#include <openssl/evp.h>
- void EVP_SignInit(EVP_MD_CTX *ctx, const EVP_MD *type);
- void EVP_SignUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
+ int EVP_SignInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
+ int EVP_SignUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
int EVP_SignFinal(EVP_MD_CTX *ctx,unsigned char *sig,unsigned int *s, EVP_PKEY *pkey);
+ void EVP_SignInit(EVP_MD_CTX *ctx, const EVP_MD *type);
+
int EVP_PKEY_size(EVP_PKEY *pkey);
=head1 DESCRIPTION
The EVP signature routines are a high level interface to digital
signatures.
-EVP_SignInit() initialises a signing context B<ctx> to using digest
-B<type>: this will typically be supplied by a function such as
-EVP_sha1().
+EVP_SignInit_ex() sets up signing context B<ctx> to use digest
+B<type> from ENGINE B<impl>. B<ctx> must be initialized with
+EVP_MD_CTX_init() before calling this function.
EVP_SignUpdate() hashes B<cnt> bytes of data at B<d> into the
-signature context B<ctx>. This funtion can be called several times on the
+signature context B<ctx>. This function can be called several times on the
same B<ctx> to include additional data.
-EVP_SignFinal() signs the data in B<ctx> using the private key B<pkey>
-and places the signature in B<sig>. If the B<s> parameter is not NULL
-then the number of bytes of data written (i.e. the length of the signature)
+EVP_SignFinal() signs the data in B<ctx> using the private key B<pkey> and
+places the signature in B<sig>. B<sig> must be at least EVP_PKEY_size(pkey)
+bytes in size. B<s> is an OUT parameter, and not used as an IN parameter.
+The number of bytes of data written (i.e. the length of the signature)
will be written to the integer at B<s>, at most EVP_PKEY_size(pkey) bytes
-will be written. After calling EVP_SignFinal() no additional calls to
-EVP_SignUpdate() can be made, but EVP_SignInit() can be called to initialiase
-a new signature operation.
+will be written.
+
+EVP_SignInit() initializes a signing context B<ctx> to use the default
+implementation of digest B<type>.
EVP_PKEY_size() returns the maximum size of a signature in bytes. The actual
signature returned by EVP_SignFinal() may be smaller.
=head1 RETURN VALUES
-EVP_SignInit() and EVP_SignUpdate() do not return values.
-
-EVP_SignFinal() returns 1 for success and 0 for failure.
+EVP_SignInit_ex(), EVP_SignUpdate() and EVP_SignFinal() return 1
+for success and 0 for failure.
EVP_PKEY_size() returns the maximum size of a signature in bytes.
-The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
+The error codes can be obtained by L<ERR_get_error(3)>.
=head1 NOTES
Due to the link between message digests and public key algorithms the correct
digest algorithm must be used with the correct public key type. A list of
algorithms and associated public key algorithms appears in
-L<EVP_DigestInit(3)|EVP_DigestInit(3)>.
+L<EVP_DigestInit(3)>.
When signing with DSA private keys the random number generator must be seeded
or the operation will fail. The random number generator does not need to be
seeded for RSA signatures.
+The call to EVP_SignFinal() internally finalizes a copy of the digest context.
+This means that calls to EVP_SignUpdate() and EVP_SignFinal() can be called
+later to digest and sign additional data.
+
+Since only a copy of the digest context is ever finalized the context must
+be cleaned up after use by calling EVP_MD_CTX_cleanup() or a memory leak
+will occur.
+
=head1 BUGS
-Several of the functions do not return values: maybe they should. Although the
-internal digest operations will never fail some future hardware based operations
-might.
+Older versions of this documentation wrongly stated that calls to
+EVP_SignUpdate() could not be made after calling EVP_SignFinal().
-=head1 SEE ALSO
+Since the private key is passed in the call to EVP_SignFinal() any error
+relating to the private key (for example an unsuitable key and digest
+combination) will not be indicated until after potentially large amounts of
+data have been passed through EVP_SignUpdate().
-L<EVP_VerifyInit(3)|EVP_VerifyInit(3)>,
-L<EVP_DigestInit(3)|EVP_DigestInit(3)>, L<err(3)|err(3)>,
-L<evp(3)|evp(3)>, L<hmac(3)|hmac(3)>, L<md2(3)|md2(3)>,
-L<md5(3)|md5(3)>, L<mdc2(3)|mdc2(3)>, L<ripemd(3)|ripemd(3)>,
-L<sha(3)|sha(3)>, L<digest(1)|digest(1)>
+It is not possible to change the signing parameters using these function.
-=head1 HISTORY
+The previous two bugs are fixed in the newer EVP_SignDigest*() function.
+
+=head1 SEE ALSO
-EVP_SignInit(), EVP_SignUpdate() and EVP_SignFinal() are
-available in all versions of SSLeay and OpenSSL.
+L<EVP_VerifyInit(3)>,
+L<EVP_DigestInit(3)>, L<err(3)>,
+L<evp(3)>, L<hmac(3)>, L<md2(3)>,
+L<md5(3)>, L<mdc2(3)>, L<ripemd(3)>,
+L<sha(3)>, L<dgst(1)>
=cut
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