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CVE-2020-10704: libcli ldap_message: Add search size limits to ldap_decode

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Add search request size limits to ldap_decode calls.

The ldap server uses the smb.conf variable
"ldap max search request size" which defaults to 250Kb.
For cldap the limit is hard coded as 4096.

Credit to OSS-Fuzz

REF: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=20454
BUG: https://bugzilla.samba.org/show_bug.cgi?id=14334

Signed-off-by: Gary Lockyer <gary@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
This commit is contained in:
Gary Lockyer 2020-04-08 08:49:23 +12:00 committed by Gary Lockyer
parent 28ee4acc83
commit 3149ea0a8a
10 changed files with 80 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
docs-xml/smbdotconf/ldap/ldapmaxsearchrequest.xml Normal file
View File

@ -0,0 +1,18 @@
<samba:parameter name="ldap max search request size"
context="G"
type="integer"
xmlns:samba="http://www.samba.org/samba/DTD/samba-doc">
<description>
<para>
This parameter specifies the maximum permitted size (in bytes)
for an LDAP search request.
</para>
<para>
If the request size exceeds this limit the request will be
rejected.
</para>
</description>
<value type="default">256000</value>
<value type="example">4194304</value>
</samba:parameter>

9
lib/fuzzing/fuzz_ldap_decode.c
View File

@ -32,6 +32,12 @@ int LLVMFuzzerTestOneInput(uint8_t *buf, size_t len)
TALLOC_CTX *mem_ctx = talloc_init(__FUNCTION__);
struct asn1_data *asn1;
struct ldap_message *ldap_msg;
struct ldap_request_limits limits = {
/*
* The default size is currently 256000 bytes
*/
.max_search_size = 256000
};
NTSTATUS status;
/*
@ -50,7 +56,8 @@ int LLVMFuzzerTestOneInput(uint8_t *buf, size_t len)
goto out;
}
status = ldap_decode(asn1, samba_ldap_control_handlers(), ldap_msg);
status = ldap_decode(
asn1, &limits, samba_ldap_control_handlers(), ldap_msg);
out:
talloc_free(mem_ctx);

2
lib/param/loadparm.c
View File

@ -3060,6 +3060,8 @@ struct loadparm_context *loadparm_init(TALLOC_CTX *mem_ctx)
lp_ctx, "ldap max anonymous request size", "256000");
lpcfg_do_global_parameter(
lp_ctx, "ldap max authenticated request size", "16777216");
lpcfg_do_global_parameter(
lp_ctx, "ldap max search request size", "256000");
for (i = 0; parm_table[i].label; i++) {
if (!(lp_ctx->flags[i] & FLAG_CMDLINE)) {

18
libcli/cldap/cldap.c
View File

@ -111,6 +111,11 @@ struct cldap_search_state {
struct tevent_req *req;
};
/*
* For CLDAP we limit the maximum search request size to 4kb
*/
#define MAX_SEARCH_REQUEST 4096
static int cldap_socket_destructor(struct cldap_socket *c)
{
while (c->searches.list) {
@ -228,6 +233,9 @@ static bool cldap_socket_recv_dgram(struct cldap_socket *c,
void *p;
struct cldap_search_state *search;
NTSTATUS status;
struct ldap_request_limits limits = {
.max_search_size = MAX_SEARCH_REQUEST
};
if (in->recv_errno != 0) {
goto error;
@ -246,7 +254,7 @@ static bool cldap_socket_recv_dgram(struct cldap_socket *c,
}
/* this initial decode is used to find the message id */
status = ldap_decode(asn1, NULL, in->ldap_msg);
status = ldap_decode(asn1, &limits, NULL, in->ldap_msg);
if (!NT_STATUS_IS_OK(status)) {
goto nterror;
}
@ -774,6 +782,9 @@ NTSTATUS cldap_search_recv(struct tevent_req *req,
struct cldap_search_state);
struct ldap_message *ldap_msg;
NTSTATUS status;
struct ldap_request_limits limits = {
.max_search_size = MAX_SEARCH_REQUEST
};
if (tevent_req_is_nterror(req, &status)) {
goto failed;
@ -784,7 +795,7 @@ NTSTATUS cldap_search_recv(struct tevent_req *req,
goto nomem;
}
status = ldap_decode(state->response.asn1, NULL, ldap_msg);
status = ldap_decode(state->response.asn1, &limits, NULL, ldap_msg);
if (!NT_STATUS_IS_OK(status)) {
goto failed;
}
@ -800,7 +811,8 @@ NTSTATUS cldap_search_recv(struct tevent_req *req,
*io->out.response = ldap_msg->r.SearchResultEntry;
/* decode the 2nd part */
status = ldap_decode(state->response.asn1, NULL, ldap_msg);
status = ldap_decode(
state->response.asn1, &limits, NULL, ldap_msg);
if (!NT_STATUS_IS_OK(status)) {
goto failed;
}

1
libcli/ldap/ldap_message.c
View File

@ -1162,6 +1162,7 @@ static bool ldap_decode_attribs(TALLOC_CTX *mem_ctx, struct asn1_data *data,
/* This routine returns LDAP status codes */
_PUBLIC_ NTSTATUS ldap_decode(struct asn1_data *data,
const struct ldap_request_limits *limits,
const struct ldap_control_handler *control_handlers,
struct ldap_message *msg)
{

