1 files changed, 204 insertions, 0 deletions

diff --git a/src/rs256.c b/src/rs256.c
new file mode 100644
index 0000000..9f30163
--- /dev/null
+++ b/src/rs256.c
@@ -0,0 +1,204 @@
+/*
+ * Copyright (c) 2018 Yubico AB. All rights reserved.
+ * Use of this source code is governed by a BSD-style
+ * license that can be found in the LICENSE file.
+ */
+
+#include <openssl/bn.h>
+#include <openssl/rsa.h>
+#include <openssl/evp.h>
+#include <openssl/obj_mac.h>
+
+#include <string.h>
+#include "fido.h"
+#include "fido/rs256.h"
+
+#if OPENSSL_VERSION_NUMBER < 0x10100000L
+static int
+RSA_bits(const RSA *r)
+{
+        return (BN_num_bits(r->n));
+}
+
+static int
+RSA_set0_key(RSA *r, BIGNUM *n, BIGNUM *e, BIGNUM *d)
+{
+        r->n = n;
+        r->e = e;
+        r->d = d;
+
+        return (1);
+}
+
+static void
+RSA_get0_key(const RSA *r, const BIGNUM **n, const BIGNUM **e, const BIGNUM **d)
+{
+        *n = r->n;
+        *e = r->e;
+        *d = r->d;
+}
+#endif /* OPENSSL_VERSION_NUMBER < 0x10100000L */
+
+static int
+decode_bignum(const cbor_item_t *item, void *ptr, size_t len)
+{
+        if (cbor_isa_bytestring(item) == false ||
+            cbor_bytestring_is_definite(item) == false ||
+            cbor_bytestring_length(item) != len) {
+                fido_log_debug("%s: cbor type", __func__);
+                return (-1);
+        }
+
+        memcpy(ptr, cbor_bytestring_handle(item), len);
+
+        return (0);
+}
+
+static int
+decode_rsa_pubkey(const cbor_item_t *key, const cbor_item_t *val, void *arg)
+{
+        rs256_pk_t *k = arg;
+
+        if (cbor_isa_negint(key) == false ||
+            cbor_int_get_width(key) != CBOR_INT_8)
+                return (0); /* ignore */
+
+        switch (cbor_get_uint8(key)) {
+        case 0: /* modulus */
+                return (decode_bignum(val, &k->n, sizeof(k->n)));
+        case 1: /* public exponent */
+                return (decode_bignum(val, &k->e, sizeof(k->e)));
+        }
+
+        return (0); /* ignore */
+}
+
+int
+rs256_pk_decode(const cbor_item_t *item, rs256_pk_t *k)
+{
+        if (cbor_isa_map(item) == false ||
+            cbor_map_is_definite(item) == false ||
+            cbor_map_iter(item, k, decode_rsa_pubkey) < 0) {
+                fido_log_debug("%s: cbor type", __func__);
+                return (-1);
+        }
+
+        return (0);
+}
+
+rs256_pk_t *
+rs256_pk_new(void)
+{
+        return (calloc(1, sizeof(rs256_pk_t)));
+}
+
+void
+rs256_pk_free(rs256_pk_t **pkp)
+{
+        rs256_pk_t *pk;
+
+        if (pkp == NULL || (pk = *pkp) == NULL)
+                return;
+
+        explicit_bzero(pk, sizeof(*pk));
+        free(pk);
+
+        *pkp = NULL;
+}
+
+int
+rs256_pk_from_ptr(rs256_pk_t *pk, const void *ptr, size_t len)
+{
+        if (len < sizeof(*pk))
+                return (FIDO_ERR_INVALID_ARGUMENT);
+
+        memcpy(pk, ptr, sizeof(*pk));
+
+        return (FIDO_OK);
+}
+
+EVP_PKEY *
+rs256_pk_to_EVP_PKEY(const rs256_pk_t *k)
+{
+        RSA             *rsa = NULL;
+        EVP_PKEY        *pkey = NULL;
+        BIGNUM          *n = NULL;
+        BIGNUM          *e = NULL;
+        int              ok = -1;
+
+        if ((n = BN_new()) == NULL || (e = BN_new()) == NULL)
+                goto fail;
+
+        if (BN_bin2bn(k->n, sizeof(k->n), n) == NULL ||
+            BN_bin2bn(k->e, sizeof(k->e), e) == NULL) {
+                fido_log_debug("%s: BN_bin2bn", __func__);
+                goto fail;
+        }
+
+        if ((rsa = RSA_new()) == NULL || RSA_set0_key(rsa, n, e, NULL) == 0) {
+                fido_log_debug("%s: RSA_set0_key", __func__);
+                goto fail;
+        }
+
+        /* at this point, n and e belong to rsa */
+        n = NULL;
+        e = NULL;
+
+        if ((pkey = EVP_PKEY_new()) == NULL ||
+            EVP_PKEY_assign_RSA(pkey, rsa) == 0) {
+                fido_log_debug("%s: EVP_PKEY_assign_RSA", __func__);
+                goto fail;
+        }
+
+        rsa = NULL; /* at this point, rsa belongs to evp */
+
+        ok = 0;
+fail:
+        if (n != NULL)
+                BN_free(n);
+        if (e != NULL)
+                BN_free(e);
+        if (rsa != NULL)
+                RSA_free(rsa);
+        if (ok < 0 && pkey != NULL) {
+                EVP_PKEY_free(pkey);
+                pkey = NULL;
+        }
+
+        return (pkey);
+}
+
+int
+rs256_pk_from_RSA(rs256_pk_t *pk, const RSA *rsa)
+{
+        const BIGNUM    *n = NULL;
+        const BIGNUM    *e = NULL;
+        const BIGNUM    *d = NULL;
+        int              k;
+
+        if (RSA_bits(rsa) != 2048) {
+                fido_log_debug("%s: invalid key length", __func__);
+                return (FIDO_ERR_INVALID_ARGUMENT);
+        }
+
+        RSA_get0_key(rsa, &n, &e, &d);
+
+        if (n == NULL || e == NULL) {
+                fido_log_debug("%s: RSA_get0_key", __func__);
+                return (FIDO_ERR_INTERNAL);
+        }
+
+        if ((k = BN_num_bytes(n)) < 0 || (size_t)k > sizeof(pk->n) ||
+            (k = BN_num_bytes(e)) < 0 || (size_t)k > sizeof(pk->e)) {
+                fido_log_debug("%s: invalid key", __func__);
+                return (FIDO_ERR_INTERNAL);
+        }
+
+        if ((k = BN_bn2bin(n, pk->n)) < 0 || (size_t)k > sizeof(pk->n) ||
+            (k = BN_bn2bin(e, pk->e)) < 0 || (size_t)k > sizeof(pk->e)) {
+                fido_log_debug("%s: BN_bn2bin", __func__);
+                return (FIDO_ERR_INTERNAL);
+        }
+
+        return (FIDO_OK);
+}