Laszlo Ersek
2022-Feb-24 12:12 UTC
[Libguestfs] [libguestfs-common PATCH 2/2] options: decrypt LUKS-on-LV devices
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 at redhat.com> >> >> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1658126 >> Signed-off-by: Laszlo Ersek <lersek at 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. >
Laszlo Ersek
2022-Feb-25 10:59 UTC
[Libguestfs] [libguestfs-common PATCH 2/2] options: decrypt LUKS-on-LV devices
On 02/24/22 13:12, Laszlo Ersek wrote:> 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 at redhat.com> >>> >>> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1658126 >>> Signed-off-by: Laszlo Ersek <lersek at 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.On a second thought, if it's OK with you: I'd prefer merging this series as-is, and then posting additional patches on top: - assume GUESTFS_HAVE_LUKS_UUID - assume GUESTFS_HAVE_CRYPTSETUP_OPEN - bump libguestfs version requirement in virt-v2v.git/m4/guestfs-libraries.m4 to 1.44 - remove "XXX Should we set GUESTFS_CRYPTSETUP_OPEN_READONLY" - allocate "mapname" with asprintf() on all paths. The reason I'd like to do these afterwards is that none of these warts are introduced/created by this series, and I had put lots of testing into the series (not just at the end, but mid-series too). If I rebased and needed to resolved conflicts, all that testing would have to be redone. I'd really like to avoid that. Thanks! Laszlo> > 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. >> >