tar: optional support for restoring selinux context
function old new delta
get_header_tar 1690 1976 +286
data_extract_all 821 881 +60
.rodata 151446 151503 +57
get_header_cpio 1044 1077 +33
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/0 up/down: 436/0) Total: 436 bytes
Signed-off-by: J. Tang <tang@jtang.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/archival/Config.in b/archival/Config.in
index c99896b..deacc28 100644
--- a/archival/Config.in
+++ b/archival/Config.in
@@ -289,6 +289,14 @@
With this option busybox supports GNU tar -m
(do not preserve time) option.
+config FEATURE_TAR_SELINUX
+ bool "Support for extracting SELinux labels"
+ default n
+ depends on TAR && SELINUX
+ help
+ With this option busybox supports restoring SELinux labels
+ when extracting files from tar archives.
+
config UNCOMPRESS
bool "uncompress"
default n
diff --git a/archival/libunarchive/data_extract_all.c b/archival/libunarchive/data_extract_all.c
index 58b0533..cc48942 100644
--- a/archival/libunarchive/data_extract_all.c
+++ b/archival/libunarchive/data_extract_all.c
@@ -12,6 +12,17 @@
int dst_fd;
int res;
+#if ENABLE_FEATURE_TAR_SELINUX
+ char *sctx = archive_handle->tar__next_file_sctx;
+ if (!sctx)
+ sctx = archive_handle->tar__global_sctx;
+ if (sctx) { /* setfscreatecon is 4 syscalls, avoid if possible */
+ setfscreatecon(sctx);
+ free(archive_handle->tar__next_file_sctx);
+ archive_handle->tar__next_file_sctx = NULL;
+ }
+#endif
+
if (archive_handle->ah_flags & ARCHIVE_CREATE_LEADING_DIRS) {
char *slash = strrchr(file_header->name, '/');
if (slash) {
@@ -45,7 +56,7 @@
"same age file exists", file_header->name);
}
data_skip(archive_handle);
- return;
+ goto ret;
}
else if ((unlink(file_header->name) == -1) && (errno != EISDIR)) {
bb_perror_msg_and_die("can't remove old file %s",
@@ -158,4 +169,12 @@
utimes(file_header->name, t);
}
}
+
+ ret: ;
+#if ENABLE_FEATURE_TAR_SELINUX
+ if (sctx) {
+ /* reset the context after creating an entry */
+ setfscreatecon(NULL);
+ }
+#endif
}
diff --git a/archival/libunarchive/get_header_tar.c b/archival/libunarchive/get_header_tar.c
index d5b86ff..cf0b9ab 100644
--- a/archival/libunarchive/get_header_tar.c
+++ b/archival/libunarchive/get_header_tar.c
@@ -103,6 +103,63 @@
}
#define GET_OCTAL(a) getOctal((a), sizeof(a))
+#if ENABLE_FEATURE_TAR_SELINUX
+/* Scan a PAX header for SELinux contexts, via "RHT.security.selinux" keyword.
+ * This is what Red Hat's patched version of tar uses.
+ */
+# define SELINUX_CONTEXT_KEYWORD "RHT.security.selinux"
+static char *get_selinux_sctx_from_pax_hdr(archive_handle_t *archive_handle, unsigned sz)
+{
+ char *buf, *p;
+ char *result;
+
+ p = buf = xmalloc(sz + 1);
+ /* prevent bb_strtou from running off the buffer */
+ buf[sz] = '\0';
+ xread(archive_handle->src_fd, buf, sz);
+ archive_handle->offset += sz;
+
+ result = NULL;
+ while (sz != 0) {
+ char *end, *value;
+ unsigned len;
+
+ /* Every record has this format: "LEN NAME=VALUE\n" */
+ len = bb_strtou(p, &end, 10);
+ /* expect errno to be EINVAL, because the character
+ * following the digits should be a space
+ */
+ p += len;
+ sz -= len;
+ if ((int)sz < 0
+ || len == 0
+ || errno != EINVAL
+ || *end != ' '
+ ) {
+ bb_error_msg("malformed extended header, skipped");
+ // More verbose version:
+ //bb_error_msg("malformed extended header at %"OFF_FMT"d, skipped",
+ // archive_handle->offset - (sz + len));
+ break;
+ }
+ /* overwrite the terminating newline with NUL
+ * (we do not bother to check that it *was* a newline)
+ */
+ p[-1] = '\0';
+ /* Is it selinux security context? */
+ value = end + 1;
+ if (strncmp(value, SELINUX_CONTEXT_KEYWORD"=", sizeof(SELINUX_CONTEXT_KEYWORD"=") - 1) == 0) {
+ value += sizeof(SELINUX_CONTEXT_KEYWORD"=") - 1;
+ result = xstrdup(value);
+ break;
+ }
+ }
+
+ free(buf);
+ return result;
+}
+#endif
+
void BUG_tar_header_size(void);
char FAST_FUNC get_header_tar(archive_handle_t *archive_handle)
{
@@ -150,7 +207,7 @@
if (sizeof(tar) != 512)
BUG_tar_header_size();
-#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
+#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS || ENABLE_FEATURE_TAR_SELINUX
again:
#endif
/* Align header */
@@ -392,8 +449,13 @@
case 'S': /* Sparse file */
case 'V': /* Volume header */
#endif
+#if !ENABLE_FEATURE_TAR_SELINUX
case 'g': /* pax global header */
- case 'x': { /* pax extended header */
+ case 'x': /* pax extended header */
+#else
+ skip_ext_hdr:
+#endif
+ {
off_t sz;
bb_error_msg("warning: skipping header '%c'", tar.typeflag);
sz = (file_header->size + 511) & ~(off_t)511;
@@ -404,6 +466,18 @@
/* return get_header_tar(archive_handle); */
goto again_after_align;
}
+#if ENABLE_FEATURE_TAR_SELINUX
+ case 'g': /* pax global header */
+ case 'x': { /* pax extended header */
+ char **pp;
+ if ((uoff_t)file_header->size > 0xfffff) /* paranoia */
+ goto skip_ext_hdr;
+ pp = (tar.typeflag == 'g') ? &archive_handle->tar__global_sctx : &archive_handle->tar__next_file_sctx;
+ free(*pp);
+ *pp = get_selinux_sctx_from_pax_hdr(archive_handle, file_header->size);
+ goto again;
+ }
+#endif
default:
bb_error_msg_and_die("unknown typeflag: 0x%x", tar.typeflag);
}