Re: [PATCH] basenc: Paddingless input/output for base64url

[Imre Rad]

Ah, good catch, thanks. Let me send a new version on Monday. Adding a new
test as well.
Imre

On Fri, Aug 19, 2022 at 5:25 PM Michael Cook <michael@waxrat.com> wrote:

> +base64url_decode_ctx_wrapper_no_padding (struct base_decode_context *ctx,
> +                              char const *restrict in, idx_t inlen,
> +                              char *restrict out, idx_t *outlen)
> +{
> +    bool b = base64url_decode_ctx_wrapper(ctx, in, inlen, out, outlen);
> +    if (!b && ctx->i <= 2)
> +        b = true;
> +    return true;
>
> Looks like you meant that to be `return b;`?
>
>
> On Fri, Aug 19, 2022 at 11:22 AM Imre Rad via GNU coreutils General
> Discussion <coreutils@gnu.org> wrote:
>
>> * src/basenc.c (ignore-padding):
>> Padding is optional for base64url encoding and many web
>> services produce and expect payload without padding.
>> New command line argument (--ignore-padding) for basenc
>> allows generating paddingless base64url outputs and
>> you can also use it for decoding without scary
>> warnings on stderr.
>> * tests/local.mk (reference to new test):
>> Reference to the new test.
>> ---
>>  src/basenc.c   | 50 +++++++++++++++++++++++++++++++++++++++++---------
>>  tests/local.mk |  1 +
>>  2 files changed, 42 insertions(+), 9 deletions(-)
>>
>> diff --git a/src/basenc.c b/src/basenc.c
>> index 04857d59e..52bd66054 100644
>> --- a/src/basenc.c
>> +++ b/src/basenc.c
>> @@ -68,7 +68,8 @@ enum
>>    BASE16_OPTION,
>>    BASE2MSBF_OPTION,
>>    BASE2LSBF_OPTION,
>> -  Z85_OPTION
>> +  Z85_OPTION,
>> +  IGNORE_PADDING
>>  };
>>  #endif
>>
>> @@ -78,6 +79,7 @@ static struct option const long_options[] =
>>    {"wrap", required_argument, 0, 'w'},
>>    {"ignore-garbage", no_argument, 0, 'i'},
>>  #if BASE_TYPE == 42
>> +  {"ignore-padding", no_argument, 0, IGNORE_PADDING},
>>    {"base64",    no_argument, 0, BASE64_OPTION},
>>    {"base64url", no_argument, 0, BASE64URL_OPTION},
>>    {"base32",    no_argument, 0, BASE32_OPTION},
>> @@ -146,6 +148,8 @@ Base%d encode or decode FILE, or standard input, to
>> standard output.\n\
>>  "), stdout);
>>  #if BASE_TYPE == 42
>>        fputs (_("\
>> +      --ignore-padding  base64url only: ignore missing padding at
>> decoding,\n\
>> +                        don't pad at encoding\n\
>>        --z85             ascii85-like encoding (ZeroMQ spec:32/Z85);\n\
>>                          when encoding, input length must be a multiple of
>> 4;\n\
>>                          when decoding, input length must be a multiple of
>> 5\n\
>> @@ -335,7 +339,6 @@ base64url_decode_ctx_init_wrapper (struct
>> base_decode_context *ctx)
>>    init_inbuf (ctx);
>>  }
>>
>> -
>>  static bool
>>  base64url_decode_ctx_wrapper (struct base_decode_context *ctx,
>>                                char const *restrict in, idx_t inlen,
>> @@ -368,7 +371,16 @@ base64url_decode_ctx_wrapper (struct
>> base_decode_context *ctx,
>>    return b;
>>  }
>>
>> -
>> +static bool
>> +base64url_decode_ctx_wrapper_no_padding (struct base_decode_context *ctx,
>> +                              char const *restrict in, idx_t inlen,
>> +                              char *restrict out, idx_t *outlen)
>> +{
>> +    bool b = base64url_decode_ctx_wrapper(ctx, in, inlen, out, outlen);
>> +    if (!b && ctx->i <= 2)
>> +        b = true;
>> +    return true;
>> +}
>>
>>  static int
>>  base32_length_wrapper (int len)
