fscrypt keys have used the $FSTYP as prefix. However this format is being
deprecated and newer kernels are expected to use the generic 'fscrypt:'
prefix instead. This patch adds support for this new prefix, and only
uses $FSTYP on filesystems that didn't initially supported it, i.e. ext4 and
f2fs. This will allow old kernels to be tested.
Signed-off-by: Luís Henriques <lhenriques@xxxxxxx>
---
common/encrypt | 36 +++++++++++++++++++++++++-----------
1 file changed, 25 insertions(+), 11 deletions(-)
Changes since v2:
- updated _get_fs_keyprefix() and commit description
Changes since v1:
- ubifs now follows into the default case (i.e. to use the 'fscrypt' key
prefix)
- dropped local variable from _get_fs_keyprefix()
diff --git a/common/encrypt b/common/encrypt
index f90c4ef05a3f..e2683f99dcc2 100644
--- a/common/encrypt
+++ b/common/encrypt
@@ -250,6 +250,25 @@ _num_to_hex()
fi
}
+# When fscrypt keys are added using the legacy mechanism (process-subscribed
+# keyrings rather than filesystem keyrings), they are normally named
+# "fscrypt:KEYDESC" where KEYDESC is the 16-character key descriptor hex string.
+# However, ext4 and f2fs didn't add support for the "fscrypt" prefix until
+# kernel v4.8 and v4.6, respectively. Before that, they used "ext4" and "f2fs",
+# respectively. To allow testing ext4 and f2fs encryption on kernels older than
+# this, we use these filesystem-specific prefixes for ext4 and f2fs.
+_get_fs_keyprefix()
+{
+ case $FSTYP in
+ ext4|f2fs)
+ echo $FSTYP
+ ;;
+ *)
+ echo fscrypt
+ ;;
+ esac
+}
+
# Add the specified raw encryption key to the session keyring, using the
# specified key descriptor.
_add_session_encryption_key()
@@ -268,18 +287,11 @@ _add_session_encryption_key()
# };
#
# The kernel ignores 'mode' but requires that 'size' be 64.
- #
- # Keys are named $FSTYP:KEYDESC where KEYDESC is the 16-character key
- # descriptor hex string. Newer kernels (ext4 4.8 and later, f2fs 4.6
- # and later) also allow the common key prefix "fscrypt:" in addition to
- # their filesystem-specific key prefix ("ext4:", "f2fs:"). It would be
- # nice to use the common key prefix, but for now use the filesystem-
- # specific prefix to make it possible to test older kernels...
- #
local mode=$(_num_to_hex 0 4)
local size=$(_num_to_hex 64 4)
+ local prefix=$(_get_fs_keyprefix)
echo -n -e "${mode}${raw}${size}" |
- $KEYCTL_PROG padd logon $FSTYP:$keydesc @s >>$seqres.full
+ $KEYCTL_PROG padd logon $prefix:$keydesc @s >>$seqres.full
}
#
@@ -302,7 +314,8 @@ _generate_session_encryption_key()
_unlink_session_encryption_key()
{
local keydesc=$1
- local keyid=$($KEYCTL_PROG search @s logon $FSTYP:$keydesc)
+ local prefix=$(_get_fs_keyprefix)
+ local keyid=$($KEYCTL_PROG search @s logon $prefix:$keydesc)
$KEYCTL_PROG unlink $keyid >>$seqres.full
}
@@ -310,7 +323,8 @@ _unlink_session_encryption_key()
_revoke_session_encryption_key()
{
local keydesc=$1
- local keyid=$($KEYCTL_PROG search @s logon $FSTYP:$keydesc)
+ local prefix=$(_get_fs_keyprefix)
+ local keyid=$($KEYCTL_PROG search @s logon $prefix:$keydesc)
$KEYCTL_PROG revoke $keyid >>$seqres.full
}
