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

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

1 files changed, 877 insertions, 0 deletions

diff --git a/ssh-sk.c b/ssh-sk.c
new file mode 100644
index 0000000..fbeb393
--- /dev/null
+++ b/ssh-sk.c
@@ -0,0 +1,877 @@
+/* $OpenBSD: ssh-sk.c,v 1.39 2022/07/20 03:29:14 djm Exp $ */
+/*
+ * 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.
+ */
+
+/* #define DEBUG_SK 1 */
+
+#include "includes.h"
+
+#ifdef ENABLE_SK
+
+#include <dlfcn.h>
+#include <stddef.h>
+#ifdef HAVE_STDINT_H
+# include <stdint.h>
+#endif
+#include <string.h>
+#include <stdio.h>
+
+#if defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC)
+#include <openssl/objects.h>
+#include <openssl/ec.h>
+#endif /* WITH_OPENSSL && OPENSSL_HAS_ECC */
+
+#include "log.h"
+#include "misc.h"
+#include "sshbuf.h"
+#include "sshkey.h"
+#include "ssherr.h"
+#include "digest.h"
+
+#include "ssh-sk.h"
+#include "sk-api.h"
+#include "crypto_api.h"
+
+/*
+ * Almost every use of OpenSSL in this file is for ECDSA-NISTP256.
+ * This is strictly a larger hammer than necessary, but it reduces changes
+ * with upstream.
+ */
+#ifndef OPENSSL_HAS_ECC
+# undef WITH_OPENSSL
+#endif
+
+struct sshsk_provider {
+	char *path;
+	void *dlhandle;
+
+	/* Return the version of the middleware API */
+	uint32_t (*sk_api_version)(void);
+
+	/* Enroll a U2F key (private key generation) */
+	int (*sk_enroll)(int alg, const uint8_t *challenge,
+	    size_t challenge_len, const char *application, uint8_t flags,
+	    const char *pin, struct sk_option **opts,
+	    struct sk_enroll_response **enroll_response);
+
+	/* Sign a challenge */
+	int (*sk_sign)(int alg, const uint8_t *message, size_t message_len,
+	    const char *application,
+	    const uint8_t *key_handle, size_t key_handle_len,
+	    uint8_t flags, const char *pin, struct sk_option **opts,
+	    struct sk_sign_response **sign_response);
+
+	/* Enumerate resident keys */
+	int (*sk_load_resident_keys)(const char *pin, struct sk_option **opts,
+	    struct sk_resident_key ***rks, size_t *nrks);
+};
+
+/* Built-in version */
+int ssh_sk_enroll(int alg, const uint8_t *challenge,
+    size_t challenge_len, const char *application, uint8_t flags,
+    const char *pin, struct sk_option **opts,
+    struct sk_enroll_response **enroll_response);
+int ssh_sk_sign(int alg, const uint8_t *message, size_t message_len,
+    const char *application,
+    const uint8_t *key_handle, size_t key_handle_len,
+    uint8_t flags, const char *pin, struct sk_option **opts,
+    struct sk_sign_response **sign_response);
+int ssh_sk_load_resident_keys(const char *pin, struct sk_option **opts,
+    struct sk_resident_key ***rks, size_t *nrks);
+
+static void
+sshsk_free(struct sshsk_provider *p)
+{
+	if (p == NULL)
+		return;
+	free(p->path);
+	if (p->dlhandle != NULL)
+		dlclose(p->dlhandle);
+	free(p);
+}
+
+static struct sshsk_provider *
+sshsk_open(const char *path)
+{
+	struct sshsk_provider *ret = NULL;
+	uint32_t version;
+
+	if (path == NULL || *path == '\0') {
+		error("No FIDO SecurityKeyProvider specified");
+		return NULL;
+	}
+	if ((ret = calloc(1, sizeof(*ret))) == NULL) {
+		error_f("calloc failed");
+		return NULL;
+	}
+	if ((ret->path = strdup(path)) == NULL) {
+		error_f("strdup failed");
