diff --git a/.hgignore b/.hgignore
new file mode 100644
index 000000000..393823816
--- /dev/null
+++ b/.hgignore
@@ -0,0 +1,2 @@
+.*\.o
+.*~
diff --git a/Makefile.in b/Makefile.in
index 286e25a79..d94f87ba2 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -30,7 +30,7 @@ COMMONOBJS=dbutil.o buffer.o dbhelpers.o \
 		queue.o \
 		atomicio.o compat.o fake-rfc2553.o \
 		ltc_prng.o ecc.o ecdsa.o crypto_desc.o \
-		gensignkey.o gendss.o genrsa.o
+		gensignkey.o gendss.o genrsa.o fuzz-common.o 
 
 SVROBJS=svr-kex.o svr-auth.o sshpty.o \
 		svr-authpasswd.o svr-authpubkey.o svr-authpubkeyoptions.o svr-session.o svr-service.o \
@@ -224,8 +224,27 @@ distclean: clean tidy
 tidy:
 	-rm -f *~ *.gcov */*~
 
-# run this manually for fuzzing. hostkeys.c is checked in.
-hostkeys:
+## Fuzzing targets
+
+# exclude svr-main.o to avoid duplicate main
+svrfuzzobjs=$(subst svr-main.o, ,$(dropbearobjs))
+CLANG=clang
+
+# fuzzers that don't use libfuzzer, just a standalone harness that feeds inputs
+fuzzstandalone: LIBS+=fuzz-harness.o
+fuzzstandalone: fuzz-harness.o fuzzers
+
+# build all the fuzzers. This will require fail to link unless built with
+# make fuzzers LIBS=-lFuzzer.a 
+# or similar - the library provides main().
+fuzzers: fuzzer-preauth
+
+fuzzer-preauth: fuzzer-preauth.o $(HEADERS) $(LIBTOM_DEPS) Makefile $(svrfuzzobjs)
+	$(CC) $@.o $(LDFLAGS) $(svrfuzzobjs) -o $@$(EXEEXT) $(LIBTOM_LIBS) $(LIBS) @CRYPTLIB@
+
+# run this to update hardcoded hostkeys for for fuzzing. 
+# hostkeys.c is checked in to hg.
+fuzz-hostkeys:
 	dropbearkey -t rsa -f keyr
 	dropbearkey -t dss -f keyd
 	dropbearkey -t ecdsa -size 256 -f keye
diff --git a/dbrandom.c b/dbrandom.c
index f4fc94d5b..01974113d 100644
--- a/dbrandom.c
+++ b/dbrandom.c
@@ -28,6 +28,7 @@
 #include "bignum.h"
 #include "dbrandom.h"
 #include "runopts.h"
+#include "fuzz.h"
 
 
 /* this is used to generate unique output from the same hashpool */
@@ -147,7 +148,7 @@ void addrandom(unsigned char * buf, unsigned int len)
 	hash_state hs;
 
 #ifdef DROPBEAR_FUZZ
-	if (opts.fuzz.fuzzing || opts.fuzz.recordf) {
+	if (fuzz.fuzzing || fuzz.recordf) {
 		return;
 	}
 #endif
@@ -165,7 +166,7 @@ void addrandom(unsigned char * buf, unsigned int len)
 static void write_urandom()
 {
 #ifdef DROPBEAR_FUZZ
-	if (opts.fuzz.fuzzing || opts.fuzz.recordf) {
+	if (fuzz.fuzzing || fuzz.recordf) {
 		return;
 	}
 #endif
@@ -203,7 +204,7 @@ void seedrandom() {
 	clock_t clockval;
 
