https://bugs.openldap.org/show_bug.cgi?id=9920
Issue ID: 9920
Summary: MDB_PAGE_FULL with master3 (encryption) because there
is no room for the authentication data (MAC)
Product: LMDB
Version: unspecified
Hardware: x86_64
OS: Mac OS
Status: UNCONFIRMED
Keywords: needs_review
Severity: normal
Priority: ---
Component: liblmdb
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Created attachment 915
--> https://bugs.openldap.org/attachment.cgi?id=915&action=edit
proposed patch
Hello,
on master3, using the encryption at rest feature,
I am testing as follow:
- on a new named database, i set the encryption function with
mdb_env_set_encrypt(env, encfunc, &enckey, 32)
- note that I chose to have a size parameter (The size of authentication data
in bytes, if any. Set this to zero for unauthenticated encryption mechanisms.)
of 32 bytes.
- I add 2 entries on the DB, trying to saturate the first page. I chose to add
a key of 33 Bytes and a value of 1977 Bytes, so the size of each node is 2010
Bytes (obviously the 2 keys are different).
- This passes and the DB has just one leaf_pages, no overflow_pages, no
branch_pages, an a depth of 1.
- If I add one byte to the values I insert (starting again from a blank DB),
then , instead of seeing 2 overflow_pages, I get an error : MDB_PAGE_FULL.
- this clearly should not have happened.
- Here is some tracing :
add to leaf page 2 index 0, data size 48 key size 7 [74657374646200]
add to leaf page 3 index 0, data size 1978 key size 33
[000000000000000000000000000000000000000000000000000000000000000000]
add to branch page 5 index 0, data size 0 key size 0 [null]
add to branch page 5 index 1, data size 0 key size 33
[000000000000000000000000000000000000000000000000000000000000000000]
add to leaf page 4 index 0, data size 1978 key size 33
[000000000000000000000000000000000000000000000000000000000000000000]
add to leaf page 4 index 1, data size 1978 key size 33
[020202020202020202020202020202020202020202020202020202020202020202]
not enough room in page 4, got 1 ptrs
upper-lower = 2020 - 2 = 2016
node size = 2020
Looking at the code, I understand that there is a problem at line 9005 :
} else if (node_size + data->mv_size > mc->mc_txn->mt_env->me_nodemax) {
where me_nodemax is incorrect, as it is not taking into account that some bytes
will be needed for the MAC authentication code, which size is in
env->me_esumsize.
me_nodemax is calculated at line 5349:
env->me_nodemax = (((env->me_psize - PAGEHDRSZ ) / MDB_MINKEYS) & -2)
- sizeof(indx_t);
So I substract me_esumsize with a "- env->me_esumsize" here:
env->me_nodemax = (((env->me_psize - PAGEHDRSZ - env->me_esumsize) /
MDB_MINKEYS) & -2)
- sizeof(indx_t);
I also substract it from me_maxfree_1pg in the line above, and in pmax in line
10435.
I do not know if my patch is correct, but it solves the issue.
Maybe there are other places in the code where the me_esumsize should be
substracted from the available size. By example, when calculating the number of
overflow pages in OVPAGES, it does not take into account me_esumsize, but I
think it is ok, because there is only one MAC for the entire set of OV pages,
and there is room for it in the first OV page.
See the attached proposed patch.
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