lib/kdb/kdb_log.c

/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <k5-int.h>
#include <stdlib.h>
#include <limits.h>
#include <syslog.h>
#include "kdb5.h"
#include "kdb_log.h"
#include "kdb5int.h"

#ifndef MAP_FAILED
#define MAP_FAILED ((void *)-1)
#endif

/* This module includes all the necessary functions that create and modify the
 * Kerberos principal update and header logs. */

#define getpagesize() sysconf(_SC_PAGESIZE)

static int pagesize = 0;

#define INIT_ULOG(ctx)                          \
    log_ctx = ctx->kdblog_context;              \
    assert(log_ctx != NULL);                    \
    ulog = log_ctx->ulog;                       \
    assert(ulog != NULL)

/* Initialize context->kdblog_context if it does not yet exist, and return it.
 * Return NULL on allocation failure. */
static kdb_log_context *
create_log_context(krb5_context context)
{
    kdb_log_context *log_ctx;

    if (context->kdblog_context != NULL)
        return context->kdblog_context;
    log_ctx = calloc(1, sizeof(*log_ctx));
    if (log_ctx == NULL)
        return NULL;
    log_ctx->ulogfd = -1;
    context->kdblog_context = log_ctx;
    return log_ctx;
}

static inline krb5_boolean
time_equal(const kdbe_time_t *a, const kdbe_time_t *b)
{
    return a->seconds == b->seconds && a->useconds == b->useconds;
}

static void
time_current(kdbe_time_t *out)
{
    struct timeval timestamp;

    (void)gettimeofday(&timestamp, NULL);
    out->seconds = timestamp.tv_sec;
    out->useconds = timestamp.tv_usec;
}

/* Sync update entry to disk. */
static void
sync_update(kdb_hlog_t *ulog, kdb_ent_header_t *upd)
{
    unsigned long start, end, size;

    if (!pagesize)
        pagesize = getpagesize();

    start = (unsigned long)upd & ~(pagesize - 1);

    end = ((unsigned long)upd + ulog->kdb_block + (pagesize - 1)) &
        ~(pagesize - 1);

    size = end - start;
    if (msync((caddr_t)start, size, MS_SYNC)) {
        /* Couldn't sync to disk, let's panic. */
        syslog(LOG_ERR, _("could not sync ulog update to disk"));
        abort();
    }
}

/* Sync memory to disk for the update log header. */
static void
sync_header(kdb_hlog_t *ulog)
{
    if (!pagesize)
        pagesize = getpagesize();

    if (msync((caddr_t)ulog, pagesize, MS_SYNC)) {
        /* Couldn't sync to disk, let's panic. */
        syslog(LOG_ERR, _("could not sync ulog header to disk"));
        abort();
    }
}

/* Return true if the ulog entry for sno matches sno and timestamp. */
static krb5_boolean
check_sno(kdb_log_context *log_ctx, kdb_sno_t sno,
          const kdbe_time_t *timestamp)
{
    unsigned int indx = (sno - 1) % log_ctx->ulogentries;
    kdb_ent_header_t *ent = INDEX(log_ctx->ulog, indx);

    return ent->kdb_entry_sno == sno && time_equal(&ent->kdb_time, timestamp);
}

/*
 * Check last against our ulog and determine whether it is up to date
 * (UPDATE_NIL), so far out of date that a full dump is required
 * (UPDATE_FULL_RESYNC_NEEDED), or okay to update with ulog entries
 * (UPDATE_OK).
 */
static update_status_t
get_sno_status(kdb_log_context *log_ctx, const kdb_last_t *last)
{
    kdb_hlog_t *ulog = log_ctx->ulog;

    /* If last matches the ulog's last serial number and time exactly, it are
     * up to date even if the ulog is empty. */
    if (last->last_sno == ulog->kdb_last_sno &&
        time_equal(&last->last_time, &ulog->kdb_last_time))
        return UPDATE_NIL;

    /* If our ulog is empty or does not contain last_sno, a full resync is
     * required. */
    if (ulog->kdb_num == 0 || last->last_sno > ulog->kdb_last_sno ||
        last->last_sno < ulog->kdb_first_sno)
        return UPDATE_FULL_RESYNC_NEEDED;

    /* If the timestamp in our ulog entry does not match last, then sno was
     * reused and a full resync is required. */
    if (!check_sno(log_ctx, last->last_sno, &last->last_time))
        return UPDATE_FULL_RESYNC_NEEDED;

    /* last is not fully up to date, but can be updated using our ulog. */
    return UPDATE_OK;
}

