Use conditional compilation for cryptographic functions.

This gets rid of the rest of the symbolic links. However, as a consequence, the
crypto header files have now moved to src/, and can no longer contain
library-specific declarations. Therefore, cipher_t, digest_t, ecdh_t, ecdsa_t
and rsa_t are now all opaque types, and only pointers to those types can be
used.

src/gcrypt/ecdh.c

@@ -0,0 +1,37 @@
+/*
+    ecdh.c -- Diffie-Hellman key exchange handling
+    Copyright (C) 2011-2013 Guus Sliepen <guus@tinc-vpn.org>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "../system.h"
+
+#include "../ecdh.h"
+#include "../logger.h"
+#include "../utils.h"
+#include "../xalloc.h"
+
+ecdh_t *ecdh_generate_public(void *pubkey) {
+	logger(DEBUG_ALWAYS, LOG_ERR, "EC support using libgcrypt not implemented");
+	return NULL;
+}
+
+bool ecdh_compute_shared(ecdh_t *ecdh, const void *pubkey, void *shared) {
+	return false
+}
+
+void ecdh_free(ecdh_t *ecdh) {
+}

src/gcrypt/ecdsa.c

@@ -0,0 +1,67 @@
+/*
+    ecdsa.c -- ECDSA key handling
+    Copyright (C) 2011-2013 Guus Sliepen <guus@tinc-vpn.org>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "../system.h"
+
+#include "../logger.h"
+#include "../ecdsa.h"
+#include "../utils.h"
+#include "../xalloc.h"
+
+// Get and set ECDSA keys
+//
+ecdsa_t *ecdsa_set_base64_public_key(const char *p) {
+	logger(DEBUG_ALWAYS, LOG_ERR, "EC support using libgcrypt not implemented");
+	return NULL;
+}
+
+char *ecdsa_get_base64_public_key(ecdsa_t *ecdsa) {
+	return NULL;
+}
+
+// Read PEM ECDSA keys
+
+ecdsa_t *ecdsa_read_pem_public_key(FILE *fp) {
+	logger(DEBUG_ALWAYS, LOG_ERR, "EC support using libgcrypt not implemented");
+	return NULL;
+}
+
+ecdsa_t *ecdsa_read_pem_private_key(FILE *fp) {
+	logger(DEBUG_ALWAYS, LOG_ERR, "EC support using libgcrypt not implemented");
+	return NULL;
+}
+
+size_t ecdsa_size(ecdsa_t *ecdsa) {
+	return 0;
+}
+
+bool ecdsa_sign(ecdsa_t *ecdsa, const void *in, size_t len, void *sig) {
+	return false;
+}
+
+bool ecdsa_verify(ecdsa_t *ecdsa, const void *in, size_t len, const void *sig) {
+	return false;
+}
+
+bool ecdsa_active(ecdsa_t *ecdsa) {
+	return false;
+}
+
+void ecdsa_free(ecdsa_t *ecdsa) {
+}

src/gcrypt/ecdsagen.c

@@ -0,0 +1,41 @@
+/*
+    ecdsagen.c -- ECDSA key generation and export
+    Copyright (C) 2011-2013 Guus Sliepen <guus@tinc-vpn.org>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "../system.h"
+
+#include "../ecdsagen.h"
+#include "../utils.h"
+#include "../xalloc.h"
+
+// Generate ECDSA key
+
+ecdsa_t *ecdsa_generate(void) {
+	logger(DEBUG_ALWAYS, LOG_ERR, "EC support using libgcrypt not implemented");
+	return NULL;
+}
+
+// Write PEM ECDSA keys
+
+bool ecdsa_write_pem_public_key(ecdsa_t *ecdsa, FILE *fp) {
+	return false;
+}
+
+bool ecdsa_write_pem_private_key(ecdsa_t *ecdsa, FILE *fp) {
+	return false;
+}

src/gcrypt/prf.c

@@ -0,0 +1,29 @@
+/*
+    prf.c -- Pseudo-Random Function for key material generation
+    Copyright (C) 2011-2013 Guus Sliepen <guus@tinc-vpn.org>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "../system.h"
+
+#include "digest.h"
+#include "../digest.h"
+#include "../prf.h"
+
+bool prf(const char *secret, size_t secretlen, char *seed, size_t seedlen, char *out, size_t outlen) {
+	logger(DEBUG_ALWAYS, LOG_ERR, "PRF support using libgcrypt not implemented");
+	return false;
+}