isc/unix/entropy.c

	entropy.c revision 28a55095f78f1c67fa7c154989ac997d4f714cb6
/*
 * Copyright (C) 2000-2008, 2012, 2016, 2017  Internet Systems Consortium, Inc. ("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

/* $Id: entropy.c,v 1.82 2008/12/01 23:47:45 tbox Exp $ */

/* \file unix/entropy.c
 * \brief
 * This is the system dependent part of the ISC entropy API.
 */

#include <config.h>

#include <sys/param.h>  /* Openserver 5.0.6A and FD_SETSIZE */
#include <sys/types.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/un.h>

#ifdef HAVE_NANOSLEEP
#include <time.h>
#endif
#include <unistd.h>

#include <isc/platform.h>
#include <isc/print.h>
#include <isc/strerror.h>
#include <isc/string.h>

#ifdef ISC_PLATFORM_NEEDSYSSELECTH
#include <sys/select.h>
#endif

#include "errno2result.h"

/*%
 * There is only one variable in the entropy data structures that is not
 * system independent, but pulling the structure that uses it into this file
 * ultimately means pulling several other independent structures here also to
 * resolve their interdependencies.  Thus only the problem variable's type
 * is defined here.
 */
#define FILESOURCE_HANDLE_TYPE  int

typedef struct {
    int handle;
    enum    {
        isc_usocketsource_disconnected,
        isc_usocketsource_connecting,
        isc_usocketsource_connected,
        isc_usocketsource_ndesired,
        isc_usocketsource_wrote,
        isc_usocketsource_reading
    } status;
    size_t  sz_to_recv;
} isc_entropyusocketsource_t;

#include "../entropy.c"

static unsigned int
get_from_filesource(isc_entropysource_t *source, isc_uint32_t desired) {
    isc_entropy_t *ent = source->ent;
    unsigned char buf[128];
    int fd = source->sources.file.handle;
    ssize_t n, ndesired;
    unsigned int added;

    if (source->bad)
        return (0);

    desired = desired / 8 + (((desired & 0x07) > 0) ? 1 : 0);

    added = 0;
    while (desired > 0) {
        ndesired = ISC_MIN(desired, sizeof(buf));
        n = read(fd, buf, ndesired);
        if (n < 0) {
            if (errno == EAGAIN || errno == EINTR)
                goto out;
            goto err;
        }
        if (n == 0)
            goto err;

        entropypool_adddata(ent, buf, n, n * 8);
        added += n * 8;
        desired -= n;
    }
    goto out;

 err:
    (void)close(fd);
    source->sources.file.handle = -1;
    source->bad = ISC_TRUE;

 out:
    return (added);
}

static unsigned int
get_from_usocketsource(isc_entropysource_t *source, isc_uint32_t desired) {
    isc_entropy_t *ent = source->ent;
    unsigned char buf[128];
    int fd = source->sources.usocket.handle;
    ssize_t n = 0, ndesired;
    unsigned int added;
    size_t sz_to_recv = source->sources.usocket.sz_to_recv;

    if (source->bad)
        return (0);

    desired = desired / 8 + (((desired & 0x07) > 0) ? 1 : 0);

    added = 0;
    while (desired > 0) {
        ndesired = ISC_MIN(desired, sizeof(buf));
 eagain_loop:

        switch ( source->sources.usocket.status ) {
        case isc_usocketsource_ndesired:
            buf[0] = ndesired;
            if ((n = sendto(fd, buf, 1, 0, NULL, 0)) < 0) {
                if (errno == EWOULDBLOCK || errno == EINTR ||
                    errno == ECONNRESET)
                    goto out;
                goto err;
            }
            INSIST(n == 1);
            source->sources.usocket.status =
                        isc_usocketsource_wrote;
            goto eagain_loop;

        case isc_usocketsource_connecting:
        case isc_usocketsource_connected:
            buf[0] = 1;
            buf[1] = ndesired;
            if ((n = sendto(fd, buf, 2, 0, NULL, 0)) < 0) {
                if (errno == EWOULDBLOCK || errno == EINTR ||
                    errno == ECONNRESET)
                    goto out;
                goto err;
            }
            if (n == 1) {
                source->sources.usocket.status =
                    isc_usocketsource_ndesired;
                goto eagain_loop;
            }
            INSIST(n == 2);
            source->sources.usocket.status =
                        isc_usocketsource_wrote;
            /* FALLTHROUGH */

