#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() initializes 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 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 initialize
-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.
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().
+
+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().
+
+It is not possible to change the signing parameters using these function.
+
+The previous two bugs are fixed in the newer EVP_SignDigest*() function.
=head1 SEE ALSO
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)>
+L<sha(3)|sha(3)>, L<dgst(1)|dgst(1)>
=head1 HISTORY
EVP_SignInit(), EVP_SignUpdate() and EVP_SignFinal() are
available in all versions of SSLeay and OpenSSL.
+EVP_SignInit_ex() was added in OpenSSL 0.9.7.
+
=cut