Fix parameter types in sshkdf

Handling of parameter OSSL_KDF_PARAM_SSHKDF_TYPE mixed integer and string
parameters.  This caused endianness problems on big-endian machines.  As a
result, it is not possible to pass FIPS tests since the parameter was stored
with an integer value but read via a cast to char pointer.  While this works
on little endian machines, big endian s390 read the most significant bits
instead of the least significant (as done by, e.g., x86).  Change the
parameter to char array and fix the usages.

Signed-off-by: Juergen Christ <jchrist@linux.ibm.com>

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Patrick Steuer <patrick.steuer@de.ibm.com>
(Merged from https://github.com/openssl/openssl/pull/13781)

2 files changed, 12 insertions, 11 deletions

diff --git a/doc/man7/EVP_KDF-SSHKDF.pod b/doc/man7/EVP_KDF-SSHKDF.pod
index 454bb6b699..2b2f0cc227 100644
--- a/doc/man7/EVP_KDF-SSHKDF.pod
+++ b/doc/man7/EVP_KDF-SSHKDF.pod
@@ -41,9 +41,9 @@ These parameters work as described in L<EVP_KDF(3)/PARAMETERS>.
 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>) <integer>
+=item "type" (B<OSSL_KDF_PARAM_SSHKDF_TYPE>) <UTF8 string>
 
-This parameter sets the type for the SSHHKDF operation.
+This parameter sets the type for the SSHKDF operation.
 There are six supported types:
 
 =over 4
@@ -51,32 +51,32 @@ There are six supported types:
 =item EVP_KDF_SSHKDF_TYPE_INITIAL_IV_CLI_TO_SRV
 
 The Initial IV from client to server.
-A single char of value 65 (ASCII char 'A').
+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
-A single char of value 66 (ASCII char 'B').
+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
-A single char of value 67 (ASCII char 'C').
+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
-A single char of value 68 (ASCII char 'D').
+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
-A single char of value 69 (ASCII char 'E').
+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
-A single char of value 70 (ASCII char 'F').
+Char array initializer of value {70, 0}, i.e., ASCII string "F".
 
 =back
 
@@ -103,6 +103,7 @@ This example derives an 8 byte IV using SHA-256 with a 1K "key" and appropriate
 
  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...";
@@ -122,8 +123,8 @@ This example derives an 8 byte IV using SHA-256 with a 1K "key" and appropriate
                                           xcghash, (size_t)32);
  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
                                           session_id, (size_t)32);
- *p++ = OSSL_PARAM_construct_int(OSSL_KDF_PARAM_SSHKDF_TYPE,
-                                 EVP_KDF_SSHKDF_TYPE_INITIAL_IV_CLI_TO_SRV);
+ *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_SSHKDF_TYPE,
+                                         type, sizeof(type));
  *p = OSSL_PARAM_construct_end();
  if (EVP_KDF_CTX_set_params(kctx, params) <= 0)
      /* Error */
diff --git a/doc/man7/provider-kdf.pod b/doc/man7/provider-kdf.pod
index 07aaf373c6..be0bc7b51b 100644
--- a/doc/man7/provider-kdf.pod
+++ b/doc/man7/provider-kdf.pod
@@ -246,7 +246,7 @@ Sets the xcghash in the associated KDF ctx.
 
 Sets the session ID in the associated KDF ctx.
 
-=item "type" (B<OSSL_KDF_PARAM_SSHKDF_TYPE>) <integer>
+=item "type" (B<OSSL_KDF_PARAM_SSHKDF_TYPE>) <UTF8 string>
 
 Sets the SSH KDF type parameter in the associated KDF ctx.
 There are six supported types: