feat(psa): add delegated attestation partition API

Delegated attestation is a service provided by RSS to: - Derive a delegated attestation key: Realm Attestation Key - Query the platform attestation token Signed-off-by: Tamas Ban <tamas.ban@arm.com> Change-Id: I3edf09fcbef24bca7c8a000ffac8c1ab64dfb812
2 years ago · 4b09ffef49
3 changed files with 342 additions and 0 deletions
--- a/include/lib/psa/delegated_attestation.h
+++ b/include/lib/psa/delegated_attestation.h
@ -0,0 +1,109 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+/* This file describes the Delegated Attestation API */
+
+#ifndef DELEGATED_ATTESTATION_H
+#define DELEGATED_ATTESTATION_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "psa/error.h"
+
+/* RSS Delegated Attestation message types that distinguish its services. */
+#define RSS_DELEGATED_ATTEST_GET_DELEGATED_KEY      1001U
+#define RSS_DELEGATED_ATTEST_GET_PLATFORM_TOKEN     1002U
+
+/**
+ * The aim of these APIs to get a derived signing key (private only) for the
+ * delegated attestation model and obtain the corresponding platform attestation
+ * token. In the delegated attestation model the final token consist of more
+ * than one subtokens which are signed by different entities. There is a
+ * cryptographical binding between the tokens. The derived delegated attestation
+ * key is bind to the platform token (details below).
+ *
+ * Expected usage model:
+ *  - First rss_delegated_attest_get_delegated_key() API need to be called to
+ *    obtain the private part of the delegated attestation key. The public part
+ *    of key is computed by the cryptographic library when the key is
+ *    registered.
+ *  - Secondly the rss_delegated_attest_get_token() must be called to obtain
+ *    platform attestation token. The hash of the public key (computed by
+ *    the hash_algo indicated in the rss_delegated_attest_get_delegated_key()
+ *    call) must be the input of this call. This ensures that nothing but the
+ *    previously derived delegated key is bindable to the platform token.
+ */
+
+/**
+ * Get a delegated attestation key (DAK).
+ *
+ * The aim of the delegated attestation key is to enable other SW components
+ * within the system to sign an attestation token which is different than the
+ * initial/platform token. The initial attestation token MUST contain the hash
+ * of the public delegated key to make a cryptographical binding (hash lock)
+ * between the key and the token.
+ * The initial attestation token has two roles in this scenario:
+ *   - Attest the device boot status and security lifecycle.
+ *   - Attest the delegated attestation key.
+ * The delegated attestation key is derived from a preprovisioned seed. The
+ * input for the key derivation is the platform boot status. The system can be
+ * attestated with the two tokens together.
+ *
+ * ecc_curve     The type of the elliptic curve to which the requested
+ *               attestation key belongs. Please check the note section for
+ *               limitations.
+ * key_bits      The size of the requested attestation key, in bits.
+ * key_buf       Pointer to the buffer where the delegated attestation key will
+ *               be stored.
+ * key_buf_size  Size of allocated buffer for the key, in bytes.
+ * key_size      Size of the key that has been returned, in bytes.
+ * hash_algo     The hash algorithm that will be used later by the owner of the
+ *               requested delegated key for binding it to the platform
+ *               attestation token.
+ *
+ * Returns error code as specified in psa_status_t.
+ *
+ * Notes:
+ *   - Currently, only the PSA_ECC_FAMILY_SECP_R1 curve type is supported.
+ *   - The delegated attestation key must be derived before requesting for the
+ *     platform attestation token as they are cryptographically linked together.
+ */
+psa_status_t
+rss_delegated_attest_get_delegated_key(uint8_t   ecc_curve,
+				       uint32_t  key_bits,
+				       uint8_t  *key_buf,
+				       size_t    key_buf_size,
+				       size_t   *key_size,
+				       uint32_t  hash_algo);
+
+/**
+ * Get platform attestation token
+ *
+ * dak_pub_hash       Pointer to buffer where the hash of the public DAK is
+ *                    stored.