+		goto fail;
+	}
+	/* Skip the rest if we're using the linked in middleware */
+	if (strcasecmp(ret->path, "internal") == 0) {
+#ifdef ENABLE_SK_INTERNAL
+		ret->sk_enroll = ssh_sk_enroll;
+		ret->sk_sign = ssh_sk_sign;
+		ret->sk_load_resident_keys = ssh_sk_load_resident_keys;
+		return ret;
+#else
+		error("internal security key support not enabled");
+		goto fail;
+#endif
+	}
+	if ((ret->dlhandle = dlopen(path, RTLD_NOW)) == NULL) {
+		error("Provider \"%s\" dlopen failed: %s", path, dlerror());
+		goto fail;
+	}
+	if ((ret->sk_api_version = dlsym(ret->dlhandle,
+	    "sk_api_version")) == NULL) {
+		error("Provider \"%s\" dlsym(sk_api_version) failed: %s",
+		    path, dlerror());
+		goto fail;
+	}
+	version = ret->sk_api_version();
+	debug_f("provider %s implements version 0x%08lx", ret->path,
+	    (u_long)version);
+	if ((version & SSH_SK_VERSION_MAJOR_MASK) != SSH_SK_VERSION_MAJOR) {
+		error("Provider \"%s\" implements unsupported "
+		    "version 0x%08lx (supported: 0x%08lx)",
+		    path, (u_long)version, (u_long)SSH_SK_VERSION_MAJOR);
+		goto fail;
+	}
+	if ((ret->sk_enroll = dlsym(ret->dlhandle, "sk_enroll")) == NULL) {
+		error("Provider %s dlsym(sk_enroll) failed: %s",
+		    path, dlerror());
+		goto fail;
+	}
+	if ((ret->sk_sign = dlsym(ret->dlhandle, "sk_sign")) == NULL) {
+		error("Provider \"%s\" dlsym(sk_sign) failed: %s",
+		    path, dlerror());
+		goto fail;
+	}
+	if ((ret->sk_load_resident_keys = dlsym(ret->dlhandle,
+	    "sk_load_resident_keys")) == NULL) {
+		error("Provider \"%s\" dlsym(sk_load_resident_keys) "
+		    "failed: %s", path, dlerror());
+		goto fail;
+	}
+	/* success */
+	return ret;
+fail:
+	sshsk_free(ret);
+	return NULL;
+}
+
+static void
+sshsk_free_enroll_response(struct sk_enroll_response *r)
+{
+	if (r == NULL)
+		return;
+	freezero(r->key_handle, r->key_handle_len);
+	freezero(r->public_key, r->public_key_len);
+	freezero(r->signature, r->signature_len);
+	freezero(r->attestation_cert, r->attestation_cert_len);
+	freezero(r->authdata, r->authdata_len);
+	freezero(r, sizeof(*r));
+}
+
+static void
+sshsk_free_sign_response(struct sk_sign_response *r)
+{
+	if (r == NULL)
+		return;
+	freezero(r->sig_r, r->sig_r_len);
+	freezero(r->sig_s, r->sig_s_len);
+	freezero(r, sizeof(*r));
+}
+
+#ifdef WITH_OPENSSL
+/* Assemble key from response */
+static int
+sshsk_ecdsa_assemble(struct sk_enroll_response *resp, struct sshkey **keyp)
+{
+	struct sshkey *key = NULL;
+	struct sshbuf *b = NULL;
+	EC_POINT *q = NULL;
+	int r;
+
+	*keyp = NULL;
+	if ((key = sshkey_new(KEY_ECDSA_SK)) == NULL) {
+		error_f("sshkey_new failed");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	key->ecdsa_nid = NID_X9_62_prime256v1;
+	if ((key->ecdsa = EC_KEY_new_by_curve_name(key->ecdsa_nid)) == NULL ||
+	    (q = EC_POINT_new(EC_KEY_get0_group(key->ecdsa))) == NULL ||
+	    (b = sshbuf_new()) == NULL) {
+		error_f("allocation failed");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshbuf_put_string(b,
+	    resp->public_key, resp->public_key_len)) != 0) {
+		error_fr(r, "sshbuf_put_string");
+		goto out;
+	}
+	if ((r = sshbuf_get_ec(b, q, EC_KEY_get0_group(key->ecdsa))) != 0) {
+		error_fr(r, "parse");
+		r = SSH_ERR_INVALID_FORMAT;
+		goto out;
+	}
+	if (sshkey_ec_validate_public(EC_KEY_get0_group(key->ecdsa), q) != 0) {
