st_mode)) {
        node->filetype.tag = directory;
        body.f_name = strndup(file, PATH_MAX);
        msg = haggis_msg_init(NodeCreated, body);
        haggis_mq_push(mq, msg);
    } else if (S_ISFIFO(st.st_mode)) {
        node->filetype.tag = fifo;
        if (st.st_nlink > 1) {
            target = haggis_linkmap_get_or_add(map, st.st_ino, file);
            if (target != NULL) {
                haggis_init_hardlink_node(node, target, map, mq);
                return node;
            }
        }
        body.f_name = strndup(file, PATH_MAX);
        msg = haggis_msg_init(NodeCreated, body);
        haggis_mq_push(mq, msg);
    } else if (S_ISLNK(st.st_mode)) {
        node->filetype.tag = softlink;
        ssize_t res = readlink(file, pathbuf, PATH_MAX);
        if (res == -1) {
            haggis_node_deinit(node);
            return NULL;
        }
        target = malloc(res + 1);
        memcpy(target, pathbuf, (unsigned long)res);
        haggis_filename_init(target, &node->filetype.target);
        body.f_name = strndup(file, PATH_MAX);
        msg = haggis_msg_init(NodeCreated, body);
        haggis_mq_push(mq, msg);
    } else if (S_ISREG(st.st_mode)) {
        res = haggis_init_file_node(node, &st, a, map, mq);
        if (res != 0)
            return NULL;
    } else {
        free(node);
        return NULL;
    }
    return node;
}

char *get_full_path(haggis_filename *fname, char *basedir) {
    char *path;
    int pathlen;

    if (basedir == NULL) {
        path = calloc(1, (int)fname->len.val + 1);
        if (path == NULL)
            return NULL;
        memcpy(path, fname->name, fname->len.val);
    } else {
        if (fname->name[0] == '/') {
            pathlen = strnlen(basedir, PATH_MAX) + (int)fname->len.val + 1;
            path = calloc(1, pathlen);
            if (path == NULL)
                return NULL;
            snprintf(path, pathlen, "%s%s", basedir, fname->name);
        } else {
            pathlen = strnlen(basedir, PATH_MAX) + (int)fname->len.val + 2;
            path = calloc(1, pathlen);
            if (path == NULL)
                return NULL;
            snprintf(path, pathlen, "%s/%s", basedir, fname->name);
        }
    }
    return path;
}

int mkdir_p(char *dir) {
    struct stat st;

    if (!stat(dir, &st))
        return 0;

    if (mkdir_p(dirname(strndup(dir, PATH_MAX))))
        return 1;
    return mkdir(dir, 0755);
}

int haggis_extract_dev(haggis_node *node, char *basedir) {
    dev_t dev;
    mode_t mode = 0;
    char *path;
    int ret, major, minor;

    assert(geteuid() == 0);
    assert(node->filetype.tag == block || node->filetype.tag == character);
    path = get_full_path(&node->name, basedir);
    if (path == NULL)
        return errno;
    if (mkdir_p(dirname(strndup(path, PATH_MAX)))) {
        free(path);
        return 2;
    }
    major = (int)node->filetype.dev.major.val;
    minor = (int)node->filetype.dev.minor.val;
    dev = makedev(major, minor);
    if (node->filetype.tag == block) {
        mode = (mode_t)node->mode.val | S_IFBLK;
    } else if (node->filetype.tag == character) {
        mode = (mode_t)node->mode.val | S_IFCHR;
    }
    if (access(path, F_OK) == 0)
        unlink(path);
    ret = mknod(path, mode, dev);
    free(path);
    return ret;
}

int haggis_extract_fifo(haggis_node *node, char *basedir) {
    mode_t mode;
    char *path;
    int ret;

    assert(node->filetype.tag == fifo);
    path = get_full_path(&node->name, basedir);
    if (path == NULL)
        return 1;
    if (mkdir_p(dirname(strndup(path, PATH_MAX)))) {
        free(path);
        return 2;
    }
    mode = (mode_t)node->mode.val;
    if (access(path, F_OK) == 0)
        unlink(path);
    ret = mkfifo(path, mode);
    free(path);
    if (ret != 0)
        return errno;
    return 0;
}

int haggis_extract_symlink(haggis_node *node, char *basedir) {
    char *path, *target;
    int ret;
    struct stat st;

    assert(node->filetype.tag == softlink);
    path = get_full_path(&node->name, basedir);
    if (path == NULL)
        return 1;
    if (mkdir_p(dirname(strndup(path, PATH_MAX)))) {
        free(path);
        return 2;
    }
    target = node->filetype.target.name;
    if (lstat(path, &st) == 0)
        unlink(path);
    ret = symlink(target, path);
    free(path);
    if (ret != 0)
        return errno;
    return 0;
}

int haggis_extract_hardlink(haggis_node *node, char *basedir) {
    char *path, *target;
    int ret;
    FILE *fd;

