Add support for NSS library

This adds support for the NSSLOWHASH API provided by the freebl3
library.

hash_nss.c

@@ -0,0 +1,89 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2011
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * 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.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Routines implementing crypto hashing using NSSLOWHASH API of the NSS library.
+
+  */
+
+#include <nss.h>
+#include <hasht.h>
+#include <nsslowhash.h>
+
+/* #include "config.h" */
+#include "hash.h"
+
+static NSSLOWInitContext *ictx;
+
+struct hash {
+  HASH_HashType type;
+  const char *name;
+  NSSLOWHASHContext *context;
+};
+
+static struct hash hashes[] = {
+  { HASH_AlgMD5, "MD5", NULL },
+  { HASH_AlgSHA1, "SHA1", NULL },
+  { HASH_AlgSHA256, "SHA256", NULL },
+  { HASH_AlgSHA384, "SHA384", NULL },
+  { HASH_AlgSHA512, "SHA512", NULL },
+  { 0, NULL, NULL }
+};
+
+int
+HSH_GetHashId(const char *name)
+{
+  int i;
+
+  for (i = 0; hashes[i].name; i++) {
+    if (!strcmp(name, hashes[i].name))
+      break;
+  }
+
+  if (!hashes[i].name)
+    return -1; /* not found */
+
+  if (!ictx && !(ictx = NSSLOW_Init()))
+    return -1; /* couldn't init NSS */
+
+  if (!hashes[i].context &&
+      !(hashes[i].context = NSSLOWHASH_NewContext(ictx, hashes[i].type)))
+    return -1; /* couldn't init hash */
+
+  return i;
+}
+
+unsigned int
+HSH_Hash(int id, const unsigned char *in1, unsigned int in1_len,
+    const unsigned char *in2, unsigned int in2_len,
+    unsigned char *out, unsigned int out_len)
+{
+  unsigned int ret;
+
+  NSSLOWHASH_Begin(hashes[id].context);
+  NSSLOWHASH_Update(hashes[id].context, in1, in1_len);
+  if (in2)
+    NSSLOWHASH_Update(hashes[id].context, in2, in2_len);
+  NSSLOWHASH_End(hashes[id].context, out, &ret, out_len);
+
+  return ret;
+}