54 lines
1.7 KiB
C
54 lines
1.7 KiB
C
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// Copyright 2010-2016 Espressif Systems (Shanghai) PTE LTD
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "bootloader_random.h"
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#include "soc/wdev_reg.h"
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#ifndef BOOTLOADER_BUILD
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#include "esp_system.h"
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#endif
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void bootloader_fill_random(void *buffer, size_t length)
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{
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uint8_t *buffer_bytes = (uint8_t *)buffer;
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uint32_t random;
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/* TODO: enable HW RNG clock
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Until this clock is enabled, this is not secure
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*/
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for (int i = 0; i < length; i++) {
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if (i == 0 || i % 4 == 0) { /* redundant check is for a compiler warning */
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#ifdef BOOTLOADER_BUILD
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/* HW RNG generates 32 bits entropy per 16 APB cycles,
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in bootloader CPU clock == APB clock.
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We are being conservative here and waiting at least
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that long, as loop shift overhead, etc will add more
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cycles.
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*/
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asm volatile("nop; nop; nop; nop;");
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asm volatile("nop; nop; nop; nop;");
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asm volatile("nop; nop; nop; nop;");
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asm volatile("nop; nop; nop; nop;");
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random = REG_READ(WDEV_RND_REG);
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#else
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random = esp_random();
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#endif
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}
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buffer_bytes[i] = random >> ((i % 4) * 8);
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}
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}
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