+ * dak_pub_hash_size  Size of the hash value, in bytes.
+ * token_buf          Pointer to the buffer where the platform attestation token
+ *                    will be stored.
+ * token_buf_size     Size of allocated buffer for token, in bytes.
+ * token_size         Size of the token that has been returned, in bytes.
+ *
+ * Returns error code as specified in psa_status_t.
+ *
+ * A delegated attestation key must be derived before requesting for the
+ * platform attestation token as they are cryptographically linked together.
+ * Otherwise, the token request will fail and the PSA_ERROR_INVALID_ARGUMENT
+ * code will be returned.
+ */
+psa_status_t
+rss_delegated_attest_get_token(const uint8_t *dak_pub_hash,
+			       size_t         dak_pub_hash_size,
+			       uint8_t       *token_buf,
+			       size_t         token_buf_size,
+			       size_t        *token_size);
+
+#endif /* DELEGATED_ATTESTATION_H */
--- a/include/lib/psa/psa_manifest/sid.h
+++ b/include/lib/psa/psa_manifest/sid.h
@ -14,4 +14,7 @@
 /******** PSA_SP_MEASURED_BOOT ********/
 #define RSS_MEASURED_BOOT_HANDLE			(0x40000110U)

+/******** PSA_SP_DELAGATED_ATTESTATION ********/
+#define RSS_DELEGATED_SERVICE_HANDLE			(0x40000111U)
+
 #endif /* PSA_MANIFEST_SID_H */
--- a/lib/psa/delegated_attestation.c
+++ b/lib/psa/delegated_attestation.c
@ -0,0 +1,230 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+#include <string.h>
+
+#include <delegated_attestation.h>
+#include <psa/client.h>
+#include <psa_manifest/sid.h>
+
+#if !PLAT_RSS_NOT_SUPPORTED
+psa_status_t
+rss_delegated_attest_get_delegated_key(uint8_t   ecc_curve,
+				       uint32_t  key_bits,
+				       uint8_t  *key_buf,
+				       size_t    key_buf_size,
+				       size_t   *key_size,
+				       uint32_t  hash_algo)
+{
+	psa_status_t status;
+	psa_invec in_vec[] = {
+		{&ecc_curve, sizeof(ecc_curve)},
+		{&key_bits,  sizeof(key_bits)},
+		{&hash_algo, sizeof(hash_algo)}
+	};
+	psa_outvec out_vec[] = {
+		{key_buf, key_buf_size}
+	};
+
+	if (key_size == NULL) {
+		return PSA_ERROR_INVALID_ARGUMENT;
+	}
+
+	status = psa_call(RSS_DELEGATED_SERVICE_HANDLE,
+			  RSS_DELEGATED_ATTEST_GET_DELEGATED_KEY,
+			  in_vec,  IOVEC_LEN(in_vec),
+			  out_vec, IOVEC_LEN(out_vec));
+	if (status == PSA_SUCCESS) {
+		*key_size = out_vec[0].len;
+	}
+
+	return status;
