1 files changed, 78 insertions, 0 deletions
diff --git a/fuzzer-kexecdh.c b/fuzzer-kexecdh.c
new file mode 100644
index 0000000..db08c2b
--- /dev/null
+++ b/fuzzer-kexecdh.c
@@ -0,0 +1,78 @@
+#include "fuzz.h"
+#include "session.h"
+#include "fuzz-wrapfd.h"
+#include "debug.h"
+#include "runopts.h"
+#include "algo.h"
+#include "bignum.h"
+
+int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+	static int once = 0;
+	static const struct dropbear_kex *ecdh[3]; /* 256, 384, 521 */
+	static struct key_context* keep_newkeys = NULL;
+	#define NUM_PARAMS 800
+	static struct kex_ecdh_param *ecdh_params[NUM_PARAMS];
+
+	if (!once) {
+		fuzz_common_setup();
+		fuzz_svr_setup();
+
+		/* ses gets zeroed by fuzz_set_input */
+		keep_newkeys = (struct key_context*)m_malloc(sizeof(struct key_context));
+		ecdh[0] = fuzz_get_algo(sshkex, "ecdh-sha2-nistp256");
+		ecdh[1] = fuzz_get_algo(sshkex, "ecdh-sha2-nistp384");
+		ecdh[2] = fuzz_get_algo(sshkex, "ecdh-sha2-nistp521");
+		assert(ecdh[0]);
+		assert(ecdh[1]);
+		assert(ecdh[2]);
+		keep_newkeys->algo_hostkey = DROPBEAR_SIGNKEY_ECDSA_NISTP256;
+		ses.newkeys = keep_newkeys;
+
+		/* Pre-generate parameters */
+		int i;
+		for (i = 0; i < NUM_PARAMS; i++) {
+			ses.newkeys->algo_kex = ecdh[i % 3];
+			ecdh_params[i] = gen_kexecdh_param();
+		}
+
+		once = 1;
+	}
+
+	if (fuzz_set_input(Data, Size) == DROPBEAR_FAILURE) {
+		return 0;
+	}
+
+	m_malloc_set_epoch(1);
+
+	if (setjmp(fuzz.jmp) == 0) {
+		/* Based on recv_msg_kexdh_init()/send_msg_kexdh_reply() 
+		with DROPBEAR_KEX_ECDH */
+		ses.newkeys = keep_newkeys;
+
+		/* random choice of ecdh 256, 384, 521 */
+		unsigned char b = buf_getbyte(fuzz.input);
+		ses.newkeys->algo_kex = ecdh[b % 3];
+
+		/* Choose from the collection of ecdh params */
+		unsigned int e = buf_getint(fuzz.input);
+		struct kex_ecdh_param *ecdh_param = ecdh_params[e % NUM_PARAMS];
+
+		buffer * ecdh_qs = buf_getstringbuf(fuzz.input);
+
+		ses.kexhashbuf = buf_new(4);
+		buf_putint(ses.kexhashbuf, 12345);
+		kexecdh_comb_key(ecdh_param, ecdh_qs, svr_opts.hostkey);
+
+		/* kexhashbuf is freed in kexdh_comb_key */
+		m_free(ses.dh_K);
+		buf_free(ecdh_qs);
+
+		m_malloc_free_epoch(1, 0);
+	} else {
+		m_malloc_free_epoch(1, 1);
+		TRACE(("dropbear_exit longjmped"))
+		/* dropbear_exit jumped here */
+	}
+
+	return 0;
+}