Rearrange the file tree.

[u/mdw/catacomb] / rand / noise.h

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+/* -*-c-*-
+ *
+ * Acquisition of environmental noise (Unix-specific)
+ *
+ * (c) 1998 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------*
+ *
+ * This file is part of Catacomb.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * Catacomb 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 Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with Catacomb; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+#ifndef CATACOMB_NOISE_H
+#define CATACOMB_NOISE_H
+
+#ifdef __cplusplus
+  extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <sys/types.h>
+
+#ifndef CATACOMB_RAND_H
+#  include "rand.h"
+#endif
+
+/*----- Noise source definition -------------------------------------------*/
+
+extern const rand_source noise_source;
+
+/*----- Magic numbers -----------------------------------------------------*/
+
+#define NOISE_NOSETUID ((uid_t)-1)
+#define NOISE_NOSETGID ((gid_t)-1)
+
+/*----- Functions provided ------------------------------------------------*/
+
+/* --- @noise_timer@ --- *
+ *
+ * Arguments:  @rand_pool *r@ = pointer to a randomness pool
+ *
+ * Returns:    Nonzero if some randomness was contributed.
+ *
+ * Use:                Contributes the current time to the randomness pool.
+ *             A guess at the number of useful bits contributed is made,
+ *             based on first and second order bit differences.  This isn't
+ *             ever-so reliable, but it's better than nothing.
+ */
+
+extern int noise_timer(rand_pool */*r*/);
+
+/* --- @noise_devrandom@ --- *
+ *
+ * Arguments:  @rand_pool *r@ = pointer to a randomness pool
+ *
+ * Returns:    Nonzero if some randomness was contributed.
+ *
+ * Use:                Attempts to obtain some randomness from the system entropy
+ *             pool.  All bits from the device are assumed to be good.
+ */
+
+extern int noise_devrandom(rand_pool */*r*/);
+
+/* --- @noise_setid@ --- *
+ *
+ * Arguments:  @uid_t uid@ = uid to set
+ *             @gid_t gid@ = gid to set
+ *
+ * Returns:    ---
+ *
+ * Use:                Sets the user and group ids to be used by @noise_filter@
+ *             when running child processes.  This is useful to avoid
+ *             giving shell commands (even carefully written ones) undue
+ *             privileges.  This interface is Unix-specific.
+ */
+
+extern void noise_setid(uid_t /*uid*/, gid_t /*gid*/);
+
+/* --- @noise_filter@ --- *
+ *
+ * Arguments:  @rand_pool *r@ = pointer to a randomness pool
+ *             @int good@ = number of good bits per 1024 bits
+ *             @const char *c@ = shell command to run
+ *
+ * Returns:    Nonzero if some randomness was contributed.
+ *
+ * Use:                Attempts to execute a shell command, and dump it into the
+ *             randomness pool.  A very rough estimate of the number of
+ *             good bits is made, based on the size of the command's output.
+ *             This function calls @waitpid@, so be careful.  Before execing
+ *             the command, the process uid and gid are set to the values
+ *             given to @noise_setid@, and an attempt is made to reset the
+ *             list of supplementary groups.  The environment passed to
+ *             the command has been severly lobotimized.  If the command
+ *             fails to complete within a short time period, it is killed.
+ *             Paranoid use of close-on-exec flags for file descriptors is
+ *             recommended.
+ *
+ *             This interface is Unix-specific.
+ */
+
+extern int noise_filter(rand_pool */*r*/, int /*good*/, const char */*c*/);
+
+/* --- @noise_freewheel@ --- *
+ *
+ * Arguments:  @rand_pool *r@ = pointer to a randomness pool
+ *
+ * Returns:    Nonzero if some randomness was contributed.
+ *
+ * Use:                Runs a free counter for a short while as a desparate attempt
+ *             to get randomness from somewhere.  This is actually quite
+ *             effective.
+ */
+
+int noise_freewheel(rand_pool */*r*/);
+
+/* --- @noise_enquire@ --- *
+ *
+ * Arguments:  @rand_pool *r@ = pointer to a randomness pool
+ *
+ * Returns:    Nonzero if some randomness was contributed.
+ *
+ * Use:                Runs some shell commands to enquire about the prevailing
+ *             environment.  This can gather quite a lot of low-quality
+ *             entropy.
+ */
+
+extern int noise_enquire(rand_pool */*r*/);
+
+/* --- @noise_acquire@ --- *
+ *
+ * Arguments:  @rand_pool *r@ = pointer to a randomness pool
+ *
+ * Returns:    ---
+ *
+ * Use:                Acquires some randomness from somewhere.
+ */
+
+extern void noise_acquire(rand_pool */*r*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+  }
+#endif
+
+#endif