openldap-bugs

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20960 discussions

Re: (ITS#8477) OpenLDAP.org has a broken TLS certificate
by hyc＠symas.com 10 Aug '16

10 Aug '16

demiobenour(a)gmail.com wrote: > Full_Name: Demi Obenour > Version: N/A > OS: N/A > URL: ftp://ftp.openldap.org/incoming/ > Submission from: (NULL) (2601:840:8100:6720:2ae3:47ff:fe02:d99e) > > > OpenLDAP.org has an expired self-signed TLS certificate, This is intentional. > which makes it > impossible to securely access the Git repositories over HTTPS. The repos are only intended to be used via git: and http: anyway. This needs to be > fixed to avoid man-in-the-middle attacks, which would allow arbitrary code > execution on the developer's machine. When I discussed this with Kurt, we decided to leave things as-is. Replacing an expired self-signed cert with a non-expired self-signed cert wouldn't change anything, you still need to set an explicit exception in your client to trust the cert. -- -- Howard Chu CTO, Symas Corp. http://www.symas.com Director, Highland Sun http://highlandsun.com/hyc/ Chief Architect, OpenLDAP http://www.openldap.org/project/

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(ITS#8477) OpenLDAP.org has a broken TLS certificate
by demiobenour＠gmail.com 10 Aug '16

10 Aug '16

Full_Name: Demi Obenour Version: N/A OS: N/A URL: ftp://ftp.openldap.org/incoming/ Submission from: (NULL) (2601:840:8100:6720:2ae3:47ff:fe02:d99e) OpenLDAP.org has an expired self-signed TLS certificate, which makes it impossible to securely access the Git repositories over HTTPS. This needs to be fixed to avoid man-in-the-middle attacks, which would allow arbitrary code execution on the developer's machine.

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Re: (ITS#8475) Feature request: MDB low durability transactions
by bentrask＠comcast.net 10 Aug '16

10 Aug '16

Okay, thanks for taking the time to discuss, and of course for all your work on MDB! Ben On 08/10/2016 08:50 AM, Hallvard Breien Furuseth wrote: > Nope, you're as confused as I was originally:-) LDMB doesn't know or > care when a page was written. A page can be reused when the snapshot > which _freed_ it is known to be durable and there are no older readers. > (We could improve that by tracking page history better. Maybe later.) > > "Known to be durable" = sync datapages, write metapage, sync metapage, > note that the metapage was synced. (We implicitly note that when > writing next txn's metapage, since we must have synced first.) From > a data safety point of view, txns which do all that are the real txns. > Anything else is fluff, like no-sync txns if we implement them. Their > metapages must go somewhere they *won't* be confused with durable ones. > > Think of such a fluffy commit as saving an intermediate stage of a > real txn. That's irrelevant to a later write-txn wanting to not touch > the last two durable snapshots. It's only relevant vs. oldest reader. > > So. 3rd metapage and variants - I've tried and Howard pointed out > the flaws, Howard tried and I said here we go again. We do not need > another round, but it's just as well to have it summarized here. > > (This discussion ignores MDB_NOSYNC and partly MDB_NOLOCK - if the > user enables either, it's his responsibility to compensate.) >

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Re: (ITS#8475) Feature request: MDB low durability transactions
by h.b.furuseth＠usit.uio.no 10 Aug '16

10 Aug '16

Nope, you're as confused as I was originally:-) LDMB doesn't know or care when a page was written. A page can be reused when the snapshot which _freed_ it is known to be durable and there are no older readers. (We could improve that by tracking page history better. Maybe later.) "Known to be durable" = sync datapages, write metapage, sync metapage, note that the metapage was synced. (We implicitly note that when writing next txn's metapage, since we must have synced first.) From a data safety point of view, txns which do all that are the real txns. Anything else is fluff, like no-sync txns if we implement them. Their metapages must go somewhere they *won't* be confused with durable ones. Think of such a fluffy commit as saving an intermediate stage of a real txn. That's irrelevant to a later write-txn wanting to not touch the last two durable snapshots. It's only relevant vs. oldest reader. So. 3rd metapage and variants - I've tried and Howard pointed out the flaws, Howard tried and I said here we go again. We do not need another round, but it's just as well to have it summarized here. (This discussion ignores MDB_NOSYNC and partly MDB_NOLOCK - if the user enables either, it's his responsibility to compensate.) -- Hallvard

