From 2f172ede7115d0a2730a3b689131042ba559e272 Mon Sep 17 00:00:00 2001 From: David Oberhollenzer Date: Wed, 19 Jun 2019 15:04:17 +0200 Subject: Split generic tar code off to static library Signed-off-by: David Oberhollenzer --- lib/tar/write_header.c | 248 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 248 insertions(+) create mode 100644 lib/tar/write_header.c (limited to 'lib/tar/write_header.c') diff --git a/lib/tar/write_header.c b/lib/tar/write_header.c new file mode 100644 index 0000000..80db327 --- /dev/null +++ b/lib/tar/write_header.c @@ -0,0 +1,248 @@ +/* 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 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 void init_header(tar_header_t *hdr, const struct stat *sb, + const char *name, const char *slink_target) +{ + memset(hdr, 0, sizeof(*hdr)); + + name_to_tar_header(hdr, name); + memcpy(hdr->magic, TAR_MAGIC, sizeof(hdr->magic)); + memcpy(hdr->version, TAR_VERSION, sizeof(hdr->version)); + write_octal(hdr->mode, sb->st_mode & ~S_IFMT, 6); + write_octal(hdr->uid, sb->st_uid, 6); + write_octal(hdr->gid, sb->st_gid, 6); + write_octal(hdr->mtime, sb->st_mtime, 11); + write_octal(hdr->size, 0, 11); + write_octal(hdr->devmajor, 0, 6); + write_octal(hdr->devminor, 0, 6); + + switch (sb->st_mode & S_IFMT) { + case S_IFREG: + write_octal(hdr->size, sb->st_size & 077777777777L, 11); + break; + case S_IFLNK: + if (sb->st_size < (off_t)sizeof(hdr->linkname)) + strcpy(hdr->linkname, slink_target); + break; + case S_IFCHR: + case S_IFBLK: + write_octal(hdr->devmajor, major(sb->st_rdev), 6); + write_octal(hdr->devminor, minor(sb->st_rdev), 6); + break; + } + + sprintf(hdr->uname, "%u", sb->st_uid); + sprintf(hdr->gname, "%u", sb->st_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 bool need_pax_header(const struct stat *sb, const char *name) +{ + tar_header_t tmp; + + if (sb->st_uid > 0777777 || sb->st_gid > 0777777) + return true; + + if (S_ISREG(sb->st_mode) && sb->st_size > 077777777777L) + return true; + + if (S_ISLNK(sb->st_mode) && sb->st_size >= (off_t)sizeof(tmp.linkname)) + return true; + + if (name_to_tar_header(&tmp, 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 struct stat *sb, const char *name, + const char *slink_target) +{ + char temp[64], *ptr; + struct stat fakesb; + tar_header_t hdr; + ssize_t ret; + size_t len; + + memset(buffer, 0, sizeof(buffer)); + memset(&fakesb, 0, sizeof(fakesb)); + fakesb.st_mode = S_IFREG | 0644; + + sprintf(temp, "pax%lu", pax_hdr_counter); + init_header(&hdr, &fakesb, temp, NULL); + hdr.typeflag = TAR_TYPE_PAX; + + sprintf(temp, "%u", sb->st_uid); + ptr = buffer; + ptr = write_pax_entry(ptr, "uid", temp); + ptr = write_pax_entry(ptr, "uname", temp); + + sprintf(temp, "%lu", sb->st_mtime); + ptr = write_pax_entry(ptr, "mtime", temp); + + sprintf(temp, "%u", sb->st_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(sb->st_mode)) { + ptr = write_pax_entry(ptr, "linkpath", slink_target); + } else if (S_ISREG(sb->st_mode)) { + sprintf(temp, "%lu", sb->st_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 struct stat *sb, const char *name, + const char *slink_target) +{ + const char *reason; + tar_header_t hdr; + ssize_t ret; + + if (need_pax_header(sb, name)) { + if (write_pax_header(fd, sb, name, slink_target)) + return -1; + + sprintf(buffer, "pax%lu_data", pax_hdr_counter++); + name = buffer; + } + + init_header(&hdr, sb, name, slink_target); + + switch (sb->st_mode & S_IFMT) { + case S_IFCHR: hdr.typeflag = TAR_TYPE_CHARDEV; break; + case S_IFBLK: hdr.typeflag = TAR_TYPE_BLOCKDEV; break; + case S_IFLNK: hdr.typeflag = TAR_TYPE_SLINK; break; + case S_IFREG: 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