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Subject[PATCH 6/8] eCryptfs: Fix Tag 11 parsing code
Fix up the Tag 11 parsing code to handle size limits and boundaries
more explicitly. Pay attention to *8* bytes for the key identifier
(literal data), no more, no less.

Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
---
fs/ecryptfs/keystore.c | 76 +++++++++++++++++-------------------------------
1 files changed, 27 insertions(+), 49 deletions(-)

diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
index 4caa45d..8c695e3 100644
--- a/fs/ecryptfs/keystore.c
+++ b/fs/ecryptfs/keystore.c
@@ -803,82 +803,60 @@ parse_tag_11_packet(unsigned char *data, unsigned char *contents,

(*packet_size) = 0;
(*tag_11_contents_size) = 0;
-
- /* check that:
- * one byte for the Tag 11 ID flag
- * two bytes for the Tag 11 length
- * do not exceed the maximum_packet_size
+ /* This format is inspired by OpenPGP; see RFC 2440
+ * packet tag 11
+ *
+ * Tag 11 identifier (1 byte)
+ * Max Tag 11 packet size (max 3 bytes)
+ * Binary format specifier (1 byte)
+ * Filename length (1 byte)
+ * Filename ("_CONSOLE") (8 bytes)
+ * Modification date (4 bytes)
+ * Literal data (arbitrary)
+ *
+ * We need at least 16 bytes of data for the packet to even be
+ * valid.
*/
- if (unlikely((*packet_size) + 3 > max_packet_size)) {
- ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
+ if (max_packet_size < 16) {
+ printk(KERN_ERR "Maximum packet size too small\n");
rc = -EINVAL;
goto out;
}
-
- /* check for Tag 11 identifyer - one byte */
if (data[(*packet_size)++] != ECRYPTFS_TAG_11_PACKET_TYPE) {
- ecryptfs_printk(KERN_WARNING,
- "Invalid tag 11 packet format\n");
+ printk(KERN_WARNING "Invalid tag 11 packet format\n");
rc = -EINVAL;
goto out;
}
-
- /* get Tag 11 content length - one or two bytes */
- rc = parse_packet_length(&data[(*packet_size)], &body_size,
- &length_size);
- if (rc) {
- ecryptfs_printk(KERN_WARNING,
- "Invalid tag 11 packet format\n");
+ if ((rc = parse_packet_length(&data[(*packet_size)], &body_size,
+ &length_size))) {
+ printk(KERN_WARNING "Invalid tag 11 packet format\n");
goto out;
}
- (*packet_size) += length_size;
-
- if (body_size < 13) {
- ecryptfs_printk(KERN_WARNING, "Invalid body size ([%d])\n",
- body_size);
+ if (body_size < 14) {
+ printk(KERN_WARNING "Invalid body size ([%d])\n", body_size);
rc = -EINVAL;
goto out;
}
- /* We have 13 bytes of surrounding packet values */
- (*tag_11_contents_size) = (body_size - 13);
-
- /* now we know the length of the remainting Tag 11 packet size:
- * 14 fix bytes for: special flag one, special flag two,
- * 12 skipped bytes
- * body_size bytes minus the stuff above is the Tag 11 content
- */
- /* FIXME why is the body size one byte smaller than the actual
- * size of the body?
- * this seems to be an error here as well as in
- * write_tag_11_packet() */
+ (*packet_size) += length_size;
+ (*tag_11_contents_size) = (body_size - 14);
if (unlikely((*packet_size) + body_size + 1 > max_packet_size)) {
- ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
+ printk(KERN_ERR "Packet size exceeds max\n");
rc = -EINVAL;
goto out;
}
-
- /* special flag one - one byte */
if (data[(*packet_size)++] != 0x62) {
- ecryptfs_printk(KERN_WARNING, "Unrecognizable packet\n");
+ printk(KERN_WARNING "Unrecognizable packet\n");
rc = -EINVAL;
goto out;
}
-
- /* special flag two - one byte */
if (data[(*packet_size)++] != 0x08) {
- ecryptfs_printk(KERN_WARNING, "Unrecognizable packet\n");
+ printk(KERN_WARNING "Unrecognizable packet\n");
rc = -EINVAL;
goto out;
}
-
- /* skip the next 12 bytes */
- (*packet_size) += 12; /* We don't care about the filename or
- * the timestamp */
-
- /* get the Tag 11 contents - tag_11_contents_size bytes */
+ (*packet_size) += 12; /* Ignore filename and modification date */
memcpy(contents, &data[(*packet_size)], (*tag_11_contents_size));
(*packet_size) += (*tag_11_contents_size);
-
out:
if (rc) {
(*packet_size) = 0;
--
1.4.4.4
-
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