From: Eric Biggers <ebiggers@xxxxxxxxxx>
When the key for an inode is not found but the inode is using the
test_dummy_encryption policy, automatically add the
test_dummy_encryption key to the filesystem keyring. This eliminates
the need for all the individual filesystems to do this at mount time,
which is a bit tricky to clean up from on failure.
Note: this covers the call to fscrypt_find_master_key() from inode key
setup, but not from the fscrypt ioctls. So, this isn't *exactly* the
same as the key being present from the very beginning. I think we can
tolerate that, though, since the inode key setup caller is the only one
that actually matters in the context of test_dummy_encryption.
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
fs/crypto/fscrypt_private.h | 1 +
fs/crypto/keysetup.c | 25 +++++++++++++++++++++++--
fs/crypto/policy.c | 3 +--
3 files changed, 25 insertions(+), 4 deletions(-)
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 316a778cec0ff..17dd33d9a522e 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -651,6 +651,7 @@ bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
const union fscrypt_policy *policy2);
int fscrypt_policy_to_key_spec(const union fscrypt_policy *policy,
struct fscrypt_key_specifier *key_spec);
+const union fscrypt_policy *fscrypt_get_dummy_policy(struct super_block *sb);
bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
const struct inode *inode);
int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 94757ccd30568..20323c0ba4c5e 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -438,6 +438,7 @@ static int setup_file_encryption_key(struct fscrypt_info *ci,
bool need_dirhash_key,
struct fscrypt_master_key **mk_ret)
{
+ struct super_block *sb = ci->ci_inode->i_sb;
struct fscrypt_key_specifier mk_spec;
struct fscrypt_master_key *mk;
int err;
@@ -450,8 +451,28 @@ static int setup_file_encryption_key(struct fscrypt_info *ci,
if (err)
return err;
- mk = fscrypt_find_master_key(ci->ci_inode->i_sb, &mk_spec);
- if (!mk) {
+ mk = fscrypt_find_master_key(sb, &mk_spec);
+ if (unlikely(!mk)) {
+ const union fscrypt_policy *dummy_policy =
+ fscrypt_get_dummy_policy(sb);
+
+ /*
+ * Add the test_dummy_encryption key on-demand. In principle,
+ * it should be added at mount time. Do it here instead so that
+ * the individual filesystems don't need to worry about adding
+ * this key at mount time and cleaning up on mount failure.
+ */
+ if (dummy_policy &&
+ fscrypt_policies_equal(dummy_policy, &ci->ci_policy)) {
+ struct fscrypt_dummy_policy tmp = { dummy_policy };
+
+ err = fscrypt_add_test_dummy_key(sb, &tmp);
+ if (err)
+ return err;
+ mk = fscrypt_find_master_key(sb, &mk_spec);
+ }
+ }
+ if (unlikely(!mk)) {
if (ci->ci_policy.version != FSCRYPT_POLICY_V1)
return -ENOKEY;
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index 893661b523769..69dca4ff5f488 100644
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -53,8 +53,7 @@ int fscrypt_policy_to_key_spec(const union fscrypt_policy *policy,
}
}
-static const union fscrypt_policy *
-fscrypt_get_dummy_policy(struct super_block *sb)
+const union fscrypt_policy *fscrypt_get_dummy_policy(struct super_block *sb)
{
if (!sb->s_cop->get_dummy_policy)
return NULL;
--
2.39.1
