Re: [Libguestfs] [libguestfs-common PATCH 2/2] options: decrypt LUKS-on-LV devices

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&gt; > > Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1658126 > Signed-off-by: Laszlo Ersek <lersek(a)redhat.com&gt; > --- > 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.

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.