drsblobs.idl: supplementalCredentialsSubBlob make it possible to parse strange blobs

Windows omits the uint16 num_packages field when the packages array is empty.
This happens if the UF_SMARTCARD_REQUIRED flag is set for an account.

A user was created with a password and then userAccountControl was changed to
UF_NORMAL_ACCOUNT|UF_SMARTCARD_REQUIRED. In that case I'm getting
(as the whole supplementalCredentialsBlob):

[0000] 00 00 00 00 62 00 00 00   00 00 00 00 20 00 20 00   ....b... .... . .
[0010] 20 00 20 00 20 00 20 00   20 00 20 00 20 00 20 00    . . . .  . . . .
[0020] 20 00 20 00 20 00 20 00   20 00 20 00 20 00 20 00    . . . .  . . . .
[0030] 20 00 20 00 20 00 20 00   20 00 20 00 20 00 20 00    . . . .  . . . .
[0040] 20 00 20 00 20 00 20 00   20 00 20 00 20 00 20 00    . . . .  . . . .
[0050] 20 00 20 00 20 00 20 00   20 00 20 00 20 00 20 00    . . . .  . . . .
[0060] 20 00 20 00 20 00 20 00   20 00 20 00 50 00 30       . . . .  . .P.0

I've also got cases (where I created an account with
UF_NORMAL_ACCOUNT|UF_ACCOUNTDISABLE|UF_SMARTCARD_REQUIRED
in the LDAP add) with the following strange blobs:

One time:
[0000] 00 00 00 00 00 00 00 00   00 00 00 00 00
and once:
[0000] 00 00 00 00 00 00 00 00   00 00 00 00 53

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11441

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Günther Deschner <gd@samba.org>

1 files changed, 26 insertions, 4 deletions

diff --git a/librpc/ndr/ndr_drsblobs.c b/librpc/ndr/ndr_drsblobs.c
index db842d330ad..b0d3f50b4a4 100644
--- a/librpc/ndr/ndr_drsblobs.c
+++ b/librpc/ndr/ndr_drsblobs.c
@@ -155,10 +155,16 @@ _PUBLIC_ enum ndr_err_code ndr_push_supplementalCredentialsSubBlob(struct ndr_pu
 	uint32_t cntr_packages_0;
 	NDR_PUSH_CHECK_FLAGS(ndr, ndr_flags);
 	if (ndr_flags & NDR_SCALARS) {
+		if ((r->signature != SUPPLEMENTAL_CREDENTIALS_SIGNATURE)
+		    && (r->num_packages == 0)) {
+			return NDR_ERR_SUCCESS;
+		}
 		NDR_CHECK(ndr_push_align(ndr, 3));
 		NDR_CHECK(ndr_push_charset(ndr, NDR_SCALARS, SUPPLEMENTAL_CREDENTIALS_PREFIX, 0x30, sizeof(uint16_t), CH_UTF16));
 		NDR_CHECK(ndr_push_supplementalCredentialsSignature(ndr, NDR_SCALARS, SUPPLEMENTAL_CREDENTIALS_SIGNATURE));
-		NDR_CHECK(ndr_push_uint16(ndr, NDR_SCALARS, r->num_packages));
+		if (r->num_packages > 0) {
+			NDR_CHECK(ndr_push_uint16(ndr, NDR_SCALARS, r->num_packages));
+		}
 		for (cntr_packages_0 = 0; cntr_packages_0 < (r->num_packages); cntr_packages_0++) {
 			NDR_CHECK(ndr_push_supplementalCredentialsPackage(ndr, NDR_SCALARS, &r->packages[cntr_packages_0]));
 		}
@@ -177,11 +183,27 @@ _PUBLIC_ enum ndr_err_code ndr_pull_supplementalCredentialsSubBlob(struct ndr_pu
 	TALLOC_CTX *_mem_save_packages_0 = NULL;
 	NDR_PULL_CHECK_FLAGS(ndr, ndr_flags);
 	if (ndr_flags & NDR_SCALARS) {
+		uint32_t remaining = 0;
 		NDR_CHECK(ndr_pull_align(ndr, 3));
 		size_prefix_0 = 0x30;
-		NDR_CHECK(ndr_pull_charset(ndr, NDR_SCALARS, &r->prefix, size_prefix_0, sizeof(uint16_t), CH_UTF16));
-		NDR_CHECK(ndr_pull_supplementalCredentialsSignature(ndr, NDR_SCALARS, &r->signature));
-		NDR_CHECK(ndr_pull_uint16(ndr, NDR_SCALARS, &r->num_packages));
+		remaining = ndr->data_size - ndr->offset;
+		if (remaining >= size_prefix_0) {
+			NDR_CHECK(ndr_pull_charset(ndr, NDR_SCALARS, &r->prefix, size_prefix_0, sizeof(uint16_t), CH_UTF16));
+		} else {
+			r->prefix = NULL;
+		}
+		remaining = ndr->data_size - ndr->offset;
+		if (remaining >= 2) {
+			NDR_CHECK(ndr_pull_supplementalCredentialsSignature(ndr, NDR_SCALARS, &r->signature));
+		} else {
+			r->signature = 0;
+		}
+		remaining = ndr->data_size - ndr->offset;
+		if (remaining > 0) {
+			NDR_CHECK(ndr_pull_uint16(ndr, NDR_SCALARS, &r->num_packages));
+		} else {
+			r->num_packages = 0;
+		}
 		size_packages_0 = r->num_packages;
 		NDR_PULL_ALLOC_N(ndr, r->packages, size_packages_0);
 		_mem_save_packages_0 = NDR_PULL_GET_MEM_CTX(ndr);