From e2f9334cd84ff8dd4c65c850825e089a6c747601 Mon Sep 17 00:00:00 2001 From: David Oberhollenzer Date: Wed, 12 Jun 2019 17:11:08 +0200 Subject: Add utility to turn a squashfs image into a POSIX tar archvie Signed-off-by: David Oberhollenzer --- tar/write_header.c | 260 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 260 insertions(+) create mode 100644 tar/write_header.c (limited to 'tar/write_header.c') diff --git a/tar/write_header.c b/tar/write_header.c new file mode 100644 index 0000000..9073056 --- /dev/null +++ b/tar/write_header.c @@ -0,0 +1,260 @@ +/* SPDX-License-Identifier: GPL-3.0-or-later */ +#include "util.h" +#include "tar.h" + +#include +#include +#include + +static unsigned long pax_hdr_counter = 0; +static char buffer[4096]; + +static void write_octal(char *dst, unsigned int value, int digits) +{ + char temp[64]; + + sprintf(temp, "%0*o ", digits, value); + memcpy(dst, temp, strlen(temp)); +} + +static void init_header(tar_header_t *hdr, const fstree_t *fs, + const tree_node_t *n) +{ + memset(hdr, 0, sizeof(*hdr)); + + memcpy(hdr->magic, TAR_MAGIC, strlen(TAR_MAGIC)); + memcpy(hdr->version, TAR_VERSION, strlen(TAR_VERSION)); + + write_octal(hdr->mode, n->mode & ~S_IFMT, 6); + write_octal(hdr->uid, n->uid, 6); + write_octal(hdr->gid, n->gid, 6); + write_octal(hdr->size, 0, 11); + write_octal(hdr->mtime, fs->default_mtime, 11); + write_octal(hdr->devmajor, 0, 6); + write_octal(hdr->devminor, 0, 6); + + sprintf(hdr->uname, "%u", n->uid); + sprintf(hdr->gname, "%u", n->gid); +} + +static void update_checksum(tar_header_t *hdr) +{ + unsigned int chksum = 0; + size_t i; + + memset(hdr->chksum, ' ', sizeof(hdr->chksum)); + + for (i = 0; i < sizeof(*hdr); ++i) + chksum += ((unsigned char *)hdr)[i]; + + write_octal(hdr->chksum, chksum, 6); + hdr->chksum[6] = '\0'; + hdr->chksum[7] = ' '; +} + +static int name_to_tar_header(tar_header_t *hdr, const char *path) +{ + size_t len = strlen(path); + const char *ptr; + + if ((len + 1) <= sizeof(hdr->name)) { + memcpy(hdr->name, path, len); + return 0; + } + + for (ptr = path; ; ++ptr) { + ptr = strchr(ptr, '/'); + if (ptr == NULL) + return -1; + + len = ptr - path; + if (len >= sizeof(hdr->prefix)) + continue; + if (strlen(ptr + 1) >= sizeof(hdr->name)) + continue; + break; + } + + memcpy(hdr->prefix, path, ptr - path); + memcpy(hdr->name, ptr + 1, strlen(ptr + 1)); + return 0; +} + +static bool need_pax_header(const tree_node_t *n, const char *name) +{ + tar_header_t temp; + + if (n->uid > 0777777 || n->gid > 0777777) + return true; + + if (S_ISREG(n->mode) && n->data.file->size > 077777777777UL) + return true; + + if (S_ISLNK(n->mode)) { + if (strlen(n->data.slink_target) >= sizeof(temp.linkname)) + return true; + } + + if (name_to_tar_header(&temp, name)) + return true; + + return false; +} + +static char *write_pax_entry(char *dst, const char *key, const char *value) +{ + size_t i, len, prefix = 0, oldprefix; + + do { + len = prefix + 1 + strlen(key) + 1 + strlen(value) + 1; + + oldprefix = prefix; + prefix = 1; + + for (i = len; i >= 10; i /= 10) + ++prefix; + } while (oldprefix != prefix); + + sprintf(dst, "%zu %s=%s\n", len, key, value); + + return dst + len; +} + +static int write_pax_header(int fd, const fstree_t *fs, const tree_node_t *n, + const char *name) +{ + char temp[64], *ptr; + tar_header_t hdr; + ssize_t ret; + size_t len; + + memset(buffer, 0, sizeof(buffer)); + memset(&hdr, 0, sizeof(hdr)); + + sprintf(hdr.name, "pax%lu", pax_hdr_counter); + memcpy(hdr.magic, TAR_MAGIC, strlen(TAR_MAGIC)); + memcpy(hdr.version, TAR_VERSION, strlen(TAR_VERSION)); + write_octal(hdr.mode, 0644, 6); + write_octal(hdr.uid, 0, 6); + write_octal(hdr.gid, 0, 6); + write_octal(hdr.mtime, 0, 11); + write_octal(hdr.devmajor, 0, 6); + write_octal(hdr.devminor, 0, 6); + sprintf(hdr.uname, "%u", 0); + sprintf(hdr.gname, "%u", 0); + hdr.typeflag = TAR_TYPE_PAX; + + ptr = buffer; + sprintf(temp, "%u", n->uid); + ptr = write_pax_entry(ptr, "uid", temp); + ptr = write_pax_entry(ptr, "uname", temp); + + sprintf(temp, "%u", fs->default_mtime); + ptr = write_pax_entry(ptr, "mtime", temp); + + sprintf(temp, "%u", n->gid); + ptr = write_pax_entry(ptr, "gid", temp); + ptr = write_pax_entry(ptr, "gname", temp); + + ptr = write_pax_entry(ptr, "path", name); + + if (S_ISLNK(n->mode)) { + ptr = write_pax_entry(ptr, "linkpath", n->data.slink_target); + } else if (S_ISREG(n->mode)) { + sprintf(temp, "%lu", n->data.file->size); + ptr = write_pax_entry(ptr, "size", temp); + } + + len = strlen(buffer); + write_octal(hdr.size, len, 11); + update_checksum(&hdr); + + ret = write_retry(fd, &hdr, sizeof(hdr)); + if (ret < 0) + goto fail_wr; + if ((size_t)ret < sizeof(hdr)) + goto fail_trunc; + + ret = write_retry(fd, buffer, len); + if (ret < 0) + goto fail_wr; + if ((size_t)ret < len) + goto fail_trunc; + + return padd_file(fd, len, 512); +fail_wr: + perror("writing pax header"); + return -1; +fail_trunc: + fputs("writing pax header: truncated write\n", stderr); + return -1; +} + +int write_tar_header(int fd, const fstree_t *fs, const tree_node_t *n, + const char *name) +{ + const char *reason; + tar_header_t hdr; + ssize_t ret; + + if (need_pax_header(n, name)) { + if (write_pax_header(fd, fs, n, name)) + return -1; + + init_header(&hdr, fs, n); + sprintf(hdr.name, "pax%lu_data", pax_hdr_counter++); + } else { + init_header(&hdr, fs, n); + name_to_tar_header(&hdr, name); + } + + switch (n->mode & S_IFMT) { + case S_IFCHR: + case S_IFBLK: + write_octal(hdr.devmajor, major(n->data.devno), 6); + write_octal(hdr.devminor, minor(n->data.devno), 6); + hdr.typeflag = S_ISBLK(n->mode) ? TAR_TYPE_BLOCKDEV : + TAR_TYPE_CHARDEV; + break; + case S_IFLNK: + if (strlen(n->data.slink_target) < sizeof(hdr.linkname)) + strcpy(hdr.linkname, n->data.slink_target); + + hdr.typeflag = TAR_TYPE_SLINK; + break; + case S_IFREG: + write_octal(hdr.size, n->data.file->size & 077777777777UL, 11); + hdr.typeflag = TAR_TYPE_FILE; + break; + case S_IFDIR: + hdr.typeflag = TAR_TYPE_DIR; + break; + case S_IFIFO: + hdr.typeflag = TAR_TYPE_FIFO; + break; + case S_IFSOCK: + reason = "cannot pack socket"; + goto out_skip; + default: + reason = "unknown type"; + goto out_skip; + } + + update_checksum(&hdr); + + ret = write_retry(fd, &hdr, sizeof(hdr)); + + if (ret < 0) { + perror("writing header record"); + } else if ((size_t)ret < sizeof(hdr)) { + fputs("writing header record: truncated write\n", stderr); + ret = -1; + } else { + ret = 0; + } + + return ret; +out_skip: + fprintf(stderr, "WARNING: skipping '%s' (%s)\n", name, reason); + return 1; +} -- cgit v1.2.3