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Old 11-14-2008, 09:03 PM
Jim Lieb
 
Default UBUNTU: SAUCE: Encryption keys can span a page boundary

OriginalAuthor: Michael Halcrow <mhalcrow@us.ibm.com>
Bug: #292429

Key buffers sent to virt_to_scatterlist() may span a page boundary. If the virtual pages are not
physically contiguous, an error occurs when the second part of the key is lost. Using a 2 element
scatterlist array allows virt_to_scatterlist() to correclty consume the second array element when the
key buffer spans a page boundary.

This patch is not in the upstream yet. We expect it may appear
in a different form later.

Committer: Jim Lieb <lieb@canonical.com>
Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Jim Lieb <jim.lieb@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
---
fs/ecryptfs/keystore.c | 31 ++++++++++++++-----------------
1 files changed, 14 insertions(+), 17 deletions(-)

diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
index f5b76a3..59b9833 100644
--- a/fs/ecryptfs/keystore.c
+++ b/fs/ecryptfs/keystore.c
@@ -1037,17 +1037,14 @@ static int
decrypt_passphrase_encrypted_session_key(struct ecryptfs_auth_tok *auth_tok,
struct ecryptfs_crypt_stat *crypt_stat)
{
- struct scatterlist dst_sg;
- struct scatterlist src_sg;
+ struct scatterlist dst_sg[2];
+ struct scatterlist src_sg[2];
struct mutex *tfm_mutex;
struct blkcipher_desc desc = {
.flags = CRYPTO_TFM_REQ_MAY_SLEEP
};
int rc = 0;

- sg_init_table(&dst_sg, 1);
- sg_init_table(&src_sg, 1);
-
if (unlikely(ecryptfs_verbosity > 0)) {
ecryptfs_printk(
KERN_DEBUG, "Session key encryption key (size [%d]):
",
@@ -1066,8 +1063,8 @@ decrypt_passphrase_encrypted_session_key(struct ecryptfs_auth_tok *auth_tok,
}
rc = virt_to_scatterlist(auth_tok->session_key.encrypted_key,
auth_tok->session_key.encrypted_key_size,
- &src_sg, 1);
- if (rc != 1) {
+ src_sg, 2);
+ if (rc < 1 || rc > 2) {
printk(KERN_ERR "Internal error whilst attempting to convert "
"auth_tok->session_key.encrypted_key to scatterlist; "
"expected rc = 1; got rc = [%d]. "
@@ -1079,8 +1076,8 @@ decrypt_passphrase_encrypted_session_key(struct ecryptfs_auth_tok *auth_tok,
auth_tok->session_key.encrypted_key_size;
rc = virt_to_scatterlist(auth_tok->session_key.decrypted_key,
auth_tok->session_key.decrypted_key_size,
- &dst_sg, 1);
- if (rc != 1) {
+ dst_sg, 2);
+ if (rc < 1 || rc > 2) {
printk(KERN_ERR "Internal error whilst attempting to convert "
"auth_tok->session_key.decrypted_key to scatterlist; "
"expected rc = 1; got rc = [%d]
", rc);
@@ -1096,7 +1093,7 @@ decrypt_passphrase_encrypted_session_key(struct ecryptfs_auth_tok *auth_tok,
rc = -EINVAL;
goto out;
}
- rc = crypto_blkcipher_decrypt(&desc, &dst_sg, &src_sg,
+ rc = crypto_blkcipher_decrypt(&desc, dst_sg, src_sg,
auth_tok->session_key.encrypted_key_size);
mutex_unlock(tfm_mutex);
if (unlikely(rc)) {
@@ -1541,8 +1538,8 @@ write_tag_3_packet(char *dest, size_t *remaining_bytes,
size_t i;
size_t encrypted_session_key_valid = 0;
char session_key_encryption_key[ECRYPTFS_MAX_KEY_BYTES];
- struct scatterlist dst_sg;
- struct scatterlist src_sg;
+ struct scatterlist dst_sg[2];
+ struct scatterlist src_sg[2];
struct mutex *tfm_mutex = NULL;
u8 cipher_code;
size_t packet_size_length;
@@ -1621,8 +1618,8 @@ write_tag_3_packet(char *dest, size_t *remaining_bytes,
ecryptfs_dump_hex(session_key_encryption_key, 16);
}
rc = virt_to_scatterlist(crypt_stat->key, key_rec->enc_key_size,
- &src_sg, 1);
- if (rc != 1) {
+ src_sg, 2);
+ if (rc < 1 || rc > 2) {
ecryptfs_printk(KERN_ERR, "Error generating scatterlist "
"for crypt_stat session key; expected rc = 1; "
"got rc = [%d]. key_rec->enc_key_size = [%d]
",
@@ -1631,8 +1628,8 @@ write_tag_3_packet(char *dest, size_t *remaining_bytes,
goto out;
}
rc = virt_to_scatterlist(key_rec->enc_key, key_rec->enc_key_size,
- &dst_sg, 1);
- if (rc != 1) {
+ dst_sg, 2);
+ if (rc < 1 || rc > 2) {
ecryptfs_printk(KERN_ERR, "Error generating scatterlist "
"for crypt_stat encrypted session key; "
"expected rc = 1; got rc = [%d]. "
@@ -1653,7 +1650,7 @@ write_tag_3_packet(char *dest, size_t *remaining_bytes,
rc = 0;
ecryptfs_printk(KERN_DEBUG, "Encrypting [%d] bytes of the key
",
crypt_stat->key_size);
- rc = crypto_blkcipher_encrypt(&desc, &dst_sg, &src_sg,
+ rc = crypto_blkcipher_encrypt(&desc, dst_sg, src_sg,
(*key_rec).enc_key_size);
mutex_unlock(tfm_mutex);
if (rc) {
--
1.5.6.3


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