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basenc: auto pad base32 and base64 inputs when decoding

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Padding of encoded data is useful in cases where
base64 encoded data is concatenated / streamed.
I.e. where there are padding chars _within_ the stream.
In other cases padding is optional and can be inferred.
Note we continue to treat partial padding as invalid,
as that would be indicative of truncation.

* src/basenc.c (do_decode): Auto pad the end of the input.
* NEWS: Mention the change in behavior.
* tests/misc/base64.pl: Adjust to not fail for missing padding.
Addresses https://bugs.gnu.org/66265
This commit is contained in:
Pádraig Brady
2023-10-05 17:00:51 +01:00
parent a2434d3e58
commit 378dc38f48
3 changed files with 63 additions and 8 deletions
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NEWS
+3
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@@ -16,6 +16,9 @@ GNU coreutils NEWS -*- outline -*-
** Changes in behavior
base32 and base64 no longer require padding when decoding.
Previously an error was given for non padded encoded data.
ls --dired now implies long format output without hyperlinks enabled,
and will take precedence over previously specified formats or hyperlink mode.
src/basenc.c
+58 -4
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@@ -23,6 +23,7 @@
#include <sys/types.h>
#include "system.h"
#include "assure.h"
#include "c-ctype.h"
#include "fadvise.h"
#include "quote.h"
@@ -172,10 +173,37 @@ from any other non-alphabet bytes in the encoded stream.\n"),
exit (status);
}
#if BASE_TYPE != 64
static int
base32_required_padding (int len)
{
int partial = len % 8;
return partial ? 8 - partial : 0;
}
#endif
#if BASE_TYPE != 32
static int
base64_required_padding (int len)
{
int partial = len % 4;
return partial ? 4 - partial : 0;
}
#endif
#if BASE_TYPE == 42
static int
no_required_padding (int len)
{
return 0;
}
#endif
#define ENC_BLOCKSIZE (1024 * 3 * 10)
#if BASE_TYPE == 32
# define BASE_LENGTH BASE32_LENGTH
# define REQUIRED_PADDING base32_required_padding
/* Note that increasing this may decrease performance if --ignore-garbage
is used, because of the memmove operation below. */
# define DEC_BLOCKSIZE (1024 * 5)
@@ -191,6 +219,7 @@ static_assert (DEC_BLOCKSIZE % 40 == 0); /* Complete encoded blocks are used. */
# define isbase isbase32
#elif BASE_TYPE == 64
# define BASE_LENGTH BASE64_LENGTH
# define REQUIRED_PADDING base64_required_padding
/* Note that increasing this may decrease performance if --ignore-garbage
is used, because of the memmove operation below. */
# define DEC_BLOCKSIZE (1024 * 3)
@@ -208,6 +237,7 @@ static_assert (DEC_BLOCKSIZE % 12 == 0); /* Complete encoded blocks are used. */
# define BASE_LENGTH base_length
# define REQUIRED_PADDING required_padding
/* Note that increasing this may decrease performance if --ignore-garbage
is used, because of the memmove operation below. */
@@ -216,6 +246,7 @@ static_assert (DEC_BLOCKSIZE % 40 == 0); /* complete encoded blocks for base32*/
static_assert (DEC_BLOCKSIZE % 12 == 0); /* complete encoded blocks for base64*/
static int (*base_length) (int i);
static int (*required_padding) (int i);
static bool (*isbase) (char ch);
static void (*base_encode) (char const *restrict in, idx_t inlen,
char *restrict out, idx_t outlen);
@@ -486,7 +517,6 @@ base32hex_decode_ctx_wrapper (struct base_decode_context *ctx,
return b;
}
static bool
isbase16 (char ch)
{
@@ -1011,6 +1041,7 @@ do_decode (FILE *in, char const *infile, FILE *out, bool ignore_garbage)
idx_t sum;