/* Extend update log file. */
static krb5_error_code
extend_file_to(int fd, unsigned int new_size)
{
    off_t current_offset;
    static const char zero[512];
    ssize_t wrote_size;
    size_t write_size;

    current_offset = lseek(fd, 0, SEEK_END);
    if (current_offset < 0)
        return errno;
    if (new_size > INT_MAX)
        return EINVAL;
    while (current_offset < (off_t)new_size) {
        write_size = new_size - current_offset;
        if (write_size > 512)
            write_size = 512;
        wrote_size = write(fd, zero, write_size);
        if (wrote_size < 0)
            return errno;
        if (wrote_size == 0)
            return EINVAL;
        current_offset += wrote_size;
        write_size = new_size - current_offset;
    }
    return 0;
}

/*
 * Resize the array elements.  We reinitialize the update log rather than
 * unrolling the the log and copying it over to a temporary log for obvious
 * performance reasons.  Replicas will subsequently do a full resync, but the
 * need for resizing should be very small.
 */
static krb5_error_code
resize(kdb_hlog_t *ulog, uint32_t ulogentries, int ulogfd,
       unsigned int recsize)
{
    unsigned int new_block, new_size;

    if (ulog == NULL)
        return KRB5_LOG_ERROR;

    new_size = sizeof(kdb_hlog_t);
    new_block = (recsize / ULOG_BLOCK) + 1;
    new_block *= ULOG_BLOCK;
    new_size += ulogentries * new_block;

    if (new_size > MAXLOGLEN)
        return KRB5_LOG_ERROR;

    /* Reinit log with new block size. */
    memset(ulog, 0, sizeof(*ulog));
    ulog->kdb_hmagic = KDB_ULOG_HDR_MAGIC;
    ulog->db_version_num = KDB_VERSION;
    ulog->kdb_state = KDB_STABLE;
    ulog->kdb_block = new_block;
    sync_header(ulog);

    /* Expand log considering new block size. */
    return extend_file_to(ulogfd, new_size);
}

/* Set the ulog to contain only a dummy entry with the given serial number and
 * timestamp. */
static void
set_dummy(kdb_log_context *log_ctx, kdb_sno_t sno, const kdbe_time_t *kdb_time)
{
    kdb_hlog_t *ulog = log_ctx->ulog;
    kdb_ent_header_t *ent = INDEX(ulog, (sno - 1) % log_ctx->ulogentries);

    memset(ent, 0, sizeof(*ent));
    ent->kdb_umagic = KDB_ULOG_MAGIC;
    ent->kdb_entry_sno = sno;
    ent->kdb_time = *kdb_time;
    sync_update(ulog, ent);

    ulog->kdb_num = 1;
    ulog->kdb_first_sno = ulog->kdb_last_sno = sno;
    ulog->kdb_first_time = ulog->kdb_last_time = *kdb_time;
}

/* Reinitialize the ulog header, starting from sno 1 with the current time. */
static void
reset_ulog(kdb_log_context *log_ctx)
{
    kdbe_time_t kdb_time;
    kdb_hlog_t *ulog = log_ctx->ulog;

    memset(ulog, 0, sizeof(*ulog));
    ulog->kdb_hmagic = KDB_ULOG_HDR_MAGIC;
    ulog->db_version_num = KDB_VERSION;
    ulog->kdb_block = ULOG_BLOCK;

    /* Create a dummy entry to remember the timestamp for downstreams. */
    time_current(&kdb_time);
    set_dummy(log_ctx, 1, &kdb_time);
    ulog->kdb_state = KDB_STABLE;
    sync_header(ulog);
}

/*
 * If any database operations will be invoked while the ulog lock is held, the
 * caller must explicitly lock the database before locking the ulog, or
 * deadlock may result.
 */
static krb5_error_code
lock_ulog(krb5_context context, int mode)
{
    kdb_log_context *log_ctx = NULL;
    kdb_hlog_t *ulog = NULL;

    INIT_ULOG(context);
    return krb5_lock_file(context, log_ctx->ulogfd, mode);
}

static void
unlock_ulog(krb5_context context)
{
    (void)lock_ulog(context, KRB5_LOCKMODE_UNLOCK);
}

