Support custom URI schemes for the keylocation property

Every platform has their own preferred methods for implementing URI 
schemes beyond the currently supported file scheme (e.g. 'https' on 
FreeBSD would likely use libfetch, while Linux distros and illumos
would probably use libcurl, etc). It would be helpful if libzfs can 
be extended to support additional schemes in a simple manner.

A table of (scheme, handler_function) pairs is added to libzfs_crypto.c, 
and the existing functions in libzfs_crypto.c so that when the key 
format is ZFS_KEYFORMAT_URI, the scheme from the URI string is 
extracted, and a matching handler it located in the aforementioned 
table (returning an error if no matching handler is found). The handler 
function is then invoked to retrieve the key material (in the format 
specified by the keyformat property) and the key is loaded or the 
handler can return an error to abort the key loading process.

Reviewed by: Sean Eric Fagan <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Jason King <[email protected]>
Closes #10218 

1 files changed, 13 insertions, 1 deletions

diff --git a/lib/libzfs/libzfs_util.c b/lib/libzfs/libzfs_util.c
index 71ac72ee1..cb96d8da8 100644
--- a/lib/libzfs/libzfs_util.c
+++ b/lib/libzfs/libzfs_util.c
@@ -21,7 +21,7 @@
 
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2018, Joyent, Inc. All rights reserved.
+ * Copyright 2020 Joyent, Inc. All rights reserved.
  * Copyright (c) 2011, 2018 by Delphix. All rights reserved.
  * Copyright 2016 Igor Kozhukhov <[email protected]>
  * Copyright (c) 2017 Datto Inc.
@@ -55,6 +55,12 @@
 #include <zfs_fletcher.h>
 #include <libzutil.h>
 
+/*
+ * We only care about the scheme in order to match the scheme
+ * with the handler. Each handler should validate the full URI
+ * as necessary.
+ */
+#define	URI_REGEX	"^\\([A-Za-z][A-Za-z0-9+.\\-]*\\):"
 
 int
 libzfs_errno(libzfs_handle_t *hdl)
@@ -881,6 +887,11 @@ libzfs_init(void)
 		return (NULL);
 	}
 
+	if (regcomp(&hdl->libzfs_urire, URI_REGEX, 0) != 0) {
+		free(hdl);
+		return (NULL);
+	}
+
 	if ((hdl->libzfs_fd = open(ZFS_DEV, O_RDWR|O_EXCL)) < 0) {
 		free(hdl);
 		return (NULL);
@@ -953,6 +964,7 @@ libzfs_fini(libzfs_handle_t *hdl)
 	namespace_clear(hdl);
 	libzfs_mnttab_fini(hdl);
 	libzfs_core_fini();
+	regfree(&hdl->libzfs_urire);
 	fletcher_4_fini();
 	free(hdl);
 }