Fix ECDSA_SIG docs

They incorrectly said that i2d_ECDSA_SIG returns 0 on error. In fact it
returns a negative value on error.

We fix this by moving the i2d_ECDSA_SIG/d2i_ECDSA_SIG docs onto the same
page as all the other d2i/i2d docs.

Fixes #9517
Reviewed-by: NNicola Tuveri <nic.tuv@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/9533)

(cherry picked from commit bbda79976b5c5095c5e6557311c86c623ba335f1)

doc/man3/ECDSA_SIG_new.pod

@@ -3,10 +3,10 @@
 =head1 NAME
 
 ECDSA_SIG_get0, ECDSA_SIG_get0_r, ECDSA_SIG_get0_s, ECDSA_SIG_set0,
-ECDSA_SIG_new, ECDSA_SIG_free, i2d_ECDSA_SIG, d2i_ECDSA_SIG, ECDSA_size,
-ECDSA_sign, ECDSA_do_sign, ECDSA_verify, ECDSA_do_verify, ECDSA_sign_setup,
-ECDSA_sign_ex, ECDSA_do_sign_ex - low level elliptic curve digital signature
-algorithm (ECDSA) functions
+ECDSA_SIG_new, ECDSA_SIG_free, ECDSA_size, ECDSA_sign, ECDSA_do_sign,
+ECDSA_verify, ECDSA_do_verify, ECDSA_sign_setup, ECDSA_sign_ex,
+ECDSA_do_sign_ex - low level elliptic curve digital signature algorithm (ECDSA)
+functions
 
 =head1 SYNOPSIS
 
@@ -18,8 +18,6 @@ algorithm (ECDSA) functions
  const BIGNUM *ECDSA_SIG_get0_r(const ECDSA_SIG *sig);
  const BIGNUM *ECDSA_SIG_get0_s(const ECDSA_SIG *sig);
  int ECDSA_SIG_set0(ECDSA_SIG *sig, BIGNUM *r, BIGNUM *s);
- int i2d_ECDSA_SIG(const ECDSA_SIG *sig, unsigned char **pp);
- ECDSA_SIG *d2i_ECDSA_SIG(ECDSA_SIG **sig, const unsigned char **pp, long len);
  int ECDSA_size(const EC_KEY *eckey);
 
  int ECDSA_sign(int type, const unsigned char *dgst, int dgstlen,
@@ -68,15 +66,8 @@ function transfers the memory management of the values to the ECDSA_SIG object,
 and therefore the values that have been passed in should not be freed directly
 after this function has been called.
 
-i2d_ECDSA_SIG() creates the DER encoding of the ECDSA signature B<sig> and
-writes the encoded signature to B<*pp> (note: if B<pp> is NULL i2d_ECDSA_SIG()
-returns the expected length in bytes of the DER encoded signature).
-i2d_ECDSA_SIG() returns the length of the DER encoded signature (or 0 on
-error).
-
-d2i_ECDSA_SIG() decodes a DER encoded ECDSA signature and returns the decoded
-signature in a newly allocated B<ECDSA_SIG> structure. B<*sig> points to the
-buffer containing the DER encoded signature of size B<len>.
+See L<i2d_ECDSA_SIG(3)> and L<d2i_ECDSA_SIG(3)> for information about encoding
+and decoding ECDSA signatures to/from DER.
 
 ECDSA_size() returns the maximum length of a DER encoded ECDSA signature
 created with the private EC key B<eckey>.
@@ -202,7 +193,9 @@ ANSI X9.62, US Federal Information Processing Standard FIPS 186-2
 
 L<EC_KEY_new(3)>,
 L<EVP_DigestSignInit(3)>,
-L<EVP_DigestVerifyInit(3)>
+L<EVP_DigestVerifyInit(3)>,
+L<i2d_ECDSA_SIG(3)>,
+L<d2i_ECDSA_SIG(3)>
 
 =head1 COPYRIGHT
 

doc/man3/d2i_X509.pod

@@ -53,6 +53,7 @@ d2i_DSA_PUBKEY_bio,
 d2i_DSA_PUBKEY_fp,
 d2i_DSA_SIG,
 d2i_DSAparams,
+d2i_ECDSA_SIG,
 d2i_ECPKParameters,
 d2i_ECParameters,
 d2i_ECPrivateKey,
@@ -229,6 +230,7 @@ i2d_DSA_PUBKEY_bio,
 i2d_DSA_PUBKEY_fp,
 i2d_DSA_SIG,
 i2d_DSAparams,
+i2d_ECDSA_SIG,
 i2d_ECPKParameters,
 i2d_ECParameters,
 i2d_ECPrivateKey,
@@ -472,6 +474,10 @@ Represents a DSA public key using a B<SubjectPublicKeyInfo> structure.
 Use a non-standard OpenSSL format and should be avoided; use B<DSA_PUBKEY>,
 B<PEM_write_PrivateKey(3)>, or similar instead.
 
+=item B<ECDSA_SIG>
+
+Represents an ECDSA signature.
+
 =item B<RSAPublicKey>
 
 Represents a PKCS#1 RSA public key structure.

include/openssl/ec.h

@@ -1138,7 +1138,8 @@ void ECDSA_SIG_free(ECDSA_SIG *sig);
  *  (*pp += length of the DER encoded signature)).
  *  \param  sig  pointer to the ECDSA_SIG object
  *  \param  pp   pointer to a unsigned char pointer for the output or NULL
- *  \return the length of the DER encoded ECDSA_SIG object or 0
+ *  \return the length of the DER encoded ECDSA_SIG object or a negative value
+ *          on error
  */
 int i2d_ECDSA_SIG(const ECDSA_SIG *sig, unsigned char **pp);