Adding upstream version 1:9.2p1.upstream/1%9.2p1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

38 files changed, 1954 insertions, 0 deletions

diff --git a/regress/misc/Makefile b/regress/misc/Makefile
new file mode 100644
index 0000000..b9149f2
--- /dev/null
+++ b/regress/misc/Makefile
@@ -0,0 +1,3 @@
+SUBDIR=		sk-dummy
+
+.include <bsd.subdir.mk>
diff --git a/regress/misc/fuzz-harness/Makefile b/regress/misc/fuzz-harness/Makefile
new file mode 100644
index 0000000..0b4238f
--- /dev/null
+++ b/regress/misc/fuzz-harness/Makefile
@@ -0,0 +1,55 @@
+# NB. libssh and libopenbsd-compat should be built with the same sanitizer opts.
+CC=clang-11
+CXX=clang++-11
+FUZZ_FLAGS=-fsanitize=address,fuzzer -fno-omit-frame-pointer
+FUZZ_LIBS=-lFuzzer
+
+CXXFLAGS=-O2 -g -Wall -Wextra -Wno-unused-parameter -I ../../.. $(FUZZ_FLAGS)
+CFLAGS=$(CXXFLAGS)
+LDFLAGS=-L ../../.. -L ../../../openbsd-compat -g $(FUZZ_FLAGS)
+LIBS=-lssh -lopenbsd-compat -lmd -lcrypto -lfido2 -lcbor $(FUZZ_LIBS)
+SK_NULL_OBJS=ssh-sk-null.o
+COMMON_DEPS=../../../libssh.a
+
+TARGETS=pubkey_fuzz sig_fuzz authopt_fuzz authkeys_fuzz sshsig_fuzz \
+	sshsigopt_fuzz privkey_fuzz kex_fuzz agent_fuzz
+
+all: $(TARGETS)
+
+.cc.o:
+	$(CXX) $(CXXFLAGS) -c $< -o $@
+
+pubkey_fuzz: pubkey_fuzz.o $(SK_NULL_OBJS) $(COMMON_DEPS)
+	$(CXX) -o $@ pubkey_fuzz.o $(SK_NULL_OBJS) $(LDFLAGS) $(LIBS)
+
+sig_fuzz: sig_fuzz.o $(SK_NULL_OBJS) $(COMMON_DEPS)
+	$(CXX) -o $@ sig_fuzz.o $(SK_NULL_OBJS) $(LDFLAGS) $(LIBS)
+
+authopt_fuzz: authopt_fuzz.o $(SK_NULL_OBJS) $(COMMON_DEPS)
+	$(CXX) -o $@ authopt_fuzz.o $(SK_NULL_OBJS) ../../../auth-options.o $(LDFLAGS) $(LIBS)
+
+authkeys_fuzz: authkeys_fuzz.o $(SK_NULL_OBJS) $(COMMON_DEPS)
+	$(CXX) -o $@ authkeys_fuzz.o $(SK_NULL_OBJS) ../../../auth-options.o ../../../auth2-pubkeyfile.o $(LDFLAGS) $(LIBS)
+
+sshsig_fuzz: sshsig_fuzz.o $(SK_NULL_OBJS) $(COMMON_DEPS)
+	$(CXX) -o $@ sshsig_fuzz.o $(SK_NULL_OBJS) ../../../sshsig.o $(LDFLAGS) $(LIBS)
+
+sshsigopt_fuzz: sshsigopt_fuzz.o $(SK_NULL_OBJS) $(COMMON_DEPS)
+	$(CXX) -o $@ sshsigopt_fuzz.o $(SK_NULL_OBJS) ../../../sshsig.o $(LDFLAGS) $(LIBS)
+
+privkey_fuzz: privkey_fuzz.o $(SK_NULL_OBJS) $(COMMON_DEPS)
+	$(CXX) -o $@ privkey_fuzz.o $(SK_NULL_OBJS) $(LDFLAGS) $(LIBS)
+
+kex_fuzz: kex_fuzz.o $(SK_NULL_OBJS) $(COMMON_DEPS)
+	$(CXX) -o $@ kex_fuzz.o $(SK_NULL_OBJS) $(LDFLAGS) $(LIBS) -lz
+
+agent_fuzz: agent_fuzz.o agent_fuzz_helper.o sk-dummy.o ../../../ssh-sk.o $(COMMON_DEPS)
+	$(CXX) -o $@ agent_fuzz.o agent_fuzz_helper.o sk-dummy.o ../../../ssh-sk.o $(LDFLAGS) $(LIBS) -lz
+
+agent_fuzz_helper.o: agent_fuzz_helper.c ../../../ssh-agent.c
+
+sk-dummy.o: ../sk-dummy/sk-dummy.c
+	$(CC) $(CFLAGS) -c -o $@ ../sk-dummy/sk-dummy.c -DSK_DUMMY_INTEGRATE=1 $(LDFLAGS)
+
+clean:
+	-rm -f *.o $(TARGETS)
diff --git a/regress/misc/fuzz-harness/README b/regress/misc/fuzz-harness/README
new file mode 100644
index 0000000..ae6fbe7
--- /dev/null
+++ b/regress/misc/fuzz-harness/README
@@ -0,0 +1 @@
+This directory contains fuzzing harnesses for use with clang's libfuzzer.
diff --git a/regress/misc/fuzz-harness/agent_fuzz.cc b/regress/misc/fuzz-harness/agent_fuzz.cc
new file mode 100644
index 0000000..ad85b2f
--- /dev/null
+++ b/regress/misc/fuzz-harness/agent_fuzz.cc
@@ -0,0 +1,15 @@
+// cc_fuzz_target test for ssh-agent.
+extern "C" {
+
+#include <stdint.h>
+#include <sys/types.h>
+
+extern void test_one(const uint8_t* s, size_t slen);
+
+int LLVMFuzzerTestOneInput(const uint8_t* s, size_t slen)
+{
+	test_one(s, slen);
+	return 0;
+}
+
+} // extern
diff --git a/regress/misc/fuzz-harness/agent_fuzz_helper.c b/regress/misc/fuzz-harness/agent_fuzz_helper.c
new file mode 100644
index 0000000..1d41982
--- /dev/null
+++ b/regress/misc/fuzz-harness/agent_fuzz_helper.c
@@ -0,0 +1,177 @@
+#include "fixed-keys.h"
+#include <assert.h>
+
+#define main(ac, av) xxxmain(ac, av)
+#include "../../../ssh-agent.c"
+
+void test_one(const uint8_t* s, size_t slen);
+
+static int
+devnull_or_die(void)
+{
+	int fd;
+
+	if ((fd = open("/dev/null", O_RDWR)) == -1) {
+		error_f("open /dev/null: %s", strerror(errno));
+		abort();
+	}
+	return fd;
+}
+
+static struct sshkey *
+pubkey_or_die(const char *s)
+{
+	char *tmp, *cp;
+	struct sshkey *pubkey;
+	int r;
+
+	tmp = cp = xstrdup(s);
+	if ((pubkey = sshkey_new(KEY_UNSPEC)) == NULL)
+		abort();
+	if ((r = sshkey_read(pubkey, &cp)) != 0) {
+		error_fr(r, "parse");
+		abort();
+	}
+	free(tmp);
+	return pubkey;
+}
+
+static struct sshkey *
+privkey_or_die(const char *s)
+{
+	int r;
+	struct sshbuf *b;
+	struct sshkey *privkey;
+
+	if ((b = sshbuf_from(s, strlen(s))) == NULL) {
+		error_f("sshbuf_from failed");
+		abort();
+	}
+	if ((r = sshkey_parse_private_fileblob(b, "", &privkey, NULL)) != 0) {
+		error_fr(r, "parse");
+		abort();
+	}
+	sshbuf_free(b);
+	return privkey;
+}
+
+static void
+add_key(const char *privkey, const char *certpath)
+{
+	Identity *id;
+	int r;
+	struct sshkey *cert;
+
+	id = xcalloc(1, sizeof(Identity));
+	TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
+	idtab->nentries++;
+	id->key = privkey_or_die(privkey);
+	id->comment = xstrdup("rhododaktulos Eos");
+	if (sshkey_is_sk(id->key))
+		id->sk_provider = xstrdup("internal");
+
+	/* Now the cert too */
+	id = xcalloc(1, sizeof(Identity));
+	TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
+	idtab->nentries++;
+	id->key = privkey_or_die(privkey);
+	cert = pubkey_or_die(certpath);
+	if ((r = sshkey_to_certified(id->key)) != 0) {
+		error_fr(r, "sshkey_to_certified");
+		abort();
+	}
+	if ((r = sshkey_cert_copy(cert, id->key)) != 0) {
+		error_fr(r, "sshkey_cert_copy");
+		abort();
+	}
+	sshkey_free(cert);
+	id->comment = xstrdup("outis");
+	if (sshkey_is_sk(id->key))
+		id->sk_provider = xstrdup("internal");
+}
+
+static void
+cleanup_idtab(void)
+{
+	Identity *id;
+
+	if (idtab == NULL) return;
+	for (id = TAILQ_FIRST(&idtab->idlist); id;
+	    id = TAILQ_FIRST(&idtab->idlist)) {
+		TAILQ_REMOVE(&idtab->idlist, id, next);
+		free_identity(id);
+	}
+	free(idtab);
+	idtab = NULL;
+}
+
+static void
+reset_idtab(void)
+{
+	cleanup_idtab();
+	idtab_init();
+	// Load keys.
+	add_key(PRIV_RSA, CERT_RSA);
+	add_key(PRIV_DSA, CERT_DSA);
+	add_key(PRIV_ECDSA, CERT_ECDSA);
+	add_key(PRIV_ED25519, CERT_ED25519);
+	add_key(PRIV_ECDSA_SK, CERT_ECDSA_SK);
+	add_key(PRIV_ED25519_SK, CERT_ED25519_SK);
+}
+
+static void
+cleanup_sockettab(void)
+{
+	u_int i;
+	for (i = 0; i < sockets_alloc; i++) {
+		if (sockets[i].type != AUTH_UNUSED)
+			close_socket(sockets + i);
+	}
+	free(sockets);
+	sockets = NULL;
+	sockets_alloc = 0;
+}
+
+static void
+reset_sockettab(int devnull)
+{
+	int fd;
+
+	cleanup_sockettab();
+	if ((fd = dup(devnull)) == -1) {
+		error_f("dup: %s", strerror(errno));
+		abort();
+	}
+	new_socket(AUTH_CONNECTION, fd);
+	assert(sockets[0].type == AUTH_CONNECTION);
+	assert(sockets[0].fd == fd);
+}
+
+#define MAX_MESSAGES 256
+void
+test_one(const uint8_t* s, size_t slen)
+{
+	static int devnull = -1;
+	size_t i, olen, nlen;
+
+	if (devnull == -1) {
+		log_init(__progname, SYSLOG_LEVEL_DEBUG3,
+		    SYSLOG_FACILITY_AUTH, 1);
+		devnull = devnull_or_die();
+		allowed_providers = xstrdup("");
+		setenv("DISPLAY", "", 1); /* ban askpass */
+	}
+
+	reset_idtab();
+	reset_sockettab(devnull);
+	(void)sshbuf_put(sockets[0].input, s, slen);
+	for (i = 0; i < MAX_MESSAGES; i++) {
+		olen = sshbuf_len(sockets[0].input);
+		process_message(0);
+		nlen = sshbuf_len(sockets[0].input);
+		if (nlen == 0 || nlen == olen)
+			break;
+	}
+	cleanup_idtab();
+	cleanup_sockettab();
+}
diff --git a/regress/misc/fuzz-harness/authkeys_fuzz.cc b/regress/misc/fuzz-harness/authkeys_fuzz.cc
new file mode 100644
index 0000000..8b3e54e
--- /dev/null
+++ b/regress/misc/fuzz-harness/authkeys_fuzz.cc
@@ -0,0 +1,81 @@
+#include <stddef.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdlib.h>
+#include <pwd.h>
+#include <unistd.h>
+
+extern "C" {
+
+#include "hostfile.h"
+#include "auth.h"
+#include "auth-options.h"
+#include "sshkey.h"
+
+// testdata/id_ed25519.pub and testdata/id_ed25519-cert.pub
+const char *pubkey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIDPQXmEVMVLmeFRyafKMVWgPDkv8/uRBTwmcEDatZzMD"; 
+const char *certtext = "ssh-ed25519-cert-v01@openssh.com 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 id_ed25519.pub";
+
+// stubs
+void auth_debug_add(const char *fmt,...)
