Extend blkid utilities for signatures wiping.

For older distributions there's fallback mode for missing
blkid_do_wipe function. We erase signatures based on offsets
and lengths detected by blkid.

configure.ac

@@ -438,6 +438,16 @@ if test x$enable_blkid = xyes ; then
 	PKG_CHECK_MODULES([BLKID], [blkid],[AC_DEFINE([HAVE_BLKID], 1, [Define to 1 to use blkid for detection of disk signatures.])],[LIBBLKID_LIBS="-lblkid"])
 
 	AC_CHECK_HEADERS(blkid/blkid.h,,[AC_MSG_ERROR([You need blkid development library installed.])])
+	AC_CHECK_DECL([blkid_do_wipe],
+		      [ AC_DEFINE([HAVE_BLKID_WIPE], 1, [Define to 1 to use blkid_do_wipe.])
+			enable_blkid_wipe=yes
+		      ],,
+		      [#include <blkid/blkid.h>])
+	AC_CHECK_DECL([blkid_probe_step_back],
+		      [ AC_DEFINE([HAVE_BLKID_STEP_BACK], 1, [Define to 1 to use blkid_probe_step_back.])
+			enable_blkid_step_back=yes
+		      ],,
+		      [#include <blkid/blkid.h>])
 	AC_CHECK_DECLS([ blkid_reset_probe,
 			 blkid_probe_set_device,
 			 blkid_probe_filter_superblocks_type,
@@ -449,6 +459,8 @@ if test x$enable_blkid = xyes ; then
 		       [#include <blkid/blkid.h>])
 fi
 AM_CONDITIONAL(HAVE_BLKID, test x$enable_blkid = xyes)
+AM_CONDITIONAL(HAVE_BLKID_WIPE, test x$enable_blkid_wipe = xyes)
+AM_CONDITIONAL(HAVE_BLKID_STEP_BACK, test x$enable_blkid_step_back = xyes)
 
 dnl Magic for cryptsetup.static build.
 if test x$enable_static_cryptsetup = xyes; then

lib/utils_blkid.c

@@ -25,14 +25,52 @@
 #include <unistd.h>
 
 #include "utils_blkid.h"
+#include "utils_io.h"
 
 #ifdef HAVE_BLKID
 #include <blkid/blkid.h>
+/* make bad checksums flag optional */
+#ifndef BLKID_SUBLKS_BADCSUM
+#define BLKID_SUBLKS_BADCSUM 0
+#endif
 struct blkid_handle {
 	int fd;
 	blkid_probe pr;
 };
+#ifndef HAVE_BLKID_WIPE
+static size_t crypt_getpagesize(void)
+{
+	long r = sysconf(_SC_PAGESIZE);
+	return r <= 0 ? 4096 : (size_t)r;
+}
 #endif
+#endif
+
+void blk_set_chains_for_wipes(struct blkid_handle *h)
+{
+#ifdef HAVE_BLKID
+	blkid_probe_enable_partitions(h->pr, 1);
+	blkid_probe_set_partitions_flags(h->pr, 0
+#ifdef HAVE_BLKID_WIPE
+	| BLKID_PARTS_MAGIC
+#endif
+	);
+
+	blkid_probe_enable_superblocks(h->pr, 1);
+	blkid_probe_set_superblocks_flags(h->pr, BLKID_SUBLKS_LABEL   |
+						 BLKID_SUBLKS_UUID    |
+						 BLKID_SUBLKS_TYPE    |
+						 BLKID_SUBLKS_USAGE   |
+						 BLKID_SUBLKS_VERSION |
+						 BLKID_SUBLKS_MAGIC   |
+						 BLKID_SUBLKS_BADCSUM);
+#endif
+}
+
+void blk_set_chains_for_full_print(struct blkid_handle *h)
+{
+	blk_set_chains_for_wipes(h);
+}
 
 void blk_set_chains_for_fast_detection(struct blkid_handle *h)
 {
@@ -68,6 +106,35 @@ int blk_init_by_path(struct blkid_handle **h, const char *path)
 	return r;
 }
 
+int blk_init_by_fd(struct blkid_handle **h, int fd)
+{
+	int r = -ENOTSUP;
+#ifdef HAVE_BLKID
+	struct blkid_handle *tmp = malloc(sizeof(*h));
+	if (!tmp)
+		return -ENOMEM;
+
+	tmp->pr = blkid_new_probe();
+	if (!tmp->pr) {
+		free(tmp);
+		return -EINVAL;
+	}
+
+	if (blkid_probe_set_device(tmp->pr, fd, 0, 0)) {
+		blkid_free_probe(tmp->pr);
+		free(tmp);
+		return -EINVAL;
+	}
+
+	tmp->fd = fd;
+
+	*h = tmp;
+
+	r = 0;
+#endif
+	return r;
+}
+
 int blk_superblocks_filter_luks(struct blkid_handle *h)
 {
 	int r = -ENOTSUP;
@@ -81,6 +148,20 @@ int blk_superblocks_filter_luks(struct blkid_handle *h)
 	return r;
 }
 
