base64.c

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// SPDX-License-Identifier: BSD-3-Clause
 
/*
 * Base64 encoding/decoding (RFC1341)
 * Copyright (c) 2005-2011, Jouni Malinen <j@w1.fi>
 *
 * Original file from FreeBSD code
 * https://cgit.freebsd.org/src/tree/contrib/wpa/src/utils/base64.c?id=f05cddf940db
 */
 
 
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
 
#include "base64.h"
 
static const unsigned char base64_table[65] =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
unsigned char *base64_encode(const unsigned char *src, size_t len,
                  size_t *out_len)
{
    unsigned char *out, *pos;
    const unsigned char *end, *in;
    size_t olen;
    int line_len;
 
    olen = len * 4 / 3 + 4; /* 3-byte blocks to 4-byte */
    olen += olen / 72; /* line feeds */
    olen++; /* nul termination */
    if (olen < len)
        return NULL; /* integer overflow */
    out = malloc(olen);
    if (!out)
        return NULL;
 
    end = src + len;
    in = src;
    pos = out;
    line_len = 0;
    while (end - in >= 3) {
        *pos++ = base64_table[in[0] >> 2];
        *pos++ = base64_table[((in[0] & 0x03) << 4) | (in[1] >> 4)];
        *pos++ = base64_table[((in[1] & 0x0f) << 2) | (in[2] >> 6)];
        *pos++ = base64_table[in[2] & 0x3f];
        in += 3;
        line_len += 4;
        if (line_len >= 72) {
            *pos++ = '\n';
            line_len = 0;
        }
    }
 
    if (end - in) {
        *pos++ = base64_table[in[0] >> 2];
        if (end - in == 1) {
            *pos++ = base64_table[(in[0] & 0x03) << 4];
            *pos++ = '=';
        } else {
            *pos++ = base64_table[((in[0] & 0x03) << 4) |
                          (in[1] >> 4)];
            *pos++ = base64_table[(in[1] & 0x0f) << 2];
        }
        *pos++ = '=';
        line_len += 4;
    }
 
    if (line_len)
        *pos++ = '\n';
 
    *pos = '\0';
    if (out_len)
        *out_len = pos - out;
    return out;
}
 
 
unsigned char *base64_decode(const unsigned char *src, size_t len,
                  size_t *out_len)
{
    unsigned char dtable[256], *out, *pos, block[4], tmp;
    size_t i, count, olen;
    int pad = 0;
 
    memset(dtable, 0x80, 256);
    for (i = 0; i < sizeof(base64_table) - 1; i++)
        dtable[base64_table[i]] = (unsigned char)i;
    dtable['='] = 0;
 
    count = 0;
    for (i = 0; i < len; i++) {
        if (dtable[src[i]] != 0x80)
            count++;
    }
 
    if (count == 0 || count % 4)
        return NULL;
 
    olen = count / 4 * 3;
    out = malloc(olen);
    if (!out)
        return NULL;
    pos = out;
 
    count = 0;
    for (i = 0; i < len; i++) {
        tmp = dtable[src[i]];
        if (tmp == 0x80)
            continue;
 
        if (src[i] == '=')
            pad++;
        block[count] = tmp;
        count++;
        if (count == 4) {
            *pos++ = (block[0] << 2) | (block[1] >> 4);
            *pos++ = (block[1] << 4) | (block[2] >> 2);
            *pos++ = (block[2] << 6) | block[3];
            count = 0;
            if (pad) {
                if (pad == 1) {
                    pos--;
                } else if (pad == 2) {
                    pos -= 2;
                } else {
                    /* Invalid padding */
                    free(out);
                    return NULL;
                }
                break;
            }
        }
    }
 
    *out_len = pos - out;
    return out;
}