From 8386bf91f5cda763364eae726d64b035fa7dd40f Mon Sep 17 00:00:00 2001
From: Adam Chlipala <adamc@hcoop.net>
Date: Thu, 4 Feb 2010 13:07:12 -0500
Subject: mhash will use saved signature

---
 src/c/mhash.c | 47 ++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 44 insertions(+), 3 deletions(-)

diff --git a/src/c/mhash.c b/src/c/mhash.c
index becb9d97..91a3f78f 100644
--- a/src/c/mhash.c
+++ b/src/c/mhash.c
@@ -1,4 +1,5 @@
 #include <mhash.h>
+#include <fcntl.h>
 
 #define KEYSIZE 16
 #define PASSSIZE 4
@@ -12,14 +13,54 @@ int uw_hash_blocksize = HASH_BLOCKSIZE;
 static int password[PASSSIZE];
 static unsigned char private_key[KEYSIZE];
 
+char *uw_sig_file = NULL;
+
+static void random_password() {
+  int i;
+
+  for (i = 0; i < PASSSIZE; ++i)
+    password[i] = rand();
+}
+
 void uw_init_crypto() {
   KEYGEN kg = {{HASH_ALGORITHM, HASH_ALGORITHM}};
-  int i;
 
   assert(mhash_get_block_size(HASH_ALGORITHM) == HASH_BLOCKSIZE);
 
-  for (i = 0; i < PASSSIZE; ++i)
-    password[i] = rand();
+  if (uw_sig_file) {
+    int fd;
+
+    if (access(uw_sig_file, 0)) {
+      random_password();
+      
+      if ((fd = open(uw_sig_file, O_WRONLY | O_CREAT, 0700)) < 0) {
+        fprintf(stderr, "Can't open signature file %s\n", uw_sig_file);
+        perror("open");
+        exit(1);
+      }
+
+      if (write(fd, &password, sizeof password) != sizeof password) {
+        fprintf(stderr, "Error writing signature file\n");
+        exit(1);
+      }
+
+      close(fd);
+    } else {
+      if ((fd = open(uw_sig_file, O_RDONLY)) < 0) {
+        fprintf(stderr, "Can't open signature file %s\n", uw_sig_file);
+        perror("open");
+        exit(1);
+      }
+
+      if (read(fd, &password, sizeof password) != sizeof password) {
+        fprintf(stderr, "Error reading signature file\n");
+        exit(1);
+      }
+
+      close(fd);
+    }
+  } else
+    random_password();
 
   if (mhash_keygen_ext(KEYGEN_ALGORITHM, kg,
                        private_key, sizeof(private_key),
-- 
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