5
libcli/ldap/ldap_message.h
View File

@ -213,10 +213,15 @@ struct ldap_control_handler {
bool (*encode)(void *mem_ctx, void *in, DATA_BLOB *out);
};
struct ldap_request_limits {
unsigned max_search_size;
};
struct asn1_data;
struct ldap_message *new_ldap_message(TALLOC_CTX *mem_ctx);
NTSTATUS ldap_decode(struct asn1_data *data,
const struct ldap_request_limits *limits,
const struct ldap_control_handler *control_handlers,
struct ldap_message *msg);
bool ldap_encode(struct ldap_message *msg,

24
libcli/ldap/tests/ldap_message_test.c
View File

@ -117,6 +117,9 @@ static void test_empty_input(void **state)
NTSTATUS status;
uint8_t buf[0];
size_t len = 0;
struct ldap_request_limits limits = {
.max_search_size = 256000,
};
asn1 = asn1_init(test_ctx, ASN1_MAX_TREE_DEPTH);
@ -127,7 +130,8 @@ static void test_empty_input(void **state)
ldap_msg = talloc(test_ctx, struct ldap_message);
assert_non_null(ldap_msg);
status = ldap_decode(asn1, samba_ldap_control_handlers(), ldap_msg);
status = ldap_decode(
asn1, &limits, samba_ldap_control_handlers(), ldap_msg);
assert_ldap_status_equal(LDAP_PROTOCOL_ERROR, status);
}
@ -149,6 +153,9 @@ static void test_recursion_depth_large(void **state)
uint8_t *buffer = NULL;
const size_t BUFF_SIZE = 1048576;
size_t len;
struct ldap_request_limits limits = {
.max_search_size = 256000,
};
/*
@ -169,7 +176,8 @@ static void test_recursion_depth_large(void **state)
ldap_msg = talloc(test_ctx, struct ldap_message);
assert_non_null(ldap_msg);
status = ldap_decode(asn1, samba_ldap_control_handlers(), ldap_msg);
status = ldap_decode(
asn1, &limits, samba_ldap_control_handlers(), ldap_msg);
assert_ldap_status_equal(LDAP_PROTOCOL_ERROR, status);
}
@ -189,6 +197,9 @@ static void test_recursion_depth_equals_max(void **state)
uint8_t *buffer = NULL;
const size_t BUFF_SIZE = 1048576;
size_t len;
struct ldap_request_limits limits = {
.max_search_size = 256000,
};
buffer = talloc_zero_array(test_ctx, uint8_t, BUFF_SIZE);
@ -205,7 +216,8 @@ static void test_recursion_depth_equals_max(void **state)
ldap_msg = talloc(test_ctx, struct ldap_message);
assert_non_null(ldap_msg);
status = ldap_decode(asn1, samba_ldap_control_handlers(), ldap_msg);
status = ldap_decode(
asn1, &limits, samba_ldap_control_handlers(), ldap_msg);
assert_true(NT_STATUS_IS_OK(status));
}
@ -225,6 +237,9 @@ static void test_recursion_depth_greater_than_max(void **state)
uint8_t *buffer = NULL;
const size_t BUFF_SIZE = 1048576;
size_t len;
struct ldap_request_limits limits = {
.max_search_size = 256000,
};
buffer = talloc_zero_array(test_ctx, uint8_t, BUFF_SIZE);
@ -241,7 +256,8 @@ static void test_recursion_depth_greater_than_max(void **state)
ldap_msg = talloc(test_ctx, struct ldap_message);
assert_non_null(ldap_msg);
status = ldap_decode(asn1, samba_ldap_control_handlers(), ldap_msg);
status = ldap_decode(
asn1, &limits, samba_ldap_control_handlers(), ldap_msg);
assert_ldap_status_equal(LDAP_PROTOCOL_ERROR, status);
}

1
source3/param/loadparm.c
View File

@ -958,6 +958,7 @@ static void init_globals(struct loadparm_context *lp_ctx, bool reinit_globals)
Globals.ldap_max_anonymous_request_size = 256000;
Globals.ldap_max_authenticated_request_size = 16777216;
Globals.ldap_max_search_request_size = 256000;
/* Now put back the settings that were set with lp_set_cmdline() */
apply_lp_set_cmdline();

8
source4/ldap_server/ldap_server.c
View File

@ -538,6 +538,7 @@ static void ldapsrv_call_read_done(struct tevent_req *subreq)
struct asn1_data *asn1;
DATA_BLOB blob;
int ret = LDAP_SUCCESS;
struct ldap_request_limits limits = {0};
conn->sockets.read_req = NULL;
@ -593,7 +594,12 @@ static void ldapsrv_call_read_done(struct tevent_req *subreq)
return;
}
status = ldap_decode(asn1, samba_ldap_control_handlers(),
limits.max_search_size =
lpcfg_ldap_max_search_request_size(conn->lp_ctx);
status = ldap_decode(
asn1,
&limits,
samba_ldap_control_handlers(),
call->request);
if (!NT_STATUS_IS_OK(status)) {
ldapsrv_terminate_connection(conn, nt_errstr(status));

3
source4/libcli/ldap/ldap_client.c
View File

@ -277,6 +277,7 @@ static void ldap_connection_recv_done(struct tevent_req *subreq)
struct ldap_message *msg;
struct asn1_data *asn1;
DATA_BLOB blob;
struct ldap_request_limits limits = {0};
msg = talloc_zero(conn, struct ldap_message);
if (msg == NULL) {
@ -306,7 +307,7 @@ static void ldap_connection_recv_done(struct tevent_req *subreq)
asn1_load_nocopy(asn1, blob.data, blob.length);
status = ldap_decode(asn1, samba_ldap_control_handlers(), msg);
status = ldap_decode(asn1, &limits, samba_ldap_control_handlers(), msg);
asn1_free(asn1);
if (!NT_STATUS_IS_OK(status)) {
TALLOC_FREE(msg);