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Re: (ITS#8474) Securely Erase BerElement Buffer After Use
by alcronin＠cisco.com 09 Aug '16

09 Aug '16

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Re: (ITS#8474) Securely Erase BerElement Buffer After Use
by hyc＠symas.com 08 Aug '16

08 Aug '16

Alan Cronin (alcronin) wrote: > Hi Howard, > > I can change the code so that it overwrites the memory from ldap_free_request_int() instead. This will cover the execution using a bind (both synchronous and asynchronous). Is there any other places where the password would be in the buffer that needs to be cleared? The reason for inserting it into ber_free_buf() was that it would clear all places. I see, you're looking at the client side. What about the slapd side? There are 2 main places where passwords occur - Bind, and PasswordModify exop. They might also occur in Add and Modify requests. Add is not so unusual, Modify should not happen since clients should use PasswordModify instead. > Some compilers will optimize calls to memset() so that only the first character will be changed. Leaving the rest of the string intact. That's clearly a compiler bug then. If you have examples of such situations you should report that to the respective compiler maintainers. > This is why the iteration is in place. > > Thanks for looking into this patch. > > Alan > > On 05/08/2016, 19:50, "Howard Chu" <hyc(a)symas.com> wrote: > > alcronin(a)cisco.com wrote: > > Full_Name: Alan Cronin > > Version: 2.4.44 > > OS: Windows 8.1 > > URL: https://dl.dropboxusercontent.com/u/82343475/SecurelyEraseBuffer.diff > > Submission from: (NULL) (2001:420:4041:2003:f942:59a5:545f:b334) > > > > > > The following patch is a modification to the OpenLDAP BerElement buffer. The > > buffer can be used to contain the LDAP request including the password for > > authentication. While this is free'd when it is no longer needed, the contents > > of the buffer is not overwritten from memory. This can lead to someone reading > > the memory of the process and determining what the password is. The change > > included in this patch will iterate over the memory and clear it. This will > > remove any trace of the password by the time execution is handed back to the > > caller. > > Why would you insert a performance pessimization into every use of the LBER > library, rather than just erasing the password from a Bind request? > > Why would you use an explicitly coded loop setting one character at a time, > instead of using libc's memset() which has probably been well optimized? > > > The attached patch file is derived from OpenLDAP Software. All of the > > modifications to OpenLDAP Software represented in the following patch(es) were > > developed by Alan Cronin alcronin(a)cisco.com. I have not assigned rights and/or > > interest in this work to any party. > > The attached file is derived from OpenLDAP Software. All of the modifications to > > OpenLDAP Software represented in the following patch(es) were developed by Cisco > > Systems, Inc.. Cisco Systems, Inc. has not assigned rights and/or interest in > > this work to any party. I, Alan Cronin am authorized by Cisco Systems, Inc., my > > employer, to release this work under the following terms. > > Cisco Systems, Inc. hereby place the following modifications to OpenLDAP > > Software (and only these modifications) into the public domain. Hence, these > > modifications may be freely used and/or redistributed for any purpose with or > > without attribution and/or other notice. > > > > > > > -- > -- Howard Chu > CTO, Symas Corp. http://www.symas.com > Director, Highland Sun http://highlandsun.com/hyc/ > Chief Architect, OpenLDAP http://www.openldap.org/project/ > > -- -- Howard Chu CTO, Symas Corp. http://www.symas.com Director, Highland Sun http://highlandsun.com/hyc/ Chief Architect, OpenLDAP http://www.openldap.org/project/

