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-rw-r--r--lib/tar/read_header.c415
1 files changed, 415 insertions, 0 deletions
diff --git a/lib/tar/read_header.c b/lib/tar/read_header.c
new file mode 100644
index 0000000..bdb2d20
--- /dev/null
+++ b/lib/tar/read_header.c
@@ -0,0 +1,415 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "util.h"
+#include "tar.h"
+
+#include <sys/sysmacros.h>
+#include <string.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include <stdio.h>
+
+enum {
+ PAX_SIZE = 0x001,
+ PAX_UID = 0x002,
+ PAX_GID = 0x004,
+ PAX_DEV_MAJ = 0x008,
+ PAX_DEV_MIN = 0x010,
+ PAX_NAME = 0x020,
+ PAX_SLINK_TARGET = 0x040,
+ PAX_ATIME = 0x080,
+ PAX_MTIME = 0x100,
+ PAX_CTIME = 0x200,
+};
+
+static int read_octal(const char *str, int digits, uint64_t *out)
+{
+ uint64_t result = 0;
+
+ while (digits > 0 && *str >= '0' && *str <= '7') {
+ if (result > 0x1FFFFFFFFFFFFFFFUL) {
+ fputs("numeric overflow parsing tar header\n", stderr);
+ return -1;
+ }
+
+ result = (result << 3) | (*(str++) - '0');
+ --digits;
+ }
+
+ *out = result;
+ return 0;
+}
+
+static int read_binary(const char *str, int digits, uint64_t *out)
+{
+ uint64_t x, result = 0;
+
+ while (digits > 0) {
+ if (result > 0x00FFFFFFFFFFFFFFUL) {
+ fputs("numeric overflow parsing tar header\n", stderr);
+ return -1;
+ }
+
+ x = *((const unsigned char *)str++);
+ result = (result << 8) | x;
+ --digits;
+ }
+
+ *out = result;
+ return 0;
+}
+
+static int read_number(const char *str, int digits, uint64_t *out)
+{
+ if (*((unsigned char *)str) & 0x80) {
+ if (read_binary(str, digits, out))
+ return -1;
+ *out &= 0x7FFFFFFFFFFFFFFF;
+ return 0;
+ }
+
+ return read_octal(str, digits, out);
+}
+
+static bool is_zero_block(const tar_header_t *hdr)
+{
+ const unsigned char *ptr = (const unsigned char *)hdr;
+
+ return ptr[0] == '\0' && memcmp(ptr, ptr + 1, sizeof(*hdr) - 1) == 0;
+}
+
+static bool is_checksum_valid(const tar_header_t *hdr)
+{
+ unsigned int chksum = 0;
+ tar_header_t copy;
+ uint64_t ref;
+ size_t i;
+
+ if (read_octal(hdr->chksum, sizeof(hdr->chksum), &ref))
+ return false;
+
+ memcpy(&copy, hdr, sizeof(*hdr));
+ memset(copy.chksum, ' ', sizeof(copy.chksum));
+
+ for (i = 0; i < sizeof(copy); ++i)
+ chksum += ((unsigned char *)&copy)[i];
+
+ return chksum == ref;
+}
+
+static bool is_magic_valid(const tar_header_t *hdr)
+{
+ if (memcmp(hdr->magic, TAR_MAGIC, sizeof(hdr->magic)) != 0)
+ return false;
+
+ if (memcmp(hdr->version, TAR_VERSION, sizeof(hdr->version)) != 0)
+ return false;
+
+ return true;
+}
+
+static int pax_read_decimal(const char *str, uint64_t *out)
+{
+ uint64_t result = 0;
+
+ while (*str >= '0' && *str <= '9') {
+ if (result > 0xFFFFFFFFFFFFFFFFUL / 10) {
+ fputs("numeric overflow parsing pax header\n", stderr);
+ return -1;
+ }
+
+ result = (result * 10) + (*(str++) - '0');
+ }
+
+ *out = result;
+ return 0;
+}
+
+static int read_pax_header(int fd, uint64_t entsize, unsigned int *set_by_pax,
+ tar_header_decoded_t *out)
+{
+ char *buffer, *line;
+ uint64_t field;
+ ssize_t ret;
+ uint64_t i;