+{
+}
+
+void
+auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote)
+{
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
+{
+	char *tmp, *o, *cp = (char *)malloc(size + 1 + strlen(pubkey) + 1);
+	struct sshauthopt *opts = NULL;
+	struct passwd *pw = getpwuid(getuid());
+	static struct sshkey *key, *cert;
+
+	if (key == NULL) {
+		if ((key = sshkey_new(KEY_UNSPEC)) == NULL ||
+		    (cert = sshkey_new(KEY_UNSPEC)) == NULL)
+			abort();
+		if ((o = tmp = strdup(pubkey)) == NULL ||
+		    sshkey_read(key, &tmp) != 0)
+			abort();
+		free(o);
+		if ((o = tmp = strdup(certtext)) == NULL ||
+		    sshkey_read(cert, &tmp) != 0)
+			abort();
+		free(o);
+	}
+	if (cp == NULL || pw == NULL || key == NULL || cert == NULL)
+		abort();
+
+	// Cleanup whitespace at input EOL.
+	for (; size > 0 && strchr(" \t\r\n", data[size - 1]) != NULL; size--) ;
+
+	// Append a pubkey that will match.
+	memcpy(cp, data, size);
+	cp[size] = ' ';
+	memcpy(cp + size + 1, pubkey, strlen(pubkey) + 1);
+
+	// Try key.
+	if ((tmp = strdup(cp)) == NULL)
+		abort();
+	(void) auth_check_authkey_line(pw, key, tmp, "127.0.0.1", "localhost",
+	    "fuzz", &opts);
+	free(tmp);
+	sshauthopt_free(opts);
+
+	// Try cert.
+	if ((tmp = strdup(cp)) == NULL)
+		abort();
+	(void) auth_check_authkey_line(pw, cert, tmp, "127.0.0.1", "localhost",
+	    "fuzz", &opts);
+	free(tmp);
+	sshauthopt_free(opts);
+
+	free(cp);
+	return 0;
+}
+
+} // extern "C"
diff --git a/regress/misc/fuzz-harness/authopt_fuzz.cc b/regress/misc/fuzz-harness/authopt_fuzz.cc
new file mode 100644
index 0000000..a76d5a3
--- /dev/null
+++ b/regress/misc/fuzz-harness/authopt_fuzz.cc
@@ -0,0 +1,33 @@
+#include <stddef.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdlib.h>
+
+extern "C" {
+
+#include "auth-options.h"
+
+int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
+{
+	char *cp = (char *)malloc(size + 1);
+	struct sshauthopt *opts = NULL, *merge = NULL, *add = sshauthopt_new();
+
+	if (cp == NULL || add == NULL)
+		goto out;
+	memcpy(cp, data, size);
+	cp[size] = '\0';
+	if ((opts = sshauthopt_parse(cp, NULL)) == NULL)
+		goto out;
+	if ((merge = sshauthopt_merge(opts, add, NULL)) == NULL)
+		goto out;
+
+ out:
+	free(cp);
+	sshauthopt_free(add);
+	sshauthopt_free(opts);
+	sshauthopt_free(merge);
+	return 0;
+}
+
+} // extern "C"
diff --git a/regress/misc/fuzz-harness/fixed-keys.h b/regress/misc/fuzz-harness/fixed-keys.h
new file mode 100644
index 0000000..c6e7c6c
--- /dev/null
+++ b/regress/misc/fuzz-harness/fixed-keys.h
@@ -0,0 +1,119 @@
+/*
+ * Some keys used by fuzzers
+ */
+
+#define PRIV_RSA \
+"-----BEGIN OPENSSH PRIVATE KEY-----\n"\
+"b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAABFwAAAAdzc2gtcn\n"\
+"NhAAAAAwEAAQAAAQEA3+epf+VGKoGPaAZXrf6S0cyumQnddkGBnVFX0A5eh37RtLug0qY5\n"\
+"thxsBUbGGVr9mTd2QXwLujBwYg5l1MP/Fmg+5312Zgx9pHmS+qKULbar0hlNgptNEb+aNU\n"\
+"d3o9qg3aXqXm7+ZnjAV05ef/mxNRN2ZvuEkw7cRppTJcbBI+vF3lXuCXnX2klDI95Gl2AW\n"\
+"3WHRtanqLHZXuBkjjRBDKc7MUq/GP1hmLiAd95dvU7fZjRlIEsP84zGEI1Fb0L/kmPHcOt\n"\
+"iVfHft8CtmC9v6+94JrOiPBBNScV+dyrgAGPsdKdr/1vIpQmCNiI8s3PCiD8J7ZiBaYm0I\n"\
+"8fq5G/qnUwAAA7ggw2dXIMNnVwAAAAdzc2gtcnNhAAABAQDf56l/5UYqgY9oBlet/pLRzK\n"\
+"6ZCd12QYGdUVfQDl6HftG0u6DSpjm2HGwFRsYZWv2ZN3ZBfAu6MHBiDmXUw/8WaD7nfXZm\n"\
+"DH2keZL6opQttqvSGU2Cm00Rv5o1R3ej2qDdpepebv5meMBXTl5/+bE1E3Zm+4STDtxGml\n"\
+"MlxsEj68XeVe4JedfaSUMj3kaXYBbdYdG1qeosdle4GSONEEMpzsxSr8Y/WGYuIB33l29T\n"\
+"t9mNGUgSw/zjMYQjUVvQv+SY8dw62JV8d+3wK2YL2/r73gms6I8EE1JxX53KuAAY+x0p2v\n"\
+"/W8ilCYI2Ijyzc8KIPwntmIFpibQjx+rkb+qdTAAAAAwEAAQAAAQEArWm5B4tFasppjUHM\n"\
+"SsAuajtCxtizI1Hc10EW59cZM4vvUzE2f6+qZvdgWj3UU/L7Et23w0QVuSCnCerox379ZB\n"\
+"ddEOFFAAiQjwBx65hbd4RRUymxtIQfjq18++LcMJW1nbVQ7c69ThQbtALIggmbS+ZE/8Gx\n"\
+"jkwmIrCH0Ww8TlpsPe+mNHuyNk7UEZoXLm22lNLqq5qkIL5JgT6M2iNJpMOJy9/CKi6kO4\n"\
+"JPuVwjdG4C5pBPaMN3KJ1IvAlSlLGNaXnfXcn85gWfsCjsZmH3liey2NJamqp/w83BrKUg\n"\
+"YZvMR2qeWZaKkFTahpzN5KRK1BFeB37O0P84Dzh1biDX8QAAAIEAiWXW8ePYFwLpa2mFIh\n"\
+"VvRTdcrN70rVK5eWVaL3pyS4vGA56Jixq86dHveOnbSY+iNb1jQidtXc8SWUt2wtHqZ32h\n"\
+"Lji9/hMSKqe9SEP3xvDRDmUJqsVw0ySyrFrzm4160QY6RKU3CIQCVFslMZ9fxmrfZ/hxoU\n"\
+"0X3FVsxmC4+kwAAACBAPOc1YERpV6PjANBrGR+1o1RCdACbm5myc42QzSNIaOZmgrYs+Gt\n"\
+"7+EcoqSdbJzHJNCNQfF+A+vjbIkFiuZqq/5wwr59qXx5OAlijLB/ywwKmTWq6lp//Zxny+\n"\
+"ka3sIGNO14eQvmxNDnlLL+RIZleCTEKBXSW6CZhr+uHMZFKKMtAAAAgQDrSkm+LbILB7H9\n"\
+"jxEBZLhv53aAn4u81kFKQOJ7PzzpBGSoD12i7oIJu5siSD5EKDNVEr+SvCf0ISU3BuMpzl\n"\
+"t3YrPrHRheOFhn5e3j0e//zB8rBC0DGB4CtTDdeh7rOXUL4K0pz+8wEpNkV62SWxhC6NRW\n"\
+"I79JhtGkh+GtcnkEfwAAAAAB\n"\
+"-----END OPENSSH PRIVATE KEY-----\n"
+#define PUB_RSA \
+"ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDf56l/5UYqgY9oBlet/pLRzK6ZCd12QYGdUVfQDl6HftG0u6DSpjm2HGwFRsYZWv2ZN3ZBfAu6MHBiDmXUw/8WaD7nfXZmDH2keZL6opQttqvSGU2Cm00Rv5o1R3ej2qDdpepebv5meMBXTl5/+bE1E3Zm+4STDtxGmlMlxsEj68XeVe4JedfaSUMj3kaXYBbdYdG1qeosdle4GSONEEMpzsxSr8Y/WGYuIB33l29Tt9mNGUgSw/zjMYQjUVvQv+SY8dw62JV8d+3wK2YL2/r73gms6I8EE1JxX53KuAAY+x0p2v/W8ilCYI2Ijyzc8KIPwntmIFpibQjx+rkb+qdT"
+#define CERT_RSA \
+"ssh-rsa-cert-v01@openssh.com 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 id_rsa.pub"
+#define PRIV_DSA \
+"-----BEGIN OPENSSH PRIVATE KEY-----\n"\
+"b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAABsgAAAAdzc2gtZH\n"\
+"NzAAAAgQCsGTfjpQ465EOkfQXJM9BOvfRQE0fqlykAls+ncz+T7hrbeScRu8xpwzsznJNm\n"\
+"xlW8o6cUDiHmBJ5OHgamUC9N7YJeU/6fnOAZifgN8mqK6k8pKHuje8ANOiYgHLl0yiASQA\n"\
+"3//qMyzZ+W/hemoLSmLAbEqlfWVeyYx+wta1Vm+QAAABUAvWyehvUvdHvQxavYgS5p0t5Q\n"\
+"d7UAAACBAIRA9Yy+f4Kzqpv/qICPO3zk42UuP7WAhSW2nCbQdLlCiSTxcjKgcvXNRckwJP\n"\
+"44JjSHOtJy/AMtJrPIbLYG6KuWTdBlEHFiG6DafvLG+qPMSL2bPjXTOhuOMbCHIZ+5WBkW\n"\
+"THeG/Nv11iI01Of9V6tXkig23K370flkRkXFi9MdAAAAgCt6YUcQkNwG7B/e5M1FZsLP9O\n"\
+"kVB3BwLAOjmWdHpyhu3HpwSJa3XLEvhXN0i6IVI2KgPo/2GtYA6rHt14L+6u1pmhh8sAvQ\n"\
+"ksp3qZB+xh/NP+hBqf0sbHX0yYbzKOvI5SCc/kKK6yagcBZOsubM/KC8TxyVgmD5c6WzYs\n"\
+"h5TEpvAAAB2PHjRbbx40W2AAAAB3NzaC1kc3MAAACBAKwZN+OlDjrkQ6R9Bckz0E699FAT\n"\
+"R+qXKQCWz6dzP5PuGtt5JxG7zGnDOzOck2bGVbyjpxQOIeYEnk4eBqZQL03tgl5T/p+c4B\n"\
+"mJ+A3yaorqTykoe6N7wA06JiAcuXTKIBJADf/+ozLNn5b+F6agtKYsBsSqV9ZV7JjH7C1r\n"\
+"VWb5AAAAFQC9bJ6G9S90e9DFq9iBLmnS3lB3tQAAAIEAhED1jL5/grOqm/+ogI87fOTjZS\n"\
+"4/tYCFJbacJtB0uUKJJPFyMqBy9c1FyTAk/jgmNIc60nL8Ay0ms8hstgboq5ZN0GUQcWIb\n"\
+"oNp+8sb6o8xIvZs+NdM6G44xsIchn7lYGRZMd4b82/XWIjTU5/1Xq1eSKDbcrfvR+WRGRc\n"\
+"WL0x0AAACAK3phRxCQ3AbsH97kzUVmws/06RUHcHAsA6OZZ0enKG7cenBIlrdcsS+Fc3SL\n"\
+"ohUjYqA+j/Ya1gDqse3Xgv7q7WmaGHywC9CSynepkH7GH80/6EGp/SxsdfTJhvMo68jlIJ\n"\
+"z+QorrJqBwFk6y5sz8oLxPHJWCYPlzpbNiyHlMSm8AAAAUUA+OGldMi76ClO/sstpdbBUE\n"\
+"lq8AAAAAAQI=\n"\
+"-----END OPENSSH PRIVATE KEY-----\n"
+#define PUB_DSA \
+"ssh-dss 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"
+#define CERT_DSA \
+"ssh-dss-cert-v01@openssh.com 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 id_dsa.pub"
+#define PRIV_ECDSA \
+"-----BEGIN OPENSSH PRIVATE KEY-----\n"\
+"b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAaAAAABNlY2RzYS\n"\
+"1zaGEyLW5pc3RwMjU2AAAACG5pc3RwMjU2AAAAQQTDJ0VlMv+0rguNzaJ1DF2KueHaxRSQ\n"\
+"6LpIxGbulrg1a8RPbnMXwag5GcDiDllD2lDUJUuBEWyjXA0rZoZX35ELAAAAoE/Bbr5PwW\n"\
+"6+AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBMMnRWUy/7SuC43N\n"\
+"onUMXYq54drFFJDoukjEZu6WuDVrxE9ucxfBqDkZwOIOWUPaUNQlS4ERbKNcDStmhlffkQ\n"\
+"sAAAAhAIhE6hCID5oOm1TDktc++KFKyScjLifcZ6Cgv5xSSyLOAAAAAAECAwQFBgc=\n"\
+"-----END OPENSSH PRIVATE KEY-----\n"
+#define PUB_ECDSA \
+"ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBMMnRWUy/7SuC43NonUMXYq54drFFJDoukjEZu6WuDVrxE9ucxfBqDkZwOIOWUPaUNQlS4ERbKNcDStmhlffkQs="
+#define CERT_ECDSA \
+"ecdsa-sha2-nistp256-cert-v01@openssh.com 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 id_ecdsa.pub"
+#define PRIV_ED25519 \
+"-----BEGIN OPENSSH PRIVATE KEY-----\n"\
+"b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW\n"\
+"QyNTUxOQAAACAz0F5hFTFS5nhUcmnyjFVoDw5L/P7kQU8JnBA2rWczAwAAAIhWlP99VpT/\n"\
+"fQAAAAtzc2gtZWQyNTUxOQAAACAz0F5hFTFS5nhUcmnyjFVoDw5L/P7kQU8JnBA2rWczAw\n"\
+"AAAEDE1rlcMC0s0X3TKVZAOVavZOywwkXw8tO5dLObxaCMEDPQXmEVMVLmeFRyafKMVWgP\n"\
+"Dkv8/uRBTwmcEDatZzMDAAAAAAECAwQF\n"\
+"-----END OPENSSH PRIVATE KEY-----\n"
+#define PUB_ED25519 \