+		error("Authenticator returned invalid ECDSA key");
+		r = SSH_ERR_KEY_INVALID_EC_VALUE;
+		goto out;
+	}
+	if (EC_KEY_set_public_key(key->ecdsa, q) != 1) {
+		/* XXX assume it is a allocation error */
+		error_f("allocation failed");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	/* success */
+	*keyp = key;
+	key = NULL; /* transferred */
+	r = 0;
+ out:
+	EC_POINT_free(q);
+	sshkey_free(key);
+	sshbuf_free(b);
+	return r;
+}
+#endif /* WITH_OPENSSL */
+
+static int
+sshsk_ed25519_assemble(struct sk_enroll_response *resp, struct sshkey **keyp)
+{
+	struct sshkey *key = NULL;
+	int r;
+
+	*keyp = NULL;
+	if (resp->public_key_len != ED25519_PK_SZ) {
+		error_f("invalid size: %zu", resp->public_key_len);
+		r = SSH_ERR_INVALID_FORMAT;
+		goto out;
+	}
+	if ((key = sshkey_new(KEY_ED25519_SK)) == NULL) {
+		error_f("sshkey_new failed");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((key->ed25519_pk = malloc(ED25519_PK_SZ)) == NULL) {
+		error_f("malloc failed");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	memcpy(key->ed25519_pk, resp->public_key, ED25519_PK_SZ);
+	/* success */
+	*keyp = key;
+	key = NULL; /* transferred */
+	r = 0;
+ out:
+	sshkey_free(key);
+	return r;
+}
+
+static int
+sshsk_key_from_response(int alg, const char *application, uint8_t flags,
+    struct sk_enroll_response *resp, struct sshkey **keyp)
+{
+	struct sshkey *key = NULL;
+	int r = SSH_ERR_INTERNAL_ERROR;
+
+	*keyp = NULL;
+
+	/* Check response validity */
+	if (resp->public_key == NULL || resp->key_handle == NULL) {
+		error_f("sk_enroll response invalid");
+		r = SSH_ERR_INVALID_FORMAT;
+		goto out;
+	}
+	switch (alg) {
+#ifdef WITH_OPENSSL
+	case SSH_SK_ECDSA:
+		if ((r = sshsk_ecdsa_assemble(resp, &key)) != 0)
+			goto out;
+		break;
+#endif /* WITH_OPENSSL */
+	case SSH_SK_ED25519:
+		if ((r = sshsk_ed25519_assemble(resp, &key)) != 0)
+			goto out;
+		break;
+	default:
+		error_f("unsupported algorithm %d", alg);
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	key->sk_flags = flags;
+	if ((key->sk_key_handle = sshbuf_new()) == NULL ||
+	    (key->sk_reserved = sshbuf_new()) == NULL) {
+		error_f("allocation failed");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((key->sk_application = strdup(application)) == NULL) {
+		error_f("strdup application failed");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshbuf_put(key->sk_key_handle, resp->key_handle,
+	    resp->key_handle_len)) != 0) {
+		error_fr(r, "put key handle");
+		goto out;
+	}
+	/* success */
+	r = 0;
+	*keyp = key;
+	key = NULL;
+ out:
+	sshkey_free(key);
+	return r;
+}
+
+static int
+skerr_to_ssherr(int skerr)
+{
+	switch (skerr) {
+	case SSH_SK_ERR_UNSUPPORTED:
+		return SSH_ERR_FEATURE_UNSUPPORTED;
+	case SSH_SK_ERR_PIN_REQUIRED:
+		return SSH_ERR_KEY_WRONG_PASSPHRASE;
+	case SSH_SK_ERR_DEVICE_NOT_FOUND:
+		return SSH_ERR_DEVICE_NOT_FOUND;
+	case SSH_SK_ERR_CREDENTIAL_EXISTS:
+		return SSH_ERR_KEY_BAD_PERMISSIONS;
+	case SSH_SK_ERR_GENERAL:
+	default:
+		return SSH_ERR_INVALID_FORMAT;
+	}
+}
+
+static void
+sshsk_free_options(struct sk_option **opts)
+{
+	size_t i;
+
+	if (opts == NULL)
+		return;
+	for (i = 0; opts[i] != NULL; i++) {
+		free(opts[i]->name);
+		free(opts[i]->value);
+		free(opts[i]);
+	}
+	free(opts);