 #ifdef DROPBEAR_FUZZ
-	if (opts.fuzz.fuzzing || opts.fuzz.recordf) {
+	if (fuzz.fuzzing || fuzz.recordf) {
 		seedfuzz();
 		return;
 	}
diff --git a/fuzz-common.c b/fuzz-common.c
new file mode 100644
index 000000000..cc6c12546
--- /dev/null
+++ b/fuzz-common.c
@@ -0,0 +1,78 @@
+#include "includes.h"
+
+#ifdef DROPBEAR_FUZZ
+
+#include "includes.h"
+#include "fuzz.h"
+#include "dbutil.h"
+#include "runopts.h"
+
+struct dropbear_fuzz_options fuzz;
+
+static void load_fixed_hostkeys(void);
+
+static void common_setup_fuzzer(void) {
+    fuzz.fuzzing = 1;
+}
+
+void svr_setup_fuzzer(void) {
+    struct passwd *pw;
+
+    common_setup_fuzzer();
+
+    char *argv[] = { 
+        "-E", 
+    };
+
+    int argc = sizeof(argv) / sizeof(*argv);
+    svr_getopts(argc, argv);
+
+    /* user lookups might be slow, cache it */
+    pw = getpwuid(getuid());
+    dropbear_assert(pw);
+    fuzz.pw_name = m_strdup(pw->pw_name);
+    fuzz.pw_dir = m_strdup(pw->pw_dir);
+    fuzz.pw_shell = m_strdup(pw->pw_shell);
+    fuzz.pw_passwd = m_strdup("!!zzznope");
+
+    load_fixed_hostkeys();
+}
+
+static void load_fixed_hostkeys(void) {
+#include "fuzz-hostkeys.c"   
+
+    buffer *b = buf_new(3000);
+    enum signkey_type type;
+
+    TRACE(("load fixed hostkeys"))
+
+    svr_opts.hostkey = new_sign_key();
+
+    buf_setlen(b, 0);
+    buf_putbytes(b, keyr, keyr_len);
+    buf_setpos(b, 0);
+    type = DROPBEAR_SIGNKEY_RSA;
+    if (buf_get_priv_key(b, svr_opts.hostkey, &type) == DROPBEAR_FAILURE) {
+        dropbear_exit("failed fixed rsa hostkey");
+    }
+
+    buf_setlen(b, 0);
+    buf_putbytes(b, keyd, keyd_len);
+    buf_setpos(b, 0);
+    type = DROPBEAR_SIGNKEY_DSS;
+    if (buf_get_priv_key(b, svr_opts.hostkey, &type) == DROPBEAR_FAILURE) {
+        dropbear_exit("failed fixed dss hostkey");
+    }
+
+    buf_setlen(b, 0);
+    buf_putbytes(b, keye, keye_len);
+    buf_setpos(b, 0);
+    type = DROPBEAR_SIGNKEY_ECDSA_NISTP256;
+    if (buf_get_priv_key(b, svr_opts.hostkey, &type) == DROPBEAR_FAILURE) {
+        dropbear_exit("failed fixed ecdsa hostkey");
+    }
+
+    buf_free(b);
+}
+
+#endif /* DROPBEAR_FUZZ */
diff --git a/fuzz-harness.c b/fuzz-harness.c
new file mode 100644
index 000000000..19b01e368
--- /dev/null
+++ b/fuzz-harness.c
@@ -0,0 +1,8 @@
+#include "includes.h"
+
+extern int LLVMFuzzerTestOneInput(const unsigned char *data, size_t size);
+
+int main(int argc, char ** argv) {
+    LLVMFuzzerTestOneInput("hello", 5);
+    return 0;
+}
diff --git a/hostkeys.c b/fuzz-hostkeys.c
similarity index 100%
rename from hostkeys.c
rename to fuzz-hostkeys.c
diff --git a/fuzz.h b/fuzz.h
new file mode 100644
index 000000000..e7360e33b
--- /dev/null
+++ b/fuzz.h
@@ -0,0 +1,35 @@
+#ifndef DROPBEAR_FUZZ_H
+#define DROPBEAR_FUZZ_H
+
+#include "includes.h"
+#include "buffer.h"
+
+#ifdef DROPBEAR_FUZZ
+
+void svr_setup_fuzzer(void);
+
+struct dropbear_fuzz_options {
+    int fuzzing;
+
+    // to record an unencrypted stream
+    FILE* recordf;
+
+    // fuzzing input
+    buffer input;
+
+    // dropbear_exit() jumps back
+    sigjmp_buf jmp;
+
+    uid_t pw_uid;
+    gid_t pw_gid;
+    char* pw_name;
+    char* pw_dir;
+    char* pw_shell;
+    char* pw_passwd;
+};
+
+extern struct dropbear_fuzz_options fuzz;
+
+#endif
+
+#endif /* DROPBEAR_FUZZ_H */
diff --git a/fuzzer-preauth.c b/fuzzer-preauth.c
new file mode 100644
index 000000000..6a40108dc
--- /dev/null
+++ b/fuzzer-preauth.c
@@ -0,0 +1,31 @@
+#include "fuzz.h"
+#include "dbrandom.h"
+#include "session.h"
+
+static int setup_fuzzer(void) {
+	svr_setup_fuzzer();
+	return 0;
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+	static int once = 0;
+	if (!once) {
+		setup_fuzzer();
+		once = 1;
+	}
+
+	fuzz.input.data = (unsigned char*)Data;
+	fuzz.input.size = Size;
+	fuzz.input.len = Size;
+	fuzz.input.pos = 0;
+
+	seedrandom();
+
+	if (setjmp(fuzz.jmp) == 0) {
+		svr_session(-1, -1);
+	} else {
+		// dropbear_exit jumped here
+	}
+
+	return 0;
+}
diff --git a/packet.c b/packet.c
index f10e63911..235069b03 100644
--- a/packet.c
+++ b/packet.c
@@ -36,6 +36,7 @@
 #include "channel.h"
 #include "netio.h"
 #include "runopts.h"
+#include "fuzz.h"
 
