1 files changed, 167 insertions, 0 deletions

diff --git a/src/reclaim/vc_crypto.c b/src/reclaim/vc_crypto.c
new file mode 100644
index 000000000..83b720666
--- /dev/null
+++ b/src/reclaim/vc_crypto.c
@@ -0,0 +1,167 @@
+/*
+     This file is part of GNUnet
+     Copyright (C) 2022 GNUnet e.V.
+
+     GNUnet is free software: you can redistribute it and/or modify it
+     under the terms of the GNU Affero General Public License as published
+     by the Free Software Foundation, either version 3 of the License,
+     or (at your option) any later version.
+
+     GNUnet 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
+     Affero General Public License for more details.
+
+     You should have received a copy of the GNU Affero General Public License
+     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+ */
+
+/**
+ * @file reclaim/libgnunet_reclaim_vc_crypto.c
+ * @author Tristan Schwieren
+ */
+
+#include "platform.h"
+#include "gnunet_util_lib.h"
+#include "gnunet_identity_service.h"
+#include "gnunet_signatures.h"
+#include <jansson.h>
+
+
+/**
+ * @brief Genereate the missing signature for a verifiable presentation
+ * @param pres A verifiable presentation with an empty signature field
+ * @param pk The private key which is used to generate the Signature
+ * @param result The verifiable presentation containing a valid signature is returned
+ */
+char * 
+generate_signature_vp(json_t * pres, 
+                      const struct GNUNET_IDENTITY_PrivateKey * pk)
+{
+    // TODO: make sig multibase
+    char * data;
+    json_t * proof;
+
+    struct GNUNET_IDENTITY_Signature sig;
+    ssize_t sig_size;
+
+    struct GNUNET_CRYPTO_EccSignaturePurpose * sig_purpose;
+    ssize_t sig_purpose_size;
+
+    void * sig_buf;
+    ssize_t sig_buf_size;
+
+    char * sig_str;
+    ssize_t sig_str_size;
+
+    char * sig_str_final;
+
+    // Add empty signature key-value -> encode json -> delete empty signature key-value
+    // FIXME: Needs a real Canonicalization Scheme 
+    proof = json_object_get(pres, "proof");
+    json_object_set(proof, "signature", json_string(""));
+    data = json_dumps(pres, JSON_COMPACT);
+    json_object_del(proof, "signature");
+    free(proof);
+
+    // Generate Signature
+    sig_purpose_size = sizeof(struct GNUNET_CRYPTO_EccSignaturePurpose) + strlen(data);
+    sig_purpose = malloc(sig_purpose_size);
+    sig_purpose->size = htonl(sig_purpose_size);
+    sig_purpose->purpose = htonl(GNUNET_SIGNATURE_PURPOSE_TEST); 
+    memcpy(&sig_purpose[1], (void *) data, strlen(data));
+
+    GNUNET_IDENTITY_sign_(pk, 
+                         sig_purpose, 
+                         &sig);
+                    
+    free(data);
+    free(sig_purpose);
+
+    // Convert Signature to string
+    sig_size = GNUNET_IDENTITY_signature_get_length(&sig);
+    sig_buf = malloc(sig_size);
+    sig_buf_size = GNUNET_IDENTITY_write_signature_to_buffer(&sig, sig_buf, sig_size);
+    sig_str_size = GNUNET_STRINGS_base64_encode(sig_buf, sig_buf_size, &sig_str);
+    free(sig_buf);
+
+    return sig_str;
+}
+
+/**
+ * @brief Verfiy the the Proof of the verfiable presentation
+ * @return Return 1 if the verfiable Presentation has been issued by the subject and not been manipulated in any way. Return 0 if not
+ */
+int 
+verify_vp(char * vp)
+{
+    json_t * pres;
+
+    char * data;
+    json_t * proof;
+    const char * verification_method;
+    char * pubk_str;
+    struct GNUNET_IDENTITY_PublicKey * pubk;
+
+    struct GNUNET_IDENTITY_Signature * sig;
+    ssize_t sig_size;
+
+    struct GNUNET_CRYPTO_EccSignaturePurpose * sig_purpose;
+    ssize_t sig_purpose_size;
+
+    void * sig_buf;
+    ssize_t sig_buf_size;
+
+    const char * sig_str;
+    ssize_t sig_str_size;
+
+    int valid;
+
+    pres = json_loads(vp, JSON_DECODE_ANY, NULL);
+
+    // Add empty signature key-value -> encode json -> delete empty signature key-value
+    // FIXME: Needs a real Canonicalization Scheme 
+    proof = json_object_get(pres, "proof");
+    json_object_del(proof, "signature");
+    json_object_set(proof, "signature", json_string(""));
+    data = json_dumps(pres, JSON_COMPACT);
+
+    // Get pubkey from reclaim did
+    verification_method = json_string_value(json_object_get(proof, "verificationMethod"));
+    pubk_str = malloc(sizeof(char)*100); // FIXME: Get the real public key len
+    sscanf(verification_method, "did:reclaim:%s#key-1", pubk_str);
+    GNUNET_IDENTITY_public_key_from_string(pubk_str, pubk);
+    free(pubk_str);
+
+    // Get signature
+    sig_str = json_string_value(json_object_get(proof, "signature"));
+    sig_str_size = strlen(sig_str);
+    sig_buf = malloc(sig_str_size);
+    sig_buf_size = GNUNET_STRINGS_base64_decode(sig_str, sig_str_size, sig_buf);
+    sig_size = GNUNET_IDENTITY_read_signature_from_buffer(sig, sig_buf, sig_buf_size);
+    
+    free(proof);
+    free(pres);
+    free(sig_buf);
+
+    // Generate Purpose
+    sig_purpose_size = sizeof(struct GNUNET_CRYPTO_EccSignaturePurpose) + strlen(data);
+    sig_purpose = malloc(sig_purpose_size);
+    sig_purpose->size = htonl(sig_purpose_size);
+    sig_purpose->purpose = htonl(GNUNET_SIGNATURE_PURPOSE_TEST); 
+    memcpy(&sig_purpose[1], (void *) data, strlen(data));
+
+    valid = GNUNET_IDENTITY_signature_verify_(GNUNET_SIGNATURE_PURPOSE_TEST,
+                                              sig_purpose,
+                                              sig,
+                                              pubk);
+
+    free(data);
+    free(sig_purpose);
+    free(pubk);
+    free(sig);
+
+    return valid;
+}
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