+}
+
+static int
+sshsk_add_option(struct sk_option ***optsp, size_t *noptsp,
+    const char *name, const char *value, uint8_t required)
+{
+	struct sk_option **opts = *optsp;
+	size_t nopts = *noptsp;
+
+	if ((opts = recallocarray(opts, nopts, nopts + 2, /* extra for NULL */
+	    sizeof(*opts))) == NULL) {
+		error_f("array alloc failed");
+		return SSH_ERR_ALLOC_FAIL;
+	}
+	*optsp = opts;
+	*noptsp = nopts + 1;
+	if ((opts[nopts] = calloc(1, sizeof(**opts))) == NULL) {
+		error_f("alloc failed");
+		return SSH_ERR_ALLOC_FAIL;
+	}
+	if ((opts[nopts]->name = strdup(name)) == NULL ||
+	    (opts[nopts]->value = strdup(value)) == NULL) {
+		error_f("alloc failed");
+		return SSH_ERR_ALLOC_FAIL;
+	}
+	opts[nopts]->required = required;
+	return 0;
+}
+
+static int
+make_options(const char *device, const char *user_id,
+    struct sk_option ***optsp)
+{
+	struct sk_option **opts = NULL;
+	size_t nopts = 0;
+	int r, ret = SSH_ERR_INTERNAL_ERROR;
+
+	if (device != NULL &&
+	    (r = sshsk_add_option(&opts, &nopts, "device", device, 0)) != 0) {
+		ret = r;
+		goto out;
+	}
+	if (user_id != NULL &&
+	    (r = sshsk_add_option(&opts, &nopts, "user", user_id, 0)) != 0) {
+		ret = r;
+		goto out;
+	}
+	/* success */
+	*optsp = opts;
+	opts = NULL;
+	nopts = 0;
+	ret = 0;
+ out:
+	sshsk_free_options(opts);
+	return ret;
+}
+
+
+static int
+fill_attestation_blob(const struct sk_enroll_response *resp,
+    struct sshbuf *attest)
+{
+	int r;
+
+	if (attest == NULL)
+		return 0; /* nothing to do */
+	if ((r = sshbuf_put_cstring(attest, "ssh-sk-attest-v01")) != 0 ||
+	    (r = sshbuf_put_string(attest,
+	    resp->attestation_cert, resp->attestation_cert_len)) != 0 ||
+	    (r = sshbuf_put_string(attest,
+	    resp->signature, resp->signature_len)) != 0 ||
+	    (r = sshbuf_put_string(attest,
+	    resp->authdata, resp->authdata_len)) != 0 ||
+	    (r = sshbuf_put_u32(attest, 0)) != 0 || /* resvd flags */
+	    (r = sshbuf_put_string(attest, NULL, 0)) != 0 /* resvd */) {
+		error_fr(r, "compose");
+		return r;
+	}
+	/* success */
+	return 0;
+}
+
+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)
+{
+	struct sshsk_provider *skp = NULL;
+	struct sshkey *key = NULL;
+	u_char randchall[32];
+	const u_char *challenge;
+	size_t challenge_len;
+	struct sk_enroll_response *resp = NULL;
+	struct sk_option **opts = NULL;
+	int r = SSH_ERR_INTERNAL_ERROR;
+	int alg;
+
+	debug_f("provider \"%s\", device \"%s\", application \"%s\", "
+	    "userid \"%s\", flags 0x%02x, challenge len %zu%s",
+	    provider_path, device, application, userid, flags,
+	    challenge_buf == NULL ? 0 : sshbuf_len(challenge_buf),
+	    (pin != NULL && *pin != '\0') ? " with-pin" : "");
+
+	*keyp = NULL;
+	if (attest)
+		sshbuf_reset(attest);
+
+	if ((r = make_options(device, userid, &opts)) != 0)
+		goto out;
+
+	switch (type) {
+#ifdef WITH_OPENSSL
+	case KEY_ECDSA_SK:
+		alg = SSH_SK_ECDSA;
+		break;
+#endif /* WITH_OPENSSL */
+	case KEY_ED25519_SK:
+		alg = SSH_SK_ED25519;
+		break;
+	default:
+		error_f("unsupported key type");
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	if (provider_path == NULL) {
+		error_f("missing provider");
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	if (application == NULL || *application == '\0') {
+		error_f("missing application");
