On Fri, Jul 16, 2021 at 01:04:21PM +0200, Hannes Reinecke wrote:
> +/**
> + * base64_decode() - base64-decode some bytes
> + * @src: the base64-encoded string to decode
> + * @len: number of bytes to decode
> + * @dst: (output) the decoded bytes.
> + *
> + * Decodes the base64-encoded bytes @src according to RFC 4648.
> + *
> + * Return: number of decoded bytes
> + */
> +int base64_decode(const char *src, int len, u8 *dst)
> +{
> + int i, bits = 0, pad = 0;
> + u32 ac = 0;
> + size_t dst_len = 0;
> +
> + for (i = 0; i < len; i++) {
> + int c, p = -1;
> +
> + if (src[i] == '=') {
> + pad++;
> + if (i + 1 < len && src[i + 1] == '=')
> + pad++;
> + break;
> + }
> + for (c = 0; c < strlen(lookup_table); c++) {
> + if (src[i] == lookup_table[c]) {
> + p = c;
> + break;
> + }
> + }
> + if (p < 0)
> + break;
> + ac = (ac << 6) | p;
> + bits += 6;
> + if (bits < 24)
> + continue;
> + while (bits) {
> + bits -= 8;
> + dst[dst_len++] = (ac >> bits) & 0xff;
> + }
> + ac = 0;
> + }
> + dst_len -= pad;
> + return dst_len;
> +}
> +EXPORT_SYMBOL_GPL(base64_decode);
This should return an error if the input isn't valid base64.
- Eric
