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Subject[PATCH v2 2/3] fscrypt: Don't allow v1 policies with casefolding
From
Casefolding currently requires a derived key for computing the siphash.
This is available for v2 policies, but not v1, so we disallow it for v1.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
---
fs/crypto/keysetup.c | 7 ++++---
fs/crypto/policy.c | 39 +++++++++++++++++++++++++++++++++++++++
fs/inode.c | 7 +++++++
include/linux/fscrypt.h | 11 +++++++++++
4 files changed, 61 insertions(+), 3 deletions(-)

diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index c1bd897c9310..7445ab76e0b3 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -224,10 +224,11 @@ static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
FS_KEY_DERIVATION_NONCE_SIZE,
(u8 *)&ci->ci_hash_key,
sizeof(ci->ci_hash_key));
- if (!err)
- ci->ci_hash_key_initialized = true;
+ if (err)
+ return err;
+ ci->ci_hash_key_initialized = true;
}
- return err;
+ return 0;
}

/*
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index f1cff83c151a..9e937cfa732c 100644
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -124,6 +124,12 @@ static bool fscrypt_supported_v1_policy(const struct fscrypt_policy_v1 *policy,
policy->filenames_encryption_mode))
return false;

+ if (IS_CASEFOLDED(inode)) {
+ fscrypt_warn(inode,
+ "v1 policy does not support casefolded directories");
+ return false;
+ }
+
return true;
}

@@ -579,3 +585,36 @@ int fscrypt_inherit_context(struct inode *parent, struct inode *child,
return preload ? fscrypt_get_encryption_info(child): 0;
}
EXPORT_SYMBOL(fscrypt_inherit_context);
+
+static int fscrypt_set_casefolding_allowed(struct inode *inode)
+{
+ union fscrypt_policy policy;
+ int err = fscrypt_get_policy(inode, &policy);
+
+ if (err)
+ return err;
+
+ if (policy.version != FSCRYPT_POLICY_V2)
+ return -EINVAL;
+
+ return 0;
+}
+
+int fscrypt_ioc_setflags_prepare(struct inode *inode,
+ unsigned int oldflags,
+ unsigned int flags)
+{
+ int err;
+
+ /*
+ * When a directory is encrypted, the CASEFOLD flag can only be turned
+ * on if the fscrypt policy supports it.
+ */
+ if (IS_ENCRYPTED(inode) && (flags & ~oldflags & FS_CASEFOLD_FL)) {
+ err = fscrypt_set_casefolding_allowed(inode);
+ if (err)
+ return err;
+ }
+
+ return 0;
+}
diff --git a/fs/inode.c b/fs/inode.c
index 96d62d97694e..77f3e6e2e934 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -20,6 +20,7 @@
#include <linux/ratelimit.h>
#include <linux/list_lru.h>
#include <linux/iversion.h>
+#include <linux/fscrypt.h>
#include <trace/events/writeback.h>
#include "internal.h"

@@ -2242,6 +2243,8 @@ EXPORT_SYMBOL(current_time);
int vfs_ioc_setflags_prepare(struct inode *inode, unsigned int oldflags,
unsigned int flags)
{
+ int err;
+
/*
* The IMMUTABLE and APPEND_ONLY flags can only be changed by
* the relevant capability.
@@ -2252,6 +2255,10 @@ int vfs_ioc_setflags_prepare(struct inode *inode, unsigned int oldflags,
!capable(CAP_LINUX_IMMUTABLE))
return -EPERM;

+ err = fscrypt_ioc_setflags_prepare(inode, oldflags, flags);
+ if (err)
+ return err;
+
return 0;
}
EXPORT_SYMBOL(vfs_ioc_setflags_prepare);
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index 1dfbed855bee..2c292f19c6b9 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -142,6 +142,10 @@ extern int fscrypt_ioctl_get_policy_ex(struct file *, void __user *);
extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
extern int fscrypt_inherit_context(struct inode *, struct inode *,
void *, bool);
+extern int fscrypt_ioc_setflags_prepare(struct inode *inode,
+ unsigned int oldflags,
+ unsigned int flags);
+
/* keyring.c */
extern void fscrypt_sb_free(struct super_block *sb);
extern int fscrypt_ioctl_add_key(struct file *filp, void __user *arg);
@@ -383,6 +387,13 @@ static inline int fscrypt_inherit_context(struct inode *parent,
return -EOPNOTSUPP;
}

+static inline int fscrypt_ioc_setflags_prepare(struct inode *inode,
+ unsigned int oldflags,
+ unsigned int flags)
+{
+ return 0;
+}
+
/* keyring.c */
static inline void fscrypt_sb_free(struct super_block *sb)
{
--
2.24.1.735.g03f4e72817-goog
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