299 lines
7.8 KiB
C
299 lines
7.8 KiB
C
/*
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* RFC 1521 base64 encoding/decoding
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*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
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*/
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#include <limits.h>
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#include "common.h"
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#if defined(MBEDTLS_BASE64_C)
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#include "mbedtls/base64.h"
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#include "base64_internal.h"
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#include "constant_time_internal.h"
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#include <stdint.h>
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#if defined(MBEDTLS_SELF_TEST)
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#include <string.h>
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#include "mbedtls/platform.h"
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#endif /* MBEDTLS_SELF_TEST */
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MBEDTLS_STATIC_TESTABLE
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unsigned char mbedtls_ct_base64_enc_char(unsigned char value)
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{
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unsigned char digit = 0;
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/* For each range of values, if value is in that range, mask digit with
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* the corresponding value. Since value can only be in a single range,
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* only at most one masking will change digit. */
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digit |= mbedtls_ct_uchar_in_range_if(0, 25, value, 'A' + value);
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digit |= mbedtls_ct_uchar_in_range_if(26, 51, value, 'a' + value - 26);
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digit |= mbedtls_ct_uchar_in_range_if(52, 61, value, '0' + value - 52);
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digit |= mbedtls_ct_uchar_in_range_if(62, 62, value, '+');
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digit |= mbedtls_ct_uchar_in_range_if(63, 63, value, '/');
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return digit;
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}
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MBEDTLS_STATIC_TESTABLE
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signed char mbedtls_ct_base64_dec_value(unsigned char c)
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{
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unsigned char val = 0;
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/* For each range of digits, if c is in that range, mask val with
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* the corresponding value. Since c can only be in a single range,
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* only at most one masking will change val. Set val to one plus
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* the desired value so that it stays 0 if c is in none of the ranges. */
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val |= mbedtls_ct_uchar_in_range_if('A', 'Z', c, c - 'A' + 0 + 1);
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val |= mbedtls_ct_uchar_in_range_if('a', 'z', c, c - 'a' + 26 + 1);
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val |= mbedtls_ct_uchar_in_range_if('0', '9', c, c - '0' + 52 + 1);
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val |= mbedtls_ct_uchar_in_range_if('+', '+', c, c - '+' + 62 + 1);
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val |= mbedtls_ct_uchar_in_range_if('/', '/', c, c - '/' + 63 + 1);
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/* At this point, val is 0 if c is an invalid digit and v+1 if c is
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* a digit with the value v. */
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return val - 1;
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}
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/*
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* Encode a buffer into base64 format
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*/
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int mbedtls_base64_encode(unsigned char *dst, size_t dlen, size_t *olen,
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const unsigned char *src, size_t slen)
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{
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size_t i, n;
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int C1, C2, C3;
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unsigned char *p;
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if (slen == 0) {
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*olen = 0;
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return 0;
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}
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n = slen / 3 + (slen % 3 != 0);
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if (n > (SIZE_MAX - 1) / 4) {
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*olen = SIZE_MAX;
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return MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL;
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}
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n *= 4;
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if ((dlen < n + 1) || (NULL == dst)) {
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*olen = n + 1;
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return MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL;
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}
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n = (slen / 3) * 3;
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for (i = 0, p = dst; i < n; i += 3) {
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C1 = *src++;
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C2 = *src++;
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C3 = *src++;
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*p++ = mbedtls_ct_base64_enc_char((C1 >> 2) & 0x3F);
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*p++ = mbedtls_ct_base64_enc_char((((C1 & 3) << 4) + (C2 >> 4))
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& 0x3F);
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*p++ = mbedtls_ct_base64_enc_char((((C2 & 15) << 2) + (C3 >> 6))
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& 0x3F);
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*p++ = mbedtls_ct_base64_enc_char(C3 & 0x3F);
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}
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if (i < slen) {
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C1 = *src++;
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C2 = ((i + 1) < slen) ? *src++ : 0;
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*p++ = mbedtls_ct_base64_enc_char((C1 >> 2) & 0x3F);
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*p++ = mbedtls_ct_base64_enc_char((((C1 & 3) << 4) + (C2 >> 4))
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& 0x3F);
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if ((i + 1) < slen) {
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*p++ = mbedtls_ct_base64_enc_char(((C2 & 15) << 2) & 0x3F);
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} else {
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*p++ = '=';
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}
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*p++ = '=';
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}
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*olen = p - dst;
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*p = 0;
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return 0;
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}
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/*
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* Decode a base64-formatted buffer
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*/
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int mbedtls_base64_decode(unsigned char *dst, size_t dlen, size_t *olen,
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const unsigned char *src, size_t slen)
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{
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size_t i; /* index in source */
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size_t n; /* number of digits or trailing = in source */
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uint32_t x; /* value accumulator */
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unsigned accumulated_digits = 0;
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unsigned equals = 0;
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int spaces_present = 0;
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unsigned char *p;
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/* First pass: check for validity and get output length */
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for (i = n = 0; i < slen; i++) {
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/* Skip spaces before checking for EOL */
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spaces_present = 0;
