tool: add rand.

The rand subcommand outputs entropy to stdout.

Change-Id: I95c2769a1784a8dd4c21efc15009080006d51349
Reviewed-on: https://boringssl-review.googlesource.com/4325
Reviewed-by: Adam Langley <agl@google.com>

tool/CMakeLists.txt

diff --git a/tool/CMakeLists.txt b/tool/CMakeLists.txt
index d542f26..67f59a7 100644
--- a/tool/CMakeLists.txt
+++ b/tool/CMakeLists.txt
@@ -8,6 +8,7 @@
   const.cc
   digest.cc
   pkcs12.cc
+  rand.cc
   server.cc
   speed.cc
   tool.cc

tool/rand.cc

diff --git a/tool/rand.cc b/tool/rand.cc
new file mode 100644
index 0000000..ea97bfa
--- /dev/null
+++ b/tool/rand.cc
@@ -0,0 +1,94 @@
+/* Copyright (c) 2015, Google Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
+
+#include <string>
+#include <vector>
+
+#include <stdint.h>
+
+#include <openssl/rand.h>
+
+#include "internal.h"
+
+
+static const struct argument kArguments[] = {
+    {
+     "-hex", kBooleanArgument,
+     "Hex encoded output."
+    },
+    {
+     "", kOptionalArgument, "",
+    },
+};
+
+bool Rand(const std::vector<std::string> &args) {
+  bool forever = true, hex = false;
+  size_t len = 0;
+
+  if (!args.empty()) {
+    std::vector<std::string> args_copy(args);
+    const std::string &last_arg = args.back();
+
+    if (last_arg.size() > 0 && last_arg[0] != '-') {
+      char *endptr;
+      unsigned long long num = strtoull(last_arg.c_str(), &endptr, 10);
+      if (*endptr == 0) {
+        len = num;
+        forever = false;
+        args_copy.pop_back();
+      }
+    }
+
+    std::map<std::string, std::string> args_map;
+    if (!ParseKeyValueArguments(&args_map, args_copy, kArguments)) {
+      PrintUsage(kArguments);
+      return false;
+    }
+
+    hex = args_map.count("-hex") > 0;
+  }
+
+  uint8_t buf[4096];
+  uint8_t hex_buf[8192];
+
+  size_t done = 0;
+  while (forever || done < len) {
+    size_t todo = sizeof(buf);
+    if (!forever && todo > len - done) {
+      todo = len - done;
+    }
+    RAND_bytes(buf, todo);
+    if (hex) {
+      static const char hextable[] = "0123456789abdef";
+      for (unsigned i = 0; i < todo; i++) {
+        hex_buf[i*2] = hextable[buf[i] >> 4];
+        hex_buf[i*2 + 1] = hextable[buf[i] & 0xf];
+      }
+      if (fwrite(hex_buf, todo*2, 1, stdout) != 1) {
+        return false;
+      }
+    } else {
+      if (fwrite(buf, todo, 1, stdout) != 1) {
+        return false;
+      }
+    }
+    done += todo;
+  }
+
+  if (hex && fwrite("\n", 1, 1, stdout) != 1) {
+    return false;
+  }
+
+  return true;
+}

tool/tool.cc

diff --git a/tool/tool.cc b/tool/tool.cc
index 36e3de9..4bd7d1a 100644
--- a/tool/tool.cc
+++ b/tool/tool.cc
@@ -36,6 +36,7 @@
 bool SHA512Sum(const std::vector<std::string> &args);
 bool DoPKCS12(const std::vector<std::string> &args);
 bool Speed(const std::vector<std::string> &args);
+bool Rand(const std::vector<std::string> &args);
 
 typedef bool (*tool_func_t)(const std::vector<std::string> &args);
 
@@ -57,6 +58,7 @@
   { "sha256sum", SHA256Sum },
   { "sha384sum", SHA384Sum },
   { "sha512sum", SHA512Sum },
+  { "rand", Rand },
   { "", nullptr },
 };