Implement SSH KDF

SSH's KDF is defined in RFC 4253 in Section 7.2

Signed-off-by: Simo Sorce <simo@redhat.com>

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7290)

1 files changed, 175 insertions, 0 deletions

diff --git a/doc/man7/EVP_KDF_SSHKDF.pod b/doc/man7/EVP_KDF_SSHKDF.pod
new file mode 100644
index 0000000000..9c9734e7c3
--- /dev/null
+++ b/doc/man7/EVP_KDF_SSHKDF.pod
@@ -0,0 +1,175 @@
+=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 Numeric identity
+
+B<EVP_KDF_SSHKDF> is the numeric identity for this implementation; it
+can be used with the EVP_KDF_CTX_new_id() function.
+
+=head2 Supported controls
+
+The supported controls are:
+
+=over 4
+
+=item B<EVP_KDF_CTRL_SET_MD>
+
+=item B<EVP_KDF_CTRL_SET_KEY>
+
+These controls work as described in L<EVP_KDF_CTX(3)/CONTROLS>.
+
+=item B<EVP_KDF_CTRL_SET_SSHKDF_XCGHASH>
+
+=item B<EVP_KDF_CTRL_SET_SSHKDF_SESSION_ID>
+
+These controls expect two arguments: C<unsigned char *buffer>, C<size_t length>
+
+They set the respective values to the first B<length> bytes of the buffer
+B<buffer>. If a value is already set, the contents are replaced.
+
+EVP_KDF_ctrl_str() takes two type strings for these controls:
+
+=over 4
+
+=item "xcghash"
+
+=item "session_id"
+
+The value string is used as is.
+
+=item "hexxcghash"
+
+=item "hexsession_id"
+
+The value string is expected to be a hexadecimal number, which will be
+decoded before being passed on as the control value.
+
+=back
+
+=item B<EVP_KDF_CTRL_SET_SSHKDF_TYPE>
+
+This control expects one argument: C<int mode>
+
+Sets the type for the SSHHKDF operation. There are six supported types:
+
+=over 4
+
+=item EVP_KDF_SSHKDF_TYPE_ININITAL_IV_CLI_TO_SRV
+
+The Initial IV from client to server.
+A single char of value 65 (ASCII char 'A').
+
+=item EVP_KDF_SSHKDF_TYPE_ININITAL_IV_SRV_TO_CLI
+
+The Initial IV from server to client
+A single char of value 66 (ASCII char 'B').
+
+=item EVP_KDF_SSHKDF_TYPE_ENCRYPTION_KEY_CLI_TO_SRV
+
+The Encryption Key from client to server
+A single char of value 67 (ASCII char 'C').
+
+=item EVP_KDF_SSHKDF_TYPE_ENCRYPTION_KEY_SRV_TO_CLI
+
+The Encryption Key from server to client
+A single char of value 68 (ASCII char 'D').
+
+=item EVP_KDF_SSHKDF_TYPE_INTEGRITY_KEY_CLI_TO_SRV
+
+The Integrity Key from client to server
+A single char of value 69 (ASCII char 'E').
+
+=item EVP_KDF_SSHKDF_TYPE_INTEGRITY_KEY_SRV_TO_CLI
+
+The Integrity Key from client to server
+A single char of value 70 (ASCII char 'F').
+
+=back
+
+EVP_KDF_ctrl_str() type string: "type"
+
+The value is a string of length one character. The only valid values
+are the numerical values of the ASCII caracters: "A" (65) to "F" (70).
+
+=back
+
+=head1 NOTES
+
+A context for SSHKDF can be obtained by calling:
+
+ EVP_KDF_CTX *kctx = EVP_KDF_CTX_new_id(EVP_KDF_SSHKDF);
+
+The output length of the SSHKDF derivation is specified via the C<keylen>
+parameter to the L<EVP_KDF_derive(3)> function.
+Since the SSHKDF output length is variable, calling L<EVP_KDF_size()>
+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 EXAMPLE
+
+This example derives an 8 byte IV using SHA-256 with a 1K "key" and appropriate
+"xcghash" and "session_id" values:
+
+ EVP_KDF_CTX *kctx;
+ 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);
+ kctx = EVP_KDF_CTX_new_id(EVP_KDF_SSHKDF);
+
+ if (EVP_KDF_CTX_set_md(kctx, EVP_sha256()) <= 0)
+     /* Error */
+ if (EVP_KDF_CTX_set1_key(kctx, key, 1024) <= 0)
+     /* Error */
+ if (EVP_KDF_CTX_set1_sshkdf_xcghash(kctx, xcghash, 32) <= 0)
+     /* Error */
+ if (EVP_KDF_CTX_set1_sshkdf_session_id(kctx, session_id, 32) <= 0)
+     /* Error */
+ if (EVP_KDF_CTX_set_sshkdf_type(kctx,
+                    EVP_KDF_SSHKDF_TYPE_ININITAL_IV_CLI_TO_SRV) <= 0)
+     /* Error */
+ if (EVP_KDF_derive(kctx, out, &outlen) <= 0)
+     /* Error */
+
+
+=head1 CONFORMING TO
+
+RFC 4253
+
+=head1 SEE ALSO
+
+L<EVP_KDF_CTX>,
+L<EVP_KDF_CTX_new_id(3)>,
+L<EVP_KDF_CTX_free(3)>,
+L<EVP_KDF_ctrl(3)>,
+L<EVP_KDF_size(3)>,
+L<EVP_KDF_derive(3)>,
+L<EVP_KDF_CTX(3)/CONTROLS>
+
+=head1 COPYRIGHT
+
+Copyright 2016-2018 The OpenSSL Project Authors. All Rights Reserved.
+
+Licensed under the OpenSSL license (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
+