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	if (challenge_buf == NULL) {
+		debug_f("using random challenge");
+		arc4random_buf(randchall, sizeof(randchall));
+		challenge = randchall;
+		challenge_len = sizeof(randchall);
+	} else if (sshbuf_len(challenge_buf) == 0) {
+		error("Missing enrollment challenge");
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	} else {
+		challenge = sshbuf_ptr(challenge_buf);
+		challenge_len = sshbuf_len(challenge_buf);
+		debug3_f("using explicit challenge len=%zd", challenge_len);
+	}
+	if ((skp = sshsk_open(provider_path)) == NULL) {
+		r = SSH_ERR_INVALID_FORMAT; /* XXX sshsk_open return code? */
+		goto out;
+	}
+	/* XXX validate flags? */
+	/* enroll key */
+	if ((r = skp->sk_enroll(alg, challenge, challenge_len, application,
+	    flags, pin, opts, &resp)) != 0) {
+		debug_f("provider \"%s\" failure %d", provider_path, r);
+		r = skerr_to_ssherr(r);
+		goto out;
+	}
+
+	if ((r = sshsk_key_from_response(alg, application, resp->flags,
+	    resp, &key)) != 0)
+		goto out;
+
+	/* Optionally fill in the attestation information */
+	if ((r = fill_attestation_blob(resp, attest)) != 0)
+		goto out;
+
+	/* success */
+	*keyp = key;
+	key = NULL; /* transferred */
+	r = 0;
+ out:
+	sshsk_free_options(opts);
+	sshsk_free(skp);
+	sshkey_free(key);
+	sshsk_free_enroll_response(resp);
+	explicit_bzero(randchall, sizeof(randchall));
+	return r;
+}
+
+#ifdef WITH_OPENSSL
+static int
+sshsk_ecdsa_sig(struct sk_sign_response *resp, struct sshbuf *sig)
+{
+	struct sshbuf *inner_sig = NULL;
+	int r = SSH_ERR_INTERNAL_ERROR;
+
+	/* Check response validity */
+	if (resp->sig_r == NULL || resp->sig_s == NULL) {
+		error_f("sk_sign response invalid");
+		r = SSH_ERR_INVALID_FORMAT;
+		goto out;
+	}
+	if ((inner_sig = sshbuf_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	/* Prepare and append inner signature object */
+	if ((r = sshbuf_put_bignum2_bytes(inner_sig,
+	    resp->sig_r, resp->sig_r_len)) != 0 ||
+	    (r = sshbuf_put_bignum2_bytes(inner_sig,
+	    resp->sig_s, resp->sig_s_len)) != 0) {
+		error_fr(r, "compose inner");
+		goto out;
+	}
+	if ((r = sshbuf_put_stringb(sig, inner_sig)) != 0 ||
+	    (r = sshbuf_put_u8(sig, resp->flags)) != 0 ||
+	    (r = sshbuf_put_u32(sig, resp->counter)) != 0) {
+		error_fr(r, "compose");
+		goto out;
+	}
+#ifdef DEBUG_SK
+	fprintf(stderr, "%s: sig_r:\n", __func__);
+	sshbuf_dump_data(resp->sig_r, resp->sig_r_len, stderr);
+	fprintf(stderr, "%s: sig_s:\n", __func__);
+	sshbuf_dump_data(resp->sig_s, resp->sig_s_len, stderr);
+	fprintf(stderr, "%s: inner:\n", __func__);
+	sshbuf_dump(inner_sig, stderr);
+#endif
+	r = 0;
+ out:
+	sshbuf_free(inner_sig);
+	return r;
+}
+#endif /* WITH_OPENSSL */
+
+static int
+sshsk_ed25519_sig(struct sk_sign_response *resp, struct sshbuf *sig)
+{
+	int r = SSH_ERR_INTERNAL_ERROR;
+
+	/* Check response validity */
+	if (resp->sig_r == NULL) {
+		error_f("sk_sign response invalid");
+		r = SSH_ERR_INVALID_FORMAT;
+		goto out;
+	}
+	if ((r = sshbuf_put_string(sig,
+	    resp->sig_r, resp->sig_r_len)) != 0 ||
+	    (r = sshbuf_put_u8(sig, resp->flags)) != 0 ||
+	    (r = sshbuf_put_u32(sig, resp->counter)) != 0) {
+		error_fr(r, "compose");
+		goto out;
+	}
+#ifdef DEBUG_SK
+	fprintf(stderr, "%s: sig_r:\n", __func__);