+
+ buffer = malloc(entsize + 1);
+ if (buffer == NULL)
+ goto fail_errno;
+
+ ret = read_retry(fd, buffer, entsize);
+ if (ret < 0)
+ goto fail_errno;
+ if ((size_t)ret < entsize)
+ goto fail_eof;
+
+ if (skip_padding(fd, entsize))
+ goto fail;
+
+ buffer[entsize] = '\0';
+
+ for (i = 0; i < entsize; ++i) {
+ while (i < entsize && isspace(buffer[i]))
+ ++i;
+ while (i < entsize && isdigit(buffer[i]))
+ ++i;
+ while (i < entsize && isspace(buffer[i]))
+ ++i;
+ if (i >= entsize)
+ break;
+
+ line = buffer + i;
+
+ while (i < entsize && buffer[i] != '\n')
+ ++i;
+
+ buffer[i] = '\0';
+
+ if (!strncmp(line, "uid=", 4)) {
+ pax_read_decimal(line + 4, &field);
+ out->sb.st_uid = field;
+ *set_by_pax |= PAX_UID;
+ } else if (!strncmp(line, "gid=", 4)) {
+ pax_read_decimal(line + 4, &field);
+ out->sb.st_gid = field;
+ *set_by_pax |= PAX_GID;
+ } else if (!strncmp(line, "path=", 5)) {
+ free(out->name);
+ out->name = strdup(line + 5);
+ if (out->name == NULL)
+ goto fail_errno;
+ *set_by_pax |= PAX_NAME;
+ } else if (!strncmp(line, "size=", 5)) {
+ pax_read_decimal(line + 5, &field);
+ out->sb.st_size = field;
+ *set_by_pax |= PAX_SIZE;
+ } else if (!strncmp(line, "linkpath=", 9)) {
+ free(out->link_target);
+ out->link_target = strdup(line + 9);
+ if (out->link_target == NULL)
+ goto fail_errno;
+ *set_by_pax |= PAX_SLINK_TARGET;
+ } else if (!strncmp(line, "atime=", 6)) {
+ pax_read_decimal(line + 6, &field);
+ out->sb.st_atime = field;
+ *set_by_pax |= PAX_ATIME;
+ } else if (!strncmp(line, "mtime=", 6)) {
+ pax_read_decimal(line + 6, &field);
+ out->sb.st_mtime = field;
+ *set_by_pax |= PAX_MTIME;
+ } else if (!strncmp(line, "ctime=", 6)) {
+ pax_read_decimal(line + 6, &field);
+ out->sb.st_ctime = field;
+ *set_by_pax |= PAX_CTIME;
+ }
+ }
+
+ free(buffer);
+ return 0;
+fail_errno:
+ perror("reading pax header");
+ goto fail;
+fail_eof:
+ fputs("reading pax header: unexpected end of file\n", stderr);
+ goto fail;
+fail:
+ free(buffer);
+ return -1;
+}
+
+static int decode_header(const tar_header_t *hdr, unsigned int set_by_pax,
+ tar_header_decoded_t *out)
+{
+ uint64_t field;
+ size_t count;
+
+ if (!(set_by_pax & PAX_NAME)) {
+ if (hdr->prefix[0] == '\0') {
+ count = strlen(hdr->name) + 1;
+ count += strlen(hdr->prefix) + 1;
+
+ out->name = malloc(count);
+
+ if (out->name != NULL) {
+ sprintf(out->name, "%s/%s",
+ hdr->prefix, hdr->name);
+ }
+ } else {
+ out->name = strdup(hdr->name);
+ }
+
+ if (out->name == NULL) {
+ perror("decoding filename");
+ return -1;
+ }
+ }
+
+ if (!(set_by_pax & PAX_SIZE)) {
+ if (read_number(hdr->size, sizeof(hdr->size), &field))
+ return -1;
+ out->sb.st_size = field;
+ }
+
+ if (!(set_by_pax & PAX_UID)) {
+ if (read_number(hdr->uid, sizeof(hdr->uid), &field))
+ return -1;
+ out->sb.st_uid = field;
+ }
+
+ if (!(set_by_pax & PAX_GID)) {
+ if (read_number(hdr->gid, sizeof(hdr->gid), &field))
+ return -1;
+ out->sb.st_gid = field;
+ }
+
+ if (!(set_by_pax & PAX_DEV_MAJ)) {
+ if (read_number(hdr->devmajor, sizeof(hdr->devmajor), &field))
+ return -1;
+
