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path: root/fs/ext4/crypto_key.c
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Diffstat (limited to 'fs/ext4/crypto_key.c')
-rw-r--r--fs/ext4/crypto_key.c147
1 files changed, 115 insertions, 32 deletions
diff --git a/fs/ext4/crypto_key.c b/fs/ext4/crypto_key.c
index 9a16d1e75a49..68225223ffd8 100644
--- a/fs/ext4/crypto_key.c
+++ b/fs/ext4/crypto_key.c
@@ -29,16 +29,16 @@ static void derive_crypt_complete(struct crypto_async_request *req, int rc)
}
/**
- * ext4_derive_key_aes() - Derive a key using AES-128-ECB
+ * ext4_derive_key_v1() - Derive a key using AES-128-ECB
* @deriving_key: Encryption key used for derivation.
* @source_key: Source key to which to apply derivation.
* @derived_key: Derived key.
*
- * Return: Zero on success; non-zero otherwise.
+ * Return: 0 on success, -errno on failure
*/
-static int ext4_derive_key_aes(char deriving_key[EXT4_AES_128_ECB_KEY_SIZE],
- char source_key[EXT4_AES_256_XTS_KEY_SIZE],
- char derived_key[EXT4_AES_256_XTS_KEY_SIZE])
+static int ext4_derive_key_v1(const char deriving_key[EXT4_AES_128_ECB_KEY_SIZE],
+ const char source_key[EXT4_AES_256_XTS_KEY_SIZE],
+ char derived_key[EXT4_AES_256_XTS_KEY_SIZE])
{
int res = 0;
struct ablkcipher_request *req = NULL;
@@ -83,13 +83,96 @@ out:
return res;
}
+/**
+ * ext4_derive_key_v2() - Derive a key non-reversibly
+ * @nonce: the nonce associated with the file
+ * @master_key: the master key referenced by the file
+ * @derived_key: (output) the resulting derived key
+ *
+ * This function computes the following:
+ * derived_key[0:127] = AES-256-ENCRYPT(master_key[0:255], nonce)
+ * derived_key[128:255] = AES-256-ENCRYPT(master_key[0:255], nonce ^ 0x01)
+ * derived_key[256:383] = AES-256-ENCRYPT(master_key[256:511], nonce)
+ * derived_key[384:511] = AES-256-ENCRYPT(master_key[256:511], nonce ^ 0x01)
+ *
+ * 'nonce ^ 0x01' denotes flipping the low order bit of the last byte.
+ *
+ * Unlike the v1 algorithm, the v2 algorithm is "non-reversible", meaning that
+ * compromising a derived key does not also compromise the master key.
+ *
+ * Return: 0 on success, -errno on failure
+ */
+static int ext4_derive_key_v2(const char nonce[EXT4_KEY_DERIVATION_NONCE_SIZE],
+ const char master_key[EXT4_MAX_KEY_SIZE],
+ char derived_key[EXT4_MAX_KEY_SIZE])
+{
+ const int noncelen = EXT4_KEY_DERIVATION_NONCE_SIZE;
+ struct crypto_cipher *tfm;
+ int err;
+ int i;
+
+ /*
+ * Since we only use each transform for a small number of encryptions,
+ * requesting just "aes" turns out to be significantly faster than
+ * "ecb(aes)", by about a factor of two.
+ */
+ tfm = crypto_alloc_cipher("aes", 0, 0);
+ if (IS_ERR(tfm))
+ return PTR_ERR(tfm);
+
+ BUILD_BUG_ON(4 * EXT4_KEY_DERIVATION_NONCE_SIZE != EXT4_MAX_KEY_SIZE);
+ BUILD_BUG_ON(2 * EXT4_AES_256_ECB_KEY_SIZE != EXT4_MAX_KEY_SIZE);
+ for (i = 0; i < 2; i++) {
+ memcpy(derived_key, nonce, noncelen);
+ memcpy(derived_key + noncelen, nonce, noncelen);
+ derived_key[2 * noncelen - 1] ^= 0x01;
+ err = crypto_cipher_setkey(tfm, master_key,
+ EXT4_AES_256_ECB_KEY_SIZE);
+ if (err)
+ break;
+ crypto_cipher_encrypt_one(tfm, derived_key, derived_key);
+ crypto_cipher_encrypt_one(tfm, derived_key + noncelen,
+ derived_key + noncelen);
+ master_key += EXT4_AES_256_ECB_KEY_SIZE;
+ derived_key += 2 * noncelen;
+ }
+ crypto_free_cipher(tfm);
+ return err;
+}
+
+/**
+ * ext4_derive_key() - Derive a per-file key from a nonce and master key
+ * @ctx: the encryption context associated with the file
+ * @master_key: the master key referenced by the file
+ * @derived_key: (output) the resulting derived key
+ *
+ * Return: 0 on success, -errno on failure
+ */
+static int ext4_derive_key(const struct ext4_encryption_context *ctx,
+ const char master_key[EXT4_MAX_KEY_SIZE],
+ char derived_key[EXT4_MAX_KEY_SIZE])
+{
+ BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE != EXT4_KEY_DERIVATION_NONCE_SIZE);
+ BUILD_BUG_ON(EXT4_AES_256_XTS_KEY_SIZE != EXT4_MAX_KEY_SIZE);
+
+ /*
+ * Although the key derivation algorithm is logically independent of the
+ * choice of encryption modes, in this kernel it is bundled with HEH
+ * encryption of filenames, which is another crypto improvement that
+ * requires an on-disk format change and requires userspace to specify
+ * different encryption policies.
