lib/fuzzing: add fuzzer for sddl_parse

Apart from catching crashes in the actual parsing, we abort if the SD
we end up with will not round trip back through SDDL to an identical
SD.

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

2 files changed, 70 insertions, 0 deletions

diff --git a/lib/fuzzing/fuzz_sddl_parse.c b/lib/fuzzing/fuzz_sddl_parse.c
new file mode 100644
index 00000000000..b6c48fb7ca5
--- /dev/null
+++ b/lib/fuzzing/fuzz_sddl_parse.c
@@ -0,0 +1,65 @@
+/*
+  Fuzz sddl decoding and encoding
+  Copyright (C) Catalyst IT 2023
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 3 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "includes.h"
+#include "libcli/security/security.h"
+#include "fuzzing/fuzzing.h"
+
+#define MAX_LENGTH (100 * 1024 - 1)
+static char sddl_string[MAX_LENGTH + 1] = {0};
+static struct dom_sid dom_sid = {0};
+
+int LLVMFuzzerInitialize(int *argc, char ***argv)
+{
+	string_to_sid(&dom_sid,
+		      "S-1-5-21-2470180966-3899876309-2637894779");
+	return 0;
+}
+
+
+int LLVMFuzzerTestOneInput(uint8_t *input, size_t len)
+{
+	TALLOC_CTX *mem_ctx = NULL;
+	struct security_descriptor *sd1 = NULL;
+	struct security_descriptor *sd2 = NULL;
+	char *result = NULL;
+	bool ok;
+
+	if (len > MAX_LENGTH) {
+		return 0;
+	}
+
+	memcpy(sddl_string, input, len);
+	sddl_string[len] = '\0';
+
+	mem_ctx = talloc_new(NULL);
+
+	sd1 = sddl_decode(mem_ctx, sddl_string, &dom_sid);
+	if (sd1 == NULL) {
+		goto end;
+	}
+	result = sddl_encode(mem_ctx, sd1, &dom_sid);
+	sd2 = sddl_decode(mem_ctx, result, &dom_sid);
+	ok = security_descriptor_equal(sd1, sd2);
+	if (!ok) {
+		abort();
+	}
+end:
+	talloc_free(mem_ctx);
+	return 0;
+}
diff --git a/lib/fuzzing/wscript_build b/lib/fuzzing/wscript_build
index ee3cfc14317..187c23c7cb8 100644
--- a/lib/fuzzing/wscript_build
+++ b/lib/fuzzing/wscript_build
@@ -32,6 +32,11 @@ bld.SAMBA_BINARY('fuzz_reg_parse',
                  deps='fuzzing samba3-util smbconf REGFIO afl-fuzz-main',
                  fuzzer=True)
 
+bld.SAMBA_BINARY('fuzz_sddl_parse',
+                 source='fuzz_sddl_parse.c',
+                 deps='fuzzing samba-security  afl-fuzz-main',
+                 fuzzer=True)
+
 bld.SAMBA_BINARY('fuzz_nmblib_parse_packet',
                  source='fuzz_nmblib_parse_packet.c',
                  deps='fuzzing libsmb afl-fuzz-main',