    assert(node->filetype.tag == hardlink);
    path = get_full_path(&node->name, basedir);
    if (path == NULL)
        return 1;
    if (mkdir_p(dirname(strndup(path, PATH_MAX)))) {
        free(path);
        return 2;
    }
    target = get_full_path(&node->filetype.target, basedir);
    if (target == NULL) {
        free(path);
        return 1;
    }
    if (access(target, F_OK) == -1) {
        fd = fopen(target, "w");
        if (mkdir_p(dirname(strndup(target, PATH_MAX)))) {
            free(path);
            return 2;
        }
        if (fd == NULL) {
            free(path);
            free(target);
            return errno;
        }
        fclose(fd);
    }
    if (access(path, F_OK) == 0)
        unlink(path);
    ret = link(target, path);
    free(path);
    free(target);
    if (ret != 0)
        return errno;
    return 0;
}

int haggis_extract_dir(haggis_node *node, char *basedir) {
    char *path;

    assert(node->filetype.tag == directory);
    path = get_full_path(&node->name, basedir);
    if (mkdir_p(path)) {
        free(path);
        return errno;
    }
    free(path);
    return 0;
}

char *haggis_extract_file(haggis_node *node, char *basedir) {
    char *path;
    FILE *fd;
    size_t len;
    int ret;

    assert(node->filetype.tag == normal);
    path = get_full_path(&node->name, basedir);
    if (path == NULL) {
        return NULL;
    }
    if (mkdir_p(dirname(strndup(path, PATH_MAX)))) {
        free(path);
        return NULL;
    }
    fd = fopen(path, "w+");
    if (fd == NULL) {
        free(path);
        return NULL;
    }
    len = (size_t)node->filetype.file.len.val;
    ret = fwrite(node->filetype.file.data, len, 1, fd);
    if (ret != len) {
        free(path);
        fclose(fd);
        return NULL;
    }
    fflush(fd);
    fclose(fd);
    return path;
}

int haggis_extract_node(haggis_node *self, char *basedir, haggis_mq *mq) {
    haggis_msg *msg;
    char *path, *dir, *fullpath;
    int ret = 0;

    path = get_full_path(&self->name, basedir);
    dir = dirname(strndup(path, PATH_MAX));
    mkdir_p(dir);
    switch (self->filetype.tag) {
    case block:
    case character:
        if (geteuid() == 0) {
            ret = haggis_extract_dev(self, basedir);
        } else {
            ret = -1;
            msg = calloc(1, sizeof(haggis_msg));
            if (msg == NULL)
                return 2;
            msg->tag = DevNodeSkipped;
            msg->body.f_name = strndup(self->name.name, PATH_MAX);
            haggis_mq_push(mq, msg);
        }
        break;
    case fifo:
        ret = haggis_extract_fifo(self, basedir);
        break;
    case softlink:
        ret = haggis_extract_symlink(self, basedir);
        break;
    case hardlink:
        ret = haggis_extract_hardlink(self, basedir);
        break;
    case directory:
        ret = haggis_extract_dir(self, basedir);
        break;
    case normal:
        fullpath = haggis_extract_file(self, basedir);
        if (fullpath == NULL) {
            ret = errno;
        }
        break;
    case eof:
        return 0;
    }
    if (ret)
        return ret;
    if (geteuid() == 0) {
        ret = chown(path, (uid_t)self->uid.val, (gid_t)self->gid.val);
        if (ret != 0) {
            free(path);
            return errno;
        }
    }
    if (self->filetype.tag != softlink)
        ret = chmod(path, (mode_t)self->mode.val);
    if (ret)
        return ret;
    msg = calloc(1, sizeof(haggis_msg));
    if (msg == NULL)
        return 2;
    msg->tag = NodeExtracted;
    msg->body.f_name = strndup(self->name.name, PATH_MAX);
    haggis_mq_push(mq, msg);
    return ret;
}

int haggis_load_node(haggis_node *self, FILE *stream) {
    int res;
    u16 mode;
    haggis_typeflag tag;

    mode.val = 0;
    res = haggis_load_filename(stream, &self->name);
    if (res)
        return res;
    res = load_u32(stream, &self->uid);
    if (res != 4)
        return 2;
    res = load_u32(stream, &self->gid);
    if (res != 4)
        return 2;
    res = load_u64(stream, &self->mtime);
    if (res != 8)
        return 2;
    res = load_u16(stream, &mode);
    if (res != 2)
        return 2;
    tag = haggis_filetype_from_mode(mode);
    self->mode.bytes[0] = mode.bytes[0] & 037;
    self->mode.bytes[1] = mode.bytes[1];
    res = haggis_load_filetype(stream, tag, &self->filetype);
    if (res)
        return res;
    return 0;
}

int haggis_store_node(haggis_node *self, FILE *stream) {
    u16 mode;

    if (haggis_store_filename(stream, &self->name) !=
        (size_t)(self->name.len.val) + 2)
        return 2;
    if (store_u32(stream, &self->uid) != 4)
        return 2;
    if (store_u32(stream, &self->gid) != 4)
        return 2;
    if (store_u64(stream, &self->mtime) != 8)
        return 2;
    mode = haggis_derive_mode(self->mode, &self->filetype);
    if (store_u16(stream, &mode) != 2)
        return 2;
    return haggis_store_filetype(stream, &self->filetype);
}