Do base64url encoding with https://kore.io

base64_url.c

#include <kore/kore.h>
#include <string.h>

char * base64_url_decode(char * in) {
  size_t len;
  char * padded;
  u_int8_t * out;
  unsigned int i;

  len = strlen(in);
  int remain = (len % 4);
  if (remain == 2) {
    snprintf(padded, (len + 3), "%s==", in);
  } else if (remain == 3) {
    snprintf(padded, (len + 2), "%s=", in);
  }

  for (i = 0; i < strlen(padded); i++) {
    if (padded[i] == '_') padded[i] = '/';
    if (padded[i] == '-') padded[i] = '+';
  }

  kore_base64_decode(padded, &out, &len);
  return (char *)out;
}

char * base64_url_encode(const char * in) {
  char * base_out;
  char * out;
  unsigned int i;

  kore_base64_encode((u_int8_t *)in, strlen(in), &base_out);
  kore_strip_chars(base_out, '=', &out);

  for (i = 0; i < strlen(out); i++) {
    if (out[i] == '/') {
      out[i] = '_';
    }
    if (out[i] == '+') {
      out[i] = '-';
    }
  }
  return out;
}

char * base64_url_encode_binary(u_int8_t * in, size_t len) {
  char * base_out;
  char * out;
  unsigned int i;

  kore_base64_encode(in, len, &base_out);
  kore_strip_chars(base_out, '=', &out);

  for (i = 0; i < strlen(out); i++) {
    if (out[i] == '/') {
      out[i] = '_';
    }
    if (out[i] == '+') {
      out[i] = '-';
    }
  }
  return out;
}