libmount: add support for encrypted loopdevs

Signed-off-by: Karel Zak <kzak@redhat.com>

libmount/src/context.c

@@ -896,6 +896,26 @@ struct libmnt_cache *mnt_context_get_cache(struct libmnt_context *cxt)
 	return cxt->cache;
 }
 
+/**
+ * mnt_context_set_passwd_cb:
+ * @cxt: mount context
+ *
+ * Sets callbacks for encryption password.
+ *
+ * Returns: 0 on success, negative number in case of error.
+ */
+int mnt_context_set_passwd_cb(struct libmnt_context *cxt,
+			      char *(*get)(struct libmnt_context *),
+			      void (*release)(struct libmnt_context *, char *))
+{
+	if (!cxt)
+		return -EINVAL;
+
+	cxt->pwd_get_cb = get;
+	cxt->pwd_release_cb = release;
+	return 0;
+}
+
 /**
  * mnt_context_get_lock:
  * @cxt: mount context

libmount/src/context_loopdev.c

@@ -34,7 +34,8 @@ int mnt_context_is_loopdev(struct libmnt_context *cxt)
 
 	if (cxt->user_mountflags & (MNT_MS_LOOP |
 				    MNT_MS_OFFSET |
-				    MNT_MS_SIZELIMIT))
+				    MNT_MS_SIZELIMIT |
+				    MNT_MS_ENCRYPTION))
 		return 1;
 
 	if (cxt->mountflags & (MS_BIND | MS_MOVE | MS_PROPAGATION))
@@ -64,7 +65,7 @@ int mnt_context_is_loopdev(struct libmnt_context *cxt)
 int mnt_context_setup_loopdev(struct libmnt_context *cxt)
 {
 	const char *backing_file, *optstr, *loopdev = NULL;
-	char *val = NULL;
+	char *val = NULL, *enc = NULL, *pwd = NULL;
 	size_t len;
 	struct loopdev_cxt lc;
 	int rc = 0, lo_flags = 0;
@@ -125,6 +126,20 @@ int mnt_context_setup_loopdev(struct libmnt_context *cxt)
 			DBG(CXT, mnt_debug_h(cxt, "failed to parse sizelimit="));
 	}
 
+	/*
+	 * encryption=
+	 */
+	if (rc == 0 && (cxt->user_mountflags & MNT_MS_ENCRYPTION) &&
+	    mnt_optstr_get_option(optstr, "encryption", &val, &len) == 0) {
+		enc = strndup(val, len);
+		if (val && !enc)
+			rc = -ENOMEM;
+		if (enc && cxt->pwd_get_cb) {
+			DBG(CXT, mnt_debug_h(cxt, "asking for pass"));
+			pwd = cxt->pwd_get_cb(cxt);
+		}
+	}
+
 	if (rc)
 		goto done;
 
@@ -156,6 +171,8 @@ int mnt_context_setup_loopdev(struct libmnt_context *cxt)
 			rc = loopcxt_set_offset(&lc, offset);
 		if (!rc && sizelimit)
 			rc = loopcxt_set_sizelimit(&lc, sizelimit);
+		if (!rc && enc && pwd)
+			loopcxt_set_encryption(&lc, enc, pwd);
 		if (!rc)
 			loopcxt_set_flags(&lc, lo_flags);
 		if (rc) {
@@ -208,6 +225,11 @@ int mnt_context_setup_loopdev(struct libmnt_context *cxt)
 		loopcxt_set_fd(&lc, -1, 0);
 	}
 done:
+	free(enc);
+	if (pwd && cxt->pwd_release_cb) {
+		DBG(CXT, mnt_debug_h(cxt, "release pass"));
+		cxt->pwd_release_cb(cxt, pwd);
+	}
 	loopcxt_deinit(&lc);
 	return rc;
 }

libmount/src/libmount.h.in

@@ -431,6 +431,10 @@ extern int mnt_context_set_fstype_pattern(struct libmnt_context *cxt,
 extern int mnt_context_set_options_pattern(struct libmnt_context *cxt,
 				      const char *pattern);
 
+extern int mnt_context_set_passwd_cb(struct libmnt_context *cxt,
+			      char *(*get)(struct libmnt_context *),
+			      void (*release)(struct libmnt_context *, char *));
+
 extern int mnt_context_set_tables_errcb(struct libmnt_context *cxt,
         int (*cb)(struct libmnt_table *tb, const char *filename, int line));
 extern int mnt_context_set_fstab(struct libmnt_context *cxt,
@@ -498,6 +502,7 @@ extern int mnt_context_set_syscall_status(struct libmnt_context *cxt, int status
 #define MNT_MS_XCOMMENT (1 << 13)
 #define MNT_MS_OFFSET   (1 << 14)
 #define MNT_MS_SIZELIMIT (1 << 15)
+#define MNT_MS_ENCRYPTION (1 << 16)
 
 /*
  * mount(2) MS_* masks (MNT_MAP_LINUX map)

libmount/src/libmount.sym

@@ -213,6 +213,7 @@ global:
 	mnt_context_is_fork;
 	mnt_context_is_parent;
 	mnt_context_next_umount;
+	mnt_context_set_passwd_cb;
 	mnt_context_wait_for_children;
 	mnt_fs_is_netfs;
 	mnt_fs_is_pseudofs;

libmount/src/mountP.h

@@ -276,6 +276,9 @@ struct libmnt_context
 	int	(*table_errcb)(struct libmnt_table *tb,	/* callback for libmnt_table structs */
 			 const char *filename, int line);
 
+	char	*(*pwd_get_cb)(struct libmnt_context *);		/* get encryption password */
+	void	(*pwd_release_cb)(struct libmnt_context *, char *);	/* release password */
+
 	int	optsmode;	/* fstab optstr mode MNT_OPTSMODE_{AUTO,FORCE,IGNORE} */
 	int	loopdev_fd;	/* open loopdev */
 

libmount/src/optmap.c

@@ -147,6 +147,7 @@ static const struct libmnt_optmap userspace_opts_map[] =
    { "loop[=]", MNT_MS_LOOP },                             /* use the loop device */
    { "offset=", MNT_MS_OFFSET, MNT_NOMTAB },		   /* loop device offset */
    { "sizelimit=", MNT_MS_SIZELIMIT, MNT_NOMTAB },	   /* loop device size limit */
+   { "encryption=", MNT_MS_ENCRYPTION, MNT_NOMTAB },	   /* loop device encryption */
 
    { "nofail",  MNT_MS_NOFAIL, MNT_NOMTAB },               /* Do not fail if ENOENT on dev */