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while (i < slen && src[i] == ' ') {
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++i;
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spaces_present = 1;
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}
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/* Spaces at end of buffer are OK */
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if (i == slen) {
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break;
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}
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if ((slen - i) >= 2 &&
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src[i] == '\r' && src[i + 1] == '\n') {
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continue;
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}
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if (src[i] == '\n') {
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continue;
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}
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/* Space inside a line is an error */
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if (spaces_present) {
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return MBEDTLS_ERR_BASE64_INVALID_CHARACTER;
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}
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if (src[i] > 127) {
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return MBEDTLS_ERR_BASE64_INVALID_CHARACTER;
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}
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if (src[i] == '=') {
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if (++equals > 2) {
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return MBEDTLS_ERR_BASE64_INVALID_CHARACTER;
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}
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} else {
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if (equals != 0) {
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return MBEDTLS_ERR_BASE64_INVALID_CHARACTER;
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}
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if (mbedtls_ct_base64_dec_value(src[i]) < 0) {
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return MBEDTLS_ERR_BASE64_INVALID_CHARACTER;
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}
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}
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n++;
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}
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if (n == 0) {
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*olen = 0;
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return 0;
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}
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/* The following expression is to calculate the following formula without
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* risk of integer overflow in n:
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* n = ( ( n * 6 ) + 7 ) >> 3;
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*/
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n = (6 * (n >> 3)) + ((6 * (n & 0x7) + 7) >> 3);
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n -= equals;
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if (dst == NULL || dlen < n) {
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*olen = n;
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return MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL;
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}
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equals = 0;
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for (x = 0, p = dst; i > 0; i--, src++) {
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if (*src == '\r' || *src == '\n' || *src == ' ') {
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continue;
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}
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x = x << 6;
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if (*src == '=') {
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++equals;
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} else {
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x |= mbedtls_ct_base64_dec_value(*src);
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}
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if (++accumulated_digits == 4) {
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accumulated_digits = 0;
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*p++ = MBEDTLS_BYTE_2(x);
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if (equals <= 1) {
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*p++ = MBEDTLS_BYTE_1(x);
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}
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if (equals <= 0) {
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*p++ = MBEDTLS_BYTE_0(x);
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}
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}
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}
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*olen = p - dst;
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return 0;
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}
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#if defined(MBEDTLS_SELF_TEST)
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static const unsigned char base64_test_dec[64] =
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{
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0x24, 0x48, 0x6E, 0x56, 0x87, 0x62, 0x5A, 0xBD,
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0xBF, 0x17, 0xD9, 0xA2, 0xC4, 0x17, 0x1A, 0x01,
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0x94, 0xED, 0x8F, 0x1E, 0x11, 0xB3, 0xD7, 0x09,
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0x0C, 0xB6, 0xE9, 0x10, 0x6F, 0x22, 0xEE, 0x13,
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0xCA, 0xB3, 0x07, 0x05, 0x76, 0xC9, 0xFA, 0x31,
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0x6C, 0x08, 0x34, 0xFF, 0x8D, 0xC2, 0x6C, 0x38,
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0x00, 0x43, 0xE9, 0x54, 0x97, 0xAF, 0x50, 0x4B,
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0xD1, 0x41, 0xBA, 0x95, 0x31, 0x5A, 0x0B, 0x97
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};
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static const unsigned char base64_test_enc[] =
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"JEhuVodiWr2/F9mixBcaAZTtjx4Rs9cJDLbpEG8i7hPK"
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"swcFdsn6MWwINP+Nwmw4AEPpVJevUEvRQbqVMVoLlw==";
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/*
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* Checkup routine
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*/
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int mbedtls_base64_self_test(int verbose)
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{
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size_t len;
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const unsigned char *src;
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unsigned char buffer[128];
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if (verbose != 0) {
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mbedtls_printf(" Base64 encoding test: ");
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}
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src = base64_test_dec;
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if (mbedtls_base64_encode(buffer, sizeof(buffer), &len, src, 64) != 0 ||
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memcmp(base64_test_enc, buffer, 88) != 0) {
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if (verbose != 0) {
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mbedtls_printf("failed\n");
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}
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return 1;
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}
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if (verbose != 0) {
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mbedtls_printf("passed\n Base64 decoding test: ");
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}
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src = base64_test_enc;
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if (mbedtls_base64_decode(buffer, sizeof(buffer), &len, src, 88) != 0 ||
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memcmp(base64_test_dec, buffer, 64) != 0) {
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if (verbose != 0) {
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mbedtls_printf("failed\n");
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}
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return 1;
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}
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if (verbose != 0) {
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mbedtls_printf("passed\n\n");
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}
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return 0;
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}
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#endif /* MBEDTLS_SELF_TEST */
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#endif /* MBEDTLS_BASE64_C */
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