FreeBSD/Linux Kernel Cross Reference
sys/dev/random/random_infra.c

     /*-
      * Copyright (c) 2015 Mark R V Murray
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer
     *    in this position and unchanged.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     *
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/kernel.h>
    #include <sys/malloc.h>
    #include <sys/random.h>
    #include <sys/sysctl.h>
    
    #include <dev/random/randomdev.h>
    
    /* Set up the sysctl root node for the entropy device */
    SYSCTL_NODE(_kern, OID_AUTO, random, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
        "Cryptographically Secure Random Number Generator");
    SYSCTL_NODE(_kern_random, OID_AUTO, initial_seeding,
        CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
        "Initial seeding control and information");
    
    /*
     * N.B., this is a dangerous default, but it matches the behavior prior to
     * r346250 (and, say, OpenBSD -- although they get some guaranteed saved
     * entropy from the prior boot because of their KARL system, on RW media).
     */
    bool random_bypass_before_seeding = true;
    SYSCTL_BOOL(_kern_random_initial_seeding, OID_AUTO,
        bypass_before_seeding, CTLFLAG_RDTUN, &random_bypass_before_seeding,
        0, "If set non-zero, bypass the random device in requests for random "
        "data when the random device is not yet seeded.  This is considered "
        "dangerous.  Ordinarily, the random device will block requests until "
        "it is seeded by sufficient entropy.");
    
    /*
     * This is a read-only diagnostic that reports the combination of the former
     * tunable and actual bypass.  It is intended for programmatic inspection by
     * userspace administrative utilities after boot.
     */
    bool read_random_bypassed_before_seeding = false;
    SYSCTL_BOOL(_kern_random_initial_seeding, OID_AUTO,
        read_random_bypassed_before_seeding, CTLFLAG_RD,
        &read_random_bypassed_before_seeding, 0, "If non-zero, the random device "
        "was bypassed because the 'bypass_before_seeding' knob was enabled and a "
        "request was submitted prior to initial seeding.");
    
    /*
     * This is a read-only diagnostic that reports the combination of the former
     * tunable and actual bypass for arc4random initial seeding.  It is intended
     * for programmatic inspection by userspace administrative utilities after
     * boot.
     */
    bool arc4random_bypassed_before_seeding = false;
    SYSCTL_BOOL(_kern_random_initial_seeding, OID_AUTO,
        arc4random_bypassed_before_seeding, CTLFLAG_RD,
        &arc4random_bypassed_before_seeding, 0, "If non-zero, the random device "
        "was bypassed when initially seeding the kernel arc4random(9), because "
        "the 'bypass_before_seeding' knob was enabled and a request was submitted "
        "prior to initial seeding.");
    
    /*
     * This knob is for users who do not want additional warnings in their logs
     * because they intend to handle bypass by inspecting the status of the
     * diagnostic sysctls.
     */
    bool random_bypass_disable_warnings = false;
    SYSCTL_BOOL(_kern_random_initial_seeding, OID_AUTO,
        disable_bypass_warnings, CTLFLAG_RDTUN,
        &random_bypass_disable_warnings, 0, "If non-zero, do not log a warning "
        "if the 'bypass_before_seeding' knob is enabled and a request is "
        "submitted prior to initial seeding.");
    
    MALLOC_DEFINE(M_ENTROPY, "entropy", "Entropy harvesting buffers and data structures");
    
   #if defined(RANDOM_LOADABLE)
   const struct random_algorithm *p_random_alg_context;
   void (*_read_random)(void *, u_int);
   int (*_read_random_uio)(struct uio *, bool);
   bool (*_is_random_seeded)(void);
   #endif /* defined(RANDOM_LOADABLE) */

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