struct base_decode_context ctx;
char padbuf[8] = "========";
inbuf = xmalloc (BASE_LENGTH (DEC_BLOCKSIZE));
outbuf = xmalloc (DEC_BLOCKSIZE);
@@ -1053,10 +1084,25 @@ do_decode (FILE *in, char const *infile, FILE *out, bool ignore_garbage)
telling it to flush what is in CTX. */
for (int k = 0; k < 1 + !!feof (in); k++)
{
if (k == 1 && ctx.i == 0)
break;
if (k == 1)
{
if (ctx.i == 0)
break;
/* auto pad input (at eof). */
idx_t auto_padding = REQUIRED_PADDING (ctx.i);
if (auto_padding && (sum == 0 || inbuf[sum - 1] != '='))
{
affirm (auto_padding <= sizeof (padbuf));
IF_LINT (free (inbuf));
sum = auto_padding;
inbuf = padbuf;
}
else
sum = 0; /* process ctx buffer only */
}
idx_t n = DEC_BLOCKSIZE;
ok = base_decode_ctx (&ctx, inbuf, (k == 0 ? sum : 0), outbuf, &n);
ok = base_decode_ctx (&ctx, inbuf, sum, outbuf, &n);
if (fwrite (outbuf, 1, n, out) < n)
write_error ();
@@ -1145,6 +1191,7 @@ main (int argc, char **argv)
{
case BASE64_OPTION:
base_length = base64_length_wrapper;
required_padding = base64_required_padding;
isbase = isbase64;
base_encode = base64_encode;
base_decode_ctx_init = base64_decode_ctx_init_wrapper;
@@ -1153,6 +1200,7 @@ main (int argc, char **argv)
case BASE64URL_OPTION:
base_length = base64_length_wrapper;
required_padding = base64_required_padding;
isbase = isbase64url;
base_encode = base64url_encode;
base_decode_ctx_init = base64url_decode_ctx_init_wrapper;
@@ -1161,6 +1209,7 @@ main (int argc, char **argv)
case BASE32_OPTION:
base_length = base32_length_wrapper;
required_padding = base32_required_padding;
isbase = isbase32;
base_encode = base32_encode;
base_decode_ctx_init = base32_decode_ctx_init_wrapper;
@@ -1169,6 +1218,7 @@ main (int argc, char **argv)
case BASE32HEX_OPTION:
base_length = base32_length_wrapper;
required_padding = base32_required_padding;
isbase = isbase32hex;
base_encode = base32hex_encode;
base_decode_ctx_init = base32hex_decode_ctx_init_wrapper;
@@ -1177,6 +1227,7 @@ main (int argc, char **argv)
case BASE16_OPTION:
base_length = base16_length;
required_padding = no_required_padding;
isbase = isbase16;
base_encode = base16_encode;
base_decode_ctx_init = base16_decode_ctx_init;
@@ -1185,6 +1236,7 @@ main (int argc, char **argv)
case BASE2MSBF_OPTION:
base_length = base2_length;
required_padding = no_required_padding;
isbase = isbase2;
base_encode = base2msbf_encode;
base_decode_ctx_init = base2_decode_ctx_init;
@@ -1193,6 +1245,7 @@ main (int argc, char **argv)
case BASE2LSBF_OPTION:
base_length = base2_length;
required_padding = no_required_padding;
isbase = isbase2;
base_encode = base2lsbf_encode;
base_decode_ctx_init = base2_decode_ctx_init;
@@ -1201,6 +1254,7 @@ main (int argc, char **argv)
case Z85_OPTION:
base_length = z85_length;
required_padding = no_required_padding;
isbase = isz85;
base_encode = z85_encode;
base_decode_ctx_init = z85_decode_ctx_init;
tests/misc/base64.pl
+2 -4
View File
@@ -124,10 +124,8 @@ sub gen_tests($)
push @Tests, (
['baddecode', '--decode', {IN=>'a'}, {OUT=>""},
{ERR_SUBST => 's/.*: invalid input//'}, {ERR => "\n"}, {EXIT => 1}],
['baddecode2', '--decode', {IN=>'ab'}, {OUT=>"i"},
{ERR_SUBST => 's/.*: invalid input//'}, {ERR => "\n"}, {EXIT => 1}],
['baddecode3', '--decode', {IN=>'Zzz'}, {OUT=>"g<"},
{ERR_SUBST => 's/.*: invalid input//'}, {ERR => "\n"}, {EXIT => 1}],
['paddecode2', '--decode', {IN=>'ab'}, {OUT=>"i"}],
['paddecode3', '--decode', {IN=>'Zzz'}, {OUT=>"g<"}],
['baddecode4', '--decode', {IN=>'Zz='}, {OUT=>"g"},
{ERR_SUBST => 's/.*: invalid input//'}, {ERR => "\n"}, {EXIT => 1}],
['baddecode5', '--decode', {IN=>'Z==='}, {OUT=>""},