[PATCH] Fix undefined behavior in NDR

[Andreas Schneider]

Hi,

attached is a patch to fix undefined behavior in NDR.

Pipeline: https://gitlab.com/samba-team/devel/samba/pipelines/39044749

Please review and comment. Push if OK.


Thanks,


	Andreas


-- 
Andreas Schneider                      asn at samba.org
Samba Team                             www.samba.org
GPG-ID:     8DFF53E18F2ABC8D8F3C92237EE0FC4DCC014E3D
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>From 1dfc0522ee8bf173c6d02625cac7e0a5297b18f6 Mon Sep 17 00:00:00 2001
From: Andreas Schneider <asn at samba.org>
Date: Thu, 22 Nov 2018 15:15:03 +0100
Subject: [PATCH] librpc:ndr: Fix undefined behavior in ndr_basic

librpc/ndr/ndr_basic.c:723:2: runtime error: null pointer passed as
argument 2, which is declared to never be null

The following triggered the undefined behavior:

(gdb) bt
    at librpc/gen_ndr/ndr_drsuapi.c:2318
    fn=0x7ffff6e72983 <ndr_push_drsuapi_DsReplicaObjectIdentifier3Binary>) at ../../librpc/ndr/ndr.c:1337
    at ../../source4/dsdb/schema/schema_syntax.c:2136
    drs_str=<optimized out>) at ../../source4/dsdb/schema/tests/schema_syntax.c:122
    already_setup=<optimized out>, restricted=restricted at entry=0x0) at ../../lib/torture/torture.c:442
    at ../../lib/torture/torture.c:507
    suite=0x5555563d9490, matched=0x7fffffffcef7) at ../../source4/torture/smbtorture.c:93
    matched=0x7fffffffcef7) at ../../source4/torture/smbtorture.c:95
    at ../../source4/torture/smbtorture.c:143
(gdb) f 1
1335            NDR_CHECK(ndr_push_bytes(ndr, blob.data, blob.length));
(gdb) p blob
$2 = {data = 0x0, length = 0}

Signed-off-by: Andreas Schneider <asn at samba.org>
---
 librpc/ndr/ndr_basic.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/librpc/ndr/ndr_basic.c b/librpc/ndr/ndr_basic.c
index c874f340388..b488c7c22d9 100644
--- a/librpc/ndr/ndr_basic.c
+++ b/librpc/ndr/ndr_basic.c
@@ -719,6 +719,12 @@ _PUBLIC_ enum ndr_err_code ndr_pull_trailer_align(struct ndr_pull *ndr, size_t s
 */
 _PUBLIC_ enum ndr_err_code ndr_push_bytes(struct ndr_push *ndr, const uint8_t *data, uint32_t n)
 {
+	if (n == 0) {
+		return NDR_ERR_SUCCESS;
+	}
+	if (data == NULL) {
+		return NDR_ERR_INVALID_POINTER;
+	}
 	NDR_PUSH_NEED_BYTES(ndr, n);
 	memcpy(ndr->data + ndr->offset, data, n);
 	ndr->offset += n;
@@ -1329,6 +1335,10 @@ _PUBLIC_ enum ndr_err_code ndr_push_DATA_BLOB(struct ndr_push *ndr, int ndr_flag
 	} else {
 		NDR_CHECK(ndr_push_uint3264(ndr, NDR_SCALARS, blob.length));
 	}
+	if (blob.length == 0) {
+		return NDR_ERR_SUCCESS;
+	}
+
 	NDR_CHECK(ndr_push_bytes(ndr, blob.data, blob.length));
 	return NDR_ERR_SUCCESS;
 }
-- 
2.19.2