add example of stand alone enveloped data decode

Author: JacobBarthelmeh

pkcs7/envelopedDataDecode.c

@@ -0,0 +1,182 @@
+/* envelopedDataDecode.c
+ *
+ * Copyright (C) 2006-2020 wolfSSL Inc.
+ *
+ * This file is part of wolfSSL. (formerly known as CyaSSL)
+ *
+ * wolfSSL is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * wolfSSL is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
+ */
+
+
+#include <wolfssl/options.h>
+#include <wolfssl/wolfcrypt/settings.h>
+#include <wolfssl/wolfcrypt/pkcs7.h>
+#include <wolfssl/wolfcrypt/error-crypt.h>
+#include <wolfssl/wolfcrypt/logging.h>
+
+static int load_certs(const char* certFile, byte* cert, word32* certSz,
+    const char* keyFile, byte* key, word32* keySz)
+{
+    FILE* file;
+
+    /* certificate file */
+    file = fopen(certFile, "rb");
+    if (!file)
+        return -1;
+
+    *certSz = (word32)fread(cert, 1, *certSz, file);
+    fclose(file);
+
+    /* key file */
+    file = fopen(keyFile, "rb");
+    if (!file)
+        return -1;
+
+    *keySz = (word32)fread(key, 1, *keySz, file);
+    fclose(file);
+
+    return 0;
+}
+
+
+static int envelopedData_decrypt(byte* in, word32 inSz, byte* cert,
+                                word32 certSz, byte* key, word32 keySz,
+                                byte* out, word32 outSz)
+{
+    int ret;
+    PKCS7* pkcs7;
+
+    pkcs7 = wc_PKCS7_New(NULL, INVALID_DEVID);
+    if (pkcs7 == NULL)
+        return -1;
+
+    /* init with recipient cert */
+    ret = wc_PKCS7_InitWithCert(pkcs7, cert, certSz);
+    if (ret != 0) {
+        wc_PKCS7_Free(pkcs7);
+        return -1;
+    }
+
+    /* set recipient private key */
+    ret = wc_PKCS7_SetKey(pkcs7, key, keySz);
+    if (ret != 0) {
+        wc_PKCS7_Free(pkcs7);
+        return -1;
+    }
+
+    /* decode envelopedData, returns size */
+    ret = wc_PKCS7_DecodeEnvelopedData(pkcs7, in, inSz, out, outSz);
+    wc_PKCS7_Free(pkcs7);
+
+    if (ret <= 0) {
+        printf("Failed to decode EnvelopedData bundle error of %d\n", ret);
+    }
+    else {
+        printf("Successfully decoded EnvelopedData bundle\n");
+    }
+
+
+    return ret;
+}
+
+#ifdef HAVE_PKCS7
+
+int main(int argc, char** argv)
+{
+    int ret;
+    int encryptedSz, decryptedSz;
+    word32 certSz, keySz;
+
+    byte cert[2048];
+    byte key[2048];
+    byte* encrypted;
+    byte* decrypted;
+
+#ifdef DEBUG_WOLFSSL
+    wolfSSL_Debugging_ON();
+#endif
+
+    if (argc != 4) {
+        printf("expecting DER cert, key, and encrypted bundle as args\n");
+        printf("%s <DER cert> <DER key> <Encrypted bundle>\n", argv[0]);
+        return -1;
+    }
+
+    certSz = sizeof(cert);
+    keySz  = sizeof(key);
+    ret = load_certs(argv[1], cert, &certSz, argv[2], key, &keySz);
+    if (ret != 0)
+        return -1;
+
+    /* read encrypted bundle */
+    {
+        FILE* file;
+
+        file = fopen(argv[3], "rb");
+        if (!file) {
+            printf("unable to open file %s\n", argv[3]);
+            return -1;
+        }
+        fseek(file, 0, SEEK_END);
+        encryptedSz = (int)ftell(file);
+        rewind(file);
+
+        encrypted = (byte*)malloc(encryptedSz);
+        if (encrypted == NULL) {
+            printf("malloc failed\n");
+            return -1;
+        }
+
+        decryptedSz = encryptedSz;
+        decrypted = (byte*)malloc(decryptedSz);
+        if (decrypted == NULL) {
+            printf("malloc failed\n");
+            free(encrypted);
+            return -1;
+        }
+
+        encryptedSz = (word32)fread(encrypted, 1, encryptedSz, file);
+        printf("encrypted bundle size read = %d\n", encryptedSz);
+        fclose(file);
+    }
+
+    decryptedSz = envelopedData_decrypt(encrypted, encryptedSz,
+                                        cert, certSz, key, keySz,
+                                        decrypted, decryptedSz);
+    free(encrypted);
+    if (decryptedSz < 0) {
+        free(decrypted);
+        return -1;
+    }
+
+#ifdef DEBUG_WOLFSSL
+    printf("Decrypted content (%d byte):\n", decryptedSz);
+    WOLFSSL_BUFFER(decrypted, decryptedSz);
+#endif
+    free(decrypted);
+
+    return 0;
+}
+
+#else
+
+int main(int argc, char** argv)
+{
+    printf("Must build wolfSSL using ./configure --enable-pkcs7\n");
+    return 0;
+}
+
+#endif
+