+"ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIDPQXmEVMVLmeFRyafKMVWgPDkv8/uRBTwmcEDatZzMD"
+#define CERT_ED25519 \
+"ssh-ed25519-cert-v01@openssh.com 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 id_ed25519.pub"
+#define PRIV_ECDSA_SK \
+"-----BEGIN OPENSSH PRIVATE KEY-----\n"\
+"b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAfwAAACJzay1lY2\n"\
+"RzYS1zaGEyLW5pc3RwMjU2QG9wZW5zc2guY29tAAAACG5pc3RwMjU2AAAAQQTYyU76zop1\n"\
+"VOb4DfKWYnR5b0TOC3zw8DzObAfHWB5o6xls+tOYiEleXvIEi00Da2iCK47habZTOhLyeB\n"\
+"X2Avu5AAAABHNzaDoAAAGYqUAQSKlAEEgAAAAic2stZWNkc2Etc2hhMi1uaXN0cDI1NkBv\n"\
+"cGVuc3NoLmNvbQAAAAhuaXN0cDI1NgAAAEEE2MlO+s6KdVTm+A3ylmJ0eW9Ezgt88PA8zm\n"\
+"wHx1geaOsZbPrTmIhJXl7yBItNA2togiuO4Wm2UzoS8ngV9gL7uQAAAARzc2g6AQAAAOMt\n"\
+"LS0tLUJFR0lOIEVDIFBSSVZBVEUgS0VZLS0tLS0KTUhjQ0FRRUVJSHFsZjNsWTkxZFhwUn\n"\
+"dYZDBrS0lYWmNpeDRRcDBNSU15Ny9JMUxXSTFuWG9Bb0dDQ3FHU000OQpBd0VIb1VRRFFn\n"\
+"QUUyTWxPK3M2S2RWVG0rQTN5bG1KMGVXOUV6Z3Q4OFBBOHptd0h4MWdlYU9zWmJQclRtSW\n"\
+"hKClhsN3lCSXROQTJ0b2dpdU80V20yVXpvUzhuZ1Y5Z0w3dVE9PQotLS0tLUVORCBFQyBQ\n"\
+"UklWQVRFIEtFWS0tLS0tCgAAAAAAAAAbZGptQGRqbS5zeWQuY29ycC5nb29nbGUuY29tAQ\n"\
+"IDBAUG\n"\
+"-----END OPENSSH PRIVATE KEY-----\n"
+#define PUB_ECDSA_SK \
+"sk-ecdsa-sha2-nistp256@openssh.com AAAAInNrLWVjZHNhLXNoYTItbmlzdHAyNTZAb3BlbnNzaC5jb20AAAAIbmlzdHAyNTYAAABBBNjJTvrOinVU5vgN8pZidHlvRM4LfPDwPM5sB8dYHmjrGWz605iISV5e8gSLTQNraIIrjuFptlM6EvJ4FfYC+7kAAAAEc3NoOg=="
+#define CERT_ECDSA_SK \
+"sk-ecdsa-sha2-nistp256-cert-v01@openssh.com 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"
+#define PRIV_ED25519_SK \
+"-----BEGIN OPENSSH PRIVATE KEY-----\n"\
+"b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAASgAAABpzay1zc2\n"\
+"gtZWQyNTUxOUBvcGVuc3NoLmNvbQAAACCTJtH10vWhIDxd62edvMLg9u2cwYKyqa7332je\n"\
+"RArHjAAAAARzc2g6AAAAwN7vvE3e77xNAAAAGnNrLXNzaC1lZDI1NTE5QG9wZW5zc2guY2\n"\
+"9tAAAAIJMm0fXS9aEgPF3rZ528wuD27ZzBgrKprvffaN5ECseMAAAABHNzaDoBAAAAQEsS\n"\
+"xLFiVzfpH2mt9xh8i/zmHV646Hud4QruNBAGNl8gkybR9dL1oSA8XetnnbzC4PbtnMGCsq\n"\
+"mu999o3kQKx4wAAAAAAAAAG2RqbUBkam0uc3lkLmNvcnAuZ29vZ2xlLmNvbQECAwQFBg==\n"\
+"-----END OPENSSH PRIVATE KEY-----\n"
+#define PUB_ED25519_SK \
+"sk-ssh-ed25519@openssh.com AAAAGnNrLXNzaC1lZDI1NTE5QG9wZW5zc2guY29tAAAAIJMm0fXS9aEgPF3rZ528wuD27ZzBgrKprvffaN5ECseMAAAABHNzaDo="
+#define CERT_ED25519_SK \
+"sk-ssh-ed25519-cert-v01@openssh.com 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"
diff --git a/regress/misc/fuzz-harness/kex_fuzz.cc b/regress/misc/fuzz-harness/kex_fuzz.cc
new file mode 100644
index 0000000..d38ca85
--- /dev/null
+++ b/regress/misc/fuzz-harness/kex_fuzz.cc
@@ -0,0 +1,460 @@
+// libfuzzer driver for key exchange fuzzing.
+
+
+#include <sys/types.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+extern "C" {
+
+#include "includes.h"
+#include "ssherr.h"
+#include "ssh_api.h"
+#include "sshbuf.h"
+#include "packet.h"
+#include "myproposal.h"
+#include "xmalloc.h"
+#include "authfile.h"
+#include "log.h"
+
+#include "fixed-keys.h"
+
+// Define if you want to generate traces.
+/* #define STANDALONE 1 */
+
+static int prepare_key(struct shared_state *st, int keytype, int bits);
+
+struct shared_state {
+	size_t nkeys;
+	struct sshkey **privkeys, **pubkeys;
+};
+
+struct test_state {
+	struct sshbuf *smsgs, *cmsgs; /* output, for standalone mode */
+	struct sshbuf *sin, *cin; /* input; setup per-test in do_kex_with_key */
+	struct sshbuf *s_template, *c_template; /* main copy of input */
+};
+
+static int
+do_send_and_receive(struct ssh *from, struct ssh *to,
+    struct sshbuf *store, int clobber, size_t *n)
+{
+	u_char type;
+	size_t len;
+	const u_char *buf;
+	int r;
+
+	for (*n = 0;; (*n)++) {
+		if ((r = ssh_packet_next(from, &type)) != 0) {
+			debug_fr(r, "ssh_packet_next");
+			return r;
+		}
+		if (type != 0)
+			return 0;
+		buf = ssh_output_ptr(from, &len);
+		debug_f("%zu%s", len, clobber ? " ignore" : "");
+		if (len == 0)
+			return 0;
+		if ((r = ssh_output_consume(from, len)) != 0) {
+			debug_fr(r, "ssh_output_consume");
+			return r;
+		}
+		if (store != NULL && (r = sshbuf_put(store, buf, len)) != 0) {
+			debug_fr(r, "sshbuf_put");
+			return r;
+		}
+		if (!clobber && (r = ssh_input_append(to, buf, len)) != 0) {
+			debug_fr(r, "ssh_input_append");
+			return r;
+		}
+	}
+}
+
+static int
+run_kex(struct test_state *ts, struct ssh *client, struct ssh *server)
+{
+	int r = 0;
+	size_t cn, sn;
+
+	/* If fuzzing, replace server/client input */
+	if (ts->sin != NULL) {
+		if ((r = ssh_input_append(server, sshbuf_ptr(ts->sin),
+		    sshbuf_len(ts->sin))) != 0) {
+			error_fr(r, "ssh_input_append");
+			return r;
+		}
+		sshbuf_reset(ts->sin);
+	}
+	if (ts->cin != NULL) {
+		if ((r = ssh_input_append(client, sshbuf_ptr(ts->cin),
+		    sshbuf_len(ts->cin))) != 0) {
+			error_fr(r, "ssh_input_append");
+			return r;
+		}
+		sshbuf_reset(ts->cin);
+	}
+	while (!server->kex->done || !client->kex->done) {
+		cn = sn = 0;
+		debug_f("S:");
+		if ((r = do_send_and_receive(server, client,
+		    ts->smsgs, ts->cin != NULL, &sn)) != 0) {
+			debug_fr(r, "S->C");
+			break;
+		}
+		debug_f("C:");
+		if ((r = do_send_and_receive(client, server,
+		    ts->cmsgs, ts->sin != NULL, &cn)) != 0) {
+			debug_fr(r, "C->S");
+			break;
+		}
+		if (cn == 0 && sn == 0) {
+			debug_f("kex stalled");
+			r = SSH_ERR_PROTOCOL_ERROR;
+			break;
+		}
+	}
+	debug_fr(r, "done");
+	return r;
+}
+
+static void
+store_key(struct shared_state *st, struct sshkey *pubkey,
+    struct sshkey *privkey)
+{
+	if (st == NULL || pubkey->type < 0 || pubkey->type > INT_MAX ||
+	    privkey->type != pubkey->type ||
+	    ((size_t)pubkey->type < st->nkeys &&
+	     st->pubkeys[pubkey->type] != NULL))
+		abort();
+	if ((size_t)pubkey->type >= st->nkeys) {
+		st->pubkeys = (struct sshkey **)xrecallocarray(st->pubkeys,
+		    st->nkeys, pubkey->type + 1, sizeof(*st->pubkeys));
+		st->privkeys = (struct sshkey **)xrecallocarray(st->privkeys,
+		    st->nkeys, privkey->type + 1, sizeof(*st->privkeys));
+		st->nkeys = privkey->type + 1;
+	}
+	debug_f("store %s at %d", sshkey_ssh_name(pubkey), pubkey->type);
+	st->pubkeys[pubkey->type] = pubkey;
+	st->privkeys[privkey->type] = privkey;
+}
+
+static int
+prepare_keys(struct shared_state *st)
+{
+	if (prepare_key(st, KEY_RSA, 2048) != 0 ||
+	    prepare_key(st, KEY_DSA, 1024) != 0 ||
+	    prepare_key(st, KEY_ECDSA, 256) != 0 ||
+	    prepare_key(st, KEY_ED25519, 256) != 0) {
+		error_f("key prepare failed");
+		return -1;
+	}
+	return 0;
+}
+
+static struct sshkey *
+get_pubkey(struct shared_state *st, int keytype)
+{
+	if (st == NULL || keytype < 0 || (size_t)keytype >= st->nkeys ||
+	    st->pubkeys == NULL || st->pubkeys[keytype] == NULL)
+		abort();
+	return st->pubkeys[keytype];
+}
+
+static struct sshkey *
+get_privkey(struct shared_state *st, int keytype)
+{
+	if (st == NULL || keytype < 0 || (size_t)keytype >= st->nkeys ||
+	    st->privkeys == NULL || st->privkeys[keytype] == NULL)
+		abort();
+	return st->privkeys[keytype];
+}
+
+static int
+do_kex_with_key(struct shared_state *st, struct test_state *ts,
+    const char *kex, int keytype)
+{
+	struct ssh *client = NULL, *server = NULL;
+	struct sshkey *privkey = NULL, *pubkey = NULL;
+	struct sshbuf *state = NULL;
+	struct kex_params kex_params;
+	const char *ccp, *proposal[PROPOSAL_MAX] = { KEX_CLIENT };
+	char *myproposal[PROPOSAL_MAX] = {0}, *keyname = NULL;
+	int i, r;
+
+	ts->cin = ts->sin = NULL;
+	if (ts->c_template != NULL &&
+	    (ts->cin = sshbuf_fromb(ts->c_template)) == NULL)
+		abort();
+	if (ts->s_template != NULL &&
+	    (ts->sin = sshbuf_fromb(ts->s_template)) == NULL)
+		abort();
+
+	pubkey = get_pubkey(st, keytype);
+	privkey = get_privkey(st, keytype);
+	keyname = xstrdup(sshkey_ssh_name(privkey));
+	if (ts->cin != NULL) {
+		debug_f("%s %s clobber client %zu", kex, keyname,
+		    sshbuf_len(ts->cin));
+	} else if (ts->sin != NULL) {
+		debug_f("%s %s clobber server %zu", kex, keyname,
+		    sshbuf_len(ts->sin));
+	} else
+		debug_f("%s %s noclobber", kex, keyname);
+
+	for (i = 0; i < PROPOSAL_MAX; i++) {
+		ccp = proposal[i];
+#ifdef CIPHER_NONE_AVAIL
+		if (i == PROPOSAL_ENC_ALGS_CTOS || i == PROPOSAL_ENC_ALGS_STOC)