/*
 * Add an update to the log.  The update's kdb_entry_sno and kdb_time fields
 * must already be set.  The layout of the update log looks like:
 *
 * header log -> [ update header -> xdr(kdb_incr_update_t) ], ...
 */
static krb5_error_code
store_update(kdb_log_context *log_ctx, kdb_incr_update_t *upd)
{
    XDR xdrs;
    kdb_ent_header_t *indx_log;
    unsigned int i, recsize;
    unsigned long upd_size;
    krb5_error_code retval;
    kdb_hlog_t *ulog = log_ctx->ulog;
    uint32_t ulogentries = log_ctx->ulogentries;

    upd_size = xdr_sizeof((xdrproc_t)xdr_kdb_incr_update_t, upd);

    recsize = sizeof(kdb_ent_header_t) + upd_size;

    if (recsize > ulog->kdb_block) {
        retval = resize(ulog, ulogentries, log_ctx->ulogfd, recsize);
        if (retval)
            return retval;
    }

    ulog->kdb_state = KDB_UNSTABLE;

    i = (upd->kdb_entry_sno - 1) % ulogentries;
    indx_log = INDEX(ulog, i);

    memset(indx_log, 0, ulog->kdb_block);
    indx_log->kdb_umagic = KDB_ULOG_MAGIC;
    indx_log->kdb_entry_size = upd_size;
    indx_log->kdb_entry_sno = upd->kdb_entry_sno;
    indx_log->kdb_time = upd->kdb_time;
    indx_log->kdb_commit = FALSE;

    xdrmem_create(&xdrs, (char *)indx_log->entry_data,
                  indx_log->kdb_entry_size, XDR_ENCODE);
    if (!xdr_kdb_incr_update_t(&xdrs, upd))
        return KRB5_LOG_CONV;

    indx_log->kdb_commit = TRUE;
    sync_update(ulog, indx_log);

    /* Modify the ulog header to reflect the new update. */
    ulog->kdb_last_sno = upd->kdb_entry_sno;
    ulog->kdb_last_time = upd->kdb_time;
    if (ulog->kdb_num == 0) {
        /* We should only see this in old ulogs. */
        ulog->kdb_num = 1;
        ulog->kdb_first_sno = upd->kdb_entry_sno;
        ulog->kdb_first_time = upd->kdb_time;
    } else if (ulog->kdb_num < ulogentries) {
        ulog->kdb_num++;
    } else {
        /* We are circling; set kdb_first_sno and time to the next update. */
        i = upd->kdb_entry_sno % ulogentries;
        indx_log = INDEX(ulog, i);
        ulog->kdb_first_sno = indx_log->kdb_entry_sno;
        ulog->kdb_first_time = indx_log->kdb_time;
    }

    ulog->kdb_state = KDB_STABLE;
    sync_header(ulog);
    return 0;
}

/* Add an entry to the update log. */
krb5_error_code
ulog_add_update(krb5_context context, kdb_incr_update_t *upd)
{
    krb5_error_code ret;
    kdb_log_context *log_ctx;
    kdb_hlog_t *ulog;

    INIT_ULOG(context);
    ret = lock_ulog(context, KRB5_LOCKMODE_EXCLUSIVE);
    if (ret)
        return ret;

    /* If we have reached the last possible serial number, reinitialize the
     * ulog and start over.  Replicas will do a full resync. */
    if (ulog->kdb_last_sno == (kdb_sno_t)-1)
        reset_ulog(log_ctx);

    upd->kdb_entry_sno = ulog->kdb_last_sno + 1;
    time_current(&upd->kdb_time);
    ret = store_update(log_ctx, upd);
    unlock_ulog(context);
    return ret;
}

/* Used by the replica to update its hash db from the incr update log. */
krb5_error_code
ulog_replay(krb5_context context, kdb_incr_result_t *incr_ret, char **db_args)
{
    krb5_db_entry *entry = NULL;
    kdb_incr_update_t *upd = NULL, *fupd;
    int i, no_of_updates;
    krb5_error_code retval;
    krb5_principal dbprinc;
    char *dbprincstr;
    kdb_log_context *log_ctx;
    kdb_hlog_t *ulog = NULL;

    INIT_ULOG(context);

    retval = krb5_db_open(context, db_args,
                          KRB5_KDB_OPEN_RW | KRB5_KDB_SRV_TYPE_ADMIN);
    if (retval)
        return retval;

    no_of_updates = incr_ret->updates.kdb_ulog_t_len;
    upd = incr_ret->updates.kdb_ulog_t_val;
    fupd = upd;

    for (i = 0; i < no_of_updates; i++) {
        if (!upd->kdb_commit)
            continue;

