From e98ad464750c0894bc560d10503dae8ff90ccdac Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Sat, 14 Mar 2020 13:50:49 -0700
Subject: [PATCH 1/4] fscrypt: add FS_IOC_GET_ENCRYPTION_NONCE ioctl
Add an ioctl FS_IOC_GET_ENCRYPTION_NONCE which retrieves the nonce from
an encrypted file or directory. The nonce is the 16-byte random value
stored in the inode's encryption xattr. It is normally used together
with the master key to derive the inode's actual encryption key.
The nonces are needed by automated tests that verify the correctness of
the ciphertext on-disk. Except for the IV_INO_LBLK_64 case, there's no
way to replicate a file's ciphertext without knowing that file's nonce.
The nonces aren't secret, and the existing ciphertext verification tests
in xfstests retrieve them from disk using debugfs or dump.f2fs. But in
environments that lack these debugging tools, getting the nonces by
manually parsing the filesystem structure would be very hard.
To make this important type of testing much easier, let's just add an
ioctl that retrieves the nonce.
Link: https://lore.kernel.org/r/20200314205052.93294-2-ebiggers@kernel.org
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
Documentation/filesystems/fscrypt.rst | 11 +++++++++++
fs/crypto/fscrypt_private.h | 20 ++++++++++++++++++++
fs/crypto/keysetup.c | 16 ++--------------
fs/crypto/policy.c | 21 ++++++++++++++++++++-
include/linux/fscrypt.h | 6 ++++++
include/uapi/linux/fscrypt.h | 1 +
6 files changed, 60 insertions(+), 15 deletions(-)
diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
index bd9932344804..aa072112cfff 100644
--- a/Documentation/filesystems/fscrypt.rst
+++ b/Documentation/filesystems/fscrypt.rst
@@ -633,6 +633,17 @@ from a passphrase or other low-entropy user credential.
FS_IOC_GET_ENCRYPTION_PWSALT is deprecated. Instead, prefer to
generate and manage any needed salt(s) in userspace.
+Getting a file's encryption nonce
+---------------------------------
+
+Since Linux v5.7, the ioctl FS_IOC_GET_ENCRYPTION_NONCE is supported.
+On encrypted files and directories it gets the inode's 16-byte nonce.
+On unencrypted files and directories, it fails with ENODATA.
+
+This ioctl can be useful for automated tests which verify that the
+encryption is being done correctly. It is not needed for normal use
+of fscrypt.
+
Adding keys
-----------
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 9aae851409e5..dbced2937ec8 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -76,6 +76,26 @@ static inline int fscrypt_context_size(const union fscrypt_context *ctx)
return 0;
}
+/* Check whether an fscrypt_context has a recognized version number and size */
+static inline bool fscrypt_context_is_valid(const union fscrypt_context *ctx,
+ int ctx_size)
+{
+ return ctx_size >= 1 && ctx_size == fscrypt_context_size(ctx);
+}
+
+/* Retrieve the context's nonce, assuming the context was already validated */
+static inline const u8 *fscrypt_context_nonce(const union fscrypt_context *ctx)
+{
+ switch (ctx->version) {
+ case FSCRYPT_CONTEXT_V1:
+ return ctx->v1.nonce;
+ case FSCRYPT_CONTEXT_V2:
+ return ctx->v2.nonce;
+ }
+ WARN_ON(1);
+ return NULL;
+}
+
#undef fscrypt_policy
union fscrypt_policy {
u8 version;
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 65cb09fa6ead..cb2803844726 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -425,20 +425,8 @@ int fscrypt_get_encryption_info(struct inode *inode)
goto out;
}
- switch (ctx.version) {
- case FSCRYPT_CONTEXT_V1:
- memcpy(crypt_info->ci_nonce, ctx.v1.nonce,
