6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: HanQuan <redacted>
commit 5babe9c177c364521e3e682b949c5a8c47f4a441 upstream.
parse_tag_3_packet() set encrypted_key_size from the Tag 3 packet body
without bounding it against ECRYPTFS_MAX_KEY_BYTES (64). When
encrypted_key_size > 64, decrypt_passphrase_encrypted_session_key()
sets decrypted_key_size = encrypted_key_size and performs two
out-of-bounds writes:
1. crypto_skcipher_decrypt() writes encrypted_key_size bytes into
decrypted_key[64] via scatterlist, overflowing into the parent
ecryptfs_auth_tok struct.
2. memcpy(crypt_stat->key, decrypted_key, decrypted_key_size) writes
into crypt_stat->key[64], corrupting root_iv, keysig_list, and
mutexes in ecryptfs_crypt_stat.
Only AES-192 (cipher code 0x08) enables this because it sets
crypt_stat->key_size = 24 independently of encrypted_key_size,
allowing crypto_skcipher_setkey() to succeed while encrypted_key_size
exceeds ECRYPTFS_MAX_KEY_BYTES.
The PKI decryption path (parse_tag_65_packet) already validates
decrypted_key_size <= ECRYPTFS_MAX_KEY_BYTES; the passphrase path
omits this check.
Bound encrypted_key_size against ECRYPTFS_MAX_KEY_BYTES (64) rather
than ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES (512). The 64-byte limit also
protects the 512-byte encrypted_key[] buffer, so the former 512-byte
check is removed as redundant.
Fixes: 237fead61998 ("[PATCH] ecryptfs: fs/Makefile and fs/Kconfig")
Cc: <redacted>
Signed-off-by: HanQuan <redacted>
[tyhicks: Adjust the code comment to refer to macros representing the
buffer sizes rather than mentioning the buffer size values since they
may change in the future]
Signed-off-by: Tyler Hicks <code@tyhicks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ecryptfs/keystore.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
--- a/fs/ecryptfs/keystore.c
+++ b/fs/ecryptfs/keystore.c
@@ -1424,10 +1424,20 @@ parse_tag_3_packet(struct ecryptfs_crypt
}
(*new_auth_tok)->session_key.encrypted_key_size =
(body_size - (ECRYPTFS_SALT_SIZE + 5));
+ /*
+ * Although encrypted_key_size is copied into the
+ * encrypted_key[ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES] buffer here,
+ * it later bounds operations on a smaller buffer:
+ * decrypt_passphrase_encrypted_session_key() sets decrypted_key_size =
+ * encrypted_key_size and decrypts into
+ * decrypted_key[ECRYPTFS_MAX_KEY_BYTES], then memcpy's into
+ * crypt_stat->key[ECRYPTFS_MAX_KEY_BYTES]. Limit to
+ * ECRYPTFS_MAX_KEY_BYTES to protect those smaller buffers.
+ */
if ((*new_auth_tok)->session_key.encrypted_key_size
- > ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES) {
+ > ECRYPTFS_MAX_KEY_BYTES) {
printk(KERN_WARNING "Tag 3 packet contains key larger "
- "than ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES\n");
+ "than ECRYPTFS_MAX_KEY_BYTES\n");
rc = -EINVAL;
goto out_free;
}