SGX endorsement and platform library (#225)

- Added endorsement initialisation and finalisation functions for SGX
- Added system finalisation ecall, used within the untrusted code's finalisation routine
- Removed old stubs for SGX's HAL platform and endorsement
- Added der_utils library to aid with endorsement signature encoding
- Implemented SGX endorsement library
- Implemented SGX platform library
- Adjusting sync acquire lock's function to account for different return types
- Removed now unused hmac_sha256 library from SGX's HAL
- Added SGX's HAL der_utils and endorsement unit tests

firmware/src/hal/include/hal/endorsement.h

@@ -115,7 +115,7 @@ extern attestation_id_t attestation_id;
  */
 bool endorsement_init(char* att_file_path);
 
-#elif defined(HSM_PLATFORM_SGX) || defined(HSM_PLATFORM_LEDGER)
+#elif defined(HSM_PLATFORM_LEDGER)
 
 /**
  * @brief Initializes the endorsement module
@@ -124,6 +124,20 @@ bool endorsement_init(char* att_file_path);
  */
 bool endorsement_init();
 
+#elif defined(HSM_PLATFORM_SGX)
+
+/**
+ * @brief Initializes the endorsement module
+ *
+ * @returns whether the initialisation succeeded
+ */
+bool endorsement_init();
+
+/**
+ * @brief Finalises the endorsement module
+ */
+void endorsement_finalise();
+
 #endif
 // END of platform-dependent code
 

firmware/src/hal/sgx/src/trusted/der_utils.c

@@ -0,0 +1,62 @@
+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2021 RSK Labs Ltd
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "der_utils.h"
+#include <stddef.h>
+#include <stdbool.h>
+#include <string.h>
+
+// Helper function to encode a len-byte unsigned integer (R or S) in DER format
+static size_t der_encode_uint(uint8_t* dest, uint8_t* src, size_t len) {
+    // Check if we need a leading zero byte
+    bool lz = src[0] & 0x80;
+    // Start of source: remove leading zeroes
+    size_t trim = 0;
+    while (!src[trim] && trim < (len - 1))
+        trim++;
+    // Output
+    size_t off = 0;
+    dest[off++] = 0x02;                      // Integer tag
+    dest[off++] = len - trim + (lz ? 1 : 0); // Length byte
+    if (lz)
+        dest[off++] = 0x00;                     // Leading zero
+    memcpy(dest + off, src + trim, len - trim); // Actual integer
+    return (size_t)dest[1] + 2;
+}
+
+uint8_t der_encode_signature(uint8_t* dest, sgx_ecdsa256_signature_t* sig) {
+    uint8_t r_encoded[sizeof(sig->r) + 2],
+        s_encoded[sizeof(sig->s) + 2]; // Temporary buffers for R and S
+    uint8_t r_len = (uint8_t)der_encode_uint(r_encoded, sig->r, sizeof(sig->r));
+    uint8_t s_len = (uint8_t)der_encode_uint(s_encoded, sig->s, sizeof(sig->s));
+
+    // Start the sequence
+    dest[0] = 0x30;                             // Sequence tag
+    dest[1] = r_len + s_len;                    // Length of the sequence
+    memcpy(dest + 2, r_encoded, r_len);         // Copy encoded R
+    memcpy(dest + 2 + r_len, s_encoded, s_len); // Copy encoded S
+
+    // Return total length of DER encoded signature
+    return (uint8_t)(2 + r_len + s_len);
+}

firmware/src/hal/sgx/src/trusted/der_utils.h

@@ -0,0 +1,28 @@
+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2021 RSK Labs Ltd
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <stdint.h>
+#include <openenclave/bits/sgx/sgxtypes.h>
+
+uint8_t der_encode_signature(uint8_t* dest, sgx_ecdsa256_signature_t* sig);