+			ccp = "none";
+#endif
+		if (i == PROPOSAL_SERVER_HOST_KEY_ALGS)
+			ccp = keyname;
+		else if (i == PROPOSAL_KEX_ALGS && kex != NULL)
+			ccp = kex;
+		if ((myproposal[i] = strdup(ccp)) == NULL) {
+			error_f("strdup prop %d", i);
+			goto fail;
+		}
+	}
+	memcpy(kex_params.proposal, myproposal, sizeof(myproposal));
+	if ((r = ssh_init(&client, 0, &kex_params)) != 0) {
+		error_fr(r, "init client");
+		goto fail;
+	}
+	if ((r = ssh_init(&server, 1, &kex_params)) != 0) {
+		error_fr(r, "init server");
+		goto fail;
+	}
+	if ((r = ssh_add_hostkey(server, privkey)) != 0 ||
+	    (r = ssh_add_hostkey(client, pubkey)) != 0) {
+		error_fr(r, "add hostkeys");
+		goto fail;
+	}
+	if ((r = run_kex(ts, client, server)) != 0) {
+		error_fr(r, "kex");
+		goto fail;
+	}
+	/* XXX rekex, set_state, etc */
+ fail:
+	for (i = 0; i < PROPOSAL_MAX; i++)
+		free(myproposal[i]);
+	sshbuf_free(ts->sin);
+	sshbuf_free(ts->cin);
+	sshbuf_free(state);
+	ssh_free(client);
+	ssh_free(server);
+	free(keyname);
+	return r;
+}
+
+static int
+prepare_key(struct shared_state *st, int kt, int bits)
+{
+	const char *pubstr = NULL;
+	const char *privstr = NULL;
+	char *tmp, *cp;
+	struct sshkey *privkey = NULL, *pubkey = NULL;
+	struct sshbuf *b = NULL;
+	int r;
+
+	switch (kt) {
+	case KEY_RSA:
+		pubstr = PUB_RSA;
+		privstr = PRIV_RSA;
+		break;
+	case KEY_DSA:
+		pubstr = PUB_DSA;
+		privstr = PRIV_DSA;
+		break;
+	case KEY_ECDSA:
+		pubstr = PUB_ECDSA;
+		privstr = PRIV_ECDSA;
+		break;
+	case KEY_ED25519:
+		pubstr = PUB_ED25519;
+		privstr = PRIV_ED25519;
+		break;
+	default:
+		abort();
+	}
+	if ((b = sshbuf_from(privstr, strlen(privstr))) == NULL)
+		abort();
+	if ((r = sshkey_parse_private_fileblob(b, "", &privkey, NULL)) != 0) {
+		error_fr(r, "priv %d", kt);
+		abort();
+	}
+	sshbuf_free(b);
+	tmp = cp = xstrdup(pubstr);
+	if ((pubkey = sshkey_new(KEY_UNSPEC)) == NULL)
+		abort();
+	if ((r = sshkey_read(pubkey, &cp)) != 0) {
+		error_fr(r, "pub %d", kt);
+		abort();
+	}
+	free(tmp);
+
+	store_key(st, pubkey, privkey);
+	return 0;
+}
+
+#if defined(STANDALONE)
+
+#if 0 /* use this if generating new keys to embed above */
+static int
+prepare_key(struct shared_state *st, int keytype, int bits)
+{
+	struct sshkey *privkey = NULL, *pubkey = NULL;
+	int r;
+
+	if ((r = sshkey_generate(keytype, bits, &privkey)) != 0) {
+		error_fr(r, "generate");
+		abort();
+	}
+	if ((r = sshkey_from_private(privkey, &pubkey)) != 0) {
+		error_fr(r, "make pubkey");
+		abort();
+	}
+	store_key(st, pubkey, privkey);
+	return 0;
+}
+#endif
+
+int main(void)
+{
+	static struct shared_state *st;
+	struct test_state *ts;
+	const int keytypes[] = { KEY_RSA, KEY_DSA, KEY_ECDSA, KEY_ED25519, -1 };
+	static const char * const kextypes[] = {
+		"sntrup761x25519-sha512@openssh.com",
+		"curve25519-sha256@libssh.org",
+		"ecdh-sha2-nistp256",
+		"diffie-hellman-group1-sha1",
+		"diffie-hellman-group-exchange-sha1",
+		NULL,
+	};
+	int i, j;
+	char *path;
+	FILE *f;
+
+	log_init("kex_fuzz", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 1);
+
+	if (st == NULL) {
+		st = (struct shared_state *)xcalloc(1, sizeof(*st));
+		prepare_keys(st);
+	}
+	/* Run each kex method for each key and save client/server packets */
+	for (i = 0; keytypes[i] != -1; i++) {
+		for (j = 0; kextypes[j] != NULL; j++) {
+			ts = (struct test_state *)xcalloc(1, sizeof(*ts));
+			ts->smsgs = sshbuf_new();
+			ts->cmsgs = sshbuf_new();
+			do_kex_with_key(st, ts, kextypes[j], keytypes[i]);
+			xasprintf(&path, "S2C-%s-%s",
+			    kextypes[j], sshkey_type(st->pubkeys[keytypes[i]]));
+			debug_f("%s", path);
+			if ((f = fopen(path, "wb+")) == NULL)
+				abort();
+			if (fwrite(sshbuf_ptr(ts->smsgs), 1,
+			    sshbuf_len(ts->smsgs), f) != sshbuf_len(ts->smsgs))
+				abort();
+			fclose(f);
+			free(path);
+			//sshbuf_dump(ts->smsgs, stderr);
+			xasprintf(&path, "C2S-%s-%s",
+			    kextypes[j], sshkey_type(st->pubkeys[keytypes[i]]));
+			debug_f("%s", path);
+			if ((f = fopen(path, "wb+")) == NULL)
+				abort();
+			if (fwrite(sshbuf_ptr(ts->cmsgs), 1,
+			    sshbuf_len(ts->cmsgs), f) != sshbuf_len(ts->cmsgs))
+				abort();
+			fclose(f);
+			free(path);
+			//sshbuf_dump(ts->cmsgs, stderr);
+			sshbuf_free(ts->smsgs);
+			sshbuf_free(ts->cmsgs);
+			free(ts);
+		}
+	}
+	for (i = 0; keytypes[i] != -1; i++) {
+		xasprintf(&path, "%s.priv",
+		    sshkey_type(st->privkeys[keytypes[i]]));
+		debug_f("%s", path);
+		if (sshkey_save_private(st->privkeys[keytypes[i]], path,
+		    "", "", SSHKEY_PRIVATE_OPENSSH, NULL, 0) != 0)
+			abort();
+		free(path);
+		xasprintf(&path, "%s.pub",
+		    sshkey_type(st->pubkeys[keytypes[i]]));
+		debug_f("%s", path);
+		if (sshkey_save_public(st->pubkeys[keytypes[i]], path, "") != 0)
+			abort();
+		free(path);
+	}
+}
+#else /* !STANDALONE */
+static void
+do_kex(struct shared_state *st, struct test_state *ts, const char *kex)
+{
+	do_kex_with_key(st, ts, kex, KEY_RSA);
+	do_kex_with_key(st, ts, kex, KEY_DSA);
+	do_kex_with_key(st, ts, kex, KEY_ECDSA);
+	do_kex_with_key(st, ts, kex, KEY_ED25519);
+}
+
+static void
+kex_tests(struct shared_state *st, struct test_state *ts)
+{
+	do_kex(st, ts, "sntrup761x25519-sha512@openssh.com");
+	do_kex(st, ts, "curve25519-sha256@libssh.org");
+	do_kex(st, ts, "ecdh-sha2-nistp256");
+	do_kex(st, ts, "diffie-hellman-group1-sha1");
+	do_kex(st, ts, "diffie-hellman-group-exchange-sha1");
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
+{
+	static struct shared_state *st;
+	struct test_state *ts;
+	u_char crbuf[SSH_MAX_PRE_BANNER_LINES * 4];
+	u_char zbuf[4096] = {0};
+	static LogLevel loglevel = SYSLOG_LEVEL_INFO;
+
+	if (st == NULL) {
+		if (getenv("DEBUG") != NULL || getenv("KEX_FUZZ_DEBUG") != NULL)
+			loglevel = SYSLOG_LEVEL_DEBUG3;
+		log_init("kex_fuzz",
+		    loglevel, SYSLOG_FACILITY_AUTH, 1);
+		st = (struct shared_state *)xcalloc(1, sizeof(*st));
+		prepare_keys(st);
+	}
+
+	/* Ensure that we can complete (fail) banner exchange at least */
+	memset(crbuf, '\n', sizeof(crbuf));
+
+	ts = (struct test_state *)xcalloc(1, sizeof(*ts));
+	if ((ts->s_template = sshbuf_new()) == NULL ||
+	    sshbuf_put(ts->s_template, data, size) != 0 ||
+	    sshbuf_put(ts->s_template, crbuf, sizeof(crbuf)) != 0 ||
+	    sshbuf_put(ts->s_template, zbuf, sizeof(zbuf)) != 0)
+		abort();
+	kex_tests(st, ts);
+	sshbuf_free(ts->s_template);
+	free(ts);
+
+	ts = (struct test_state *)xcalloc(1, sizeof(*ts));
+	if ((ts->c_template = sshbuf_new()) == NULL ||
+	    sshbuf_put(ts->c_template, data, size) != 0 ||
+	    sshbuf_put(ts->c_template, crbuf, sizeof(crbuf)) != 0 ||
+	    sshbuf_put(ts->c_template, zbuf, sizeof(zbuf)) != 0)
+		abort();
+	kex_tests(st, ts);
+	sshbuf_free(ts->c_template);
+	free(ts);
+
+	return 0;
+}
+#endif /* STANDALONE */
+} /* extern "C" */
diff --git a/regress/misc/fuzz-harness/privkey_fuzz.cc b/regress/misc/fuzz-harness/privkey_fuzz.cc
new file mode 100644
index 0000000..ff0b0f7
--- /dev/null
+++ b/regress/misc/fuzz-harness/privkey_fuzz.cc
@@ -0,0 +1,21 @@
+#include <stddef.h>
+#include <stdio.h>
+#include <stdint.h>
+
+extern "C" {
+
+#include "sshkey.h"
+#include "sshbuf.h"
+
+int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
+{
+	struct sshkey *k = NULL;
+	struct sshbuf *b = sshbuf_from(data, size);
+	int r = sshkey_private_deserialize(b, &k);
+	if (r == 0) sshkey_free(k);
+	sshbuf_free(b);
+	return 0;
+}
+
+} // extern
+
diff --git a/regress/misc/fuzz-harness/pubkey_fuzz.cc b/regress/misc/fuzz-harness/pubkey_fuzz.cc
new file mode 100644
index 0000000..8bbc110
--- /dev/null
+++ b/regress/misc/fuzz-harness/pubkey_fuzz.cc
@@ -0,0 +1,18 @@
+#include <stddef.h>
+#include <stdio.h>
+#include <stdint.h>
+
+extern "C" {
+
+#include "sshkey.h"
+
+int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
+{
+	struct sshkey *k = NULL;
+	int r = sshkey_from_blob(data, size, &k);
+	if (r == 0) sshkey_free(k);
+	return 0;
+}
+
+} // extern
+
diff --git a/regress/misc/fuzz-harness/sig_fuzz.cc b/regress/misc/fuzz-harness/sig_fuzz.cc
new file mode 100644
index 0000000..b32502b
--- /dev/null
+++ b/regress/misc/fuzz-harness/sig_fuzz.cc
@@ -0,0 +1,62 @@
+// cc_fuzz_target test for public key parsing.