+ */
+ if (ctx->filenames_encryption_mode == EXT4_ENCRYPTION_MODE_AES_256_HEH)
+ return ext4_derive_key_v2(ctx->nonce, master_key, derived_key);
+ else
+ return ext4_derive_key_v1(ctx->nonce, master_key, derived_key);
+}
+
void ext4_free_crypt_info(struct ext4_crypt_info *ci)
{
if (!ci)
return;
- if (ci->ci_keyring_key)
- key_put(ci->ci_keyring_key);
crypto_free_ablkcipher(ci->ci_ctfm);
kmem_cache_free(ext4_crypt_info_cachep, ci);
}
@@ -111,7 +194,7 @@ void ext4_free_encryption_info(struct inode *inode,
ext4_free_crypt_info(ci);
}
-int _ext4_get_encryption_info(struct inode *inode)
+int ext4_get_encryption_info(struct inode *inode)
{
struct ext4_inode_info *ei = EXT4_I(inode);
struct ext4_crypt_info *crypt_info;
@@ -128,21 +211,12 @@ int _ext4_get_encryption_info(struct inode *inode)
char mode;
int res;
- if (!ext4_read_workqueue) {
- res = ext4_init_crypto();
- if (res)
- return res;
- }
+ if (ei->i_crypt_info)
+ return 0;
-retry:
- crypt_info = ACCESS_ONCE(ei->i_crypt_info);
- if (crypt_info) {
- if (!crypt_info->ci_keyring_key ||
- key_validate(crypt_info->ci_keyring_key) == 0)
- return 0;
- ext4_free_encryption_info(inode, crypt_info);
- goto retry;
- }
+ res = ext4_init_crypto();
+ if (res)
+ return res;
res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
@@ -166,7 +240,6 @@ retry:
crypt_info->ci_data_mode = ctx.contents_encryption_mode;
crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
crypt_info->ci_ctfm = NULL;
- crypt_info->ci_keyring_key = NULL;
memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
sizeof(crypt_info->ci_master_key));
if (S_ISREG(inode->i_mode))
@@ -182,6 +255,15 @@ retry:
case EXT4_ENCRYPTION_MODE_AES_256_CTS:
cipher_str = "cts(cbc(aes))";
break;
+ case EXT4_ENCRYPTION_MODE_AES_256_HEH:
+ cipher_str = "heh(aes)";
+ break;
+ case EXT4_ENCRYPTION_MODE_SPECK128_256_XTS:
+ cipher_str = "xts(speck128)";
+ break;
+ case EXT4_ENCRYPTION_MODE_SPECK128_256_CTS:
+ cipher_str = "cts(cbc(speck128))";
+ break;
default:
printk_once(KERN_WARNING
"ext4: unsupported key mode %d (ino %u)\n",
@@ -206,7 +288,6 @@ retry:
keyring_key = NULL;
goto out;
}
- crypt_info->ci_keyring_key = keyring_key;
if (keyring_key->type != &key_type_logon) {
printk_once(KERN_WARNING
"ext4: key type must be logon\n");
@@ -215,6 +296,12 @@ retry:
}
down_read(&keyring_key->sem);
ukp = user_key_payload(keyring_key);
+ if (!ukp) {
+ /* key was revoked before we acquired its semaphore */
+ res = -EKEYREVOKED;
+ up_read(&keyring_key->sem);
+ goto out;
+ }
if (ukp->datalen != sizeof(struct ext4_encryption_key)) {
res = -EINVAL;
up_read(&keyring_key->sem);
@@ -231,8 +318,7 @@ retry:
up_read(&keyring_key->sem);
goto out;
}
- res = ext4_derive_key_aes(ctx.nonce, master_key->raw,
- raw_key);
+ res = ext4_derive_key(&ctx, master_key->raw, raw_key);
up_read(&keyring_key->sem);
if (res)
goto out;
@@ -253,16 +339,13 @@ got_key:
ext4_encryption_key_size(mode));
if (res)
goto out;
- memzero_explicit(raw_key, sizeof(raw_key));
- if (cmpxchg(&ei->i_crypt_info, NULL, crypt_info) != NULL) {
- ext4_free_crypt_info(crypt_info);
- goto retry;
- }
- return 0;
+ if (cmpxchg(&ei->i_crypt_info, NULL, crypt_info) == NULL)
+ crypt_info = NULL;
out:
if (res == -ENOKEY)
res = 0;
+ key_put(keyring_key);
ext4_free_crypt_info(crypt_info);
memzero_explicit(raw_key, sizeof(raw_key));
return res;
generated by cgit v1.2.3 (git 2.25.1) at 2025-12-08 19:22:54 +0000