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Subject[PATCH 4/8] eCryptfs: Fix Tag 1 parsing code
Fix up the Tag 1 parsing code to handle size limits and boundaries
more explicitly. Initialize the new auth_tok's flags.

Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
---
fs/ecryptfs/keystore.c | 78 ++++++++++++++++++++---------------------------
1 files changed, 33 insertions(+), 45 deletions(-)
diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
index 590f29c..d84292d 100644
--- a/fs/ecryptfs/keystore.c
+++ b/fs/ecryptfs/keystore.c
@@ -512,72 +512,64 @@ parse_tag_1_packet(struct ecryptfs_crypt_stat *crypt_stat,

(*packet_size) = 0;
(*new_auth_tok) = NULL;
-
- /* we check that:
- * one byte for the Tag 1 ID flag
- * two bytes for the body size
- * do not exceed the maximum_packet_size
+ /**
+ * This format is inspired by OpenPGP; see RFC 2440
+ * packet tag 1
+ *
+ * Tag 1 identifier (1 byte)
+ * Max Tag 1 packet size (max 3 bytes)
+ * Version (1 byte)
+ * Key identifier (8 bytes; ECRYPTFS_SIG_SIZE)
+ * Cipher identifier (1 byte)
+ * Encrypted key size (arbitrary)
+ *
+ * 12 bytes minimum packet size
*/
- if (unlikely((*packet_size) + 3 > max_packet_size)) {
- ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
+ if (unlikely(max_packet_size < 12)) {
+ printk(KERN_ERR "Invalid max packet size; must be >=12\n");
rc = -EINVAL;
goto out;
}
- /* check for Tag 1 identifier - one byte */
if (data[(*packet_size)++] != ECRYPTFS_TAG_1_PACKET_TYPE) {
- ecryptfs_printk(KERN_ERR, "Enter w/ first byte != 0x%.2x\n",
- ECRYPTFS_TAG_1_PACKET_TYPE);
+ printk(KERN_ERR "Enter w/ first byte != 0x%.2x\n",
+ ECRYPTFS_TAG_1_PACKET_TYPE);
rc = -EINVAL;
goto out;
}
/* Released: wipe_auth_tok_list called in ecryptfs_parse_packet_set or
* at end of function upon failure */
auth_tok_list_item =
- kmem_cache_alloc(ecryptfs_auth_tok_list_item_cache,
- GFP_KERNEL);
+ kmem_cache_zalloc(ecryptfs_auth_tok_list_item_cache,
+ GFP_KERNEL);
if (!auth_tok_list_item) {
- ecryptfs_printk(KERN_ERR, "Unable to allocate memory\n");
+ printk(KERN_ERR "Unable to allocate memory\n");
rc = -ENOMEM;
goto out;
}
- memset(auth_tok_list_item, 0,
- sizeof(struct ecryptfs_auth_tok_list_item));
(*new_auth_tok) = &auth_tok_list_item->auth_tok;
- /* check for body size - one to two bytes
- *
- * ***** TAG 1 Packet Format *****
- * | version number | 1 byte |
- * | key ID | 8 bytes |
- * | public key algorithm | 1 byte |
- * | encrypted session key | arbitrary |
- */
- rc = parse_packet_length(&data[(*packet_size)], &body_size,
- &length_size);
- if (rc) {
- ecryptfs_printk(KERN_WARNING, "Error parsing packet length; "
- "rc = [%d]\n", rc);
+ if ((rc = parse_packet_length(&data[(*packet_size)], &body_size,
+ &length_size))) {
+ printk(KERN_WARNING "Error parsing packet length; "
+ "rc = [%d]\n", rc);
goto out_free;
}
- if (unlikely(body_size < (0x02 + ECRYPTFS_SIG_SIZE))) {
- ecryptfs_printk(KERN_WARNING, "Invalid body size ([%d])\n",
- body_size);
+ if (unlikely(body_size < (ECRYPTFS_SIG_SIZE + 2))) {
+ printk(KERN_WARNING "Invalid body size ([%d])\n", body_size);
rc = -EINVAL;
goto out_free;
}
(*packet_size) += length_size;
if (unlikely((*packet_size) + body_size > max_packet_size)) {
- ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
+ printk(KERN_WARNING "Packet size exceeds max\n");
rc = -EINVAL;
goto out_free;
}
- /* Version 3 (from RFC2440) - one byte */
if (unlikely(data[(*packet_size)++] != 0x03)) {
- ecryptfs_printk(KERN_DEBUG, "Unknown version number "
- "[%d]\n", data[(*packet_size) - 1]);
+ printk(KERN_WARNING "Unknown version number [%d]\n",
+ data[(*packet_size) - 1]);
rc = -EINVAL;
goto out_free;
}
- /* Read Signature */
ecryptfs_to_hex((*new_auth_tok)->token.private_key.signature,
&data[(*packet_size)], ECRYPTFS_SIG_SIZE);
*packet_size += ECRYPTFS_SIG_SIZE;
@@ -585,27 +577,23 @@ parse_tag_1_packet(struct ecryptfs_crypt_stat *crypt_stat,
* know which public key encryption algorithm was used */
(*packet_size)++;
(*new_auth_tok)->session_key.encrypted_key_size =
- body_size - (0x02 + ECRYPTFS_SIG_SIZE);
+ body_size - (ECRYPTFS_SIG_SIZE + 2);
if ((*new_auth_tok)->session_key.encrypted_key_size
> ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES) {
- ecryptfs_printk(KERN_ERR, "Tag 1 packet contains key larger "
- "than ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES");
+ printk(KERN_WARNING "Tag 1 packet contains key larger "
+ "than ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES");
rc = -EINVAL;
goto out;
}
- ecryptfs_printk(KERN_DEBUG, "Encrypted key size = [%d]\n",
- (*new_auth_tok)->session_key.encrypted_key_size);
memcpy((*new_auth_tok)->session_key.encrypted_key,
- &data[(*packet_size)], (body_size - 0x02 - ECRYPTFS_SIG_SIZE));
+ &data[(*packet_size)], (body_size - (ECRYPTFS_SIG_SIZE + 2)));
(*packet_size) += (*new_auth_tok)->session_key.encrypted_key_size;
(*new_auth_tok)->session_key.flags &=
~ECRYPTFS_CONTAINS_DECRYPTED_KEY;
(*new_auth_tok)->session_key.flags |=
ECRYPTFS_CONTAINS_ENCRYPTED_KEY;
(*new_auth_tok)->token_type = ECRYPTFS_PRIVATE_KEY;
- (*new_auth_tok)->flags |= ECRYPTFS_PRIVATE_KEY;
- /* TODO: Why are we setting this flag here? Don't we want the
- * userspace to decrypt the session key? */
+ (*new_auth_tok)->flags = 0;
(*new_auth_tok)->session_key.flags &=
~(ECRYPTFS_USERSPACE_SHOULD_TRY_TO_DECRYPT);
(*new_auth_tok)->session_key.flags &=
--
1.4.4.4
-
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