+
+#include <stddef.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+extern "C" {
+
+#include "includes.h"
+#include "sshkey.h"
+#include "ssherr.h"
+
+static struct sshkey *generate_or_die(int type, unsigned bits) {
+  int r;
+  struct sshkey *ret;
+  if ((r = sshkey_generate(type, bits, &ret)) != 0) {
+    fprintf(stderr, "generate(%d, %u): %s", type, bits, ssh_err(r));
+    abort();
+  }
+  return ret;
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t* sig, size_t slen)
+{
+#ifdef WITH_OPENSSL
+  static struct sshkey *rsa = generate_or_die(KEY_RSA, 2048);
+  static struct sshkey *dsa = generate_or_die(KEY_DSA, 1024);
+  static struct sshkey *ecdsa256 = generate_or_die(KEY_ECDSA, 256);
+  static struct sshkey *ecdsa384 = generate_or_die(KEY_ECDSA, 384);
+  static struct sshkey *ecdsa521 = generate_or_die(KEY_ECDSA, 521);
+#endif
+  struct sshkey_sig_details *details = NULL;
+  static struct sshkey *ed25519 = generate_or_die(KEY_ED25519, 0);
+  static const char *data = "If everyone started announcing his nose had "
+      "run away, I don’t know how it would all end";
+  static const size_t dlen = strlen(data);
+
+#ifdef WITH_OPENSSL
+  sshkey_verify(rsa, sig, slen, (const u_char *)data, dlen, NULL, 0, &details);
+  sshkey_sig_details_free(details);
+  details = NULL;
+  sshkey_verify(dsa, sig, slen, (const u_char *)data, dlen, NULL, 0, &details);
+  sshkey_sig_details_free(details);
+  details = NULL;
+  sshkey_verify(ecdsa256, sig, slen, (const u_char *)data, dlen, NULL, 0, &details);
+  sshkey_sig_details_free(details);
+  details = NULL;
+  sshkey_verify(ecdsa384, sig, slen, (const u_char *)data, dlen, NULL, 0, &details);
+  sshkey_sig_details_free(details);
+  details = NULL;
+  sshkey_verify(ecdsa521, sig, slen, (const u_char *)data, dlen, NULL, 0, &details);
+  sshkey_sig_details_free(details);
+  details = NULL;
+#endif
+  sshkey_verify(ed25519, sig, slen, (const u_char *)data, dlen, NULL, 0, &details);
+  sshkey_sig_details_free(details);
+  return 0;
+}
+
+} // extern
diff --git a/regress/misc/fuzz-harness/ssh-sk-null.cc b/regress/misc/fuzz-harness/ssh-sk-null.cc
new file mode 100644
index 0000000..948c3d9
--- /dev/null
+++ b/regress/misc/fuzz-harness/ssh-sk-null.cc
@@ -0,0 +1,52 @@
+/* $OpenBSD$ */
+/*
+ * Copyright (c) 2019 Google LLC
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+extern "C" {
+
+#include "includes.h"
+
+#include <sys/types.h>
+
+#include "ssherr.h"
+#include "ssh-sk.h"
+
+int
+sshsk_enroll(int type, const char *provider_path, const char *device,
+    const char *application, const char *userid, uint8_t flags,
+    const char *pin, struct sshbuf *challenge_buf,
+    struct sshkey **keyp, struct sshbuf *attest)
+{
+	return SSH_ERR_FEATURE_UNSUPPORTED;
+}
+
+int
+sshsk_sign(const char *provider_path, struct sshkey *key,
+    u_char **sigp, size_t *lenp, const u_char *data, size_t datalen,
+    u_int compat, const char *pin)
+{
+	return SSH_ERR_FEATURE_UNSUPPORTED;
+}
+
+int
+sshsk_load_resident(const char *provider_path, const char *device,
+    const char *pin, u_int flags, struct sshsk_resident_key ***srksp,
+    size_t *nsrksp)
+{
+	return SSH_ERR_FEATURE_UNSUPPORTED;
+}
+
+};
diff --git a/regress/misc/fuzz-harness/sshsig_fuzz.cc b/regress/misc/fuzz-harness/sshsig_fuzz.cc
new file mode 100644
index 0000000..02211a0
--- /dev/null
+++ b/regress/misc/fuzz-harness/sshsig_fuzz.cc
@@ -0,0 +1,37 @@
+// cc_fuzz_target test for sshsig verification.
+
+#include <stddef.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+extern "C" {
+
+#include "includes.h"
+#include "sshkey.h"
+#include "ssherr.h"
+#include "sshbuf.h"
+#include "sshsig.h"
+#include "log.h"
+
+int LLVMFuzzerTestOneInput(const uint8_t* sig, size_t slen)
+{
+  static const char *data = "If everyone started announcing his nose had "
+      "run away, I don’t know how it would all end";
+  struct sshbuf *signature = sshbuf_from(sig, slen);
+  struct sshbuf *message = sshbuf_from(data, strlen(data));
+  struct sshkey *k = NULL;
+  struct sshkey_sig_details *details = NULL;
+  extern char *__progname;
+
+  log_init(__progname, SYSLOG_LEVEL_QUIET, SYSLOG_FACILITY_USER, 1);
+  sshsig_verifyb(signature, message, "castle", &k, &details);
+  sshkey_sig_details_free(details);
+  sshkey_free(k);
+  sshbuf_free(signature);
+  sshbuf_free(message);
+  return 0;
+}
+
+} // extern
diff --git a/regress/misc/fuzz-harness/sshsigopt_fuzz.cc b/regress/misc/fuzz-harness/sshsigopt_fuzz.cc
new file mode 100644
index 0000000..7424fcb
--- /dev/null
+++ b/regress/misc/fuzz-harness/sshsigopt_fuzz.cc
@@ -0,0 +1,29 @@
+#include <stddef.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdlib.h>
+
+extern "C" {
+
+#include "sshsig.h"
+
+int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
+{
+	char *cp = (char *)malloc(size + 1);
+	struct sshsigopt *opts = NULL;
+
+	if (cp == NULL)
+		goto out;
+	memcpy(cp, data, size);
+	cp[size] = '\0';
+	if ((opts = sshsigopt_parse(cp, "libfuzzer", 0, NULL)) == NULL)
+		goto out;
+
+ out:
+	free(cp);
+	sshsigopt_free(opts);
+	return 0;
+}
+
+} // extern "C"
diff --git a/regress/misc/fuzz-harness/testdata/README b/regress/misc/fuzz-harness/testdata/README
new file mode 100644
index 0000000..7520530
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/README
@@ -0,0 +1,4 @@
+This is preparatory data for fuzzing testing including scripts and test keys,
+corresponding to ../fixed-keys that are used in the fuzz tests and consequent
+fuzzing seed corpora. They should not be changed unless the affected seed
+corpora are also regenerated.
diff --git a/regress/misc/fuzz-harness/testdata/create-agent-corpus.sh b/regress/misc/fuzz-harness/testdata/create-agent-corpus.sh
new file mode 100755
index 0000000..1043b9f
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/create-agent-corpus.sh
@@ -0,0 +1,44 @@
+#!/bin/sh
+
+# Exercise ssh-agent to generate fuzzing corpus
+
+# XXX assumes agent hacked up with sk-dummy.o and ssh-sk.o linked directly
+#     and dumping of e->request for each message.
+
+set -xe
+SSH_AUTH_SOCK=$PWD/sock
+rm -f agent-[0-9]* $SSH_AUTH_SOCK
+export SSH_AUTH_SOCK
+../../../../ssh-agent -D -a $SSH_AUTH_SOCK &
+sleep 1
+AGENT_PID=$!
