--- /dev/null
+/*
+ * 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 <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <stddef.h>
+#include <stdarg.h>
+
+#include "crypto_api.h"
+
+#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>
+
+/* #define SK_DEBUG 1 */
+
+/* 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
+
+#define SK_VERSION_MAJOR 0x00020000 /* current API version */
+
+/* Flags */
+#define SK_USER_PRESENCE_REQD 0x01
+
+/* Algs */
+#define SK_ECDSA 0x00
+#define SK_ED25519 0x01
+
+struct sk_enroll_response {
+ uint8_t *public_key;
+ size_t public_key_len;
+ uint8_t *key_handle;
+ size_t key_handle_len;
+ uint8_t *signature;
+ size_t signature_len;
+ uint8_t *attestation_cert;
+ size_t attestation_cert_len;
+};
+
+struct sk_sign_response {
+ uint8_t flags;
+ uint32_t counter;
+ uint8_t *sig_r;
+ size_t sig_r_len;
+ uint8_t *sig_s;
+ size_t sig_s_len;
+};
+
+/* 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,
+ 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, struct sk_sign_response **sign_response);
+
+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 SK_VERSION_MAJOR;
+}
+
+static int
+pack_key_ecdsa(struct sk_enroll_response *response)
+{
+ 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;
+}
+
+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;
+}
+
+int
+sk_enroll(int alg, const uint8_t *challenge, size_t challenge_len,
+ const char *application, uint8_t flags,
+ struct sk_enroll_response **enroll_response)
+{
+ struct sk_enroll_response *response = NULL;
+ int ret = -1;
+
+ (void)flags; /* XXX; unused */
+
+ if (enroll_response == NULL) {
+ skdebug(__func__, "enroll_response == NULL");
+ goto out;
+ }
+ *enroll_response = NULL;
+ if ((response = calloc(1, sizeof(*response))) == NULL) {
+ skdebug(__func__, "calloc response failed");
+ goto out;
+ }
+ switch(alg) {
+ case SK_ECDSA:
+ if (pack_key_ecdsa(response) != 0)
+ goto out;
+ break;
+ case 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)
+{
+ ECDSA_SIG *sig = NULL;
+ const BIGNUM *sig_r, *sig_s;
+ int ret = -1;
+ BIO *bio = NULL;
+ EVP_PKEY *pk = NULL;
+ EC_KEY *ec = NULL;
+ SHA256_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);
+ SHA256_Init(&ctx);
+ SHA256_Update(&ctx, application, strlen(application));
+ SHA256_Final(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));
+ SHA256_Init(&ctx);
+ SHA256_Update(&ctx, apphash, sizeof(apphash));
+ SHA256_Update(&ctx, &flags, sizeof(flags));
+ SHA256_Update(&ctx, countbuf, sizeof(countbuf));
+ SHA256_Update(&ctx, message, message_len);
+ SHA256_Final(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;
+}
+
+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;
+ SHA256_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);
+ SHA256_Init(&ctx);
+ SHA256_Update(&ctx, application, strlen(application));
+ SHA256_Final(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(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, struct sk_sign_response **sign_response)
+{
+ struct sk_sign_response *response = NULL;
+ int ret = -1;
+
+ if (sign_response == NULL) {
+ skdebug(__func__, "sign_response == NULL");
+ goto out;
+ }
+ *sign_response = NULL;
+ if ((response = calloc(1, sizeof(*response))) == NULL) {
+ skdebug(__func__, "calloc response failed");
+ goto out;
+ }
+ response->flags = flags;
+ response->counter = 0x12345678;
+ switch(alg) {
+ case SK_ECDSA:
+ if (sig_ecdsa(message, message_len, application,
+ response->counter, flags, key_handle, key_handle_len,
+ response) != 0)
+ goto out;
+ break;
+ case SK_ED25519:
+ if (sig_ed25519(message, message_len, 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:
+ if (response != NULL) {
+ free(response->sig_r);
+ free(response->sig_s);
+ free(response);
+ }
+ return ret;
+}
projects / thirdparty / openssh-portable.git / commitdiff
