X-Git-Url: https://git.saurik.com/apple/security.git/blobdiff_plain/80e2389990082500d76eb566d4946be3e786c3ef..d8f41ccd20de16f8ebe2ccc84d47bf1cb2b26bbb:/Security/libsecurity_apple_csp/lib/DH_exchange.cpp

diff --git a/Security/libsecurity_apple_csp/lib/DH_exchange.cpp b/Security/libsecurity_apple_csp/lib/DH_exchange.cpp
new file mode 100644
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+++ b/Security/libsecurity_apple_csp/lib/DH_exchange.cpp
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+/*
+ * Copyright (c) 2000-2002,2011-2012,2014 Apple Inc. All Rights Reserved.
+ * 
+ * The contents of this file constitute Original Code as defined in and are
+ * subject to the Apple Public Source License Version 1.2 (the 'License').
+ * You may not use this file except in compliance with the License. Please obtain
+ * a copy of the License at http://www.apple.com/publicsource and read it before
+ * using this file.
+ * 
+ * This Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS
+ * OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, INCLUDING WITHOUT
+ * LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+ * PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. Please see the License for the
+ * specific language governing rights and limitations under the License.
+ */
+
+
+/*
+ * DH_exchange.cp - Diffie-Hellman key exchange
+ */
+ 
+#include "DH_exchange.h"
+#include <Security/cssmerr.h>
+#include "DH_utils.h"
+#include "DH_keys.h"
+#include <strings.h>
+#include <opensslUtils/opensslUtils.h>
+
+void DeriveKey_DH (
+	const Context &context,
+	const CssmData &Param,			// other's public key. may be empty
+	CSSM_DATA *keyData,				// mallocd by caller
+									// we fill in keyData->Length bytes
+	AppleCSPSession &session)
+{
+	bool mallocdPrivKey;
+	size_t privSize;
+	
+	/* private DH key from context - required */
+	DH *privKey = contextToDhKey(context, session, CSSM_ATTRIBUTE_KEY,
+		CSSM_KEYCLASS_PRIVATE_KEY, CSSM_KEYUSE_DERIVE, mallocdPrivKey);
+	if(privKey == NULL) {
+		CssmError::throwMe(CSSMERR_CSP_MISSING_ATTR_KEY);
+	}
+	cspDhDebug("DeriveKey_DH, privKey %p", privKey);
+	privSize = DH_size(privKey);
+	if(privSize < keyData->Length) {
+		/* we've been asked for more bits than this key can generate */
+		CssmError::throwMe(CSSMERR_CSP_UNSUPPORTED_KEY_SIZE);
+	}
+	
+	/*
+	 * Public key ("their" key) can come from two places:
+	 * -- in the context as a CSSM_ATTRIBUTE_PUBLIC_KEY. This is how 
+	 *    public keys in X509 format must be used in this function
+	 * -- in the incoming Param, the raw unformatted (PKCS3) form 
+	 */
+	bool mallocdPubKey = false;
+	BIGNUM *pubKeyBn = NULL;
+	bool allocdPubKeyBn = false;
+	DH *pubKey = contextToDhKey(context, session, CSSM_ATTRIBUTE_PUBLIC_KEY,
+		CSSM_KEYCLASS_PUBLIC_KEY, CSSM_KEYUSE_DERIVE, mallocdPubKey);
+	if(pubKey != NULL) {
+		if(pubKey->pub_key == NULL) {
+			errorLog0("DeriveKey_DH: public key in context with no pub_key\n");
+			CssmError::throwMe(CSSMERR_CSP_INVALID_KEY);
+		}
+		pubKeyBn = pubKey->pub_key;
+		cspDhDebug("DeriveKey_DH, pubKey from context %p", pubKey);
+	}
+	else {
+		if((Param.Data == NULL) || (Param.Length == 0)) {
+			errorLog0("DeriveKey_DH: no pub_key, no Param\n");
+			CssmError::throwMe(CSSMERR_CSP_INVALID_KEY);
+		}
+		pubKeyBn = BN_bin2bn(Param.Data, (int)Param.Length, NULL);
+		if(pubKeyBn == NULL) {
+			CssmError::throwMe(CSSMERR_CSP_MEMORY_ERROR);
+		}
+		allocdPubKeyBn = true;
+		cspDhDebug("DeriveKey_DH, no pubKey in context");
+	}
+	unsigned char *buf = (unsigned char *)session.malloc(privSize);
+	int rtn = DH_compute_key(buf, pubKeyBn, privKey);
+	if(rtn > 0) {
+		/*
+		 * FIXME : I have not found a specification describing *which*
+		 * bytes of the value we just computed we are supposed to
+		 * use as the actual key bytes. We use the M.S. bytes.
+		 *
+		 * Note that due to modulo arithmetic, we may have gotten fewer
+		 * bytes than we asked for. If so, the caller will have
+		 * to deal with that if they really need privSize bytes.
+		 */
+		assert((uint32)rtn <= privSize);
+		CSSM_SIZE toMove = keyData->Length;
+		if((uint32)rtn < toMove) {
+			toMove = (uint32)rtn;
+		}
+		memmove(keyData->Data, buf, toMove);
+		keyData->Length = toMove;
+	}
+	if(mallocdPrivKey) {
+		DH_free(privKey);
+	}
+	if(mallocdPubKey) {
+		DH_free(pubKey);
+	}
+	if(allocdPubKeyBn) {
+		BN_free(pubKeyBn);
+	}
+	session.free(buf);
+	if(rtn <= 0) {
+		throwRsaDsa("DH_compute_key");
+	}
+}
+