- FS_KEY_DERIVATION_NONCE_SIZE);
- break;
- case FSCRYPT_CONTEXT_V2:
- memcpy(crypt_info->ci_nonce, ctx.v2.nonce,
- FS_KEY_DERIVATION_NONCE_SIZE);
- break;
- default:
- WARN_ON(1);
- res = -EINVAL;
- goto out;
- }
+ memcpy(crypt_info->ci_nonce, fscrypt_context_nonce(&ctx),
+ FS_KEY_DERIVATION_NONCE_SIZE);
if (!fscrypt_supported_policy(&crypt_info->ci_policy, inode)) {
res = -EINVAL;
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index cf2a9d26ef7d..10ccf945020c 100644
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -258,7 +258,7 @@ int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
{
memset(policy_u, 0, sizeof(*policy_u));
- if (ctx_size <= 0 || ctx_size != fscrypt_context_size(ctx_u))
+ if (!fscrypt_context_is_valid(ctx_u, ctx_size))
return -EINVAL;
switch (ctx_u->version) {
@@ -481,6 +481,25 @@ int fscrypt_ioctl_get_policy_ex(struct file *filp, void __user *uarg)
}
EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_policy_ex);
+/* FS_IOC_GET_ENCRYPTION_NONCE: retrieve file's encryption nonce for testing */
+int fscrypt_ioctl_get_nonce(struct file *filp, void __user *arg)
+{
+ struct inode *inode = file_inode(filp);
+ union fscrypt_context ctx;
+ int ret;
+
+ ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
+ if (ret < 0)
+ return ret;
+ if (!fscrypt_context_is_valid(&ctx, ret))
+ return -EINVAL;
+ if (copy_to_user(arg, fscrypt_context_nonce(&ctx),
+ FS_KEY_DERIVATION_NONCE_SIZE))
+ return -EFAULT;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_nonce);
+
/**
* fscrypt_has_permitted_context() - is a file's encryption policy permitted
* within its directory?
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index 556f4adf5dc5..e3c2d2a15525 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -139,6 +139,7 @@ extern void fscrypt_free_bounce_page(struct page *bounce_page);
extern int fscrypt_ioctl_set_policy(struct file *, const void __user *);
extern int fscrypt_ioctl_get_policy(struct file *, void __user *);
extern int fscrypt_ioctl_get_policy_ex(struct file *, void __user *);
+extern int fscrypt_ioctl_get_nonce(struct file *filp, void __user *arg);
extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
extern int fscrypt_inherit_context(struct inode *, struct inode *,
void *, bool);
@@ -300,6 +301,11 @@ static inline int fscrypt_ioctl_get_policy_ex(struct file *filp,
return -EOPNOTSUPP;
}
+static inline int fscrypt_ioctl_get_nonce(struct file *filp, void __user *arg)
+{
+ return -EOPNOTSUPP;
+}
+
static inline int fscrypt_has_permitted_context(struct inode *parent,
struct inode *child)
{
diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
index 0d8a6f47711c..a10e3cdc2839 100644
--- a/include/uapi/linux/fscrypt.h
+++ b/include/uapi/linux/fscrypt.h
@@ -163,6 +163,7 @@ struct fscrypt_get_key_status_arg {
#define FS_IOC_REMOVE_ENCRYPTION_KEY _IOWR('f', 24, struct fscrypt_remove_key_arg)
#define FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS _IOWR('f', 25, struct fscrypt_remove_key_arg)
#define FS_IOC_GET_ENCRYPTION_KEY_STATUS _IOWR('f', 26, struct fscrypt_get_key_status_arg)
+#define FS_IOC_GET_ENCRYPTION_NONCE _IOR('f', 27, __u8[16])
/**********************************************************************/
From 7ec9f3b47aba0fe715bf3472ed80e91c37970363 Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Sat, 14 Mar 2020 13:50:50 -0700
Subject: [PATCH 2/4] ext4: wire up FS_IOC_GET_ENCRYPTION_NONCE
This new ioctl retrieves a file's encryption nonce, which is useful for
testing. See the corresponding fs/crypto/ patch for more details.