        case isc_usocketsource_wrote:
            if (recvfrom(fd, buf, 1, 0, NULL, NULL) != 1) {
                if (errno == EAGAIN) {
                    /*
                     * The problem of EAGAIN (try again
                     * later) is a major issue on HP-UX.
                     * Solaris actually tries the recvfrom
                     * call again, while HP-UX just dies.
                     * This code is an attempt to let the
                     * entropy pool fill back up (at least
                     * that's what I think the problem is.)
                     * We go to eagain_loop because if we
                     * just "break", then the "desired"
                     * amount gets borked.
                     */
#ifdef HAVE_NANOSLEEP
                    struct timespec ts;

                    ts.tv_sec = 0;
                    ts.tv_nsec = 1000000;
                    nanosleep(&ts, NULL);
#else
                    usleep(1000);
#endif
                    goto eagain_loop;
                }
                if (errno == EWOULDBLOCK || errno == EINTR)
                    goto out;
                goto err;
            }
            source->sources.usocket.status =
                    isc_usocketsource_reading;
            sz_to_recv = buf[0];
            source->sources.usocket.sz_to_recv = sz_to_recv;
            if (sz_to_recv > sizeof(buf))
                goto err;
            /* FALLTHROUGH */

        case isc_usocketsource_reading:
            if (sz_to_recv != 0U) {
                n = recv(fd, buf, sz_to_recv, 0);
                if (n < 0) {
                    if (errno == EWOULDBLOCK ||
                        errno == EINTR)
                        goto out;
                    goto err;
                }
            } else
                n = 0;
            break;

        default:
            goto err;
        }

        if ((size_t)n != sz_to_recv)
            source->sources.usocket.sz_to_recv -= n;
        else
            source->sources.usocket.status =
                isc_usocketsource_connected;

        if (n == 0)
            goto out;

        entropypool_adddata(ent, buf, n, n * 8);
        added += n * 8;
        desired -= n;
    }
    goto out;

 err:
    close(fd);
    source->bad = ISC_TRUE;
    source->sources.usocket.status = isc_usocketsource_disconnected;
    source->sources.usocket.handle = -1;

 out:
    return (added);
}

/*
 * Poll each source, trying to get data from it to stuff into the entropy
 * pool.
 */
static void
fillpool(isc_entropy_t *ent, unsigned int desired, isc_boolean_t blocking) {
    unsigned int added;
    unsigned int remaining;
    unsigned int needed;
    unsigned int nsource;
    isc_entropysource_t *source;

    REQUIRE(VALID_ENTROPY(ent));

    needed = desired;

    /*
     * This logic is a little strange, so an explanation is in order.
     *
     * If needed is 0, it means we are being asked to "fill to whatever
     * we think is best."  This means that if we have at least a
     * partially full pool (say, > 1/4th of the pool) we probably don't
     * need to add anything.
     *
     * Also, we will check to see if the "pseudo" count is too high.
     * If it is, try to mix in better data.  Too high is currently
     * defined as 1/4th of the pool.
     *
     * Next, if we are asked to add a specific bit of entropy, make
     * certain that we will do so.  Clamp how much we try to add to
     * (DIGEST_SIZE * 8 < needed < POOLBITS - entropy).
     *
     * Note that if we are in a blocking mode, we will only try to
     * get as much data as we need, not as much as we might want
     * to build up.
     */
    if (needed == 0) {
        REQUIRE(!blocking);

        if ((ent->pool.entropy >= RND_POOLBITS / 4)
            && (ent->pool.pseudo <= RND_POOLBITS / 4))
            return;

        needed = THRESHOLD_BITS * 4;
    } else {
        needed = ISC_MAX(needed, THRESHOLD_BITS);
        needed = ISC_MIN(needed, RND_POOLBITS);
    }

    /*
     * In any case, clamp how much we need to how much we can add.
     */
    needed = ISC_MIN(needed, RND_POOLBITS - ent->pool.entropy);

    /*
     * But wait!  If we're not yet initialized, we need at least
     *  THRESHOLD_BITS
     * of randomness.
     */
    if (ent->initialized < THRESHOLD_BITS)
        needed = ISC_MAX(needed, THRESHOLD_BITS - ent->initialized);