        /* Replay this update in the database. */
        if (upd->kdb_deleted) {
            dbprincstr = k5memdup0(upd->kdb_princ_name.utf8str_t_val,
                                   upd->kdb_princ_name.utf8str_t_len, &retval);
            if (dbprincstr == NULL)
                goto cleanup;

            retval = krb5_parse_name(context, dbprincstr, &dbprinc);
            free(dbprincstr);
            if (retval)
                goto cleanup;

            retval = krb5int_delete_principal_no_log(context, dbprinc);
            krb5_free_principal(context, dbprinc);
            if (retval == KRB5_KDB_NOENTRY)
                retval = 0;
            if (retval)
                goto cleanup;
        } else {
            retval = ulog_conv_2dbentry(context, &entry, upd);
            if (retval)
                goto cleanup;

            retval = krb5int_put_principal_no_log(context, entry);
            krb5_db_free_principal(context, entry);
            if (retval)
                goto cleanup;
        }

        retval = lock_ulog(context, KRB5_LOCKMODE_EXCLUSIVE);
        if (retval)
            goto cleanup;

        /* If (unexpectedly) this update does not follow the last one we
         * stored, discard any previous ulog state. */
        if (ulog->kdb_num != 0 && upd->kdb_entry_sno != ulog->kdb_last_sno + 1)
            reset_ulog(log_ctx);

        /* Store this update in the ulog for any downstream KDCs. */
        retval = store_update(log_ctx, upd);
        unlock_ulog(context);
        if (retval)
            goto cleanup;

        upd++;
    }

cleanup:
    if (retval)
        (void)ulog_init_header(context);
    if (fupd)
        ulog_free_entries(fupd, no_of_updates);
    return retval;
}

/* Reinitialize the log header. */
krb5_error_code
ulog_init_header(krb5_context context)
{
    krb5_error_code ret;
    kdb_log_context *log_ctx;
    kdb_hlog_t *ulog;

    INIT_ULOG(context);
    ret = lock_ulog(context, KRB5_LOCKMODE_EXCLUSIVE);
    if (ret)
        return ret;
    reset_ulog(log_ctx);
    unlock_ulog(context);
    return 0;
}

/* Map the log file to memory for performance and simplicity. */
krb5_error_code
ulog_map(krb5_context context, const char *logname, uint32_t ulogentries)
{
    struct stat st;
    krb5_error_code retval;
    uint32_t filesize;
    kdb_log_context *log_ctx;
    kdb_hlog_t *ulog = NULL;
    krb5_boolean locked = FALSE;

    log_ctx = create_log_context(context);
    if (log_ctx == NULL)
        return ENOMEM;

    if (stat(logname, &st) == -1) {
        log_ctx->ulogfd = open(logname, O_RDWR | O_CREAT, 0600);
        if (log_ctx->ulogfd == -1) {
            retval = errno;
            goto cleanup;
        }

        filesize = sizeof(kdb_hlog_t) + ulogentries * ULOG_BLOCK;
        retval = extend_file_to(log_ctx->ulogfd, filesize);
        if (retval)
            goto cleanup;
    } else {
        log_ctx->ulogfd = open(logname, O_RDWR, 0600);
        if (log_ctx->ulogfd == -1) {
            retval = errno;
            goto cleanup;
        }
    }

    ulog = mmap(0, MAXLOGLEN, PROT_READ | PROT_WRITE, MAP_SHARED,
                log_ctx->ulogfd, 0);
    if (ulog == MAP_FAILED) {
        retval = errno;
        goto cleanup;
    }
    log_ctx->ulog = ulog;
    log_ctx->ulogentries = ulogentries;

    retval = lock_ulog(context, KRB5_LOCKMODE_EXCLUSIVE);
    if (retval)
        goto cleanup;
    locked = TRUE;

    if (ulog->kdb_hmagic != KDB_ULOG_HDR_MAGIC) {
        if (ulog->kdb_hmagic != 0) {
            retval = KRB5_LOG_CORRUPT;
            goto cleanup;
        }
        reset_ulog(log_ctx);
    }

    /* Reinit ulog if ulogentries changed such that we have too many entries or
     * our first or last entry was written to the wrong location. */
    if (ulog->kdb_num != 0 &&
        (ulog->kdb_num > ulogentries ||
         !check_sno(log_ctx, ulog->kdb_first_sno, &ulog->kdb_first_time) ||
         !check_sno(log_ctx, ulog->kdb_last_sno, &ulog->kdb_last_time)))
        reset_ulog(log_ctx);

    if (ulog->kdb_num != ulogentries) {
        /* Expand the ulog file if it isn't big enough. */
        filesize = sizeof(kdb_hlog_t) + ulogentries * ulog->kdb_block;
        retval = extend_file_to(log_ctx->ulogfd, filesize);
        if (retval)
            goto cleanup;
    }

cleanup:
    if (locked)
        unlock_ulog(context);
    if (retval)
        ulog_fini(context);
    return retval;
}

