mirror of
https://github.com/openssl/openssl.git
synced 2025-01-24 13:55:42 +08:00
247a1786e2
When the string "ABCDEFGH" is passed, what's considered its data, this?
{ 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H' }
or this?
{ 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', '\0' }
If it's passed as a pass phrase, should the terminating NUL byte be
considered part of the pass phrase, or not?
Our treatment of OSSL_PARAMs with the data type OSSL_PARAM_UTF8_STRING
set the length of the string to include the terminating NUL byte,
which is quite confusing. What should the recipient of such a string
believe?
Instead of perpetuating this confusion, we change the assumption to
set the OSSL_PARAM to the length of the string, not including the
terminating NUL byte, thereby giving it the same value as a strlen()
call would give.
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14168)
161 lines
4.7 KiB
Plaintext
161 lines
4.7 KiB
Plaintext
=pod
|
|
|
|
=head1 NAME
|
|
|
|
EVP_KDF-SSHKDF - The SSHKDF EVP_KDF implementation
|
|
|
|
=head1 DESCRIPTION
|
|
|
|
Support for computing the B<SSHKDF> KDF through the B<EVP_KDF> API.
|
|
|
|
The EVP_KDF-SSHKDF algorithm implements the SSHKDF key derivation function.
|
|
It is defined in RFC 4253, section 7.2 and is used by SSH to derive IVs,
|
|
encryption keys and integrity keys.
|
|
Five inputs are required to perform key derivation: The hashing function
|
|
(for example SHA256), the Initial Key, the Exchange Hash, the Session ID,
|
|
and the derivation key type.
|
|
|
|
=head2 Identity
|
|
|
|
"SSHKDF" is the name for this implementation; it
|
|
can be used with the EVP_KDF_fetch() function.
|
|
|
|
=head2 Supported parameters
|
|
|
|
The supported parameters are:
|
|
|
|
=over 4
|
|
|
|
=item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
|
|
|
|
=item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
|
|
|
|
=item "key" (B<OSSL_KDF_PARAM_KEY>) <octet string>
|
|
|
|
These parameters work as described in L<EVP_KDF(3)/PARAMETERS>.
|
|
|
|
=item "xcghash" (B<OSSL_KDF_PARAM_SSHKDF_XCGHASH>) <octet string>
|
|
|
|
=item "session_id" (B<OSSL_KDF_PARAM_SSHKDF_SESSION_ID>) <octet string>
|
|
|
|
These parameters set the respective values for the KDF.
|
|
If a value is already set, the contents are replaced.
|
|
|
|
=item "type" (B<OSSL_KDF_PARAM_SSHKDF_TYPE>) <UTF8 string>
|
|
|
|
This parameter sets the type for the SSHKDF operation.
|
|
There are six supported types:
|
|
|
|
=over 4
|
|
|
|
=item EVP_KDF_SSHKDF_TYPE_INITIAL_IV_CLI_TO_SRV
|
|
|
|
The Initial IV from client to server.
|
|
Char array initializer of value {65, 0}, i.e., ASCII string "A".
|
|
|
|
=item EVP_KDF_SSHKDF_TYPE_INITIAL_IV_SRV_TO_CLI
|
|
|
|
The Initial IV from server to client
|
|
Char array initializer of value {66, 0}, i.e., ASCII string "B".
|
|
|
|
=item EVP_KDF_SSHKDF_TYPE_ENCRYPTION_KEY_CLI_TO_SRV
|
|
|
|
The Encryption Key from client to server
|
|
Char array initializer of value {67, 0}, i.e., ASCII string "C".
|
|
|
|
=item EVP_KDF_SSHKDF_TYPE_ENCRYPTION_KEY_SRV_TO_CLI
|
|
|
|
The Encryption Key from server to client
|
|
Char array initializer of value {68, 0}, i.e., ASCII string "D".
|
|
|
|
=item EVP_KDF_SSHKDF_TYPE_INTEGRITY_KEY_CLI_TO_SRV
|
|
|
|
The Integrity Key from client to server
|
|
Char array initializer of value {69, 0}, i.e., ASCII string "E".
|
|
|
|
=item EVP_KDF_SSHKDF_TYPE_INTEGRITY_KEY_SRV_TO_CLI
|
|
|
|
The Integrity Key from client to server
|
|
Char array initializer of value {70, 0}, i.e., ASCII string "F".
|
|
|
|
=back
|
|
|
|
=back
|
|
|
|
=head1 NOTES
|
|
|
|
A context for SSHKDF can be obtained by calling:
|
|
|
|
EVP_KDF *kdf = EVP_KDF_fetch(NULL, "SSHKDF", NULL);
|
|
EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
|
|
|
|
The output length of the SSHKDF derivation is specified via the I<keylen>
|
|
parameter to the L<EVP_KDF_derive(3)> function.
|
|
Since the SSHKDF output length is variable, calling L<EVP_KDF_CTX_get_kdf_size(3)>
|
|
to obtain the requisite length is not meaningful. The caller must
|
|
allocate a buffer of the desired length, and pass that buffer to the
|
|
L<EVP_KDF_derive(3)> function along with the desired length.
|
|
|
|
=head1 EXAMPLES
|
|
|
|
This example derives an 8 byte IV using SHA-256 with a 1K "key" and appropriate
|
|
"xcghash" and "session_id" values:
|
|
|
|
EVP_KDF *kdf;
|
|
EVP_KDF_CTX *kctx;
|
|
const char type[] = EVP_KDF_SSHKDF_TYPE_INITIAL_IV_CLI_TO_SRV;
|
|
unsigned char key[1024] = "01234...";
|
|
unsigned char xcghash[32] = "012345...";
|
|
unsigned char session_id[32] = "012345...";
|
|
unsigned char out[8];
|
|
size_t outlen = sizeof(out);
|
|
OSSL_PARAM params[6], *p = params;
|
|
|
|
kdf = EVP_KDF_fetch(NULL, "SSHKDF", NULL);
|
|
kctx = EVP_KDF_CTX_new(kdf);
|
|
EVP_KDF_free(kdf);
|
|
|
|
*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
|
|
SN_sha256, strlen(SN_sha256));
|
|
*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY,
|
|
key, (size_t)1024);
|
|
*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SSHKDF_XCGHASH,
|
|
xcghash, (size_t)32);
|
|
*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
|
|
session_id, (size_t)32);
|
|
*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_SSHKDF_TYPE,
|
|
type, sizeof(type) - 1);
|
|
*p = OSSL_PARAM_construct_end();
|
|
if (EVP_KDF_CTX_set_params(kctx, params) <= 0)
|
|
/* Error */
|
|
|
|
if (EVP_KDF_derive(kctx, out, &outlen) <= 0)
|
|
/* Error */
|
|
|
|
|
|
=head1 CONFORMING TO
|
|
|
|
RFC 4253
|
|
|
|
=head1 SEE ALSO
|
|
|
|
L<EVP_KDF(3)>,
|
|
L<EVP_KDF_CTX_new(3)>,
|
|
L<EVP_KDF_CTX_free(3)>,
|
|
L<EVP_KDF_CTX_set_params(3)>,
|
|
L<EVP_KDF_CTX_get_kdf_size(3)>,
|
|
L<EVP_KDF_derive(3)>,
|
|
L<EVP_KDF(3)/PARAMETERS>
|
|
|
|
=head1 COPYRIGHT
|
|
|
|
Copyright 2016-2021 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
|
|
|