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| author | Eric Biggers <ebiggers@google.com> | 2020-03-14 13:50:49 -0700 |
|---|---|---|
| committer | Eric Biggers <ebiggers@google.com> | 2020-03-19 21:56:54 -0700 |
| commit | e98ad464750c0894bc560d10503dae8ff90ccdac (patch) | |
| tree | 2bce5db834db04e054bdc2c08bec50e2396af50c /fs/crypto/policy.c | |
| parent | 98d54f81e36ba3bf92172791eba5ca5bd813989b (diff) | |
| download | linux-e98ad464750c0894bc560d10503dae8ff90ccdac.tar.bz2 | |
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>
Diffstat (limited to 'fs/crypto/policy.c')
| -rw-r--r-- | fs/crypto/policy.c | 21 |
1 files changed, 20 insertions, 1 deletions
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? |