/* Get the last set of updates seen, (last+1) to n is returned. */
krb5_error_code
ulog_get_entries(krb5_context context, const kdb_last_t *last,
                 kdb_incr_result_t *ulog_handle)
{
    XDR xdrs;
    kdb_ent_header_t *indx_log;
    kdb_incr_update_t *upd;
    unsigned int indx, count;
    uint32_t sno;
    krb5_error_code retval;
    kdb_log_context *log_ctx;
    kdb_hlog_t *ulog = NULL;
    uint32_t ulogentries;

    INIT_ULOG(context);
    ulogentries = log_ctx->ulogentries;

    retval = lock_ulog(context, KRB5_LOCKMODE_SHARED);
    if (retval)
        return retval;

    /* If another process terminated mid-update, reset the ulog and force full
     * resyncs. */
    if (ulog->kdb_state != KDB_STABLE)
        reset_ulog(log_ctx);

    ulog_handle->ret = get_sno_status(log_ctx, last);
    if (ulog_handle->ret != UPDATE_OK)
        goto cleanup;

    sno = last->last_sno;
    count = ulog->kdb_last_sno - sno;
    upd = calloc(count, sizeof(kdb_incr_update_t));
    if (upd == NULL) {
        ulog_handle->ret = UPDATE_ERROR;
        retval = ENOMEM;
        goto cleanup;
    }
    ulog_handle->updates.kdb_ulog_t_val = upd;

    for (; sno < ulog->kdb_last_sno; sno++) {
        indx = sno % ulogentries;
        indx_log = INDEX(ulog, indx);

        memset(upd, 0, sizeof(kdb_incr_update_t));
        xdrmem_create(&xdrs, (char *)indx_log->entry_data,
                      indx_log->kdb_entry_size, XDR_DECODE);
        if (!xdr_kdb_incr_update_t(&xdrs, upd)) {
            ulog_handle->ret = UPDATE_ERROR;
            retval = KRB5_LOG_CONV;
            goto cleanup;
        }

        /* Mark commitment since we didn't want to decode and encode the incr
         * update record the first time. */
        upd->kdb_commit = indx_log->kdb_commit;
        upd++;
    }

    ulog_handle->updates.kdb_ulog_t_len = count;

    ulog_handle->lastentry.last_sno = ulog->kdb_last_sno;
    ulog_handle->lastentry.last_time.seconds = ulog->kdb_last_time.seconds;
    ulog_handle->lastentry.last_time.useconds = ulog->kdb_last_time.useconds;
    ulog_handle->ret = UPDATE_OK;

cleanup:
    unlock_ulog(context);
    return retval;
}

krb5_error_code
ulog_set_role(krb5_context ctx, iprop_role role)
{
    if (create_log_context(ctx) == NULL)
        return ENOMEM;
    ctx->kdblog_context->iproprole = role;
    return 0;
}

update_status_t
ulog_get_sno_status(krb5_context context, const kdb_last_t *last)
{
    update_status_t status;

    if (lock_ulog(context, KRB5_LOCKMODE_SHARED) != 0)
        return UPDATE_ERROR;
    status = get_sno_status(context->kdblog_context, last);
    unlock_ulog(context);
    return status;
}

krb5_error_code
ulog_get_last(krb5_context context, kdb_last_t *last_out)
{
    krb5_error_code ret;
    kdb_log_context *log_ctx;
    kdb_hlog_t *ulog;

    INIT_ULOG(context);
    ret = lock_ulog(context, KRB5_LOCKMODE_SHARED);
    if (ret)
        return ret;
    last_out->last_sno = log_ctx->ulog->kdb_last_sno;
    last_out->last_time = log_ctx->ulog->kdb_last_time;
    unlock_ulog(context);
    return 0;
}

krb5_error_code
ulog_set_last(krb5_context context, const kdb_last_t *last)
{
    krb5_error_code ret;
    kdb_log_context *log_ctx;
    kdb_hlog_t *ulog;

    INIT_ULOG(context);
    ret = lock_ulog(context, KRB5_LOCKMODE_EXCLUSIVE);
    if (ret)
        return ret;

    set_dummy(log_ctx, last->last_sno, &last->last_time);
    sync_header(ulog);
    unlock_ulog(context);
    return 0;
}

void
ulog_fini(krb5_context context)
{
    kdb_log_context *log_ctx = context->kdblog_context;

    if (log_ctx == NULL)
        return;
    if (log_ctx->ulog != NULL)
        munmap(log_ctx->ulog, MAXLOGLEN);
    if (log_ctx->ulogfd != -1)
        close(log_ctx->ulogfd);
    free(log_ctx);
    context->kdblog_context = NULL;
}