>> @@ -964,7 +976,7 @@ finish_and_exit (FILE *in, char const *infile)
>>  }
>>
>>  static _Noreturn void
>> -do_encode (FILE *in, char const *infile, FILE *out, idx_t wrap_column)
>> +do_encode (FILE *in, char const *infile, FILE *out, idx_t wrap_column,
>> bool without_padding)
>>  {
>>    idx_t current_column = 0;
>>    char *inbuf, *outbuf;
>> @@ -989,9 +1001,17 @@ do_encode (FILE *in, char const *infile, FILE *out,
>> idx_t wrap_column)
>>          {
>>            /* Process input one block at a time.  Note that ENC_BLOCKSIZE
>>               is sized so that no pad chars will appear in output. */
>> -          base_encode (inbuf, sum, outbuf, BASE_LENGTH (sum));
>> +          int to_write = BASE_LENGTH (sum);
>> +          base_encode (inbuf, sum, outbuf, to_write);
>> +          if (without_padding)
>> +          {
>> +            while (*(outbuf+to_write-1) == '=')
>> +            {
>> +                --to_write;
>> +            }
>> +          }
>>
>> -          wrap_write (outbuf, BASE_LENGTH (sum), wrap_column,
>> +          wrap_write (outbuf, to_write, wrap_column,
>>                        &current_column, out);
>>          }
>>      }
>> @@ -1084,6 +1104,13 @@ main (int argc, char **argv)
>>    bool decode = false;
>>    /* True if we should ignore non-base-alphabetic characters. */
>>    bool ignore_garbage = false;
>> +
>> +  /* True if we should ignore padding (base64url only). */
>> +#if BASE_TYPE == 42
>> +  bool o_ignore_padding = false;
>> +#endif
>> +  bool ignore_padding = false;
>> +
>>    /* Wrap encoded data around the 76th column, by default. */
>>    idx_t wrap_column = 76;
>>
>> @@ -1099,7 +1126,7 @@ main (int argc, char **argv)
>>
>>    atexit (close_stdout);
>>
>> -  while ((opt = getopt_long (argc, argv, "diw:", long_options, NULL)) !=
>> -1)
>> +  while ((opt = getopt_long (argc, argv, "dipw:", long_options, NULL)) !=
>> -1)
>>      switch (opt)
>>        {
>>        case 'd':
>> @@ -1122,6 +1149,10 @@ main (int argc, char **argv)
>>          break;
>>
>>  #if BASE_TYPE == 42
>> +      case IGNORE_PADDING:
>> +        o_ignore_padding = true;
>> +        break;
>> +
>>        case BASE64_OPTION:
>>        case BASE64URL_OPTION:
>>        case BASE32_OPTION:
>> @@ -1155,11 +1186,12 @@ main (int argc, char **argv)
>>        break;
>>
>>      case BASE64URL_OPTION:
>> +      ignore_padding = o_ignore_padding;
>>        base_length = base64_length_wrapper;
>>        isbase = isbase64url;
>>        base_encode = base64url_encode;
>>        base_decode_ctx_init = base64url_decode_ctx_init_wrapper;
>> -      base_decode_ctx = base64url_decode_ctx_wrapper;
>> +      base_decode_ctx = ignore_padding ?
>> base64url_decode_ctx_wrapper_no_padding : base64url_decode_ctx_wrapper;
>>        break;
>>
>>      case BASE32_OPTION:
>> @@ -1244,5 +1276,5 @@ main (int argc, char **argv)
>>    if (decode)
>>      do_decode (input_fh, infile, stdout, ignore_garbage);
>>    else
>> -    do_encode (input_fh, infile, stdout, wrap_column);
>> +    do_encode (input_fh, infile, stdout, wrap_column, ignore_padding);
>>  }
>> diff --git a/tests/local.mk b/tests/local.mk
>> index 0496c2873..a7703998a 100644
>> --- a/tests/local.mk
>> +++ b/tests/local.mk
>> @@ -728,6 +728,7 @@ all_tests = \
>>    tests/touch/read-only.sh \
>>    tests/touch/relative.sh \
>>    tests/touch/trailing-slash.sh \
>> +  tests/base64url/padding.sh \
>>    $(all_root_tests)
>>
>>  # See tests/factor/create-test.sh.
>> --
>> 2.30.2
>>
>