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

[Michael Cook]

+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
>