Link: https://lore.kernel.org/r/20200314205052.93294-3-ebiggers@kernel.org
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
fs/ext4/ioctl.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index a0ec750018dd..0c1d1720cf1a 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -1210,6 +1210,11 @@ resizefs_out:
return -EOPNOTSUPP;
return fscrypt_ioctl_get_key_status(filp, (void __user *)arg);
+ case FS_IOC_GET_ENCRYPTION_NONCE:
+ if (!ext4_has_feature_encrypt(sb))
+ return -EOPNOTSUPP;
+ return fscrypt_ioctl_get_nonce(filp, (void __user *)arg);
+
case EXT4_IOC_CLEAR_ES_CACHE:
{
if (!inode_owner_or_capable(inode))
@@ -1370,6 +1375,7 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
case FS_IOC_REMOVE_ENCRYPTION_KEY:
case FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS:
case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
+ case FS_IOC_GET_ENCRYPTION_NONCE:
case EXT4_IOC_SHUTDOWN:
case FS_IOC_GETFSMAP:
case FS_IOC_ENABLE_VERITY:
From ee446e1af4ff90945e2273ae0af322b8b745b8cc Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Sat, 14 Mar 2020 13:50:51 -0700
Subject: [PATCH 3/4] f2fs: wire up FS_IOC_GET_ENCRYPTION_NONCE
This new ioctl retrieves a file's encryption nonce, which is useful for
testing. See the corresponding fs/crypto/ patch for more details.
Link: https://lore.kernel.org/r/20200314205052.93294-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
fs/f2fs/file.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 0d4da644df3b..351762f77840 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -2423,6 +2423,14 @@ static int f2fs_ioc_get_encryption_key_status(struct file *filp,
return fscrypt_ioctl_get_key_status(filp, (void __user *)arg);
}
+static int f2fs_ioc_get_encryption_nonce(struct file *filp, unsigned long arg)
+{
+ if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
+ return -EOPNOTSUPP;
+
+ return fscrypt_ioctl_get_nonce(filp, (void __user *)arg);
+}
+
static int f2fs_ioc_gc(struct file *filp, unsigned long arg)
{
struct inode *inode = file_inode(filp);
@@ -3437,6 +3445,8 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
return f2fs_ioc_remove_encryption_key_all_users(filp, arg);
case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
return f2fs_ioc_get_encryption_key_status(filp, arg);
+ case FS_IOC_GET_ENCRYPTION_NONCE:
+ return f2fs_ioc_get_encryption_nonce(filp, arg);
case F2FS_IOC_GARBAGE_COLLECT:
return f2fs_ioc_gc(filp, arg);
case F2FS_IOC_GARBAGE_COLLECT_RANGE:
@@ -3611,6 +3621,7 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
case FS_IOC_REMOVE_ENCRYPTION_KEY:
case FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS:
case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
+ case FS_IOC_GET_ENCRYPTION_NONCE:
case F2FS_IOC_GARBAGE_COLLECT:
case F2FS_IOC_GARBAGE_COLLECT_RANGE:
case F2FS_IOC_WRITE_CHECKPOINT:
From 861261f2a9cc488c845fc214d9035f7a11094591 Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Sat, 14 Mar 2020 13:50:52 -0700
Subject: [PATCH 4/4] ubifs: wire up FS_IOC_GET_ENCRYPTION_NONCE
This new ioctl retrieves a file's encryption nonce, which is useful for
testing. See the corresponding fs/crypto/ patch for more details.
Link: https://lore.kernel.org/r/20200314205052.93294-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
fs/ubifs/ioctl.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/fs/ubifs/ioctl.c b/fs/ubifs/ioctl.c
index d49fc04f2d7d..3df9be2c684c 100644
--- a/fs/ubifs/ioctl.c
+++ b/fs/ubifs/ioctl.c
@@ -208,6 +208,9 @@ long ubifs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
return fscrypt_ioctl_get_key_status(file, (void __user *)arg);
+ case FS_IOC_GET_ENCRYPTION_NONCE:
+ return fscrypt_ioctl_get_nonce(file, (void __user *)arg);
+
default:
return -ENOTTY;
}
@@ -230,6 +233,7 @@ long ubifs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
case FS_IOC_REMOVE_ENCRYPTION_KEY:
case FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS:
case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
+ case FS_IOC_GET_ENCRYPTION_NONCE:
break;
default:
return -ENOIOCTLCMD;