+}
+
+psa_status_t
+rss_delegated_attest_get_token(const uint8_t *dak_pub_hash,
+			       size_t         dak_pub_hash_size,
+			       uint8_t       *token_buf,
+			       size_t         token_buf_size,
+			       size_t        *token_size)
+{
+	psa_status_t status;
+	psa_invec in_vec[] = {
+		{dak_pub_hash, dak_pub_hash_size}
+	};
+	psa_outvec out_vec[] = {
+		{token_buf, token_buf_size}
+	};
+
+	if (token_size == NULL) {
+		return PSA_ERROR_INVALID_ARGUMENT;
+	}
+
+	status = psa_call(RSS_DELEGATED_SERVICE_HANDLE,
+			  RSS_DELEGATED_ATTEST_GET_PLATFORM_TOKEN,
+			  in_vec, IOVEC_LEN(in_vec),
+			  out_vec, IOVEC_LEN(out_vec));
+	if (status == PSA_SUCCESS) {
+		*token_size = out_vec[0].len;
+	}
+
+	return status;
+}
+
+
+#else /* !PLAT_RSS_NOT_SUPPORTED */
+
+static const uint8_t delegated_key[] = {
+	0x20, 0x11, 0xC7, 0xF0, 0x3C, 0xEE, 0x43, 0x25, 0x17, 0x6E,
+	0x52, 0x4F, 0x03, 0x3C, 0x0C, 0xE1, 0xE2, 0x1A, 0x76, 0xE6,
+	0xC1, 0xA4, 0xF0, 0xB8, 0x39, 0xAA, 0x1D, 0xF6, 0x1E, 0x0E,
+	0x8A, 0x5C, 0x8A, 0x05, 0x74, 0x0F, 0x9B, 0x69, 0xEF, 0xA7,
+	0xEB, 0x1A, 0x41, 0x85, 0xBD, 0x11, 0x7F, 0x68
+}
+
+static const uint8_t platform_token[] = {
+	0xD2, 0x84, 0x43, 0xA1, 0x01, 0x26, 0xA0, 0x59,
+	0x02, 0xBE, 0xAA, 0x3A, 0x00, 0x01, 0x24, 0xFF,
+	0x58, 0x20, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB,
+	0xAB, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB,
+	0xAB, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB,
+	0xAB, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB,
+	0xAB, 0xAB, 0x3A, 0x00, 0x01, 0x24, 0xFB, 0x58,
+	0x20, 0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6,
+	0xA7, 0xA8, 0xA9, 0xAA, 0xAB, 0xAC, 0xAD, 0xAE,
+	0xAF, 0xB0, 0xB1, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6,
+	0xB7, 0xB8, 0xB9, 0xBA, 0xBB, 0xBC, 0xBD, 0xBE,
+	0xBF, 0x3A, 0x00, 0x01, 0x25, 0x00, 0x58, 0x21,
+	0x01, 0xFA, 0x58, 0x75, 0x5F, 0x65, 0x86, 0x27,
+	0xCE, 0x54, 0x60, 0xF2, 0x9B, 0x75, 0x29, 0x67,
+	0x13, 0x24, 0x8C, 0xAE, 0x7A, 0xD9, 0xE2, 0x98,
+	0x4B, 0x90, 0x28, 0x0E, 0xFC, 0xBC, 0xB5, 0x02,
+	0x48, 0x3A, 0x00, 0x01, 0x24, 0xFA, 0x58, 0x20,
+	0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA,
+	0xBB, 0xBB, 0xBB, 0xBB, 0xBB, 0xBB, 0xBB, 0xBB,
+	0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC,
+	0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD,