 static int read_packet_init(void);
 static void make_mac(unsigned int seqno, const struct key_context_directional * key_state,
@@ -78,7 +79,7 @@ void write_packet() {
 	calls write_packet() without bothering to test with select() since
 	it's likely to be necessary */
 #ifdef DROPBEAR_FUZZ
-	if (opts.fuzz.fuzzing) {
+	if (fuzz.fuzzing) {
 		// pretend to write one packet at a time
 		// TODO(fuzz): randomise amount written based on the fuzz input
 		written = iov[0].iov_len;
diff --git a/runopts.h b/runopts.h
index 1f51b1606..f7c869da8 100644
--- a/runopts.h
+++ b/runopts.h
@@ -58,29 +58,6 @@ typedef struct runopts {
 	char *mac_list;
 #endif
 
-#ifdef DROPBEAR_FUZZ
-	struct {
-		int fuzzing;
-
-		// to record an unencrypted stream
-		FILE* recordf;
-
-		// fuzzing input
-		buffer *input;
-
-		// dropbear_exit() jumps back
-		sigjmp_buf jmp;
-
-		uid_t pw_uid;
-		gid_t pw_gid;
-		char* pw_name;
-		char* pw_dir;
-		char* pw_shell;
-		char* pw_passwd;
-
-	} fuzz;
-#endif
-
 } runopts;
 
 extern runopts opts;
diff --git a/svr-auth.c b/svr-auth.c
index d00fa7a5a..9156d771d 100644
--- a/svr-auth.c
+++ b/svr-auth.c
@@ -359,7 +359,7 @@ void send_msg_userauth_failure(int partial, int incrfail) {
 		/* We delay for 300ms +- 50ms */
 		delay = 250000 + (delay % 100000);
 #ifndef DROPBEAR_FUZZ
-		if (!opts.fuzz.fuzzing) {
+		if (!fuzz.fuzzing) {
 			usleep(delay);
 		}
 #endif
diff --git a/svr-runopts.c b/svr-runopts.c
index c0b7bf279..295b6537f 100644
--- a/svr-runopts.c
+++ b/svr-runopts.c
@@ -346,19 +346,6 @@ void svr_getopts(int argc, char ** argv) {
 		}
 		opts.idle_timeout_secs = val;
 	}
-
-#ifdef DROPBEAR_FUZZ
-	if (opts.fuzz.fuzzing) {
-		struct passwd *pw;
-		/* user lookups might be slow, cache it */
-		pw = getpwuid(getuid());
-		dropbear_assert(pw);
-		opts.fuzz.pw_name = m_strdup(pw->pw_name);
-		opts.fuzz.pw_dir = m_strdup(pw->pw_dir);
-		opts.fuzz.pw_shell = m_strdup(pw->pw_shell);
-		opts.fuzz.pw_passwd = m_strdup("!!zzznope");
-	}
-#endif
 }
 