+	sshbuf_dump_data(resp->sig_r, resp->sig_r_len, stderr);
+#endif
+	r = 0;
+ out:
+	return r;
+}
+
+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)
+{
+	struct sshsk_provider *skp = NULL;
+	int r = SSH_ERR_INTERNAL_ERROR;
+	int type, alg;
+	struct sk_sign_response *resp = NULL;
+	struct sshbuf *inner_sig = NULL, *sig = NULL;
+	struct sk_option **opts = NULL;
+
+	debug_f("provider \"%s\", key %s, flags 0x%02x%s",
+	    provider_path, sshkey_type(key), key->sk_flags,
+	    (pin != NULL && *pin != '\0') ? " with-pin" : "");
+
+	if (sigp != NULL)
+		*sigp = NULL;
+	if (lenp != NULL)
+		*lenp = 0;
+	type = sshkey_type_plain(key->type);
+	switch (type) {
+#ifdef WITH_OPENSSL
+	case KEY_ECDSA_SK:
+		alg = SSH_SK_ECDSA;
+		break;
+#endif /* WITH_OPENSSL */
+	case KEY_ED25519_SK:
+		alg = SSH_SK_ED25519;
+		break;
+	default:
+		return SSH_ERR_INVALID_ARGUMENT;
+	}
+	if (provider_path == NULL ||
+	    key->sk_key_handle == NULL ||
+	    key->sk_application == NULL || *key->sk_application == '\0') {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	if ((skp = sshsk_open(provider_path)) == NULL) {
+		r = SSH_ERR_INVALID_FORMAT; /* XXX sshsk_open return code? */
+		goto out;
+	}
+#ifdef DEBUG_SK
+	fprintf(stderr, "%s: sk_flags = 0x%02x, sk_application = \"%s\"\n",
+	    __func__, key->sk_flags, key->sk_application);
+	fprintf(stderr, "%s: sk_key_handle:\n", __func__);
+	sshbuf_dump(key->sk_key_handle, stderr);
+#endif
+	if ((r = skp->sk_sign(alg, data, datalen, key->sk_application,
+	    sshbuf_ptr(key->sk_key_handle), sshbuf_len(key->sk_key_handle),
+	    key->sk_flags, pin, opts, &resp)) != 0) {
+		debug_f("sk_sign failed with code %d", r);
+		r = skerr_to_ssherr(r);
+		goto out;
+	}
+	/* Assemble signature */
+	if ((sig = sshbuf_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshbuf_put_cstring(sig, sshkey_ssh_name_plain(key))) != 0) {
+		error_fr(r, "compose outer");
+		goto out;
+	}
+	switch (type) {
+#ifdef WITH_OPENSSL
+	case KEY_ECDSA_SK:
+		if ((r = sshsk_ecdsa_sig(resp, sig)) != 0)
+			goto out;
+		break;
+#endif /* WITH_OPENSSL */
+	case KEY_ED25519_SK:
+		if ((r = sshsk_ed25519_sig(resp, sig)) != 0)
+			goto out;
+		break;
+	}
+#ifdef DEBUG_SK
+	fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n",
+	    __func__, resp->flags, resp->counter);
+	fprintf(stderr, "%s: data to sign:\n", __func__);
+	sshbuf_dump_data(data, datalen, stderr);
+	fprintf(stderr, "%s: sigbuf:\n", __func__);
+	sshbuf_dump(sig, stderr);
+#endif
+	if (sigp != NULL) {
+		if ((*sigp = malloc(sshbuf_len(sig))) == NULL) {
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
+		memcpy(*sigp, sshbuf_ptr(sig), sshbuf_len(sig));
+	}
+	if (lenp != NULL)
+		*lenp = sshbuf_len(sig);
+	/* success */
+	r = 0;
+ out:
+	sshsk_free_options(opts);
+	sshsk_free(skp);
+	sshsk_free_sign_response(resp);
+	sshbuf_free(sig);
+	sshbuf_free(inner_sig);
+	return r;
+}
+
+static void
+sshsk_free_sk_resident_keys(struct sk_resident_key **rks, size_t nrks)
+{
+	size_t i;
+
+	if (nrks == 0 || rks == NULL)
+		return;
+	for (i = 0; i < nrks; i++) {
+		free(rks[i]->application);
+		freezero(rks[i]->user_id, rks[i]->user_id_len);
+		freezero(rks[i]->key.key_handle, rks[i]->key.key_handle_len);
+		freezero(rks[i]->key.public_key, rks[i]->key.public_key_len);