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Re: (ITS#8475) Feature request: MDB low durability transactions
by bentrask＠comcast.net 08 Aug '16

08 Aug '16

On 08/08/2016 05:41 AM, Hallvard Breien Furuseth wrote: > A transaction must not reuse data pages visible in the last snapshot > known to be durable, since that's how far back LDMB may need to revert > after abnormal termination. Like a crash after MDB_NOMETASYNC may do. > > Sync the data pages from a txn, write the metapage, eventually sync > that metapage, wait out any older read-only transactions, and *then* > you can reuse the pages the txn freed. Not before. So when you don't > sync, or a read-only txn won't die, LMDB degenerates to append-only. > > ...except if you sync the metapage and exit, next LMDB run may not > know you synced it and must assume the metapage isn't yet durable. > So it might not reuse pages visible to the _previous_ durable > metapage, until it syncs. I'm rather losing track at this point, > but I think it may mean twice as may not-yet-usable pages as one > might expect. Concretely: say the current write transaction is number 10, and a long-lived reader is on number 7. Currently, MDB will be unable to reuse any pages used in transactions 7+ until the reader ends. Now say a 3rd, durable root is added. For the sake of argument, no checksums are used and in the event of a crash, only the last durable state is recovered. Say the durable transaction is number 2. Pages used in transaction 2 need to be preserved, obviously. 7+ still need to be preserved for the slow reader. But pages from transactions 3-6 can be reused. Note that the last durable transaction is controlled purely by the single writer, so tracking it is actually easier than tracking which readers are where. If a crash happens before a durable root is fully synced, then there should be a second, older durable root that hasn't been reused yet. In that case MDB recovers the way it does currently. Does this make sense? Thanks for bearing with me.

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Re: (ITS#8474) Securely Erase BerElement Buffer After Use
by alcronin＠cisco.com 08 Aug '16

08 Aug '16

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Re: (ITS#8475) Feature request: MDB low durability transactions
by h.b.furuseth＠usit.uio.no 08 Aug '16

08 Aug '16

On 08/08/16 03:51, bentrask(a)comcast.net wrote: > The idea was that the two "floating" roots would reuse pages the way MDB > does now. The 3rd durable root would have its pages preserved > separately. I can see why this would cause up to a ~2X storage increase > as the two sets diverged, but I don't see why it would need to grow > unbounded. Apologies for this stupid question. A transaction must not reuse data pages visible in the last snapshot known to be durable, since that's how far back LDMB may need to revert after abnormal termination. Like a crash after MDB_NOMETASYNC may do. Sync the data pages from a txn, write the metapage, eventually sync that metapage, wait out any older read-only transactions, and *then* you can reuse the pages the txn freed. Not before. So when you don't sync, or a read-only txn won't die, LMDB degenerates to append-only. ...except if you sync the metapage and exit, next LMDB run may not know you synced it and must assume the metapage isn't yet durable. So it might not reuse pages visible to the _previous_ durable metapage, until it syncs. I'm rather losing track at this point, but I think it may mean twice as may not-yet-usable pages as one might expect.

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Re: (ITS#8475) Feature request: MDB low durability transactions
by bentrask＠comcast.net 08 Aug '16

08 Aug '16

On 08/07/2016 09:29 PM, Howard Chu wrote: > Knowing whether or not the root pages are pristine still doesn't tell > you anything about whether the data pages are intact. The only way to > make any of these schemes work is to avoid overwriting/reusing any data > pages for the last N transactions. I.e., reverting to append-only > behavior. So the underlying question (which we have wrestled with > internally for quite some time) which you haven't asked or answered - > how many of these non-durable transactions will you support at any given > time? The idea was that the two "floating" roots would reuse pages the way MDB does now. The 3rd durable root would have its pages preserved separately. I can see why this would cause up to a ~2X storage increase as the two sets diverged, but I don't see why it would need to grow unbounded. Apologies for this stupid question.

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