+trap "kill $AGENT_PID" EXIT
+
+PRIV="id_dsa id_ecdsa id_ecdsa_sk id_ed25519 id_ed25519_sk id_rsa"
+
+# add keys
+ssh-add $PRIV
+
+# sign
+ssh-add -T *.pub
+
+# list
+ssh-add -l
+
+# remove individually
+ssh-add -d $PRIV
+
+# re-add with constraints
+ssh-add -c -t 3h $PRIV
+
+# delete all
+ssh-add -D
+
+# attempt to add a PKCS#11 token
+ssh-add -s /fake || :
+
+# attempt to delete PKCS#11
+ssh-add -e /fake || :
+
+ssh-add -L
+
diff --git a/regress/misc/fuzz-harness/testdata/id_dsa b/regress/misc/fuzz-harness/testdata/id_dsa
new file mode 100644
index 0000000..88bf556
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_dsa
@@ -0,0 +1,21 @@
+-----BEGIN OPENSSH PRIVATE KEY-----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+-----END OPENSSH PRIVATE KEY-----
diff --git a/regress/misc/fuzz-harness/testdata/id_dsa-cert.pub b/regress/misc/fuzz-harness/testdata/id_dsa-cert.pub
new file mode 100644
index 0000000..3afb87f
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_dsa-cert.pub
@@ -0,0 +1 @@
+ssh-dss-cert-v01@openssh.com AAAAHHNzaC1kc3MtY2VydC12MDFAb3BlbnNzaC5jb20AAAAguF716Yub+vVKNlONKLsfxGYWkRe/PyjfYdGRTsFaDvAAAACBAKwZN+OlDjrkQ6R9Bckz0E699FATR+qXKQCWz6dzP5PuGtt5JxG7zGnDOzOck2bGVbyjpxQOIeYEnk4eBqZQL03tgl5T/p+c4BmJ+A3yaorqTykoe6N7wA06JiAcuXTKIBJADf/+ozLNn5b+F6agtKYsBsSqV9ZV7JjH7C1rVWb5AAAAFQC9bJ6G9S90e9DFq9iBLmnS3lB3tQAAAIEAhED1jL5/grOqm/+ogI87fOTjZS4/tYCFJbacJtB0uUKJJPFyMqBy9c1FyTAk/jgmNIc60nL8Ay0ms8hstgboq5ZN0GUQcWIboNp+8sb6o8xIvZs+NdM6G44xsIchn7lYGRZMd4b82/XWIjTU5/1Xq1eSKDbcrfvR+WRGRcWL0x0AAACAK3phRxCQ3AbsH97kzUVmws/06RUHcHAsA6OZZ0enKG7cenBIlrdcsS+Fc3SLohUjYqA+j/Ya1gDqse3Xgv7q7WmaGHywC9CSynepkH7GH80/6EGp/SxsdfTJhvMo68jlIJz+QorrJqBwFk6y5sz8oLxPHJWCYPlzpbNiyHlMSm8AAAAAAAAD6AAAAAEAAAAHdWx5c3NlcwAAABcAAAAHdWx5c3NlcwAAAAhvZHlzc2V1cwAAAAAAAAAA//////////8AAAAAAAAAggAAABVwZXJtaXQtWDExLWZvcndhcmRpbmcAAAAAAAAAF3Blcm1pdC1hZ2VudC1mb3J3YXJkaW5nAAAAAAAAABZwZXJtaXQtcG9ydC1mb3J3YXJkaW5nAAAAAAAAAApwZXJtaXQtcHR5AAAAAAAAAA5wZXJtaXQtdXNlci1yYwAAAAAAAAAAAAAAMwAAAAtzc2gtZWQyNTUxOQAAACAz0F5hFTFS5nhUcmnyjFVoDw5L/P7kQU8JnBA2rWczAwAAAFMAAAALc3NoLWVkMjU1MTkAAABAjMQEZcbdUYJBjIC4GxByFDOb8tv71vDZdx7irHwaqIjx5rzpJUuOV1r8ZO4kY+Yaiun1yrWj2QYkfJrHBvD1DA== id_dsa.pub
diff --git a/regress/misc/fuzz-harness/testdata/id_dsa.pub b/regress/misc/fuzz-harness/testdata/id_dsa.pub
new file mode 100644
index 0000000..6f91c4e
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_dsa.pub
@@ -0,0 +1 @@
+ssh-dss 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
diff --git a/regress/misc/fuzz-harness/testdata/id_ecdsa b/regress/misc/fuzz-harness/testdata/id_ecdsa
new file mode 100644
index 0000000..c1a96c6
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_ecdsa
@@ -0,0 +1,8 @@
+-----BEGIN OPENSSH PRIVATE KEY-----
+b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAaAAAABNlY2RzYS
+1zaGEyLW5pc3RwMjU2AAAACG5pc3RwMjU2AAAAQQTDJ0VlMv+0rguNzaJ1DF2KueHaxRSQ
+6LpIxGbulrg1a8RPbnMXwag5GcDiDllD2lDUJUuBEWyjXA0rZoZX35ELAAAAoE/Bbr5PwW
+6+AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBMMnRWUy/7SuC43N
+onUMXYq54drFFJDoukjEZu6WuDVrxE9ucxfBqDkZwOIOWUPaUNQlS4ERbKNcDStmhlffkQ
+sAAAAhAIhE6hCID5oOm1TDktc++KFKyScjLifcZ6Cgv5xSSyLOAAAAAAECAwQFBgc=
+-----END OPENSSH PRIVATE KEY-----
diff --git a/regress/misc/fuzz-harness/testdata/id_ecdsa-cert.pub b/regress/misc/fuzz-harness/testdata/id_ecdsa-cert.pub
new file mode 100644
index 0000000..9de5999
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_ecdsa-cert.pub
@@ -0,0 +1 @@
+ecdsa-sha2-nistp256-cert-v01@openssh.com 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 id_ecdsa.pub
diff --git a/regress/misc/fuzz-harness/testdata/id_ecdsa.pub b/regress/misc/fuzz-harness/testdata/id_ecdsa.pub
new file mode 100644
index 0000000..30a7cc2
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_ecdsa.pub
@@ -0,0 +1 @@
+ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBMMnRWUy/7SuC43NonUMXYq54drFFJDoukjEZu6WuDVrxE9ucxfBqDkZwOIOWUPaUNQlS4ERbKNcDStmhlffkQs=
diff --git a/regress/misc/fuzz-harness/testdata/id_ecdsa_sk b/regress/misc/fuzz-harness/testdata/id_ecdsa_sk
new file mode 100644
index 0000000..5a364ed
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_ecdsa_sk
@@ -0,0 +1,14 @@
+-----BEGIN OPENSSH PRIVATE KEY-----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+-----END OPENSSH PRIVATE KEY-----
diff --git a/regress/misc/fuzz-harness/testdata/id_ecdsa_sk-cert.pub b/regress/misc/fuzz-harness/testdata/id_ecdsa_sk-cert.pub
new file mode 100644
index 0000000..14040fa
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_ecdsa_sk-cert.pub
@@ -0,0 +1 @@
+sk-ecdsa-sha2-nistp256-cert-v01@openssh.com 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 djm@djm.syd.corp.google.com
diff --git a/regress/misc/fuzz-harness/testdata/id_ecdsa_sk.pub b/regress/misc/fuzz-harness/testdata/id_ecdsa_sk.pub
new file mode 100644
index 0000000..1b5e829
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_ecdsa_sk.pub
@@ -0,0 +1 @@
+sk-ecdsa-sha2-nistp256@openssh.com AAAAInNrLWVjZHNhLXNoYTItbmlzdHAyNTZAb3BlbnNzaC5jb20AAAAIbmlzdHAyNTYAAABBBNjJTvrOinVU5vgN8pZidHlvRM4LfPDwPM5sB8dYHmjrGWz605iISV5e8gSLTQNraIIrjuFptlM6EvJ4FfYC+7kAAAAEc3NoOg== djm@djm.syd.corp.google.com
diff --git a/regress/misc/fuzz-harness/testdata/id_ed25519 b/regress/misc/fuzz-harness/testdata/id_ed25519
new file mode 100644
index 0000000..6a7fbac
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_ed25519
@@ -0,0 +1,7 @@
+-----BEGIN OPENSSH PRIVATE KEY-----
+b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW
+QyNTUxOQAAACAz0F5hFTFS5nhUcmnyjFVoDw5L/P7kQU8JnBA2rWczAwAAAIhWlP99VpT/
+fQAAAAtzc2gtZWQyNTUxOQAAACAz0F5hFTFS5nhUcmnyjFVoDw5L/P7kQU8JnBA2rWczAw
+AAAEDE1rlcMC0s0X3TKVZAOVavZOywwkXw8tO5dLObxaCMEDPQXmEVMVLmeFRyafKMVWgP
+Dkv8/uRBTwmcEDatZzMDAAAAAAECAwQF
+-----END OPENSSH PRIVATE KEY-----
diff --git a/regress/misc/fuzz-harness/testdata/id_ed25519-cert.pub b/regress/misc/fuzz-harness/testdata/id_ed25519-cert.pub
new file mode 100644
index 0000000..6a95fed
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_ed25519-cert.pub
@@ -0,0 +1 @@
+ssh-ed25519-cert-v01@openssh.com AAAAIHNzaC1lZDI1NTE5LWNlcnQtdjAxQG9wZW5zc2guY29tAAAAIMDQjYH6XRzH3j3MW1DdjCoAfvrHfgjnVGF+sLK0pBfqAAAAIDPQXmEVMVLmeFRyafKMVWgPDkv8/uRBTwmcEDatZzMDAAAAAAAAA+sAAAABAAAAB3VseXNzZXMAAAAXAAAAB3VseXNzZXMAAAAIb2R5c3NldXMAAAAAAAAAAP//////////AAAAAAAAAIIAAAAVcGVybWl0LVgxMS1mb3J3YXJkaW5nAAAAAAAAABdwZXJtaXQtYWdlbnQtZm9yd2FyZGluZwAAAAAAAAAWcGVybWl0LXBvcnQtZm9yd2FyZGluZwAAAAAAAAAKcGVybWl0LXB0eQAAAAAAAAAOcGVybWl0LXVzZXItcmMAAAAAAAAAAAAAADMAAAALc3NoLWVkMjU1MTkAAAAgM9BeYRUxUuZ4VHJp8oxVaA8OS/z+5EFPCZwQNq1nMwMAAABTAAAAC3NzaC1lZDI1NTE5AAAAQBj0og+s09/HpwdHZbzN0twooKPDWWrxGfnP1Joy6cDnY2BCSQ7zg9vbq11kLF8H/sKOTZWAQrUZ7LlChOu9Ogw= id_ed25519.pub
diff --git a/regress/misc/fuzz-harness/testdata/id_ed25519.pub b/regress/misc/fuzz-harness/testdata/id_ed25519.pub
new file mode 100644
index 0000000..87b6174
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_ed25519.pub
@@ -0,0 +1,2 @@
+ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIDPQXmEVMVLmeFRyafKMVWgPDkv8/uRBTwmcEDatZzMD
+
diff --git a/regress/misc/fuzz-harness/testdata/id_ed25519_sk b/regress/misc/fuzz-harness/testdata/id_ed25519_sk
new file mode 100644
index 0000000..9dcda6c
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_ed25519_sk
@@ -0,0 +1,8 @@
+-----BEGIN OPENSSH PRIVATE KEY-----
+b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAASgAAABpzay1zc2
+gtZWQyNTUxOUBvcGVuc3NoLmNvbQAAACCTJtH10vWhIDxd62edvMLg9u2cwYKyqa7332je
+RArHjAAAAARzc2g6AAAAwN7vvE3e77xNAAAAGnNrLXNzaC1lZDI1NTE5QG9wZW5zc2guY2
+9tAAAAIJMm0fXS9aEgPF3rZ528wuD27ZzBgrKprvffaN5ECseMAAAABHNzaDoBAAAAQEsS
+xLFiVzfpH2mt9xh8i/zmHV646Hud4QruNBAGNl8gkybR9dL1oSA8XetnnbzC4PbtnMGCsq
+mu999o3kQKx4wAAAAAAAAAG2RqbUBkam0uc3lkLmNvcnAuZ29vZ2xlLmNvbQECAwQFBg==
+-----END OPENSSH PRIVATE KEY-----
diff --git a/regress/misc/fuzz-harness/testdata/id_ed25519_sk-cert.pub b/regress/misc/fuzz-harness/testdata/id_ed25519_sk-cert.pub
new file mode 100644
index 0000000..9e41eec
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_ed25519_sk-cert.pub
@@ -0,0 +1 @@
+sk-ssh-ed25519-cert-v01@openssh.com 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 djm@djm.syd.corp.google.com
diff --git a/regress/misc/fuzz-harness/testdata/id_ed25519_sk.pub b/regress/misc/fuzz-harness/testdata/id_ed25519_sk.pub
new file mode 100644
index 0000000..38d1984
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_ed25519_sk.pub
@@ -0,0 +1 @@
+sk-ssh-ed25519@openssh.com AAAAGnNrLXNzaC1lZDI1NTE5QG9wZW5zc2guY29tAAAAIJMm0fXS9aEgPF3rZ528wuD27ZzBgrKprvffaN5ECseMAAAABHNzaDo= djm@djm.syd.corp.google.com
diff --git a/regress/misc/fuzz-harness/testdata/id_rsa b/regress/misc/fuzz-harness/testdata/id_rsa
new file mode 100644
index 0000000..574fecf
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_rsa
@@ -0,0 +1,27 @@
+-----BEGIN OPENSSH PRIVATE KEY-----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+-----END OPENSSH PRIVATE KEY-----
diff --git a/regress/misc/fuzz-harness/testdata/id_rsa-cert.pub b/regress/misc/fuzz-harness/testdata/id_rsa-cert.pub
new file mode 100644
