1 files changed, 75 insertions, 0 deletions
diff --git a/contrib/libottery/ottery_entropy_egd.c b/contrib/libottery/ottery_entropy_egd.c
new file mode 100644
index 0000000..7e9cb07
--- /dev/null
+++ b/contrib/libottery/ottery_entropy_egd.c
@@ -0,0 +1,75 @@
+/* Libottery by Nick Mathewson.
+
+   This software has been dedicated to the public domain under the CC0
+   public domain dedication.
+
+   To the extent possible under law, the person who associated CC0 with
+   libottery has waived all copyright and related or neighboring rights
+   to libottery.
+
+   You should have received a copy of the CC0 legalcode along with this
+   work in doc/cc0.txt.  If not, see
+      <http://creativecommons.org/publicdomain/zero/1.0/>.
+ */
+#ifndef _WIN32
+/* TODO: Support win32. */
+#include <sys/socket.h>
+
+/** Implement an entropy-source that uses the EGD protocol.  The
+ * Entropy-Gathering Daemon is program (actually, one of several programs)
+ * that watches system events, periodically runs commands whose outputs have
+ * high variance, and so on.  It communicates over a simple socket-based
+ * protocol, of which we use only a tiny piece. */
+static int
+ottery_get_entropy_egd(const struct ottery_entropy_config *cfg,
+                       struct ottery_entropy_state *state,
+                       uint8_t *out, size_t outlen)
+{
+  int sock, n, result;
+  unsigned char msg[2];
+  (void) state;
+
+  if (! cfg || ! cfg->egd_sockaddr || ! cfg->egd_socklen)
+    return OTTERY_ERR_INIT_STRONG_RNG;
+  if (outlen > 255)
+    return OTTERY_ERR_ACCESS_STRONG_RNG;
+
+  sock = socket(cfg->egd_sockaddr->sa_family, SOCK_STREAM, 0);
+  if (sock < 0)
+    return OTTERY_ERR_INIT_STRONG_RNG;
+
+  if (connect(sock, cfg->egd_sockaddr, cfg->egd_socklen) < 0) {
+    result = OTTERY_ERR_INIT_STRONG_RNG;
+    goto out;
+  }
+
+  msg[0] = 1;                      /* nonblocking request */
+  msg[1] = (unsigned char) outlen; /* for outlen bytes */
+
+  if (write(sock, msg, 2) != 2 ||
+      read(sock, msg, 1)  != 1) {
+    result = OTTERY_ERR_ACCESS_STRONG_RNG;
+    goto out;
+  }
+
+  if (msg[0] != outlen) {
+    /* TODO Use any bytes we get, even if they aren't as many as we wanted. */
+    result = OTTERY_ERR_ACCESS_STRONG_RNG;
+    goto out;
+  }
+
+  n = ottery_read_n_bytes_from_file_(sock, out, outlen);
+  if (n < 0 || (size_t)n != outlen) {
+    result = OTTERY_ERR_ACCESS_STRONG_RNG;
+    goto out;
+  }
+  result = 0;
+ out:
+  close(sock);
+  return result;
+}
+
+#define ENTROPY_SOURCE_EGD \
+  { ottery_get_entropy_egd, SRC(EGD)|DOM(EGD)|FL(STRONG) }
+
+#endif