/* $OpenBSD: ssh-sk.c,v 1.41 2024/08/15 00:51:51 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>
#include <openssl/evp.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 (lib_contains_symbol(path, "sk_api_version") != 0) {
                error("provider %s is not an OpenSSH FIDO library", path);
                goto fail;
        }
        if ((ret->dlhandle = dlopen(path, RTLD_NOW)) == NULL)
                fatal("Provider \"%s\" dlopen failed: %s", path, dlerror());
        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_KEY *ecdsa = NULL;
        EC_POINT *q = NULL;
        const EC_GROUP *g = 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 ((ecdsa = EC_KEY_new_by_curve_name(key->ecdsa_nid)) == NULL ||
            (g = EC_KEY_get0_group(ecdsa)) == NULL ||
            (q = EC_POINT_new(g)) == 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, g)) != 0) {
                error_fr(r, "parse");
                r = SSH_ERR_INVALID_FORMAT;
                goto out;
        }
        if (sshkey_ec_validate_public(g, q) != 0) {
                error("Authenticator returned invalid ECDSA key");
                r = SSH_ERR_KEY_INVALID_EC_VALUE;
                goto out;
        }
        if (EC_KEY_set_public_key(ecdsa, q) != 1) {
                /* XXX assume it is a allocation error */
                error_f("allocation failed");
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
        if ((key->pkey = EVP_PKEY_new()) == NULL) {
                error_f("allocation failed");
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
        if (EVP_PKEY_set1_EC_KEY(key->pkey, ecdsa) != 1) {
                error_f("Assigning EC_KEY failed");
                r = SSH_ERR_LIBCRYPTO_ERROR;
                goto out;
        }
        /* success */
        *keyp = key;
        key = NULL; /* transferred */
        r = 0;
 out:
        sshkey_free(key);
        sshbuf_free(b);
        EC_KEY_free(ecdsa);
        EC_POINT_free(q);
        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 */