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+/**
+ * \brief HAVEGE: HArdware Volatile Entropy Gathering and Expansion
+ *
+ * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * This file is part of mbed TLS (https://tls.mbed.org)
+ */
+/*
+ * The HAVEGE RNG was designed by Andre Seznec in 2002.
+ *
+ * http://www.irisa.fr/caps/projects/hipsor/publi.php
+ *
+ * Contact: seznec(at)irisa_dot_fr - orocheco(at)irisa_dot_fr
+ */
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_HAVEGE_C)
+
+#include "mbedtls/havege.h"
+#include "mbedtls/timing.h"
+
+#include <string.h>
+
+/* Implementation that should never be optimized out by the compiler */
+static void mbedtls_zeroize( void *v, size_t n ) {
+ volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+}
+
+/* ------------------------------------------------------------------------
+ * On average, one iteration accesses two 8-word blocks in the havege WALK
+ * table, and generates 16 words in the RES array.
+ *
+ * The data read in the WALK table is updated and permuted after each use.
+ * The result of the hardware clock counter read is used for this update.
+ *
+ * 25 conditional tests are present. The conditional tests are grouped in
+ * two nested groups of 12 conditional tests and 1 test that controls the
+ * permutation; on average, there should be 6 tests executed and 3 of them
+ * should be mispredicted.
+ * ------------------------------------------------------------------------
+ */
+
+#define SWAP(X,Y) { int *T = X; X = Y; Y = T; }
+
+#define TST1_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
+#define TST2_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
+
+#define TST1_LEAVE U1++; }
+#define TST2_LEAVE U2++; }
+
+#define ONE_ITERATION \
+ \
+ PTEST = PT1 >> 20; \
+ \
+ TST1_ENTER TST1_ENTER TST1_ENTER TST1_ENTER \
+ TST1_ENTER TST1_ENTER TST1_ENTER TST1_ENTER \
+ TST1_ENTER TST1_ENTER TST1_ENTER TST1_ENTER \
+ \
+ TST1_LEAVE TST1_LEAVE TST1_LEAVE TST1_LEAVE \
+ TST1_LEAVE TST1_LEAVE TST1_LEAVE TST1_LEAVE \
+ TST1_LEAVE TST1_LEAVE TST1_LEAVE TST1_LEAVE \
+ \
+ PTX = (PT1 >> 18) & 7; \
+ PT1 &= 0x1FFF; \
+ PT2 &= 0x1FFF; \
+ CLK = (int) mbedtls_timing_hardclock(); \
+ \
+ i = 0; \
+ A = &WALK[PT1 ]; RES[i++] ^= *A; \
+ B = &WALK[PT2 ]; RES[i++] ^= *B; \
+ C = &WALK[PT1 ^ 1]; RES[i++] ^= *C; \
+ D = &WALK[PT2 ^ 4]; RES[i++] ^= *D; \
+ \
+ IN = (*A >> (1)) ^ (*A << (31)) ^ CLK; \
+ *A = (*B >> (2)) ^ (*B << (30)) ^ CLK; \
+ *B = IN ^ U1; \
+ *C = (*C >> (3)) ^ (*C << (29)) ^ CLK; \
+ *D = (*D >> (4)) ^ (*D << (28)) ^ CLK; \
+ \
+ A = &WALK[PT1 ^ 2]; RES[i++] ^= *A; \
+ B = &WALK[PT2 ^ 2]; RES[i++] ^= *B; \
+ C = &WALK[PT1 ^ 3]; RES[i++] ^= *C; \
+ D = &WALK[PT2 ^ 6]; RES[i++] ^= *D; \
+ \
+ if( PTEST & 1 ) SWAP( A, C ); \
+ \
+ IN = (*A >> (5)) ^ (*A << (27)) ^ CLK; \
+ *A = (*B >> (6)) ^ (*B << (26)) ^ CLK; \
+ *B = IN; CLK = (int) mbedtls_timing_hardclock(); \
+ *C = (*C >> (7)) ^ (*C << (25)) ^ CLK; \
+ *D = (*D >> (8)) ^ (*D << (24)) ^ CLK; \