+ out->sb.st_rdev = makedev(field, minor(out->sb.st_rdev));
+ }
+
+ if (!(set_by_pax & PAX_DEV_MIN)) {
+ if (read_number(hdr->devminor, sizeof(hdr->devminor), &field))
+ return -1;
+
+ out->sb.st_rdev = makedev(major(out->sb.st_rdev), field);
+ }
+
+ if (!(set_by_pax & PAX_MTIME)) {
+ if (read_number(hdr->mtime, sizeof(hdr->mtime), &field))
+ return -1;
+ out->sb.st_mtime = field;
+ }
+
+ if (!(set_by_pax & PAX_ATIME))
+ out->sb.st_atime = out->sb.st_mtime;
+
+ if (!(set_by_pax & PAX_CTIME))
+ out->sb.st_ctime = out->sb.st_mtime;
+
+ if (read_octal(hdr->mode, sizeof(hdr->mode), &field))
+ return -1;
+
+ out->sb.st_mode = field & 07777;
+
+ if (hdr->typeflag == TAR_TYPE_LINK ||
+ hdr->typeflag == TAR_TYPE_SLINK) {
+ if (!(set_by_pax & PAX_SLINK_TARGET)) {
+ out->link_target = strdup(hdr->linkname);
+ if (out->link_target == NULL) {
+ perror("decoding symlink target");
+ return -1;
+ }
+ }
+ }
+
+ out->unknown_record = false;
+
+ switch (hdr->typeflag) {
+ case '\0':
+ case TAR_TYPE_FILE:
+ out->sb.st_mode |= S_IFREG;
+ break;
+ case TAR_TYPE_LINK:
+ /* XXX: hard links are not support yet */
+ out->sb.st_mode = S_IFLNK | 0777;
+ break;
+ case TAR_TYPE_SLINK:
+ out->sb.st_mode = S_IFLNK | 0777;
+ break;
+ case TAR_TYPE_CHARDEV:
+ out->sb.st_mode |= S_IFCHR;
+ break;
+ case TAR_TYPE_BLOCKDEV:
+ out->sb.st_mode |= S_IFBLK;
+ break;
+ case TAR_TYPE_DIR:
+ out->sb.st_mode |= S_IFDIR;
+ break;
+ case TAR_TYPE_FIFO:
+ out->sb.st_mode |= S_IFIFO;
+ break;
+ default:
+ out->unknown_record = true;
+ break;
+ }
+
+ return 0;
+}
+
+int read_header(int fd, tar_header_decoded_t *out)
+{
+ unsigned int set_by_pax = 0;
+ bool prev_was_zero = false;
+ uint64_t pax_size;
+ tar_header_t hdr;
+ int ret;
+
+ memset(out, 0, sizeof(*out));
+
+ for (;;) {
+ ret = read_retry(fd, &hdr, sizeof(hdr));
+ if (ret == 0)
+ goto out_eof;
+ if (ret < 0)
+ goto fail_errno;
+ if (ret < (int)sizeof(hdr))
+ goto fail_eof;
+
+ if (is_zero_block(&hdr)) {
+ if (prev_was_zero)
+ goto out_eof;
+ prev_was_zero = true;
+ continue;
+ }
+
+ prev_was_zero = false;
+
+ if (!is_magic_valid(&hdr))
+ goto fail_magic;
+
+ if (!is_checksum_valid(&hdr))
+ goto fail_chksum;
+
+ if (hdr.typeflag == TAR_TYPE_PAX) {
+ clear_header(out);
+ if (read_number(hdr.size, sizeof(hdr.size), &pax_size))
+ return -1;
+ set_by_pax = 0;
+ if (read_pax_header(fd, pax_size, &set_by_pax, out))
+ return -1;
+ continue;
+ }
+ break;
+ }
+
+ if (decode_header(&hdr, set_by_pax, out))
+ goto fail;
+
+ return 0;
+out_eof:
+ clear_header(out);
+ return 1;
+fail_errno:
+ perror("reading tar header");
+ goto fail;
+fail_eof:
+ fputs("reading tar header: unexpected end of file\n", stderr);
+ goto fail;
+fail_magic:
+ fputs("input is not a ustar tar archive!\n", stderr);
+ goto fail;
+fail_chksum:
+ fputs("invalid tar header checksum!\n", stderr);
+ goto fail;
+fail:
+ clear_header(out);
+ return -1;
+}
+
+void clear_header(tar_header_decoded_t *hdr)
+{
+ free(hdr->name);
+ free(hdr->link_target);
+ memset(hdr, 0, sizeof(*hdr));
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-29 09:06:37 +0000