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Subject[PATCH 7/8] eCryptfs: Fix Tag 11 writing code
Fix up the Tag 11 writing code to handle size limits and boundaries
more explicitly. It looks like the packet length was 1 shorter than it
should have been, chopping off the last byte of the key
identifier. This is largely inconsequential, since it is not much more
likely that a key identifier collision will occur with 7 bytes rather
than 8. This patch fixes the packet to use the full number of bytes
that were originally intended to be used for the key identifier.

Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
---
fs/ecryptfs/keystore.c | 39 ++++++++++++++++++++++-----------------
1 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
index 8c695e3..8485e77 100644
--- a/fs/ecryptfs/keystore.c
+++ b/fs/ecryptfs/keystore.c
@@ -1449,47 +1449,52 @@ out:
* Returns zero on success; non-zero on error.
*/
static int
-write_tag_11_packet(char *dest, int max, char *contents, size_t contents_length,
- size_t *packet_length)
+write_tag_11_packet(char *dest, int *remaining_bytes, char *contents,
+ size_t contents_length, size_t *packet_length)
{
size_t packet_size_length;
+ size_t max_packet_size;
int rc = 0;

(*packet_length) = 0;
- if ((13 + contents_length) > max) {
+ /* This format is inspired by OpenPGP; see RFC 2440
+ * packet tag 11 */
+ max_packet_size = (1 /* Tag 11 identifier */
+ + 3 /* Max Tag 11 packet size */
+ + 1 /* Binary format specifier */
+ + 1 /* Filename length */
+ + 8 /* Filename ("_CONSOLE") */
+ + 4 /* Modification date */
+ + contents_length); /* Literal data */
+ if (max_packet_size > (*remaining_bytes)) {
+ printk(KERN_ERR "Packet length larger than maximum allowable; "
+ "need up to [%d] bytes, but there are only [%d] "
+ "available\n", max_packet_size, (*remaining_bytes));
rc = -EINVAL;
- ecryptfs_printk(KERN_ERR, "Packet length larger than "
- "maximum allowable\n");
goto out;
}
- /* General packet header */
- /* Packet tag */
dest[(*packet_length)++] = ECRYPTFS_TAG_11_PACKET_TYPE;
- /* Packet length */
rc = write_packet_length(&dest[(*packet_length)],
- (13 + contents_length), &packet_size_length);
+ (max_packet_size - 4), &packet_size_length);
if (rc) {
- ecryptfs_printk(KERN_ERR, "Error generating tag 11 packet "
- "header; cannot generate packet length\n");
+ printk(KERN_ERR "Error generating tag 11 packet header; cannot "
+ "generate packet length. rc = [%d]\n", rc);
goto out;
}
(*packet_length) += packet_size_length;
- /* Tag 11 specific */
- /* One-octet field that describes how the data is formatted */
- dest[(*packet_length)++] = 0x62; /* binary data */
- /* One-octet filename length followed by filename */
+ dest[(*packet_length)++] = 0x62; /* binary data format specifier */
dest[(*packet_length)++] = 8;
memcpy(&dest[(*packet_length)], "_CONSOLE", 8);
(*packet_length) += 8;
- /* Four-octet number indicating modification date */
memset(&dest[(*packet_length)], 0x00, 4);
(*packet_length) += 4;
- /* Remainder is literal data */
memcpy(&dest[(*packet_length)], contents, contents_length);
(*packet_length) += contents_length;
out:
if (rc)
(*packet_length) = 0;
+ else
+ (*remaining_bytes) -= (*packet_length);
return rc;
}

--
1.4.4.4
-
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