+ \
+ A = &WALK[PT1 ^ 4]; \
+ B = &WALK[PT2 ^ 1]; \
+ \
+ PTEST = PT2 >> 1; \
+ \
+ PT2 = (RES[(i - 8) ^ PTY] ^ WALK[PT2 ^ PTY ^ 7]); \
+ PT2 = ((PT2 & 0x1FFF) & (~8)) ^ ((PT1 ^ 8) & 0x8); \
+ PTY = (PT2 >> 10) & 7; \
+ \
+ TST2_ENTER TST2_ENTER TST2_ENTER TST2_ENTER \
+ TST2_ENTER TST2_ENTER TST2_ENTER TST2_ENTER \
+ TST2_ENTER TST2_ENTER TST2_ENTER TST2_ENTER \
+ \
+ TST2_LEAVE TST2_LEAVE TST2_LEAVE TST2_LEAVE \
+ TST2_LEAVE TST2_LEAVE TST2_LEAVE TST2_LEAVE \
+ TST2_LEAVE TST2_LEAVE TST2_LEAVE TST2_LEAVE \
+ \
+ C = &WALK[PT1 ^ 5]; \
+ D = &WALK[PT2 ^ 5]; \
+ \
+ RES[i++] ^= *A; \
+ RES[i++] ^= *B; \
+ RES[i++] ^= *C; \
+ RES[i++] ^= *D; \
+ \
+ IN = (*A >> ( 9)) ^ (*A << (23)) ^ CLK; \
+ *A = (*B >> (10)) ^ (*B << (22)) ^ CLK; \
+ *B = IN ^ U2; \
+ *C = (*C >> (11)) ^ (*C << (21)) ^ CLK; \
+ *D = (*D >> (12)) ^ (*D << (20)) ^ CLK; \
+ \
+ A = &WALK[PT1 ^ 6]; RES[i++] ^= *A; \
+ B = &WALK[PT2 ^ 3]; RES[i++] ^= *B; \
+ C = &WALK[PT1 ^ 7]; RES[i++] ^= *C; \
+ D = &WALK[PT2 ^ 7]; RES[i++] ^= *D; \
+ \
+ IN = (*A >> (13)) ^ (*A << (19)) ^ CLK; \
+ *A = (*B >> (14)) ^ (*B << (18)) ^ CLK; \
+ *B = IN; \
+ *C = (*C >> (15)) ^ (*C << (17)) ^ CLK; \
+ *D = (*D >> (16)) ^ (*D << (16)) ^ CLK; \
+ \
+ PT1 = ( RES[( i - 8 ) ^ PTX] ^ \
+ WALK[PT1 ^ PTX ^ 7] ) & (~1); \
+ PT1 ^= (PT2 ^ 0x10) & 0x10; \
+ \
+ for( n++, i = 0; i < 16; i++ ) \
+ hs->pool[n % MBEDTLS_HAVEGE_COLLECT_SIZE] ^= RES[i];
+
+/*
+ * Entropy gathering function
+ */
+static void havege_fill( mbedtls_havege_state *hs )
+{
+ int i, n = 0;
+ int U1, U2, *A, *B, *C, *D;
+ int PT1, PT2, *WALK, RES[16];
+ int PTX, PTY, CLK, PTEST, IN;
+
+ WALK = hs->WALK;
+ PT1 = hs->PT1;
+ PT2 = hs->PT2;
+
+ PTX = U1 = 0;
+ PTY = U2 = 0;
+
+ (void)PTX;
+
+ memset( RES, 0, sizeof( RES ) );
+
+ while( n < MBEDTLS_HAVEGE_COLLECT_SIZE * 4 )
+ {
+ ONE_ITERATION
+ ONE_ITERATION
+ ONE_ITERATION
+ ONE_ITERATION
+ }
+
+ hs->PT1 = PT1;
+ hs->PT2 = PT2;
+
+ hs->offset[0] = 0;
+ hs->offset[1] = MBEDTLS_HAVEGE_COLLECT_SIZE / 2;
+}
+
+/*
+ * HAVEGE initialization
+ */
+void mbedtls_havege_init( mbedtls_havege_state *hs )
+{
+ memset( hs, 0, sizeof( mbedtls_havege_state ) );
+
+ havege_fill( hs );
+}
+
+void mbedtls_havege_free( mbedtls_havege_state *hs )
+{
+ if( hs == NULL )
+ return;
+
+ mbedtls_zeroize( hs, sizeof( mbedtls_havege_state ) );
+}
+
+/*
+ * HAVEGE rand function
+ */
+int mbedtls_havege_random( void *p_rng, unsigned char *buf, size_t len )
+{
+ int val;
+ size_t use_len;
+ mbedtls_havege_state *hs = (mbedtls_havege_state *) p_rng;
+ unsigned char *p = buf;
+
+ while( len > 0 )
+ {
+ use_len = len;
+ if( use_len > sizeof(int) )
+ use_len = sizeof(int);
+
+ if( hs->offset[1] >= MBEDTLS_HAVEGE_COLLECT_SIZE )
+ havege_fill( hs );
+
+ val = hs->pool[hs->offset[0]++];
+ val ^= hs->pool[hs->offset[1]++];
+
+ memcpy( p, &val, use_len );
+
+ len -= use_len;
+ p += use_len;
+ }
+
+ return( 0 );
+}
+
+#endif /* MBEDTLS_HAVEGE_C */
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