[ViewVC] Diff of: cvs/CBOR-XS/XS.pm

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.52 by root, Mon Apr 25 18:17:17 2016 UTC vs.
Revision 1.60 by root, Tue Apr 26 16:26:24 2016 UTC

 package CBOR::XS;
 use common::sense;
-our $VERSION = 1.41;
+our $VERSION = 1.5;
 our @ISA = qw(Exporter);
 our @EXPORT = qw(encode_cbor decode_cbor);
 use Exporter;
    my $x = 3.1; # some variable containing a number
    "$x";        # stringified
    $x .= "";    # another, more awkward way to stringify
    print $x;    # perl does it for you, too, quite often
-You can force whether a string ie encoded as byte or text string by using
+You can force whether a string is encoded as byte or text string by using
-C<utf8::upgrade> and C<utf8::downgrade>):
+C<utf8::upgrade> and C<utf8::downgrade> (if C<text_strings> is disabled):
   utf8::upgrade $x;   # encode $x as text string
   utf8::downgrade $x; # encode $x as byte string
 Perl doesn't define what operations up- and downgrade strings, so if the
 difference between byte and text is important, you should up- or downgrade
-your string as late as possible before encoding.
+your string as late as possible before encoding. You can also force the
+use of CBOR text strings by using C<text_keys> or C<text_strings>.
 You can force the type to be a CBOR number by numifying it:
    my $x = "3"; # some variable containing a string
    $x += 0;     # numify it, ensuring it will be dumped as a number
 These tags are decoded into L<Math::BigInt> objects. The corresponding
 C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR
 integers, and others into positive/negative CBOR bignums.
-=item 4, 5 (decimal fraction/bigfloat)
+=item 4, 5, 264, 265 (decimal fraction/bigfloat)
 Both decimal fractions and bigfloats are decoded into L<Math::BigFloat>
 objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always>
-encodes into a decimal fraction.
+encodes into a decimal fraction (either tag 4 or 264).
-CBOR cannot represent bigfloats with I<very> large exponents - conversion
+NaN and infinities are not encoded properly, as they cannot be represented
-of such big float objects is undefined.
+in CBOR.
-Also, NaN and infinities are not encoded properly.
+See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
+=item 30 (rational numbers)
+These tags are decoded into L<Math::BigRat> objects. The corresponding
+C<Math::BigRat::TO_CBOR> method encodes rational numbers with denominator
+C<1> via their numerator only, i.e., they become normal integers or
+C<bignums>.
+See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
 =item 21, 22, 23 (expected later JSON conversion)
 CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these
 tags.
 Also keep in mind that CBOR::XS might leak contents of your Perl data
 structures in its error messages, so when you serialise sensitive
 information you might want to make sure that exceptions thrown by CBOR::XS
 will not end up in front of untrusted eyes.
+=head1 BIGNUM SECURITY CONSIDERATIONS
+CBOR::XS provides a C<TO_CBOR> method for both L<Math::BigInt> and
+L<Math::BigFloat> that tries to encode the number in the simplest possible
+way, that is, either a CBOR integer, a CBOR bigint/decimal fraction (tag
+4) or an arbitrary-exponent decimal fraction (tag 264). Rational numbers
+(L<Math::BigRat>, tag 30) can also contain bignums as members.
+CBOR::XS will also understand base-2 bigfloat or arbitrary-exponent
+bigfloats (tags 5 and 265), but it will never generate these on its own.
+Using the built-in L<Math::BigInt::Calc> support, encoding and decoding
+decimal fractions is generally fast. Decoding bigints can be slow for very
+big numbers (tens of thousands of digits, something that could potentially
+be caught by limiting the size of CBOR texts), and decoding bigfloats or
+arbitrary-exponent bigfloats can be I<extremely> slow (minutes, decades)
+for large exponents (roughly 40 bit and longer).
+Additionally, L<Math::BigInt> can take advantage of other bignum
+libraries, such as L<Math::GMP>, which cannot handle big floats with large
+exponents, and might simply abort or crash your program, due to their code
+quality.
+This can be a concern if you want to parse untrusted CBOR. If it is, you
+might want to disable decoding of tag 2 (bigint) and 3 (negative bigint)
+types. You should also disable types 5 and 265, as these can be slow even
+without bigints.
+Disabling bigints will also partially or fully disable types that rely on
+them, e.g. rational numbers that use bignums.
 =head1 CBOR IMPLEMENTATION NOTES
 This section contains some random implementation notes. They do not
 describe guaranteed behaviour, but merely behaviour as-is implemented
    4 => sub { # decimal fraction, array
       require Math::BigFloat;
       Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
    },
+   264 => sub { # decimal fraction with arbitrary exponent
+      require Math::BigFloat;
+      Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
+   },
    5 => sub { # bigfloat, array
       require Math::BigFloat;
       scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
+   },
+   265 => sub { # bigfloat with arbitrary exponent
+      require Math::BigFloat;
+      scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
+   },
+   30 => sub { # rational number
+      require Math::BigRat;
+      Math::BigRat->new ("$_[1][0]/$_[1][1]") # separate parameters only work in recent versons
    },
    21 => sub { pop }, # expected conversion to base64url encoding
    22 => sub { pop }, # expected conversion to base64 encoding
    23 => sub { pop }, # expected conversion to base16 encoding
    utf8::upgrade $uri;
    tag 32, $uri
 }
 sub Math::BigInt::TO_CBOR {
-   if ($_[0] >= -2147483648 && $_[0] <= 2147483647) {
+   if (-2147483648 <= $_[0] && $_[0] <= 2147483647) {
       $_[0]->numify
    } else {
       my $hex = substr $_[0]->as_hex, 2;
       $hex = "0$hex" if 1 & length $hex; # sigh
       tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex
    }
 }
 sub Math::BigFloat::TO_CBOR {
    my ($m, $e) = $_[0]->parts;
+   -9223372036854775808 <= $e && $e <= 18446744073709551615
-   tag 4, [$e->numify, $m]
+      ? tag 4, [$e->numify, $m]
+      : tag 264, [$e, $m]
+}
+sub Math::BigRat::TO_CBOR {
+   my ($n, $d) = $_[0]->parts;
+   # older versions of BigRat need *1, as they not always return numbers
+   $d*1 == 1
+      ? $n*1
+      : tag 30, [$n*1, $d*1]
 }
 sub Time::Piece::TO_CBOR {
    tag 1, 0 + $_[0]->epoch
 }

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Comparing CBOR-XS/XS.pm (file contents): Revision 1.52 by root, Mon Apr 25 18:17:17 2016 UTC vs. Revision 1.60 by root, Tue Apr 26 16:26:24 2016 UTC

Diff Legend

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.52 by root, Mon Apr 25 18:17:17 2016 UTC vs.
Revision 1.60 by root, Tue Apr 26 16:26:24 2016 UTC