sys/hashes: add AES-CMAC implementation

sys/hashes/cmac.c

@@ -0,0 +1,113 @@
+/*
+ * Copyright (C) 2016 Fundación Inria Chile
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     sys_hashes_cmac
+ * @{
+ *
+ * @file
+ * @brief       AES_CMAC implementation
+ *
+ * @author      José Ignacio Alamos <jose.alamos@inria.cl>
+ *
+ * @}
+ */
+
+#include <inttypes.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "crypto/ciphers.h"
+#include "hashes/cmac.h"
+
+#define MIN(a, b) a < b ? a : b
+
+static void _xor128(uint8_t *x, uint8_t *y)
+{
+    for (unsigned i = 0; i < 16; i++) {
+        y[i] = x[i] ^ y[i];
+    }
+}
+
+static void _leftshift(uint8_t *x, uint8_t *y)
+{
+    for (unsigned i = 0; i < 15; i++) {
+        y[i] = (x[i] << 1) | (x[i + 1] >> 7);
+    }
+    y[15] = x[15] << 1;
+}
+
+int cmac_init(cmac_context_t *ctx, const uint8_t *key, uint8_t key_size)
+{
+    if (key_size != CMAC_BLOCK_SIZE) {
+        return CIPHER_ERR_INVALID_KEY_SIZE;
+    }
+
+    memset(ctx, 0, sizeof(cmac_context_t));
+    return cipher_init(&(ctx->aes_ctx), CIPHER_AES_128, key, key_size);
+}
+
+void cmac_update(cmac_context_t *ctx, const void *data, size_t len)
+{
+    uint8_t d[16];
+
+    while (len) {
+        uint8_t c;
+        if (ctx->M_n == 16) {
+            ctx->M_n = 0;
+            _xor128(ctx->M_last, ctx->X);
+            cipher_encrypt(&ctx->aes_ctx, ctx->X, d);
+            memcpy(ctx->X, d, CMAC_BLOCK_SIZE);
+        }
+        c = MIN(CMAC_BLOCK_SIZE - ctx->M_n, len);
+        memcpy(ctx->M_last + ctx->M_n, data, c);
+        ctx->M_n += c;
+        len -= c;
+        data = (void *) (((uint8_t *) data) + c);
+
+        if (ctx->M_n < CMAC_BLOCK_SIZE) {
+            break;
+        }
+    }
+}
+
+void cmac_final(cmac_context_t *ctx, void *digest)
+{
+    /* Generate subkeys */
+    uint8_t K[CMAC_BLOCK_SIZE];
+    uint8_t L[CMAC_BLOCK_SIZE];
+
+    memset(K, 0, CMAC_BLOCK_SIZE);
+    cipher_encrypt(&ctx->aes_ctx, K, L);
+
+    if (L[0] & 0x80) {
+        _leftshift(L, K);
+        K[15] ^= 0x87;
+    }
+    else {
+        _leftshift(L, K);
+    }
+
+    if (ctx->M_n != 16) {
+        /* Generate K2 */
+        if (K[0] & 0x80) {
+            _leftshift(K, K);
+            K[15] ^= 0x87;
+        }
+        else {
+            _leftshift(K, K);
+        }
+        /* Padding */
+        memset(ctx->M_last + ctx->M_n, 0, CMAC_BLOCK_SIZE - ctx->M_n);
+        ctx->M_last[ctx->M_n] = 0x80;
+    }
+    _xor128(K, ctx->M_last);
+    _xor128(ctx->M_last, ctx->X);
+    cipher_encrypt(&ctx->aes_ctx, ctx->X, L);
+    memcpy(digest, L, CMAC_BLOCK_SIZE);
+}

sys/include/hashes/cmac.h

@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) 2016 Fundación Inria Chile
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @defgroup    sys_hashes_cmac AES_CMAC
+ * @ingroup     sys_hashes
+ * @brief       Implementation of the AES CMAC hashing function
+
+ * @{
+ *
+ * @file
+ * @brief       AES_CMAC interface definition
+ *
+ * @author      José Ignacio Alamos <jose.alamos@inria.cl>
+ */
+
+#ifndef HASHES_CMAC_H
+#define HASHES_CMAC_H
+
+#include <stdio.h>
+#include "crypto/ciphers.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   Length of AES_CMAC block in bytes
+ */
+#define CMAC_BLOCK_SIZE 16
+
+/**
+ * @brief   AES_CMAC calculation context
+ */
+typedef struct {
+    /** AES128 context */
+    cipher_t aes_ctx;
+    /** auxiliar array for CMAC calculations **/
+    uint8_t X[CMAC_BLOCK_SIZE];
+    /** current last block **/
+    uint8_t M_last[CMAC_BLOCK_SIZE];
+    /** last byte in last block */
+    uint32_t M_n;
+} cmac_context_t;
+
+/**
+ * @brief Initialize CMAC message digest context
+ *
+ * @param[in] ctx     Pointer to the CMAC context to initialize
+ * @param[in] key     Key to be set
+ * @param[in] key_size     Size of the key
+ *
+ * @return CIPHER_INIT_SUCCESS if the initialization was successful.
+ *         CIPHER_ERR_INVALID_KEY_SIZE if the key size is not valid.
+ */
+int cmac_init(cmac_context_t *ctx, const uint8_t *key, uint8_t key_size);
+
+/**
+ * @brief Update the CMAC context with a portion of the message being hashed
+ *
+ * @param[in] ctx  Pointer to the CMAC context to update
+ * @param[in] data Input data
+ * @param[in] len  Length of @p data
+ */
+void cmac_update(cmac_context_t *ctx, const void *data, size_t len);
+
+/**
+ * @brief Finalizes the CMAC message digest
+ *
+ * @param[in] ctx     Pointer to the CMAC context
+ * @param[out] digest Result location
+ */
+void cmac_final(cmac_context_t *ctx, void *digest);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* HASHES_CMAC_H */
+/** @} */