Import OpenSSL 1.1.1f

doc/man3/EVP_PKEY_size.pod

@@ -0,0 +1,80 @@
+=pod
+
+=head1 NAME
+
+EVP_PKEY_size, EVP_PKEY_bits, EVP_PKEY_security_bits
+- EVP_PKEY information functions
+
+=head1 SYNOPSIS
+
+ #include <openssl/evp.h>
+
+ int EVP_PKEY_size(const EVP_PKEY *pkey);
+ int EVP_PKEY_bits(const EVP_PKEY *pkey);
+ int EVP_PKEY_security_bits(const EVP_PKEY *pkey);
+
+=head1 DESCRIPTION
+
+EVP_PKEY_size() returns the maximum suitable size for the output
+buffers for almost all operations that can be done with I<pkey>.
+The primary documented use is with L<EVP_SignFinal(3)> and
+L<EVP_SealInit(3)>, but it isn't limited there.  The returned size is
+also large enough for the output buffer of L<EVP_PKEY_sign(3)>,
+L<EVP_PKEY_encrypt(3)>, L<EVP_PKEY_decrypt(3)>, L<EVP_PKEY_derive(3)>.
+
+It must be stressed that, unless the documentation for the operation
+that's being performed says otherwise, the size returned by
+EVP_PKEY_size() is only preliminary and not exact, so the final
+contents of the target buffer may be smaller.  It is therefore crucial
+to take note of the size given back by the function that performs the
+operation, such as L<EVP_PKEY_sign(3)> (the I<siglen> argument will
+receive that length), to avoid bugs.
+
+EVP_PKEY_bits() returns the cryptographic length of the cryptosystem
+to which the key in I<pkey> belongs, in bits.  Note that the definition
+of cryptographic length is specific to the key cryptosystem.
+
+EVP_PKEY_security_bits() returns the number of security bits of the given
+I<pkey>, bits of security is defined in NIST SP800-57.
+
+=head1 RETURN VALUES
+
+EVP_PKEY_size(), EVP_PKEY_bits() and EVP_PKEY_security_bits() return a
+positive number, or 0 if this size isn't available.
+
+=head1 NOTES
+
+Most functions that have an output buffer and are mentioned with
+EVP_PKEY_size() have a functionality where you can pass NULL for the
+buffer and still pass a pointer to an integer and get the exact size
+that this function call delivers in the context that it's called in.
+This allows those functions to be called twice, once to find out the
+exact buffer size, then allocate the buffer in between, and call that
+function again actually output the data.  For those functions, it
+isn't strictly necessary to call EVP_PKEY_size() to find out the
+buffer size, but may be useful in cases where it's desirable to know
+the upper limit in advance.
+
+It should also be especially noted that EVP_PKEY_size() shouldn't be
+used to get the output size for EVP_DigestSignFinal(), according to
+L<EVP_DigestSignFinal(3)/NOTES>.
+
+=head1 SEE ALSO
+
+L<EVP_SignFinal(3)>,
+L<EVP_SealInit(3)>,
+L<EVP_PKEY_sign(3)>,
+L<EVP_PKEY_encrypt(3)>,
+L<EVP_PKEY_decrypt(3)>,
+L<EVP_PKEY_derive(3)>
+
+=head1 COPYRIGHT
+
+Copyright 2020 The OpenSSL Project Authors. All Rights Reserved.
+
+Licensed under the Apache License 2.0 (the "License").  You may not use
+this file except in compliance with the License.  You can obtain a copy
+in the file LICENSE in the source distribution or at
+L<https://www.openssl.org/source/license.html>.
+
+=cut