By default backup geli metadata to a file. It is quite critical 512 bytes,

once it is lost, all data is gone.

Option '-B none' can by used to prevent backup. Option '-B path' can be
used to backup metadata to a different file than the default, which is
/var/backups/<prov>.eli.

The 'geli init' command also prints backup file location and gives short
procedure how to restore metadata.

The 'geli setkey' command now warns that even after passphrase change or keys
update there could be version of the master key encrypted with old
keys/passphrase in the backup file.

Add regression tests to verify that new functionality works as expected.

Update other regression tests so they don't create backup files.

Reviewed by:	keramida, rink
Dedicated to:	a friend who lost 400GB of his live by accidentally overwritting geli metadata
MFC after:	2 weeks

2 files changed, 110 insertions, 17 deletions

diff --git a/sbin/geom/class/eli/geli.8 b/sbin/geom/class/eli/geli.8
index 280962a..a39a601 100644
--- a/sbin/geom/class/eli/geli.8
+++ b/sbin/geom/class/eli/geli.8
@@ -1,4 +1,4 @@
-.\" Copyright (c) 2005-2006 Pawel Jakub Dawidek <pjd@FreeBSD.org>
+.\" Copyright (c) 2005-2008 Pawel Jakub Dawidek <pjd@FreeBSD.org>
 .\" All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd September 16, 2006
+.Dd August 29, 2008
 .Dt GELI 8
 .Os
 .Sh NAME
@@ -53,6 +53,7 @@ utility:
 .Cm init
 .Op Fl bPv
 .Op Fl a Ar aalgo
+.Op Fl B Ar backupfile
 .Op Fl e Ar ealgo
 .Op Fl i Ar iterations
 .Op Fl K Ar newkeyfile
@@ -206,6 +207,14 @@ indicates an action to be performed:
 Initialize provider which needs to be encrypted.
 Here you can set up the cryptographic algorithm to use, key length, etc.
 The last provider's sector is used to store metadata.
+The
+.Cm init
+subcommand also automatically backups metadata in
+.Pa /var/backups/<prov>.eli
+file.
+The metadata can be recovered with the
+.Cm restore
+subcommand described below.
 .Pp
 Additional options include:
 .Bl -tag -width ".Fl a Ar aalgo"
@@ -233,6 +242,13 @@ One will still need bootable unencrypted storage with a
 .Pa /boot/
 directory, which can be a CD-ROM disc or USB pen-drive, that can be removed
 after boot.
+.It Fl B Ar backupfile
+File name to use for metadata backup instead of the default
+.Pa /var/backups/<prov>.eli .
+To inhibit backups, you can use
+.Pa none
+as the
+.Ar backupfile .
 .It Fl e Ar ealgo
 Encryption algorithm to use.
 Currently supported algorithms are:
@@ -625,6 +641,30 @@ Enter passphrase:
 # newfs /dev/da0.eli
 # mount /dev/da0.eli /mnt/secret
 .Ed
+.Pp
+.Cm geli
+backups metadata by default to the
+.Pa /var/backups/<prov>.eli
+file.
+If metadata is lost in any way (eg. by accidental overwrite), it can be restored.
+Consider the following situation:
+.Bd -literal -offset indent
+# geli init /dev/da0
+Enter new passphrase:
+Reenter new passphrase:
+
+Metadata backup can be found in /var/backups/da0.eli and
+can be restored with the following command:
+
+	# geli restore /var/backups/da0.eli /dev/da0
+
+# geli clear /dev/da0
+# geli attach /dev/da0
+geli: Cannot read metadata from /dev/da0: Invalid argument.
+# geli restore /var/backups/da0.eli /dev/da0
+# geli attach /dev/da0
+Enter passphrase:
+.Ed
 .Sh DATA AUTHENTICATION
 .Nm
 can verify data integrity when an authentication algorithm is specified.
diff --git a/sbin/geom/class/eli/geom_eli.c b/sbin/geom/class/eli/geom_eli.c
index 2e16103..d772a9a 100644
--- a/sbin/geom/class/eli/geom_eli.c
+++ b/sbin/geom/class/eli/geom_eli.c
@@ -1,5 +1,5 @@
 /*-
- * Copyright (c) 2004-2006 Pawel Jakub Dawidek <pjd@FreeBSD.org>
+ * Copyright (c) 2004-2008 Pawel Jakub Dawidek <pjd@FreeBSD.org>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -54,6 +54,8 @@ __FBSDID("$FreeBSD$");
 uint32_t lib_version = G_LIB_VERSION;
 uint32_t version = G_ELI_VERSION;
 
+#define	GELI_BACKUP_DIR	"/var/backups/"
+
 static char aalgo[] = "none";
 static char ealgo[] = "aes";
 static intmax_t keylen = 0;
@@ -61,6 +63,7 @@ static intmax_t keyno = -1;
 static intmax_t iterations = -1;
 static intmax_t sectorsize = 0;
 static char keyfile[] = "", newkeyfile[] = "";
+static char backupfile[] = "";
 
 static void eli_main(struct gctl_req *req, unsigned flags);
 static void eli_init(struct gctl_req *req);
@@ -74,10 +77,13 @@ static void eli_restore(struct gctl_req *req);
 static void eli_clear(struct gctl_req *req);
 static void eli_dump(struct gctl_req *req);
 
