/*

 *  RFC 1521 base64 encoding/decoding

 *

 *  Copyright The Mbed TLS Contributors

 *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later

 */

#include "common.h"

#if defined(MBEDTLS_BASE64_C)

#include "mbedtls/base64.h"

#include "constant_time_internal.h"

#include <stdint.h>

#if defined(MBEDTLS_SELF_TEST)

#include <string.h>

#include "mbedtls/platform.h"

#endif /* MBEDTLS_SELF_TEST */

#define BASE64_SIZE_T_MAX   ((size_t) -1)   /* SIZE_T_MAX is not standard */

/*

 * Encode a buffer into base64 format

 */

int mbedtls_base64_encode(unsigned char *dst, size_t dlen, size_t *olen,

                          const unsigned char *src, size_t slen)

{

    size_t i, n;

    int C1, C2, C3;

    unsigned char *p;

    if (slen == 0) {

        *olen = 0;

        return 0;

    }

    n = slen / 3 + (slen % 3 != 0);

    if (n > (BASE64_SIZE_T_MAX - 1) / 4) {

        *olen = BASE64_SIZE_T_MAX;

        return MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL;

    }

    n *= 4;

    if ((dlen < n + 1) || (NULL == dst)) {

        *olen = n + 1;

        return MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL;

    }

    n = (slen / 3) * 3;

    for (i = 0, p = dst; i < n; i += 3) {

        C1 = *src++;

        C2 = *src++;

        C3 = *src++;

        *p++ = mbedtls_ct_base64_enc_char((C1 >> 2) & 0x3F);

        *p++ = mbedtls_ct_base64_enc_char((((C1 &  3) << 4) + (C2 >> 4))

                                          & 0x3F);

        *p++ = mbedtls_ct_base64_enc_char((((C2 & 15) << 2) + (C3 >> 6))

                                          & 0x3F);

        *p++ = mbedtls_ct_base64_enc_char(C3 & 0x3F);

    }

    if (i < slen) {

        C1 = *src++;

        C2 = ((i + 1) < slen) ? *src++ : 0;

        *p++ = mbedtls_ct_base64_enc_char((C1 >> 2) & 0x3F);

        *p++ = mbedtls_ct_base64_enc_char((((C1 & 3) << 4) + (C2 >> 4))

                                          & 0x3F);

        if ((i + 1) < slen) {

            *p++ = mbedtls_ct_base64_enc_char(((C2 & 15) << 2) & 0x3F);

        } else {

            *p++ = '=';

        }

        *p++ = '=';

    }

    *olen = p - dst;

    *p = 0;

    return 0;

}

/*

 * Decode a base64-formatted buffer

 */

int mbedtls_base64_decode(unsigned char *dst, size_t dlen, size_t *olen,

                          const unsigned char *src, size_t slen)

{

    size_t i; /* index in source */

    size_t n; /* number of digits or trailing = in source */

    uint32_t x; /* value accumulator */

    unsigned accumulated_digits = 0;

    unsigned equals = 0;

    int spaces_present = 0;

    unsigned char *p;

    /* First pass: check for validity and get output length */

    for (i = n = 0; i < slen; i++) {

        /* Skip spaces before checking for EOL */

        spaces_present = 0;

        while (i < slen && src[i] == ' ') {

            ++i;

            spaces_present = 1;

        }

        /* Spaces at end of buffer are OK */

        if (i == slen) {

            break;

        }

        if ((slen - i) >= 2 &&

            src[i] == '\r' && src[i + 1] == '\n') {

            continue;

        }

        if (src[i] == '\n') {

            continue;

        }

        /* Space inside a line is an error */

        if (spaces_present) {

            return MBEDTLS_ERR_BASE64_INVALID_CHARACTER;

        }

        if (src[i] > 127) {

            return MBEDTLS_ERR_BASE64_INVALID_CHARACTER;

        }

        if (src[i] == '=') {

            if (++equals > 2) {

                return MBEDTLS_ERR_BASE64_INVALID_CHARACTER;