+blk_probe_status blk_probe(struct blkid_handle *h)
+{
+	blk_probe_status pr = PRB_FAIL;
+#ifdef HAVE_BLKID
+	int r = blkid_do_probe(h->pr);
+
+	if (r == 0)
+		pr = PRB_OK;
+	else if (r == 1)
+		pr = PRB_EMPTY;
+#endif
+	return pr;
+}
+
 blk_probe_status blk_safeprobe(struct blkid_handle *h)
 {
 	int r = -1;
@@ -148,6 +229,75 @@ void blk_free(struct blkid_handle *h)
 #endif
 }
 
+int blk_step_back(struct blkid_handle *h)
+{
+#ifdef HAVE_BLKID
+#ifdef HAVE_BLKID_STEP_BACK
+	return blkid_probe_step_back(h->pr);
+#else
+	blkid_reset_probe(h->pr);
+	blkid_probe_set_device(h->pr, h->fd, 0, 0);
+	return 0;
+#endif
+#else /* HAVE_BLKID */
+	return -ENOTSUP;
+#endif
+}
+
+int blk_do_wipe(struct blkid_handle *h)
+{
+#ifdef HAVE_BLKID
+#ifdef HAVE_BLKID_WIPE
+	return blkid_do_wipe(h->pr, 0);
+#else
+	const char *offset;
+	off_t offset_val;
+	void *buf;
+	ssize_t ret;
+	size_t alignment, len, bsize = blkid_probe_get_sectorsize(h->pr);
+
+	if (h->fd < 0 || !bsize)
+		return -EINVAL;
+
+	if (blk_is_partition(h)) {
+		if (blkid_probe_lookup_value(h->pr, "PTMAGIC_OFFSET", &offset, NULL))
+			return -EINVAL;
+		if (blkid_probe_lookup_value(h->pr, "PTMAGIC", NULL, &len))
+			return -EINVAL;
+	} else if (blk_is_superblock(h)) {
+		if (blkid_probe_lookup_value(h->pr, "SBMAGIC_OFFSET", &offset, NULL))
+			return -EINVAL;
+		if (blkid_probe_lookup_value(h->pr, "SBMAGIC", NULL, &len))
+			return -EINVAL;
+	} else
+		return 0;
+
+	alignment = crypt_getpagesize();
+
+	if (posix_memalign(&buf, alignment, len))
+		return -EINVAL;
+	memset(buf, 0, len);
+
+	offset_val = strtoll(offset, NULL, 10);
+
+	/* TODO: missing crypt_wipe_fd() */
+	ret = write_lseek_blockwise(h->fd, bsize, alignment, buf, len, offset_val);
+	free(buf);
+	if (ret < 0)
+		return -EIO;
+
+	if ((size_t)ret == len) {
+		blk_step_back(h);
+		return 0;
+	}
+
+	return -EIO;
+#endif
+#else /* HAVE_BLKID */
+	return -ENOTSUP;
+#endif
+}
+
 int blk_supported(void)
 {
 	int r = 0;

lib/utils_blkid.h

@@ -29,12 +29,26 @@ int blk_init_by_path(struct blkid_handle **h, const char *path);
 
 void blk_free(struct blkid_handle *h);
 
+/*
+ * WARNING: This will reset file description offset as if
+ * 	    lseek(devfd, 0, SEEK_SET) was called!
+ */
+int blk_init_by_fd(struct blkid_handle **h, int fd);
+
+void blk_free(struct blkid_handle *h);
+
+void blk_set_chains_for_wipes(struct blkid_handle *h);
+
+void blk_set_chains_for_full_print(struct blkid_handle *h);
+
 void blk_set_chains_for_fast_detection(struct blkid_handle *h);
 
 int blk_superblocks_filter_luks(struct blkid_handle *h);
 
 blk_probe_status blk_safeprobe(struct blkid_handle *h);
 
+blk_probe_status blk_probe(struct blkid_handle *h);
+
 int blk_is_partition(struct blkid_handle *h);
 
 int blk_is_superblock(struct blkid_handle *h);
@@ -43,6 +57,8 @@ const char *blk_get_partition_type(struct blkid_handle *h);
 
 const char *blk_get_superblock_type(struct blkid_handle *h);
 
+int blk_do_wipe(struct blkid_handle *h);
+
 int blk_supported(void);
 
 #endif