index 0000000..01761a3
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_rsa-cert.pub
@@ -0,0 +1 @@
+ssh-rsa-cert-v01@openssh.com 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 id_rsa.pub
diff --git a/regress/misc/fuzz-harness/testdata/id_rsa.pub b/regress/misc/fuzz-harness/testdata/id_rsa.pub
new file mode 100644
index 0000000..05015e1
--- /dev/null
+++ b/regress/misc/fuzz-harness/testdata/id_rsa.pub
@@ -0,0 +1 @@
+ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDf56l/5UYqgY9oBlet/pLRzK6ZCd12QYGdUVfQDl6HftG0u6DSpjm2HGwFRsYZWv2ZN3ZBfAu6MHBiDmXUw/8WaD7nfXZmDH2keZL6opQttqvSGU2Cm00Rv5o1R3ej2qDdpepebv5meMBXTl5/+bE1E3Zm+4STDtxGmlMlxsEj68XeVe4JedfaSUMj3kaXYBbdYdG1qeosdle4GSONEEMpzsxSr8Y/WGYuIB33l29Tt9mNGUgSw/zjMYQjUVvQv+SY8dw62JV8d+3wK2YL2/r73gms6I8EE1JxX53KuAAY+x0p2v/W8ilCYI2Ijyzc8KIPwntmIFpibQjx+rkb+qdT
diff --git a/regress/misc/sk-dummy/Makefile b/regress/misc/sk-dummy/Makefile
new file mode 100644
index 0000000..18b0a24
--- /dev/null
+++ b/regress/misc/sk-dummy/Makefile
@@ -0,0 +1,66 @@
+#	$OpenBSD: Makefile,v 1.3 2023/01/15 23:35:10 djm Exp $
+
+.include <bsd.own.mk>
+.include <bsd.obj.mk>
+
+PROG=	sk-dummy.so
+NOMAN=
+
+SSHREL=../../../../../usr.bin/ssh
+.PATH: ${.CURDIR}/${SSHREL}
+
+SRCS=sk-dummy.c
+# From usr.bin/ssh
+SRCS+=ed25519.c hash.c
+OPENSSL?=	yes
+
+CFLAGS+=	-fPIC
+
+.if (${OPENSSL:L} == "yes")
+CFLAGS+=	-DWITH_OPENSSL
+.endif
+
+# enable warnings
+WARNINGS=Yes
+
+DEBUG=-g
+CFLAGS+=	-fstack-protector-all
+CDIAGFLAGS=	-Wall
+CDIAGFLAGS+=	-Wextra
+CDIAGFLAGS+=	-Werror
+CDIAGFLAGS+=	-Wchar-subscripts
+CDIAGFLAGS+=	-Wcomment
+CDIAGFLAGS+=	-Wformat
+CDIAGFLAGS+=	-Wformat-security
+CDIAGFLAGS+=	-Wimplicit
+CDIAGFLAGS+=	-Winline
+CDIAGFLAGS+=	-Wmissing-declarations
+CDIAGFLAGS+=	-Wmissing-prototypes
+CDIAGFLAGS+=	-Wparentheses
+CDIAGFLAGS+=	-Wpointer-arith
+CDIAGFLAGS+=	-Wreturn-type
+CDIAGFLAGS+=	-Wshadow
+CDIAGFLAGS+=	-Wsign-compare
+CDIAGFLAGS+=	-Wstrict-aliasing
+CDIAGFLAGS+=	-Wstrict-prototypes
+CDIAGFLAGS+=	-Wswitch
+CDIAGFLAGS+=	-Wtrigraphs
+CDIAGFLAGS+=	-Wuninitialized
+CDIAGFLAGS+=	-Wunused
+CDIAGFLAGS+=	-Wno-unused-parameter
+.if ${COMPILER_VERSION:L} != "gcc3"
+CDIAGFLAGS+=	-Wold-style-definition
+.endif
+
+CFLAGS+=-I${.CURDIR}/${SSHREL}
+
+.if (${OPENSSL:L} == "yes")
+LDADD+= -lcrypto
+DPADD+= ${LIBCRYPTO}
+.endif
+
+$(PROG): $(OBJS)
+	$(CC) $(LDFLAGS) -shared -o $@ $(OBJS) $(LDADD)
+
+.include <bsd.prog.mk>
+
diff --git a/regress/misc/sk-dummy/fatal.c b/regress/misc/sk-dummy/fatal.c
new file mode 100644
index 0000000..c6e4b5d
--- /dev/null
+++ b/regress/misc/sk-dummy/fatal.c
@@ -0,0 +1,27 @@
+/* public domain */
+
+#include "includes.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <unistd.h>
+
+#include "log.h"
+
+void
+sshfatal(const char *file, const char *func, int line, int showfunc,
+    LogLevel level, const char *suffix, const char *fmt, ...)
+{
+	va_list ap;
+
+	if (showfunc)
+		fprintf(stderr, "%s: ", func);
+	va_start(ap, fmt);
+	vfprintf(stderr, fmt, ap);
+	va_end(ap);
+	if (suffix != NULL)
+		fprintf(stderr, ": %s", suffix);
+	fputc('\n', stderr);
+	_exit(1);
+}
diff --git a/regress/misc/sk-dummy/sk-dummy.c b/regress/misc/sk-dummy/sk-dummy.c
new file mode 100644
index 0000000..ad5e474
--- /dev/null
+++ b/regress/misc/sk-dummy/sk-dummy.c
@@ -0,0 +1,552 @@
+/*
+ * Copyright (c) 2019 Markus Friedl
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "includes.h"
+
+#ifdef HAVE_STDINT_H
+#include <stdint.h>
+#endif
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <stddef.h>
+#include <stdarg.h>
+#ifdef HAVE_SHA2_H
+#include <sha2.h>
+#endif
+
+#include "crypto_api.h"
+#include "sk-api.h"
+
+#if defined(WITH_OPENSSL) && !defined(OPENSSL_HAS_ECC)
+# undef WITH_OPENSSL
+#endif
+
+#ifdef WITH_OPENSSL
+/* We don't use sha2 from OpenSSL and they can conflict with system sha2.h */
+#define OPENSSL_NO_SHA
+#define USE_LIBC_SHA2	/* NetBSD 9 */
+#include <openssl/opensslv.h>
+#include <openssl/crypto.h>
+#include <openssl/evp.h>
+#include <openssl/bn.h>
+#include <openssl/ec.h>
+#include <openssl/ecdsa.h>
+#include <openssl/pem.h>
+
+/* Compatibility with OpenSSH 1.0.x */
+#if (OPENSSL_VERSION_NUMBER < 0x10100000L)
+#define ECDSA_SIG_get0(sig, pr, ps) \
+	do { \
+		(*pr) = sig->r; \
+		(*ps) = sig->s; \
+	} while (0)
+#endif
+#endif /* WITH_OPENSSL */
+
+/* #define SK_DEBUG 1 */
+
+#if SSH_SK_VERSION_MAJOR != 0x000a0000
+# error SK API has changed, sk-dummy.c needs an update
+#endif
+
+#ifdef SK_DUMMY_INTEGRATE
+# define sk_api_version		ssh_sk_api_version
+# define sk_enroll		ssh_sk_enroll
+# define sk_sign		ssh_sk_sign
+# define sk_load_resident_keys	ssh_sk_load_resident_keys
+#endif /* !SK_STANDALONE */
+
+static void skdebug(const char *func, const char *fmt, ...)
+    __attribute__((__format__ (printf, 2, 3)));
+
+static void
+skdebug(const char *func, const char *fmt, ...)
+{
+#if defined(SK_DEBUG)
+	va_list ap;
+
+	va_start(ap, fmt);
+	fprintf(stderr, "sk-dummy %s: ", func);
+	vfprintf(stderr, fmt, ap);
+	fputc('\n', stderr);
+	va_end(ap);
+#else
+	(void)func; /* XXX */
+	(void)fmt; /* XXX */
+#endif
+}
+
+uint32_t
+sk_api_version(void)
+{
+	return SSH_SK_VERSION_MAJOR;
+}
+
+static int
+pack_key_ecdsa(struct sk_enroll_response *response)
+{
+#ifdef OPENSSL_HAS_ECC
+	EC_KEY *key = NULL;
+	const EC_GROUP *g;
+	const EC_POINT *q;
+	int ret = -1;
+	long privlen;
+	BIO *bio = NULL;
+	char *privptr;
+
+	response->public_key = NULL;
+	response->public_key_len = 0;
+	response->key_handle = NULL;
+	response->key_handle_len = 0;
+
+	if ((key = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1)) == NULL) {
+		skdebug(__func__, "EC_KEY_new_by_curve_name");
+		goto out;
+	}
+	if (EC_KEY_generate_key(key) != 1) {
+		skdebug(__func__, "EC_KEY_generate_key");
+		goto out;
+	}
+	EC_KEY_set_asn1_flag(key, OPENSSL_EC_NAMED_CURVE);
+	if ((bio = BIO_new(BIO_s_mem())) == NULL ||
+	    (g = EC_KEY_get0_group(key)) == NULL ||
+	    (q = EC_KEY_get0_public_key(key)) == NULL) {
+		skdebug(__func__, "couldn't get key parameters");
+		goto out;
+	}
+	response->public_key_len = EC_POINT_point2oct(g, q,
+	    POINT_CONVERSION_UNCOMPRESSED, NULL, 0, NULL);
+	if (response->public_key_len == 0 || response->public_key_len > 2048) {
+		skdebug(__func__, "bad pubkey length %zu",
+		    response->public_key_len);
+		goto out;
+	}
+	if ((response->public_key = malloc(response->public_key_len)) == NULL) {
+		skdebug(__func__, "malloc pubkey failed");
+		goto out;
+	}
+	if (EC_POINT_point2oct(g, q, POINT_CONVERSION_UNCOMPRESSED,
+	    response->public_key, response->public_key_len, NULL) == 0) {
+		skdebug(__func__, "EC_POINT_point2oct failed");
+		goto out;
+	}
+	/* Key handle contains PEM encoded private key */
+	if (!PEM_write_bio_ECPrivateKey(bio, key, NULL, NULL, 0, NULL, NULL)) {
+		skdebug(__func__, "PEM_write_bio_ECPrivateKey failed");
+		goto out;
+	}
+	if ((privlen = BIO_get_mem_data(bio, &privptr)) <= 0) {
+		skdebug(__func__, "BIO_get_mem_data failed");
+		goto out;
+	}
+	if ((response->key_handle = malloc(privlen)) == NULL) {
+		skdebug(__func__, "malloc key_handle failed");
+		goto out;
+	}
+	response->key_handle_len = (size_t)privlen;
+	memcpy(response->key_handle, privptr, response->key_handle_len);
+	/* success */
+	ret = 0;
+ out:
+	if (ret != 0) {
+		if (response->public_key != NULL) {
+			memset(response->public_key, 0,
+			    response->public_key_len);
+			free(response->public_key);
+			response->public_key = NULL;
+		}
+		if (response->key_handle != NULL) {
+			memset(response->key_handle, 0,
+			    response->key_handle_len);
+			free(response->key_handle);
+			response->key_handle = NULL;
+		}
+	}
+	BIO_free(bio);
+	EC_KEY_free(key);
+	return ret;
+#else
+	return -1;
+#endif
+}
+
+static int
+pack_key_ed25519(struct sk_enroll_response *response)
+{
+	int ret = -1;
+	u_char pk[crypto_sign_ed25519_PUBLICKEYBYTES];
+	u_char sk[crypto_sign_ed25519_SECRETKEYBYTES];
+
+	response->public_key = NULL;
+	response->public_key_len = 0;
+	response->key_handle = NULL;
+	response->key_handle_len = 0;
+
+	memset(pk, 0, sizeof(pk));
+	memset(sk, 0, sizeof(sk));
+	crypto_sign_ed25519_keypair(pk, sk);
+
+	response->public_key_len = sizeof(pk);
+	if ((response->public_key = malloc(response->public_key_len)) == NULL) {
+		skdebug(__func__, "malloc pubkey failed");
+		goto out;
+	}
+	memcpy(response->public_key, pk, sizeof(pk));
+	/* Key handle contains sk */
+	response->key_handle_len = sizeof(sk);
+	if ((response->key_handle = malloc(response->key_handle_len)) == NULL) {
+		skdebug(__func__, "malloc key_handle failed");
+		goto out;
+	}
+	memcpy(response->key_handle, sk, sizeof(sk));
+	/* success */
+	ret = 0;
+ out:
+	if (ret != 0)
+		free(response->public_key);
+	return ret;
+}
+
+static int
+check_options(struct sk_option **options)
+{
+	size_t i;
+
+	if (options == NULL)
+		return 0;
+	for (i = 0; options[i] != NULL; i++) {
+		skdebug(__func__, "requested unsupported option %s",
+		    options[i]->name);
+		if (options[i]->required) {
+			skdebug(__func__, "unknown required option");
+			return -1;
+		}
+	}
+	return 0;
