upstream: add dummy security key middleware based on work by

markus@

This will allow us to test U2F/FIDO2 support in OpenSSH without
requiring real hardware.

ok markus@

OpenBSD-Regress-ID: 88b309464b8850c320cf7513f26d97ee1fdf9aae

1 files changed, 522 insertions, 0 deletions

diff --git a/regress/misc/sk-dummy/sk-dummy.c b/regress/misc/sk-dummy/sk-dummy.c
new file mode 100644
index 000000000..b223b1a0f
--- /dev/null
+++ b/regress/misc/sk-dummy/sk-dummy.c
@@ -0,0 +1,522 @@
+/*
+ * 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;
+}