    /*
     * Poll each file source to see if we can read anything useful from
     * it.  XXXMLG When where are multiple sources, we should keep a
     * record of which one we last used so we can start from it (or the
     * next one) to avoid letting some sources build up entropy while
     * others are always drained.
     */

    added = 0;
    remaining = needed;
    if (ent->nextsource == NULL) {
        ent->nextsource = ISC_LIST_HEAD(ent->sources);
        if (ent->nextsource == NULL)
            return;
    }
    source = ent->nextsource;
 again_file:
    for (nsource = 0; nsource < ent->nsources; nsource++) {
        unsigned int got;

        if (remaining == 0)
            break;

        got = 0;

        switch ( source->type ) {
        case ENTROPY_SOURCETYPE_FILE:
            got = get_from_filesource(source, remaining);
            break;

        case ENTROPY_SOURCETYPE_USOCKET:
            got = get_from_usocketsource(source, remaining);
            break;
        }

        added += got;

        remaining -= ISC_MIN(remaining, got);

        source = ISC_LIST_NEXT(source, link);
        if (source == NULL)
            source = ISC_LIST_HEAD(ent->sources);
    }
    ent->nextsource = source;

    if (blocking && remaining != 0) {
        int fds;

        fds = wait_for_sources(ent);
        if (fds > 0)
            goto again_file;
    }

    /*
     * Here, if there are bits remaining to be had and we can block,
     * check to see if we have a callback source.  If so, call them.
     */
    source = ISC_LIST_HEAD(ent->sources);
    while ((remaining != 0) && (source != NULL)) {
        unsigned int got;

        got = 0;

        if (source->type == ENTROPY_SOURCETYPE_CALLBACK)
            got = get_from_callback(source, remaining, blocking);

        added += got;
        remaining -= ISC_MIN(remaining, got);

        if (added >= needed)
            break;

        source = ISC_LIST_NEXT(source, link);
    }

    /*
     * Mark as initialized if we've added enough data.
     */
    if (ent->initialized < THRESHOLD_BITS)
        ent->initialized += added;
}

static int
wait_for_sources(isc_entropy_t *ent) {
    isc_entropysource_t *source;
    int maxfd, fd;
    int cc;
    fd_set reads;
    fd_set writes;

    maxfd = -1;
    FD_ZERO(&reads);
    FD_ZERO(&writes);

    source = ISC_LIST_HEAD(ent->sources);
    while (source != NULL) {
        if (source->type == ENTROPY_SOURCETYPE_FILE) {
            fd = source->sources.file.handle;
            if (fd >= 0) {
                maxfd = ISC_MAX(maxfd, fd);
                FD_SET(fd, &reads);
            }
        }
        if (source->type == ENTROPY_SOURCETYPE_USOCKET) {
            fd = source->sources.usocket.handle;
            if (fd >= 0) {
                switch (source->sources.usocket.status) {
                case isc_usocketsource_disconnected:
                    break;
                case isc_usocketsource_connecting:
                case isc_usocketsource_connected:
                case isc_usocketsource_ndesired:
                    maxfd = ISC_MAX(maxfd, fd);
                    FD_SET(fd, &writes);
                    break;
                case isc_usocketsource_wrote:
                case isc_usocketsource_reading:
                    maxfd = ISC_MAX(maxfd, fd);
                    FD_SET(fd, &reads);
                    break;
                }
            }
        }
        source = ISC_LIST_NEXT(source, link);
    }

    if (maxfd < 0)
        return (-1);

    cc = select(maxfd + 1, &reads, &writes, NULL, NULL);
    if (cc < 0)
        return (-1);

    return (cc);
}

static void
destroyfilesource(isc_entropyfilesource_t *source) {
    (void)close(source->handle);
}

static void
destroyusocketsource(isc_entropyusocketsource_t *source) {
    close(source->handle);
}

