Add signed bn2bin and bin2bn functions

This adds the functions BN_signed_bin2bn(), BN_signed_bn2bin(),
BN_signed_lebin2bn(), BN_signed_bn2lebin(), BN_signed_native2bn(),
and BN_signed_bn2native(), all essentially doing the same job as
BN_bin2bn(), BN_bn2binpad(), BN_lebin2bn(), BN_bn2lebinpad(),
BN_native2bn(), and BN_bn2nativepad(), except that the 'signed'
ones operate on signed number bins in 2's complement form.

Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17139)

1 files changed, 31 insertions, 11 deletions

diff --git a/doc/man3/BN_bn2bin.pod b/doc/man3/BN_bn2bin.pod
index e75b9fffb5..3e5f2deeca 100644
--- a/doc/man3/BN_bn2bin.pod
+++ b/doc/man3/BN_bn2bin.pod
@@ -2,9 +2,10 @@
 
 =head1 NAME
 
-BN_bn2binpad,
-BN_bn2bin, BN_bin2bn, BN_bn2lebinpad, BN_lebin2bn,
-BN_bn2nativepad, BN_native2bn, BN_bn2hex, BN_bn2dec, BN_hex2bn, BN_dec2bn,
+BN_bn2binpad, BN_signed_bn2bin, BN_bn2bin, BN_bin2bn, BN_signed_bin2bn,
+BN_bn2lebinpad, BN_signed_bn2lebin, BN_lebin2bn, BN_signed_lebin2bn,
+BN_bn2nativepad, BN_signed_bn2native, BN_native2bn, BN_signed_native2bn,
+BN_bn2hex, BN_bn2dec, BN_hex2bn, BN_dec2bn,
 BN_print, BN_print_fp, BN_bn2mpi, BN_mpi2bn - format conversions
 
 =head1 SYNOPSIS
@@ -13,13 +14,19 @@ BN_print, BN_print_fp, BN_bn2mpi, BN_mpi2bn - format conversions
 
  int BN_bn2bin(const BIGNUM *a, unsigned char *to);
  int BN_bn2binpad(const BIGNUM *a, unsigned char *to, int tolen);
+ int BN_signed_bn2bin(const BIGNUM *a, unsigned char *to, int tolen);
  BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret);
+ BIGNUM *BN_signed_bin2bn(const unsigned char *s, int len, BIGNUM *ret);
 
  int BN_bn2lebinpad(const BIGNUM *a, unsigned char *to, int tolen);
+ int BN_signed_bn2lebin(const BIGNUM *a, unsigned char *to, int tolen);
  BIGNUM *BN_lebin2bn(const unsigned char *s, int len, BIGNUM *ret);
+ BIGNUM *BN_signed_lebin2bn(const unsigned char *s, int len, BIGNUM *ret);
 
  int BN_bn2nativepad(const BIGNUM *a, unsigned char *to, int tolen);
+ int BN_signed_bn2native(const BIGNUM *a, unsigned char *to, int tolen);
  BIGNUM *BN_native2bn(const unsigned char *s, int len, BIGNUM *ret);
+ BIGNUM *BN_signed_native2bn(const unsigned char *s, int len, BIGNUM *ret);
 
  char *BN_bn2hex(const BIGNUM *a);
  char *BN_bn2dec(const BIGNUM *a);
@@ -43,17 +50,29 @@ and stores it at B<to>. B<tolen> indicates the length of the output buffer
 B<to>. The result is padded with zeros if necessary. If B<tolen> is less than
 BN_num_bytes(B<a>) an error is returned.
 
+BN_signed_bn2bin() converts the value of B<a> into big-endian signed 2's
+complements form and stores it at B<to>. B<tolen> indicates the length of
+the output buffer B<to>. The result is signed extended (padded with 0x00
+for positive numbers or with 0xff for negative numbers) if necessary.
+If B<tolen> is smaller than the necessary size (which may be
+C<<BN_num_bytes(B<a>) + 1>>), an error is returned.
+
 BN_bin2bn() converts the positive integer in big-endian form of length
 B<len> at B<s> into a B<BIGNUM> and places it in B<ret>. If B<ret> is
 NULL, a new B<BIGNUM> is created.
 
-BN_bn2lebinpad() and BN_lebin2bn() are identical to BN_bn2binpad() and
-BN_bin2bn() except the buffer is in little-endian format.
+BN_signed_bin2bn() converts the integer in big-endian signed 2's complement
+form of length B<len> at B<s> into a B<BIGNUM> and places it in B<ret>. If
+B<ret> is NULL, a new B<BIGNUM> is created.
+
+BN_bn2lebinpad(), BN_signed_bn2lebin() and BN_lebin2bn() are identical to
+BN_bn2binpad(), BN_signed_bn2bin() and BN_bin2bn() except the buffer is in
+little-endian format.
 
-BN_bn2nativepad() and BN_native2bn() are identical to BN_bn2binpad() and
-BN_bin2bn() except the buffer is in native format, i.e. most significant
-byte first on big-endian platforms, and least significant byte first on
-little-endian platforms.
+BN_bn2nativepad(), BN_signed_bn2native() and BN_native2bn() are identical
+to BN_bn2binpad(), BN_signed_bn2bin() and BN_bin2bn() except the buffer is
+in native format, i.e. most significant byte first on big-endian platforms,
+and least significant byte first on little-endian platforms.
 
 BN_bn2hex() and BN_bn2dec() return printable strings containing the
 hexadecimal and decimal encoding of B<a> respectively. For negative
@@ -91,8 +110,9 @@ if B<ret> is NULL.
 BN_bn2bin() returns the length of the big-endian number placed at B<to>.
 BN_bin2bn() returns the B<BIGNUM>, NULL on error.
 
-BN_bn2binpad(), BN_bn2lebinpad(), and BN_bn2nativepad() return the number of bytes written or -1 if the supplied
-buffer is too small.
+BN_bn2binpad(), BN_signed_bn2bin(), BN_bn2lebinpad(), BN_signed_bn2lebin(),
+BN_bn2nativepad(), and_signed BN_bn2native() return the number of bytes
+written or -1 if the supplied buffer is too small.
 
 BN_bn2hex() and BN_bn2dec() return a NUL-terminated string, or NULL
 on error. BN_hex2bn() and BN_dec2bn() return the number of characters