1 files changed, 98 insertions, 0 deletions

diff --git a/src/aes256.c b/src/aes256.c
new file mode 100644
index 0000000..767cdb2
--- /dev/null
+++ b/src/aes256.c
@@ -0,0 +1,98 @@
+/*
+ * 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/evp.h>
+#include <string.h>
+
+#include "fido.h"
+
+int
+aes256_cbc_enc(const fido_blob_t *key, const fido_blob_t *in, fido_blob_t *out)
+{
+        EVP_CIPHER_CTX  *ctx = NULL;
+        unsigned char    iv[32];
+        int              len;
+        int              ok = -1;
+
+        memset(iv, 0, sizeof(iv));
+        out->ptr = NULL;
+        out->len = 0;
+
+        /* sanity check */
+        if (in->len > INT_MAX || (in->len % 16) != 0 ||
+            (out->ptr = calloc(1, in->len)) == NULL) {
+                fido_log_debug("%s: in->len=%zu", __func__, in->len);
+                goto fail;
+        }
+
+        if ((ctx = EVP_CIPHER_CTX_new()) == NULL || key->len != 32 ||
+            !EVP_EncryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, key->ptr, iv) ||
+            !EVP_CIPHER_CTX_set_padding(ctx, 0) ||
+            !EVP_EncryptUpdate(ctx, out->ptr, &len, in->ptr, (int)in->len) ||
+            len < 0 || (size_t)len != in->len) {
+                fido_log_debug("%s: EVP_Encrypt", __func__);
+                goto fail;
+        }
+
+        out->len = (size_t)len;
+
+        ok = 0;
+fail:
+        if (ctx != NULL)
+                EVP_CIPHER_CTX_free(ctx);
+
+        if (ok < 0) {
+                free(out->ptr);
+                out->ptr = NULL;
+                out->len = 0;
+        }
+
+        return (ok);
+}
+
+int
+aes256_cbc_dec(const fido_blob_t *key, const fido_blob_t *in, fido_blob_t *out)
+{
+        EVP_CIPHER_CTX  *ctx = NULL;
+        unsigned char    iv[32];
+        int              len;
+        int              ok = -1;
+
+        memset(iv, 0, sizeof(iv));
+        out->ptr = NULL;
+        out->len = 0;
+
+        /* sanity check */
+        if (in->len > INT_MAX || (in->len % 16) != 0 ||
+            (out->ptr = calloc(1, in->len)) == NULL) {
+                fido_log_debug("%s: in->len=%zu", __func__, in->len);
+                goto fail;
+        }
+
+        if ((ctx = EVP_CIPHER_CTX_new()) == NULL || key->len != 32 ||
+            !EVP_DecryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, key->ptr, iv) ||
+            !EVP_CIPHER_CTX_set_padding(ctx, 0) ||
+            !EVP_DecryptUpdate(ctx, out->ptr, &len, in->ptr, (int)in->len) ||
+            len < 0 || (size_t)len > in->len + 32) {
+                fido_log_debug("%s: EVP_Decrypt", __func__);
+                goto fail;
+        }
+
+        out->len = (size_t)len;
+
+        ok = 0;
+fail:
+        if (ctx != NULL)
+                EVP_CIPHER_CTX_free(ctx);
+
+        if (ok < 0) {
+                free(out->ptr);
+                out->ptr = NULL;
+                out->len = 0;
+        }
+
+        return (ok);
+}