/*
 * Make a fd non-blocking
 */
static isc_result_t
make_nonblock(int fd) {
    int ret;
    int flags;
    char strbuf[ISC_STRERRORSIZE];
#ifdef USE_FIONBIO_IOCTL
    int on = 1;

    ret = ioctl(fd, FIONBIO, (char *)&on);
#else
    flags = fcntl(fd, F_GETFL, 0);
    flags |= PORT_NONBLOCK;
    ret = fcntl(fd, F_SETFL, flags);
#endif

    if (ret == -1) {
        isc__strerror(errno, strbuf, sizeof(strbuf));
        UNEXPECTED_ERROR(__FILE__, __LINE__,
#ifdef USE_FIONBIO_IOCTL
                 "ioctl(%d, FIONBIO, &on): %s", fd,
#else
                 "fcntl(%d, F_SETFL, %d): %s", fd, flags,
#endif
                 strbuf);

        return (ISC_R_UNEXPECTED);
    }

    return (ISC_R_SUCCESS);
}

isc_result_t
isc_entropy_createfilesource(isc_entropy_t *ent, const char *fname) {
    int fd;
    struct stat _stat;
    isc_boolean_t is_usocket = ISC_FALSE;
    isc_boolean_t is_connected = ISC_FALSE;
    isc_result_t ret;
    isc_entropysource_t *source;

    REQUIRE(VALID_ENTROPY(ent));
    REQUIRE(fname != NULL);

    LOCK(&ent->lock);

    if (stat(fname, &_stat) < 0) {
        ret = isc__errno2result(errno);
        goto errout;
    }
    /*
     * Solaris 2.5.1 does not have support for sockets (S_IFSOCK),
     * but it does return type S_IFIFO (the OS believes that
     * the socket is a fifo).  This may be an issue if we tell
     * the program to look at an actual FIFO as its source of
     * entropy.
     */
#if defined(S_ISSOCK)
    if (S_ISSOCK(_stat.st_mode))
        is_usocket = ISC_TRUE;
#endif
#if defined(S_ISFIFO) && defined(sun)
    if (S_ISFIFO(_stat.st_mode))
        is_usocket = ISC_TRUE;
#endif
    if (is_usocket)
        fd = socket(PF_UNIX, SOCK_STREAM, 0);
    else
        fd = open(fname, O_RDONLY | PORT_NONBLOCK, 0);

    if (fd < 0) {
        ret = isc__errno2result(errno);
        goto errout;
    }

    ret = make_nonblock(fd);
    if (ret != ISC_R_SUCCESS)
        goto closefd;

    if (is_usocket) {
        struct sockaddr_un sname;

        memset(&sname, 0, sizeof(sname));
        sname.sun_family = AF_UNIX;
        strlcpy(sname.sun_path, fname, sizeof(sname.sun_path));
#ifdef ISC_PLATFORM_HAVESALEN
#if !defined(SUN_LEN)
#define SUN_LEN(su) \
    (sizeof(*(su)) - sizeof((su)->sun_path) + strlen((su)->sun_path))
#endif
        sname.sun_len = SUN_LEN(&sname);
#endif

        if (connect(fd, (struct sockaddr *) &sname,
                sizeof(struct sockaddr_un)) < 0) {
            if (errno != EINPROGRESS) {
                ret = isc__errno2result(errno);
                goto closefd;
            }
        } else
            is_connected = ISC_TRUE;
    }

    source = isc_mem_get(ent->mctx, sizeof(isc_entropysource_t));
    if (source == NULL) {
        ret = ISC_R_NOMEMORY;
        goto closefd;
    }

    /*
     * From here down, no failures can occur.
     */
    source->magic = SOURCE_MAGIC;
    source->ent = ent;
    source->total = 0;
    source->bad = ISC_FALSE;
    memset(source->name, 0, sizeof(source->name));
    ISC_LINK_INIT(source, link);
    if (is_usocket) {
        source->sources.usocket.handle = fd;
        if (is_connected)
            source->sources.usocket.status =
                    isc_usocketsource_connected;
        else
            source->sources.usocket.status =
                    isc_usocketsource_connecting;
        source->sources.usocket.sz_to_recv = 0;
        source->type = ENTROPY_SOURCETYPE_USOCKET;
    } else {
        source->sources.file.handle = fd;
        source->type = ENTROPY_SOURCETYPE_FILE;
    }

    /*
     * Hook it into the entropy system.
     */
    ISC_LIST_APPEND(ent->sources, source, link);
    ent->nsources++;

    UNLOCK(&ent->lock);
    return (ISC_R_SUCCESS);

 closefd:
    (void)close(fd);

 errout:
    UNLOCK(&ent->lock);

    return (ret);
}