+}
+
+int
+sk_enroll(uint32_t alg, const uint8_t *challenge, size_t challenge_len,
+    const char *application, uint8_t flags, const char *pin,
+    struct sk_option **options, struct sk_enroll_response **enroll_response)
+{
+	struct sk_enroll_response *response = NULL;
+	int ret = SSH_SK_ERR_GENERAL;
+
+	(void)flags; /* XXX; unused */
+
+	if (enroll_response == NULL) {
+		skdebug(__func__, "enroll_response == NULL");
+		goto out;
+	}
+	*enroll_response = NULL;
+	if (check_options(options) != 0)
+		goto out; /* error already logged */
+	if ((response = calloc(1, sizeof(*response))) == NULL) {
+		skdebug(__func__, "calloc response failed");
+		goto out;
+	}
+	response->flags = flags;
+	switch(alg) {
+	case SSH_SK_ECDSA:
+		if (pack_key_ecdsa(response) != 0)
+			goto out;
+		break;
+	case SSH_SK_ED25519:
+		if (pack_key_ed25519(response) != 0)
+			goto out;
+		break;
+	default:
+		skdebug(__func__, "unsupported key type %d", alg);
+		return -1;
+	}
+	/* Have to return something here */
+	if ((response->signature = calloc(1, 1)) == NULL) {
+		skdebug(__func__, "calloc signature failed");
+		goto out;
+	}
+	response->signature_len = 0;
+
+	*enroll_response = response;
+	response = NULL;
+	ret = 0;
+ out:
+	if (response != NULL) {
+		free(response->public_key);
+		free(response->key_handle);
+		free(response->signature);
+		free(response->attestation_cert);
+		free(response);
+	}
+	return ret;
+}
+
+static void
+dump(const char *preamble, const void *sv, size_t l)
+{
+#ifdef SK_DEBUG
+	const u_char *s = (const u_char *)sv;
+	size_t i;
+
+	fprintf(stderr, "%s (len %zu):\n", preamble, l);
+	for (i = 0; i < l; i++) {
+		if (i % 16 == 0)
+			fprintf(stderr, "%04zu: ", i);
+		fprintf(stderr, "%02x", s[i]);
+		if (i % 16 == 15 || i == l - 1)
+			fprintf(stderr, "\n");
+	}
+#endif
+}
+
+static int
+sig_ecdsa(const uint8_t *message, size_t message_len,
+    const char *application, uint32_t counter, uint8_t flags,
+    const uint8_t *key_handle, size_t key_handle_len,
+    struct sk_sign_response *response)
+{
+#ifdef OPENSSL_HAS_ECC
+	ECDSA_SIG *sig = NULL;
+	const BIGNUM *sig_r, *sig_s;
+	int ret = -1;
+	BIO *bio = NULL;
+	EVP_PKEY *pk = NULL;
+	EC_KEY *ec = NULL;
+	SHA2_CTX ctx;
+	uint8_t	apphash[SHA256_DIGEST_LENGTH];
+	uint8_t	sighash[SHA256_DIGEST_LENGTH];
+	uint8_t countbuf[4];
+
+	/* Decode EC_KEY from key handle */
+	if ((bio = BIO_new(BIO_s_mem())) == NULL ||
+	    BIO_write(bio, key_handle, key_handle_len) != (int)key_handle_len) {
+		skdebug(__func__, "BIO setup failed");
+		goto out;
+	}
+	if ((pk = PEM_read_bio_PrivateKey(bio, NULL, NULL, "")) == NULL) {
+		skdebug(__func__, "PEM_read_bio_PrivateKey failed");
+		goto out;
+	}
+	if (EVP_PKEY_base_id(pk) != EVP_PKEY_EC) {
+		skdebug(__func__, "Not an EC key: %d", EVP_PKEY_base_id(pk));
+		goto out;
+	}
+	if ((ec = EVP_PKEY_get1_EC_KEY(pk)) == NULL) {
+		skdebug(__func__, "EVP_PKEY_get1_EC_KEY failed");
+		goto out;
+	}
+	/* Expect message to be pre-hashed */
+	if (message_len != SHA256_DIGEST_LENGTH) {
+		skdebug(__func__, "bad message len %zu", message_len);
+		goto out;
+	}
+	/* Prepare data to be signed */
+	dump("message", message, message_len);
+	SHA256Init(&ctx);
+	SHA256Update(&ctx, (const u_char *)application, strlen(application));
+	SHA256Final(apphash, &ctx);
+	dump("apphash", apphash, sizeof(apphash));
+	countbuf[0] = (counter >> 24) & 0xff;
+	countbuf[1] = (counter >> 16) & 0xff;
+	countbuf[2] = (counter >> 8) & 0xff;
+	countbuf[3] = counter & 0xff;
+	dump("countbuf", countbuf, sizeof(countbuf));
+	dump("flags", &flags, sizeof(flags));
+	SHA256Init(&ctx);
+	SHA256Update(&ctx, apphash, sizeof(apphash));
+	SHA256Update(&ctx, &flags, sizeof(flags));
+	SHA256Update(&ctx, countbuf, sizeof(countbuf));
+	SHA256Update(&ctx, message, message_len);
+	SHA256Final(sighash, &ctx);
+	dump("sighash", sighash, sizeof(sighash));
+	/* create and encode signature */
+	if ((sig = ECDSA_do_sign(sighash, sizeof(sighash), ec)) == NULL) {
+		skdebug(__func__, "ECDSA_do_sign failed");
+		goto out;
+	}
+	ECDSA_SIG_get0(sig, &sig_r, &sig_s);
+	response->sig_r_len = BN_num_bytes(sig_r);
+	response->sig_s_len = BN_num_bytes(sig_s);
+	if ((response->sig_r = calloc(1, response->sig_r_len)) == NULL ||
+	    (response->sig_s = calloc(1, response->sig_s_len)) == NULL) {
+		skdebug(__func__, "calloc signature failed");
+		goto out;
+	}
+	BN_bn2bin(sig_r, response->sig_r);
+	BN_bn2bin(sig_s, response->sig_s);
+	ret = 0;
+ out:
+	explicit_bzero(&ctx, sizeof(ctx));
+	explicit_bzero(&apphash, sizeof(apphash));
+	explicit_bzero(&sighash, sizeof(sighash));
+	ECDSA_SIG_free(sig);
+	if (ret != 0) {
+		free(response->sig_r);
+		free(response->sig_s);
+		response->sig_r = NULL;
+		response->sig_s = NULL;
+	}
+	BIO_free(bio);
+	EC_KEY_free(ec);
+	EVP_PKEY_free(pk);
+	return ret;
+#else
+	return -1;
+#endif
+}
+
+static int
+sig_ed25519(const uint8_t *message, size_t message_len,
+    const char *application, uint32_t counter, uint8_t flags,
+    const uint8_t *key_handle, size_t key_handle_len,
+    struct sk_sign_response *response)
+{
+	size_t o;
+	int ret = -1;
+	SHA2_CTX ctx;
+	uint8_t	apphash[SHA256_DIGEST_LENGTH];
+	uint8_t signbuf[sizeof(apphash) + sizeof(flags) +
+	    sizeof(counter) + SHA256_DIGEST_LENGTH];
+	uint8_t sig[crypto_sign_ed25519_BYTES + sizeof(signbuf)];
+	unsigned long long smlen;
+
+	if (key_handle_len != crypto_sign_ed25519_SECRETKEYBYTES) {
+		skdebug(__func__, "bad key handle length %zu", key_handle_len);
+		goto out;
+	}
+	/* Expect message to be pre-hashed */
+	if (message_len != SHA256_DIGEST_LENGTH) {
+		skdebug(__func__, "bad message len %zu", message_len);
+		goto out;
+	}
+	/* Prepare data to be signed */
+	dump("message", message, message_len);
+	SHA256Init(&ctx);
+	SHA256Update(&ctx, (const u_char *)application, strlen(application));
+	SHA256Final(apphash, &ctx);
+	dump("apphash", apphash, sizeof(apphash));
+
+	memcpy(signbuf, apphash, sizeof(apphash));
+	o = sizeof(apphash);
+	signbuf[o++] = flags;
+	signbuf[o++] = (counter >> 24) & 0xff;
+	signbuf[o++] = (counter >> 16) & 0xff;
+	signbuf[o++] = (counter >> 8) & 0xff;
+	signbuf[o++] = counter & 0xff;
+	memcpy(signbuf + o, message, message_len);
+	o += message_len;
+	if (o != sizeof(signbuf)) {
+		skdebug(__func__, "bad sign buf len %zu, expected %zu",
+		    o, sizeof(signbuf));
+		goto out;
+	}
+	dump("signbuf", signbuf, sizeof(signbuf));
+	/* create and encode signature */
+	smlen = sizeof(signbuf);
+	if (crypto_sign_ed25519(sig, &smlen, signbuf, sizeof(signbuf),
+	    key_handle) != 0) {
+		skdebug(__func__, "crypto_sign_ed25519 failed");
+		goto out;
+	}
+	if (smlen <= sizeof(signbuf)) {
+		skdebug(__func__, "bad sign smlen %llu, expected min %zu",
+		    smlen, sizeof(signbuf) + 1);
+		goto out;
+	}
+	response->sig_r_len = (size_t)(smlen - sizeof(signbuf));
+	if ((response->sig_r = calloc(1, response->sig_r_len)) == NULL) {
+		skdebug(__func__, "calloc signature failed");
+		goto out;
+	}
+	memcpy(response->sig_r, sig, response->sig_r_len);
+	dump("sig_r", response->sig_r, response->sig_r_len);
+	ret = 0;
+ out:
+	explicit_bzero(&ctx, sizeof(ctx));
+	explicit_bzero(&apphash, sizeof(apphash));
+	explicit_bzero(&signbuf, sizeof(signbuf));
+	explicit_bzero(&sig, sizeof(sig));
+	if (ret != 0) {
+		free(response->sig_r);
+		response->sig_r = NULL;
+	}
+	return ret;
+}
+
+int
+sk_sign(uint32_t alg, const uint8_t *data, size_t datalen,
+    const char *application, const uint8_t *key_handle, size_t key_handle_len,
+    uint8_t flags, const char *pin, struct sk_option **options,
+    struct sk_sign_response **sign_response)
+{
+	struct sk_sign_response *response = NULL;
+	int ret = SSH_SK_ERR_GENERAL;
+	SHA2_CTX ctx;
+	uint8_t message[32];
+
+	if (sign_response == NULL) {
+		skdebug(__func__, "sign_response == NULL");
+		goto out;
+	}
+	*sign_response = NULL;
+	if (check_options(options) != 0)
+		goto out; /* error already logged */
+	if ((response = calloc(1, sizeof(*response))) == NULL) {
+		skdebug(__func__, "calloc response failed");
+		goto out;
+	}
+	SHA256Init(&ctx);
+	SHA256Update(&ctx, data, datalen);
+	SHA256Final(message, &ctx);
+	response->flags = flags;
+	response->counter = 0x12345678;
+	switch(alg) {
+	case SSH_SK_ECDSA:
+		if (sig_ecdsa(message, sizeof(message), application,
+		    response->counter, flags, key_handle, key_handle_len,
+		    response) != 0)
+			goto out;
+		break;
+	case SSH_SK_ED25519:
+		if (sig_ed25519(message, sizeof(message), application,
+		    response->counter, flags, key_handle, key_handle_len,
+		    response) != 0)
+			goto out;
+		break;
+	default:
+		skdebug(__func__, "unsupported key type %d", alg);
+		return -1;
+	}
+	*sign_response = response;
+	response = NULL;
+	ret = 0;
+ out:
+	explicit_bzero(message, sizeof(message));
+	if (response != NULL) {
+		free(response->sig_r);
+		free(response->sig_s);
+		free(response);
+	}
+	return ret;
+}
+
+int
+sk_load_resident_keys(const char *pin, struct sk_option **options,
+    struct sk_resident_key ***rks, size_t *nrks)
+{
+	return SSH_SK_ERR_UNSUPPORTED;
+}