 static void addportandaddress(const char* spec) {
@@ -488,57 +475,12 @@ static void addhostkey(const char *keyfile) {
 	svr_opts.num_hostkey_files++;
 }
 
-#ifdef DROPBEAR_FUZZ
-static void load_fixed_hostkeys() {
-#include "hostkeys.c"	
-
-	buffer *b = buf_new(3000);
-	enum signkey_type type;
-
-	TRACE(("load fixed hostkeys"))
-
-	svr_opts.hostkey = new_sign_key();
-
-	buf_setlen(b, 0);
-	buf_putbytes(b, keyr, keyr_len);
-	buf_setpos(b, 0);
-	type = DROPBEAR_SIGNKEY_RSA;
-	if (buf_get_priv_key(b, svr_opts.hostkey, &type) == DROPBEAR_FAILURE) {
-		dropbear_exit("failed fixed rsa hostkey");
-	}
-
-	buf_setlen(b, 0);
-	buf_putbytes(b, keyd, keyd_len);
-	buf_setpos(b, 0);
-	type = DROPBEAR_SIGNKEY_DSS;
-	if (buf_get_priv_key(b, svr_opts.hostkey, &type) == DROPBEAR_FAILURE) {
-		dropbear_exit("failed fixed dss hostkey");
-	}
-
-	buf_setlen(b, 0);
-	buf_putbytes(b, keye, keye_len);
-	buf_setpos(b, 0);
-	type = DROPBEAR_SIGNKEY_ECDSA_NISTP256;
-	if (buf_get_priv_key(b, svr_opts.hostkey, &type) == DROPBEAR_FAILURE) {
-		dropbear_exit("failed fixed ecdsa hostkey");
-	}
-
-    buf_free(b);
-}
-#endif // DROPBEAR_FUZZ
 
 void load_all_hostkeys() {
 	int i;
 	int disable_unset_keys = 1;
 	int any_keys = 0;
 
-#ifdef DROPBEAR_FUZZ
-	if (opts.fuzz.fuzzing) {
-		load_fixed_hostkeys();
-		return;
-	}
-#endif
-
 	svr_opts.hostkey = new_sign_key();
 
 	for (i = 0; i < svr_opts.num_hostkey_files; i++) {
diff --git a/svr-session.c b/svr-session.c
index 0e6a9e803..41571bb8e 100644
--- a/svr-session.c
+++ b/svr-session.c
@@ -40,6 +40,7 @@
 #include "auth.h"
 #include "runopts.h"
 #include "crypto_desc.h"
+#include "fuzz.h"
 
 static void svr_remoteclosed(void);
 
@@ -182,6 +183,13 @@ void svr_dropbear_exit(int exitcode, const char* format, va_list param) {
 		session_cleanup();
 	}
 
+#ifdef DROPBEAR_FUZZ
+	// longjmp before cleaning up svr_opts
+    if (fuzz.fuzzing) {
+        longjmp(fuzz.jmp, 1);
+    }
+#endif
+
 	if (svr_opts.hostkey) {
 		sign_key_free(svr_opts.hostkey);
 		svr_opts.hostkey = NULL;
@@ -191,11 +199,6 @@ void svr_dropbear_exit(int exitcode, const char* format, va_list param) {
 		m_free(svr_opts.ports[i]);
 	}
 
-#ifdef DROPBEAR_FUZZ
-    if (opts.fuzz.fuzzing) {
-        longjmp(opts.fuzz.jmp, 1);
-    }
-#endif
     
 	exit(exitcode);