+static int eli_backup_create(struct gctl_req *req, const char *prov,
+    const char *file);
+
 /*
  * Available commands:
  *
- * init [-bhPv] [-a aalgo] [-e ealgo] [-i iterations] [-l keylen] [-K newkeyfile] prov
+ * init [-bhPv] [-a aalgo] [-B backupfile] [-e ealgo] [-i iterations] [-l keylen] [-K newkeyfile] prov
  * label - alias for 'init'
  * attach [-dprv] [-k keyfile] prov
  * detach [-fl] prov ...
@@ -97,6 +103,7 @@ struct g_command class_commands[] = {
 	    {
 		{ 'a', "aalgo", aalgo, G_TYPE_STRING },
 		{ 'b', "boot", NULL, G_TYPE_BOOL },
+		{ 'B', "backupfile", backupfile, G_TYPE_STRING },
 		{ 'e', "ealgo", ealgo, G_TYPE_STRING },
 		{ 'i', "iterations", &iterations, G_TYPE_NUMBER },
 		{ 'K', "newkeyfile", newkeyfile, G_TYPE_STRING },
@@ -105,12 +112,13 @@ struct g_command class_commands[] = {
 		{ 's', "sectorsize", &sectorsize, G_TYPE_NUMBER },
 		G_OPT_SENTINEL
 	    },
-	    NULL, "[-bPv] [-a aalgo] [-e ealgo] [-i iterations] [-l keylen] [-K newkeyfile] [-s sectorsize] prov"
+	    NULL, "[-bPv] [-a aalgo] [-B backupfile] [-e ealgo] [-i iterations] [-l keylen] [-K newkeyfile] [-s sectorsize] prov"
 	},
 	{ "label", G_FLAG_VERBOSE, eli_main,
 	    {
 		{ 'a', "aalgo", aalgo, G_TYPE_STRING },
 		{ 'b', "boot", NULL, G_TYPE_BOOL },
+		{ 'B', "backupfile", backupfile, G_TYPE_STRING },
 		{ 'e', "ealgo", ealgo, G_TYPE_STRING },
 		{ 'i', "iterations", &iterations, G_TYPE_NUMBER },
 		{ 'K', "newkeyfile", newkeyfile, G_TYPE_STRING },
@@ -514,6 +522,7 @@ eli_init(struct gctl_req *req)
 	struct g_eli_metadata md;
 	unsigned char sector[sizeof(struct g_eli_metadata)];
 	unsigned char key[G_ELI_USERKEYLEN];
+	char backfile[MAXPATHLEN];
 	const char *str, *prov;
 	unsigned secsize;
 	off_t mediasize;
@@ -648,6 +657,32 @@ eli_init(struct gctl_req *req)
 	}
 	if (verbose)
 		printf("Metadata value stored on %s.\n", prov);
+	/* Backup metadata to a file. */
+	str = gctl_get_ascii(req, "backupfile");
+	if (str[0] != '\0') {
+		/* Backupfile given be the user, just copy it. */
+		strlcpy(backfile, str, sizeof(backfile));
+	} else {
+		/* Generate file name automatically. */
+		const char *p = prov;
+		unsigned int i;
+
+		if (strncmp(p, _PATH_DEV, strlen(_PATH_DEV)) == 0)
+			p += strlen(_PATH_DEV);
+		snprintf(backfile, sizeof(backfile), "%s%s.eli",
+		    GELI_BACKUP_DIR, p);
+		/* Replace all / with _. */
+		for (i = strlen(GELI_BACKUP_DIR); backfile[i] != '\0'; i++) {
+			if (backfile[i] == '/')
+				backfile[i] = '_';
+		}
+	}
+	if (strcmp(backfile, "none") != 0 &&
+	    eli_backup_create(req, prov, backfile) == 0) {
+		printf("\nMetadata backup can be found in %s and\n", backfile);
+		printf("can be restored with the following command:\n");
+		printf("\n\t# geli restore %s %s\n\n", backfile, prov);
+	}
 }
 
 static void
@@ -887,6 +922,12 @@ eli_setkey(struct gctl_req *req)
 		eli_setkey_attached(req, &md);
 	else
 		eli_setkey_detached(req, prov, &md);
+
+	if (req->error == NULL || req->error[0] == '\0') {
+		printf("Note, that the master key encrypted with old keys "
+		    "and/or passphrase may still exists in a metadata backup "
+		    "file.\n");
+	}
 }
 
 static void
@@ -1022,24 +1063,16 @@ eli_kill(struct gctl_req *req)
 	gctl_issue(req);
 }
 
-static void
-eli_backup(struct gctl_req *req)
+static int
+eli_backup_create(struct gctl_req *req, const char *prov, const char *file)
 {
 	struct g_eli_metadata md;
-	const char *file, *prov;
 	unsigned secsize;
 	unsigned char *sector;
 	off_t mediasize;
-	int nargs, filefd, provfd;
-
-	nargs = gctl_get_int(req, "nargs");
-	if (nargs != 2) {
-		gctl_error(req, "Invalid number of arguments.");
-		return;
-	}
-	prov = gctl_get_ascii(req, "arg0");
-	file = gctl_get_ascii(req, "arg1");
+	int filefd, provfd, ret;
 
+	ret = -1;
 	provfd = filefd = -1;
 	sector = NULL;
 	secsize = 0;
@@ -1092,6 +1125,8 @@ eli_backup(struct gctl_req *req)
 		    strerror(errno));
 		goto out;
 	}
+	/* Success. */
+	ret = 0;
 out:
 	if (provfd > 0)
 		close(provfd);
@@ -1101,6 +1136,24 @@ out:
 		bzero(sector, secsize);
 		free(sector);
 	}
+	return (ret);
+}
+
+static void
+eli_backup(struct gctl_req *req)
+{
+	const char *file, *prov;
+	int nargs;
+
+	nargs = gctl_get_int(req, "nargs");
+	if (nargs != 2) {
+		gctl_error(req, "Invalid number of arguments.");
+		return;
+	}
+	prov = gctl_get_ascii(req, "arg0");
+	file = gctl_get_ascii(req, "arg1");
+
+	eli_backup_create(req, prov, file);
 }
 
 static void