Add utility to turn a squashfs image into a POSIX tar archvie

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 260 insertions, 0 deletions

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 <sys/sysmacros.h>
+#include <string.h>
+#include <stdio.h>
+
+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;
+}