            }

        } else {

            if (equals != 0) {

                return MBEDTLS_ERR_BASE64_INVALID_CHARACTER;

            }

            if (mbedtls_ct_base64_dec_value(src[i]) < 0) {

                return MBEDTLS_ERR_BASE64_INVALID_CHARACTER;

            }

        }

        n++;

    }

    if (n == 0) {

        *olen = 0;

        return 0;

    }

    /* The following expression is to calculate the following formula without

     * risk of integer overflow in n:

     *     n = ( ( n * 6 ) + 7 ) >> 3;

     */

    n = (6 * (n >> 3)) + ((6 * (n & 0x7) + 7) >> 3);

    n -= equals;

    if (dst == NULL || dlen < n) {

        *olen = n;

        return MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL;

    }

    equals = 0;

    for (x = 0, p = dst; i > 0; i--, src++) {

        if (*src == '\r' || *src == '\n' || *src == ' ') {

            continue;

        }

        x = x << 6;

        if (*src == '=') {

            ++equals;

        } else {

            x |= mbedtls_ct_base64_dec_value(*src);

        }

        if (++accumulated_digits == 4) {

            accumulated_digits = 0;

            *p++ = MBEDTLS_BYTE_2(x);

            if (equals <= 1) {

                *p++ = MBEDTLS_BYTE_1(x);

            }

            if (equals <= 0) {

                *p++ = MBEDTLS_BYTE_0(x);

            }

        }

    }

    *olen = p - dst;

    return 0;

}

#if defined(MBEDTLS_SELF_TEST)

static const unsigned char base64_test_dec[64] =

{

    0x24, 0x48, 0x6E, 0x56, 0x87, 0x62, 0x5A, 0xBD,

    0xBF, 0x17, 0xD9, 0xA2, 0xC4, 0x17, 0x1A, 0x01,

    0x94, 0xED, 0x8F, 0x1E, 0x11, 0xB3, 0xD7, 0x09,

    0x0C, 0xB6, 0xE9, 0x10, 0x6F, 0x22, 0xEE, 0x13,

    0xCA, 0xB3, 0x07, 0x05, 0x76, 0xC9, 0xFA, 0x31,

    0x6C, 0x08, 0x34, 0xFF, 0x8D, 0xC2, 0x6C, 0x38,

    0x00, 0x43, 0xE9, 0x54, 0x97, 0xAF, 0x50, 0x4B,

    0xD1, 0x41, 0xBA, 0x95, 0x31, 0x5A, 0x0B, 0x97

};

static const unsigned char base64_test_enc[] =

    "JEhuVodiWr2/F9mixBcaAZTtjx4Rs9cJDLbpEG8i7hPK"

    "swcFdsn6MWwINP+Nwmw4AEPpVJevUEvRQbqVMVoLlw==";

/*

 * Checkup routine

 */

int mbedtls_base64_self_test(int verbose)

{

    size_t len;

    const unsigned char *src;

    unsigned char buffer[128];

    if (verbose != 0) {

        mbedtls_printf("  Base64 encoding test: ");

    }

    src = base64_test_dec;

    if (mbedtls_base64_encode(buffer, sizeof(buffer), &len, src, 64) != 0 ||

        memcmp(base64_test_enc, buffer, 88) != 0) {

        if (verbose != 0) {

            mbedtls_printf("failed\n");

        }

        return 1;

    }

    if (verbose != 0) {

        mbedtls_printf("passed\n  Base64 decoding test: ");

    }

    src = base64_test_enc;

    if (mbedtls_base64_decode(buffer, sizeof(buffer), &len, src, 88) != 0 ||

        memcmp(base64_test_dec, buffer, 64) != 0) {

        if (verbose != 0) {

            mbedtls_printf("failed\n");

        }

        return 1;

    }

    if (verbose != 0) {

        mbedtls_printf("passed\n\n");

    }

    return 0;

}

#endif /* MBEDTLS_SELF_TEST */

#endif /* MBEDTLS_BASE64_C */