On 02/24/22 11:43, Richard W.M. Jones wrote:
On Wed, Feb 23, 2022 at 05:19:15PM +0100, Laszlo Ersek wrote:
> Using the previously extracted function decrypt_mountables(), look for
> LUKS devices on logical volumes (LVs) too.
>
> In the LVM-on-LUKS scheme, the names of the plaintext (decrypted) block
> devices don't matter, as these devices host Physical Volumes, and LVM
> enumerates PVs automatically -- there are no references to these decrypted
> block devices in "/etc/fstab", for example. For naming such decrypted
> devices, continue calling make_mapname().
>
> In the LUKS-on-LVM scheme however, the decrypted devices are supposed to
> hold filesystems, and "/etc/fstab" may refer to them. Such decrypted
> devices are commonly called /dev/mapper/luks-<UUID>, where <UUID> is the
> UUID inside the LUKS header. Employ this naming when decrypting Logical
> Volumes. Reuse make_mapname() as a fallback in this case.
>
> Bugzilla:
https://bugzilla.redhat.com/show_bug.cgi?id=1658126
> Signed-off-by: Laszlo Ersek <lersek(a)redhat.com>
>
> Bugzilla:
https://bugzilla.redhat.com/show_bug.cgi?id=1658126
> Signed-off-by: Laszlo Ersek <lersek(a)redhat.com>
> ---
> options/decrypt.c | 24 ++++++++++++++++++------
> 1 file changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/options/decrypt.c b/options/decrypt.c
> index 9141cf5193ad..f7c1d876b3ed 100644
> --- a/options/decrypt.c
> +++ b/options/decrypt.c
> @@ -38,8 +38,11 @@
> #include "options.h"
>
> /**
> - * Make a LUKS map name from the partition name,
> - * eg. C<"/dev/vda2" =E<gt> "cryptvda2">
> + * Make a LUKS map name from the partition or logical volume name, eg.
> + * C<"/dev/vda2" =E<gt> "cryptvda2">, or
C<"/dev/vg-ssd/lv-root7" =E<gt>
> + * "cryptvgssdlvroot7">. Note that, in logical volume device names,
> + * c_isalnum() eliminates the "/" separator from between the VG and the
LV, so
> + * this mapping is not unique; but for our purposes, it will do.
> */
> static void
> make_mapname (const char *device, char *mapname, size_t len)
> @@ -67,7 +70,7 @@ make_mapname (const char *device, char *mapname, size_t len)
>
> static bool
> decrypt_mountables (guestfs_h *g, const char * const *mountables,
> - struct key_store *ks)
> + struct key_store *ks, bool name_decrypted_by_uuid)
> {
> bool decrypted_some = false;
> const char * const *mnt_scan = mountables;
> @@ -77,7 +80,7 @@ decrypt_mountables (guestfs_h *g, const char * const *mountables,
> CLEANUP_FREE char *type = NULL;
> CLEANUP_FREE char *uuid = NULL;
> CLEANUP_FREE_STRING_LIST char **keys = NULL;
> - char mapname[32];
> + char mapname[512];
> const char * const *key_scan;
> const char *key;
>
> @@ -102,7 +105,9 @@ decrypt_mountables (guestfs_h *g, const char * const
*mountables,
> assert (keys[0] != NULL);
>
> /* Generate a node name for the plaintext (decrypted) device node. */
> - make_mapname (mountable, mapname, sizeof mapname);
> + if (!name_decrypted_by_uuid || uuid == NULL ||
> + snprintf (mapname, sizeof mapname, "luks-%s", uuid) < 0)
> + make_mapname (mountable, mapname, sizeof mapname);
This should all really be using asprintf, and not stack-allocating
large arrays. Although it's kind of not related to this change, this
change does make the stack frame larger.
asprintf() was my first idea, but reworking make_mapname() would then
require measuring the input string lenght ;)
OK, I'll insert a patch between #1 and #2 for converting make_mapname()
to asprintf(), then I'll redo this patch with asprintf() too.
Thanks
Laszlo
Saying that, when removing gnulib (libguestfs commit 0f54df53d26), I
dropped the warning about large stack frames:
-dnl Warn about large stack frames, including estimates for alloca
-dnl and variable length arrays.
-gl_WARN_ADD([-Wstack-usage=10000])
I really need to add that back ...
> /* Try each key in turn. */
> key_scan = (const char * const *)keys;
> @@ -145,15 +150,22 @@ void
> inspect_do_decrypt (guestfs_h *g, struct key_store *ks)
> {
> CLEANUP_FREE_STRING_LIST char **partitions = guestfs_list_partitions (g);
> + CLEANUP_FREE_STRING_LIST char **lvs = NULL;
> bool need_rescan;
>
> if (partitions == NULL)
> exit (EXIT_FAILURE);
>
> - need_rescan = decrypt_mountables (g, (const char * const *)partitions, ks);
> + need_rescan = decrypt_mountables (g, (const char * const *)partitions, ks,
> + false);
>
> if (need_rescan) {
> if (guestfs_lvm_scan (g, 1) == -1)
> exit (EXIT_FAILURE);
> }
> +
> + lvs = guestfs_lvs (g);
> + if (lvs == NULL)
> + exit (EXIT_FAILURE);
> + decrypt_mountables (g, (const char * const *)lvs, ks, true);
ACK
Rich.