Commit 3c35c0d4 authored by Nick Mathewson's avatar Nick Mathewson 🥔
Browse files

Add a function to provide an upper bound on base64 decoded length

parent cf7342ab

src/lib/encoding/binascii.c

+12 −0
Original line number Diff line number Diff line
@@ -179,6 +179,18 @@ base64_encode_size(size_t srclen, int flags) 
  return enclen;

}



/** Return an upper bound on the number of bytes that might be needed to hold

 * the data from decoding the base64 string <b>srclen</b>.  This is only an

 * upper bound, since some part of the base64 string might be padding or

 * space. */

size_t

base64_decode_maxsize(size_t srclen)

{

  tor_assert(srclen < INT_MAX / 3);



  return CEIL_DIV(srclen * 3, 4);

}



/** Internal table mapping 6 bit values to the Base64 alphabet. */

static const char base64_encode_table[64] = {

  'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',

src/lib/encoding/binascii.h

+1 −0
Original line number Diff line number Diff line
@@ -42,6 +42,7 @@ const char *hex_str(const char *from, size_t fromlen); 


#define BASE64_ENCODE_MULTILINE 1

size_t base64_encode_size(size_t srclen, int flags);

size_t base64_decode_maxsize(size_t srclen);

int base64_encode(char *dest, size_t destlen, const char *src, size_t srclen,

                  int flags);

int base64_decode(char *dest, size_t destlen, const char *src, size_t srclen);

src/test/test_util_format.c

+3 −1
Original line number Diff line number Diff line
@@ -392,10 +392,13 @@ test_util_format_encoded_size(void *arg) 


    base64_encode(outbuf, sizeof(outbuf), (char *)inbuf, i, 0);

    tt_int_op(strlen(outbuf), OP_EQ, base64_encode_size(i, 0));

    tt_int_op(i, OP_LE, base64_decode_maxsize(strlen(outbuf)));



    base64_encode(outbuf, sizeof(outbuf), (char *)inbuf, i,

                  BASE64_ENCODE_MULTILINE);

    tt_int_op(strlen(outbuf), OP_EQ,

              base64_encode_size(i, BASE64_ENCODE_MULTILINE));

    tt_int_op(i, OP_LE, base64_decode_maxsize(strlen(outbuf)));

  }



 done:
@@ -417,4 +420,3 @@ struct testcase_t util_format_tests[] = { 
  { "encoded_size", test_util_format_encoded_size, 0, NULL, NULL },

  END_OF_TESTCASES

};