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Commit c59becfc authored by Michael Halcrow's avatar Michael Halcrow Committed by Linus Torvalds
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eCryptfs: fix Tag 3 parsing code 

Fix up the Tag 3 parsing code to handle size limits and boundaries more
explicitly.
Signed-off-by: default avatarMichael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 13218179
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Showing with 35 additions and 54 deletions
fs/ecryptfs/keystore.c
View file @ c59becfc
......@@ -643,22 +643,30 @@ parse_tag_3_packet(struct ecryptfs_crypt_stat *crypt_stat,
(*packet_size) = 0;
(*new_auth_tok) = NULL;
/* we check that:
* one byte for the Tag 3 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 3
*
* Tag 3 identifier (1 byte)
* Max Tag 3 packet size (max 3 bytes)
* Version (1 byte)
* Cipher code (1 byte)
* S2K specifier (1 byte)
* Hash identifier (1 byte)
* Salt (ECRYPTFS_SALT_SIZE)
* Hash iterations (1 byte)
* Encrypted key (arbitrary)
*
* (ECRYPTFS_SALT_SIZE + 7) minimum packet size
*/
if (unlikely((*packet_size) + 3 > max_packet_size)) {
ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
if (max_packet_size < (ECRYPTFS_SALT_SIZE + 7)) {
printk(KERN_ERR "Max packet size too large\n");
rc = -EINVAL;
goto out;
}
/* check for Tag 3 identifyer - one byte */
if (data[(*packet_size)++] != ECRYPTFS_TAG_3_PACKET_TYPE) {
ecryptfs_printk(KERN_ERR, "Enter w/ first byte != 0x%.2x\n",
ECRYPTFS_TAG_3_PACKET_TYPE);
printk(KERN_ERR "First byte != 0x%.2x; invalid packet\n",
ECRYPTFS_TAG_3_PACKET_TYPE);
rc = -EINVAL;
goto out;
}
......@@ -667,56 +675,36 @@ parse_tag_3_packet(struct ecryptfs_crypt_stat *crypt_stat,
auth_tok_list_item =
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;
}
(*new_auth_tok) = &auth_tok_list_item->auth_tok;
/* check for body size - one to two bytes */
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 < (0x05 + ECRYPTFS_SALT_SIZE))) {
ecryptfs_printk(KERN_WARNING, "Invalid body size ([%d])\n",
body_size);
if (unlikely(body_size < (ECRYPTFS_SALT_SIZE + 5))) {
printk(KERN_WARNING "Invalid body size ([%d])\n", body_size);
rc = -EINVAL;
goto out_free;
}
(*packet_size) += length_size;
/* now we know the length of the remainting Tag 3 packet size:
* 5 fix bytes for: version string, cipher, S2K ID, hash algo,
* number of hash iterations
* ECRYPTFS_SALT_SIZE bytes for salt
* body_size bytes minus the stuff above is the encrypted key size
*/
if (unlikely((*packet_size) + body_size > max_packet_size)) {
ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
printk(KERN_ERR "Packet size exceeds max\n");
rc = -EINVAL;
goto out_free;
}
/* There are 5 characters of additional information in the
* packet */
(*new_auth_tok)->session_key.encrypted_key_size =
body_size - (0x05 + ECRYPTFS_SALT_SIZE);
ecryptfs_printk(KERN_DEBUG, "Encrypted key size = [%d]\n",
(*new_auth_tok)->session_key.encrypted_key_size);
/* Version 4 (from RFC2440) - one byte */
(body_size - (ECRYPTFS_SALT_SIZE + 5));
if (unlikely(data[(*packet_size)++] != 0x04)) {
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;
}
/* cipher - one byte */
ecryptfs_cipher_code_to_string(crypt_stat->cipher,
(u16)data[(*packet_size)]);
/* A little extra work to differentiate among the AES key
......@@ -730,33 +718,26 @@ parse_tag_3_packet(struct ecryptfs_crypt_stat *crypt_stat,
(*new_auth_tok)->session_key.encrypted_key_size;
}
ecryptfs_init_crypt_ctx(crypt_stat);
/* S2K identifier 3 (from RFC2440) */
if (unlikely(data[(*packet_size)++] != 0x03)) {
ecryptfs_printk(KERN_ERR, "Only S2K ID 3 is currently "
"supported\n");
printk(KERN_WARNING "Only S2K ID 3 is currently supported\n");
rc = -ENOSYS;
goto out_free;
}
/* TODO: finish the hash mapping */
/* hash algorithm - one byte */
switch (data[(*packet_size)++]) {
case 0x01: /* See RFC2440 for these numbers and their mappings */
/* Choose MD5 */
/* salt - ECRYPTFS_SALT_SIZE bytes */
memcpy((*new_auth_tok)->token.password.salt,
&data[(*packet_size)], ECRYPTFS_SALT_SIZE);
(*packet_size) += ECRYPTFS_SALT_SIZE;
/* This conversion was taken straight from RFC2440 */
/* number of hash iterations - one byte */
(*new_auth_tok)->token.password.hash_iterations =
((u32) 16 + (data[(*packet_size)] & 15))
<< ((data[(*packet_size)] >> 4) + 6);
(*packet_size)++;
/* encrypted session key -
* (body_size-5-ECRYPTFS_SALT_SIZE) bytes */
/* Friendly reminder:
* (*new_auth_tok)->session_key.encrypted_key_size =
* (body_size - (ECRYPTFS_SALT_SIZE + 5)); */
memcpy((*new_auth_tok)->session_key.encrypted_key,
&data[(*packet_size)],
(*new_auth_tok)->session_key.encrypted_key_size);
......@@ -766,7 +747,7 @@ parse_tag_3_packet(struct ecryptfs_crypt_stat *crypt_stat,
~ECRYPTFS_CONTAINS_DECRYPTED_KEY;
(*new_auth_tok)->session_key.flags |=
ECRYPTFS_CONTAINS_ENCRYPTED_KEY;
(*new_auth_tok)->token.password.hash_algo = 0x01;
(*new_auth_tok)->token.password.hash_algo = 0x01; /* MD5 */
break;
default:
ecryptfs_printk(KERN_ERR, "Unsupported hash algorithm: "
......
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