+	0x3A, 0x00, 0x01, 0x24, 0xF8, 0x20, 0x3A, 0x00,
+	0x01, 0x24, 0xF9, 0x00, 0x3A, 0x00, 0x01, 0x24,
+	0xFD, 0x85, 0xA5, 0x05, 0x58, 0x20, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x60,
+	0x01, 0x65, 0x42, 0x4C, 0x31, 0x5F, 0x32, 0x06,
+	0x66, 0x53, 0x48, 0x41, 0x32, 0x35, 0x36, 0x02,
+	0x58, 0x20, 0xF8, 0xB7, 0xCE, 0xAD, 0x9B, 0xE4,
+	0x5A, 0x8F, 0x5C, 0x52, 0x6F, 0x0C, 0x05, 0x25,
+	0x8F, 0xF3, 0xE9, 0x81, 0xDC, 0xBC, 0xF2, 0x05,
+	0x7F, 0x33, 0xF6, 0xBB, 0xDC, 0xD9, 0x4D, 0xA2,
+	0x34, 0x3A, 0xA5, 0x05, 0x58, 0x20, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x67,
+	0x31, 0x2E, 0x37, 0x2E, 0x32, 0x2B, 0x30, 0x01,
+	0x63, 0x42, 0x4C, 0x32, 0x06, 0x66, 0x53, 0x48,
+	0x41, 0x32, 0x35, 0x36, 0x02, 0x58, 0x20, 0x3A,
+	0xE5, 0x9E, 0x40, 0xA9, 0x6B, 0xD5, 0x29, 0x1C,
+	0xAB, 0x7A, 0x5F, 0xBD, 0x1F, 0x9A, 0xA6, 0x52,
+	0xFB, 0x77, 0x7D, 0xA3, 0xEC, 0x9C, 0x29, 0xBC,
+	0xE6, 0x5B, 0x3B, 0x43, 0xFC, 0x9D, 0x26, 0xA5,
+	0x05, 0x58, 0x20, 0xBF, 0xE6, 0xD8, 0x6F, 0x88,
+	0x26, 0xF4, 0xFF, 0x97, 0xFB, 0x96, 0xC4, 0xE6,
+	0xFB, 0xC4, 0x99, 0x3E, 0x46, 0x19, 0xFC, 0x56,
+	0x5D, 0xA2, 0x6A, 0xDF, 0x34, 0xC3, 0x29, 0x48,
+	0x9A, 0xDC, 0x38, 0x04, 0x67, 0x31, 0x2E, 0x35,
+	0x2E, 0x30, 0x2B, 0x30, 0x01, 0x64, 0x52, 0x54,
+	0x5F, 0x30, 0x06, 0x66, 0x53, 0x48, 0x41, 0x32,
+	0x35, 0x36, 0x02, 0x58, 0x20, 0x47, 0x94, 0x9D,
+	0x27, 0x33, 0x82, 0x45, 0x1A, 0xDD, 0x25, 0xF4,
+	0x9A, 0x89, 0x6F, 0x5F, 0xD9, 0xB0, 0xE8, 0x14,
+	0xD3, 0xA4, 0x9B, 0x53, 0xB0, 0x44, 0x0B, 0xCF,
+	0x32, 0x1A, 0xC4, 0xD2, 0x65, 0xA5, 0x05, 0x58,
+	0x20, 0xB3, 0x60, 0xCA, 0xF5, 0xC9, 0x8C, 0x6B,
+	0x94, 0x2A, 0x48, 0x82, 0xFA, 0x9D, 0x48, 0x23,
+	0xEF, 0xB1, 0x66, 0xA9, 0xEF, 0x6A, 0x6E, 0x4A,
+	0xA3, 0x7C, 0x19, 0x19, 0xED, 0x1F, 0xCC, 0xC0,
+	0x49, 0x04, 0x67, 0x30, 0x2E, 0x30, 0x2E, 0x37,
+	0x2B, 0x30, 0x01, 0x64, 0x52, 0x54, 0x5F, 0x31,
+	0x06, 0x66, 0x53, 0x48, 0x41, 0x32, 0x35, 0x36,
+	0x02, 0x58, 0x20, 0xCD, 0x38, 0xBE, 0xC8, 0xB7,
+	0xC0, 0x9E, 0xD5, 0x24, 0x30, 0xFE, 0xC8, 0xD0,
+	0x19, 0x12, 0x56, 0xB2, 0x7A, 0xA5, 0x53, 0x6F,
+	0xBC, 0x7D, 0x09, 0xCA, 0x11, 0xDD, 0x90, 0xD7,
+	0xD6, 0x70, 0xFD, 0xA5, 0x05, 0x58, 0x20, 0xAA,
+	0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA,
+	0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA,
+	0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA,
