136625 - nsslowcert_DecodeDERCertificate failure causes pk11_searchCertsAndTrust to deference a null 'cert' pointer

Status: RESOLVED FIXED

(NSS :: Libraries, defect, P1)

Description

[Wan-Teh Chang]

This crash was reported to us recently.

=>[1] pk11_mkHandle(slot = 0xbd128, dbKey = 0x60, class = 1879048192U), line 
2495 in "pkcs11u.c"
  [2] pk11_searchCertsAndTrust(slot = 0xbd128, derCert = 0xfe1615e0, name = 
0xfe1615c8, derSubject = 0xfe1615d4, issuerSN = 0xfe161580, email = 0xfe1615bc, 
classFlags = 1U, handles = 0x340870, pTemplate = 0xfe1617c8, ulCount = 3), line 
3800 in "pkcs11.c"
  [3] pk11_searchTokenList(slot = 0xbd128, search = 0x340870, pTemplate = 
0xfe1617c8, ulCount = 3, tokenOnly = 0xfe161668, isLoggedIn = 0), line 4041 in 
"pkcs11.c"
  [4] NSC_FindObjectsInit(hSession = 16777217U, pTemplate = 0xfe1617c8, ulCount 
= 3U), line 4098 in "pkcs11.c"
  [5] traverse_objects_by_template(tok = 0x103648, sessionOpt = (nil), 
obj_template = 0xfe1617c8, otsize = 3U, callback = 0xfe6a3da0 = 
&`libnss3.so`devobject.c`retrieve_cert(struct NSSTokenStr *t, struct 
nssSessionStr *session, CK_OBJECT_HANDLE h, void *arg), arg = 0xfe161860), line 
223 in "devobject.c"
  [6] nssToken_TraverseCertificatesBySubject(token = 0x103648, sessionOpt = 
(nil), subject = 0xfe161910, search = 0xfe161860), line 643 in "devobject.c"
  [7] NSSTrustDomain_FindBestCertificateBySubject(td = 0x1034b8, subject = 
0xfe161910, timeOpt = (nil), usage = 0xfe161904, policiesOpt = (nil)), line 638 
in "trustdomain.c"
  [8] CERT_FindCertByName(handle = 0x1034b8, name = 0x1342c4), line 337 in 
"stanpcertdb.c"

(Note that this stack is similar to the stack in
http://bugzilla.mozilla.org/show_bug.cgi?id=132548#c1.)

This crash is caused by defererencing a null pointer.
Here is what I think causes the crash:
  In pk11_searchCertsAndTrust(), the local variable
  'cert' is set to NULL because some other function
  failed earlier.  Then we pass &cert->certKey as the
  'dbKey' argument to pk11_mkHandle.

(If 'cert' is NULL, &cert->certKey is 0x60, which is
the value of 'dbKey' in the stack trace.)

I've determined that this is caused by
nsslowcert_TraversePermCertsForNickname,
nsslowcert_TraversePermCertsForSubject, or
nsslowcert_TraversePermCerts passing a null 'cert'
argument to the callback function pk11_cert_collect.
pk11_cert_collect would store the null 'cert' in the
certData.certs array.

It would be easy to modify pk11_cert_collect so that
it does not store a null 'cert' in the certData.certs
array, but we might need to find out why the
nsslowcert_TraversePermCerts* functions get a null
'cert' in the first place.  Looking at the code, I
found it's because nsslowcert_FindCertByKey(pcertdb.c:2874)
or DecodeACert (pcertdb.c:3857 and 4111) or eventually
nsslowcert_DecodeDERCertificate (pcertdb.c:3799) failed.

Comment 1

[Wan-Teh Chang]

Attachment: Patch to prevent pk11_cert_collect from storing NULL in certData.certs

This patch may prevent the crash but I am wondering if
we should fix the underlying problem, that is, the
nsslowcert_DecodeDERCertificate failure.

Comment 2

[Robert Relyea]

DER_DecodeCert could fail if the DER cert data isn't valid. This could occur
because the database had been corrupted at some point, or somehow we've injected
an invalid certificate into the database.

Wan-Teh's fix seems resonable to me. We may want to review the code and see
where else a corrupted certificate may cause us problems.

We probably should look at the cert and make sure it's a corruption problem and
not a valid cert that isn't being parsed by our templates.

bob

Comment 3

[Wan-Teh Chang]

Comment on attachment 78551 [details] [diff] [review]
Patch to prevent pk11_cert_collect from storing NULL in certData.certs

Just wanted to note that Bob has reviewed this patch
and I've checked it in on the trunk.

I specifically asked Bob whether pk11_cert_collect
should return SECSuccess if 'cert' is NULL.  I
explained that if pk11_cert_collect returns SECFailure,
nsslowcert_TraversePermCertsForSubject will abort
the cert traversal.  Bob said returning SECSuccess is
correct.

Comment 4

[Kai Engert [:KaiE:]]

We should land this on the branch. Nominating adt1.0.0. I will send mail to drivers.

Comment 5

[Randell Jesup [:jesup] (needinfo me)]

Comment on attachment 78551 [details] [diff] [review]
Patch to prevent pk11_cert_collect from storing NULL in certData.certs

a=[e-mail]

Comment 6

[Jaime Rodriguez, Jr.]

adt1.0.0+ (on ADTs behalf) checkin to 1.0. Pls check this into the trunk and 1.0
branch.

Comment 7

[Wan-Teh Chang]

I checked in the fix on the MOZILLA_1_0_0_BRANCH.

Comment 8

[Kai Engert [:KaiE:]]

Thanks, Wan-Teh. Should we check this in to NSS_CLIENT_TAG, too?

Comment 9

[Jaime Rodriguez, Jr.]

When checking a fix into 1.0, please add fixed1.0.0. Thanks!

Comment 10

[Jaime Rodriguez, Jr.]

Removing adt1.0.0+, as this is fixed on 1.0 branch.

Comment 11

[Wan-Teh Chang]

Changed the QA contact to Bishakha.

Comment 12

[Wan-Teh Chang]

I checked in the fix on the NSS_3_4_BRANCH.

Comment 13

[Wan-Teh Chang]

Set target milestone 3.4.2.

Comment 14

[Wan-Teh Chang]

Marked the bug fixed.