+		freezero(rks[i]->key.signature, rks[i]->key.signature_len);
+		freezero(rks[i]->key.attestation_cert,
+		    rks[i]->key.attestation_cert_len);
+		freezero(rks[i], sizeof(**rks));
+	}
+	free(rks);
+}
+
+static void
+sshsk_free_resident_key(struct sshsk_resident_key *srk)
+{
+	if (srk == NULL)
+		return;
+	sshkey_free(srk->key);
+	freezero(srk->user_id, srk->user_id_len);
+	free(srk);
+}
+
+
+void
+sshsk_free_resident_keys(struct sshsk_resident_key **srks, size_t nsrks)
+{
+	size_t i;
+
+	if (srks == NULL || nsrks == 0)
+		return;
+
+	for (i = 0; i < nsrks; i++)
+		sshsk_free_resident_key(srks[i]);
+	free(srks);
+}
+
+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)
+{
+	struct sshsk_provider *skp = NULL;
+	int r = SSH_ERR_INTERNAL_ERROR;
+	struct sk_resident_key **rks = NULL;
+	size_t i, nrks = 0, nsrks = 0;
+	struct sshkey *key = NULL;
+	struct sshsk_resident_key *srk = NULL, **srks = NULL, **tmp;
+	uint8_t sk_flags;
+	struct sk_option **opts = NULL;
+
+	debug_f("provider \"%s\"%s", provider_path,
+	    (pin != NULL && *pin != '\0') ? ", have-pin": "");
+
+	if (srksp == NULL || nsrksp == NULL)
+		return SSH_ERR_INVALID_ARGUMENT;
+	*srksp = NULL;
+	*nsrksp = 0;
+
+	if ((r = make_options(device, NULL, &opts)) != 0)
+		goto out;
+	if ((skp = sshsk_open(provider_path)) == NULL) {
+		r = SSH_ERR_INVALID_FORMAT; /* XXX sshsk_open return code? */
+		goto out;
+	}
+	if ((r = skp->sk_load_resident_keys(pin, opts, &rks, &nrks)) != 0) {
+		error("Provider \"%s\" returned failure %d", provider_path, r);
+		r = skerr_to_ssherr(r);
+		goto out;
+	}
+	for (i = 0; i < nrks; i++) {
+		debug3_f("rk %zu: slot %zu, alg %d, app \"%s\", uidlen %zu",
+		    i, rks[i]->slot, rks[i]->alg, rks[i]->application,
+		    rks[i]->user_id_len);
+		/* XXX need better filter here */
+		if (strncmp(rks[i]->application, "ssh:", 4) != 0)
+			continue;
+		switch (rks[i]->alg) {
+		case SSH_SK_ECDSA:
+		case SSH_SK_ED25519:
+			break;
+		default:
+			continue;
+		}
+		sk_flags = SSH_SK_USER_PRESENCE_REQD|SSH_SK_RESIDENT_KEY;
+		if ((rks[i]->flags & SSH_SK_USER_VERIFICATION_REQD))
+			sk_flags |= SSH_SK_USER_VERIFICATION_REQD;
+		if ((r = sshsk_key_from_response(rks[i]->alg,
+		    rks[i]->application, sk_flags, &rks[i]->key, &key)) != 0)
+			goto out;
+		if ((srk = calloc(1, sizeof(*srk))) == NULL) {
+			error_f("calloc failed");
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
+		srk->key = key;
+		key = NULL; /* transferred */
+		if ((srk->user_id = calloc(1, rks[i]->user_id_len)) == NULL) {
+			error_f("calloc failed");
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
+		memcpy(srk->user_id, rks[i]->user_id, rks[i]->user_id_len);
+		srk->user_id_len = rks[i]->user_id_len;
+		if ((tmp = recallocarray(srks, nsrks, nsrks + 1,
+		    sizeof(*tmp))) == NULL) {
+			error_f("recallocarray failed");
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
+		srks = tmp;
+		srks[nsrks++] = srk;
+		srk = NULL;
+		/* XXX synthesise comment */
+	}
+	/* success */
+	*srksp = srks;
+	*nsrksp = nsrks;
+	srks = NULL;
+	nsrks = 0;
+	r = 0;
+ out:
+	sshsk_free_options(opts);
+	sshsk_free(skp);
+	sshsk_free_sk_resident_keys(rks, nrks);
+	sshkey_free(key);
+	sshsk_free_resident_key(srk);
+	sshsk_free_resident_keys(srks, nsrks);
+	return r;
+}
+
+#endif /* ENABLE_SK */