+	0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0x04,
+	0x60, 0x01, 0x60, 0x06, 0x66, 0x53, 0x48, 0x41,
+	0x32, 0x35, 0x36, 0x02, 0x58, 0x20, 0x28, 0x3D,
+	0x0C, 0x25, 0x22, 0x0C, 0x87, 0x46, 0xA0, 0x58,
+	0x64, 0x6C, 0x0B, 0x14, 0x37, 0x39, 0x40, 0x9D,
+	0x2D, 0x11, 0xD1, 0xCC, 0x54, 0x51, 0xB4, 0x29,
+	0x22, 0xCD, 0x70, 0x92, 0x71, 0xC3, 0x3A, 0x00,
+	0x01, 0x25, 0x01, 0x77, 0x77, 0x77, 0x77, 0x2E,
+	0x74, 0x72, 0x75, 0x73, 0x74, 0x65, 0x64, 0x66,
+	0x69, 0x72, 0x6D, 0x77, 0x61, 0x72, 0x65, 0x2E,
+	0x6F, 0x72, 0x67, 0x3A, 0x00, 0x01, 0x24, 0xF7,
+	0x71, 0x50, 0x53, 0x41, 0x5F, 0x49, 0x4F, 0x54,
+	0x5F, 0x50, 0x52, 0x4F, 0x46, 0x49, 0x4C, 0x45,
+	0x5F, 0x31, 0x3A, 0x00, 0x01, 0x24, 0xFC, 0x70,
+	0x30, 0x36, 0x30, 0x34, 0x35, 0x36, 0x35, 0x32,
+	0x37, 0x32, 0x38, 0x32, 0x39, 0x31, 0x30, 0x30,
+	0x58, 0x40, 0x1E, 0x0D, 0x2B, 0xD8, 0x7A, 0xC9,
+	0x2D, 0xCB, 0x73, 0xD1, 0x42, 0x2F, 0xBF, 0xDA,
+	0x24, 0x71, 0xE2, 0xAF, 0xEA, 0x48, 0x60, 0x17,
+	0x23, 0x75, 0x64, 0xAC, 0xCC, 0x23, 0xA2, 0x67,
+	0xC4, 0xE7, 0x8F, 0x1C, 0x7C, 0x68, 0x49, 0x42,
+	0x4D, 0xDA, 0xC6, 0xD6, 0x21, 0x1C, 0xAA, 0x00,
+	0xDA, 0x1E, 0x68, 0x56, 0xA3, 0x48, 0xEE, 0xA7,
+	0x92, 0xA9, 0x09, 0x83, 0x42, 0x04, 0x06, 0x9E,
+	0x62, 0xBB
+};
+
+psa_status_t
+rss_delegated_attest_get_delegated_key(uint8_t   ecc_curve,
+				       uint32_t  key_bits,
+				       uint8_t  *key_buf,
+				       size_t    key_buf_size,
+				       size_t   *key_size,
+				       uint32_t  hash_algo)
+{
+	(void)ecc_curve;
+	(void)key_bits;
+	(void)hash_algo;
+
+	if (key_buf_size < sizeof(delegated_key)) {
+		return PSA_ERROR_BUFFER_TOO_SMALL;
+	}
+
+	(void)memcpy(key_buf, delegated_key, sizeof(delegated_key));
+	*key_size = sizeof(delegated_key);
+
+	return PSA_SUCCESS;
+}
+psa_status_t
+rss_delegated_attest_get_token(const uint8_t *dak_pub_hash,
+			       size_t         dak_pub_hash_size,
+			       uint8_t       *token_buf,
+			       size_t         token_buf_size,
+			       size_t        *token_size)
+{
+	(void)dak_pub_hash;
+	(void)dak_pub_hash_size;
+
+	if (token_buf_size < sizeof(platform_token)) {
+		return PSA_ERROR_BUFFER_TOO_SMALL;
+	}
+
+	(void)memcpy(token_buf, platform_token, sizeof(platform_token));
+	*token_size = sizeof(platform_token);
+
+	return PSA_SUCCESS;
+}
+#endif /* !PLAT_RSS_NOT_SUPPORTED */