mod_auth_digest.c

apache服务器源代码（版本号：2.2.2）

    }
}

/*
 * configuration code
 */

static void *create_digest_dir_config(apr_pool_t *p, char *dir)
{
    digest_config_rec *conf;

    if (dir == NULL) {
        return NULL;
    }

    conf = (digest_config_rec *) apr_pcalloc(p, sizeof(digest_config_rec));
    if (conf) {
        conf->qop_list       = apr_palloc(p, sizeof(char*));
        conf->qop_list[0]    = NULL;
        conf->nonce_lifetime = DFLT_NONCE_LIFE;
        conf->dir_name       = apr_pstrdup(p, dir);
        conf->algorithm      = DFLT_ALGORITHM;
    }

    return conf;
}

static const char *set_realm(cmd_parms *cmd, void *config, const char *realm)
{
    digest_config_rec *conf = (digest_config_rec *) config;

    /* The core already handles the realm, but it's just too convenient to
     * grab it ourselves too and cache some setups. However, we need to
     * let the core get at it too, which is why we decline at the end -
     * this relies on the fact that http_core is last in the list.
     */
    conf->realm = realm;

    /* we precompute the part of the nonce hash that is constant (well,
     * the host:port would be too, but that varies for .htaccess files
     * and directives outside a virtual host section)
     */
    apr_sha1_init(&conf->nonce_ctx);
    apr_sha1_update_binary(&conf->nonce_ctx, secret, sizeof(secret));
    apr_sha1_update_binary(&conf->nonce_ctx, (const unsigned char *) realm,
                           strlen(realm));

    return DECLINE_CMD;
}

static const char *add_authn_provider(cmd_parms *cmd, void *config,
                                      const char *arg)
{
    digest_config_rec *conf = (digest_config_rec*)config;
    authn_provider_list *newp;

    newp = apr_pcalloc(cmd->pool, sizeof(authn_provider_list));
    newp->provider_name = apr_pstrdup(cmd->pool, arg);

    /* lookup and cache the actual provider now */
    newp->provider = ap_lookup_provider(AUTHN_PROVIDER_GROUP,
                                        newp->provider_name, "0");

    if (newp->provider == NULL) {
       /* by the time they use it, the provider should be loaded and
           registered with us. */
        return apr_psprintf(cmd->pool,
                            "Unknown Authn provider: %s",
                            newp->provider_name);
    }

    if (!newp->provider->get_realm_hash) {
        /* if it doesn't provide the appropriate function, reject it */
        return apr_psprintf(cmd->pool,
                            "The '%s' Authn provider doesn't support "
                            "Digest Authentication", newp->provider_name);
    }

    /* Add it to the list now. */
    if (!conf->providers) {
        conf->providers = newp;
    }
    else {
        authn_provider_list *last = conf->providers;

        while (last->next) {
            last = last->next;
        }
        last->next = newp;
    }

    return NULL;
}

static const char *set_qop(cmd_parms *cmd, void *config, const char *op)
{
    digest_config_rec *conf = (digest_config_rec *) config;
    char **tmp;
    int cnt;

    if (!strcasecmp(op, "none")) {
        if (conf->qop_list[0] == NULL) {
            conf->qop_list = apr_palloc(cmd->pool, 2 * sizeof(char*));
            conf->qop_list[1] = NULL;
        }
        conf->qop_list[0] = "none";
        return NULL;
    }

    if (!strcasecmp(op, "auth-int")) {
        ap_log_error(APLOG_MARK, APLOG_WARNING, 0, cmd->server,
                     "Digest: WARNING: qop `auth-int' currently only works "
                     "correctly for responses with no entity");
    }
    else if (strcasecmp(op, "auth")) {
        return apr_pstrcat(cmd->pool, "Unrecognized qop: ", op, NULL);
    }

    for (cnt = 0; conf->qop_list[cnt] != NULL; cnt++)
        ;

    tmp = apr_palloc(cmd->pool, (cnt + 2) * sizeof(char*));
    memcpy(tmp, conf->qop_list, cnt*sizeof(char*));
    tmp[cnt]   = apr_pstrdup(cmd->pool, op);
    tmp[cnt+1] = NULL;
    conf->qop_list = tmp;

    return NULL;
}

static const char *set_nonce_lifetime(cmd_parms *cmd, void *config,
                                      const char *t)
{
    char *endptr;
    long  lifetime;

    lifetime = strtol(t, &endptr, 10);
    if (endptr < (t+strlen(t)) && !apr_isspace(*endptr)) {
        return apr_pstrcat(cmd->pool,
                           "Invalid time in AuthDigestNonceLifetime: ",
                           t, NULL);
    }

    ((digest_config_rec *) config)->nonce_lifetime = apr_time_from_sec(lifetime);
    return NULL;
}

static const char *set_nonce_format(cmd_parms *cmd, void *config,
                                    const char *fmt)
{
    ((digest_config_rec *) config)->nonce_format = fmt;
    return "AuthDigestNonceFormat is not implemented (yet)";
}

static const char *set_nc_check(cmd_parms *cmd, void *config, int flag)
{
    if (flag && !client_shm)
        ap_log_error(APLOG_MARK, APLOG_WARNING, 0,
                     cmd->server, "Digest: WARNING: nonce-count checking "
                     "is not supported on platforms without shared-memory "
                     "support - disabling check");

    ((digest_config_rec *) config)->check_nc = flag;
    return NULL;
}

static const char *set_algorithm(cmd_parms *cmd, void *config, const char *alg)
{
    if (!strcasecmp(alg, "MD5-sess")) {
        if (!client_shm) {
            ap_log_error(APLOG_MARK, APLOG_WARNING, 0,
                         cmd->server, "Digest: WARNING: algorithm `MD5-sess' "
                         "is not supported on platforms without shared-memory "
                         "support - reverting to MD5");
            alg = "MD5";
        }
    }
    else if (strcasecmp(alg, "MD5")) {
        return apr_pstrcat(cmd->pool, "Invalid algorithm in AuthDigestAlgorithm: ", alg, NULL);
    }

    ((digest_config_rec *) config)->algorithm = alg;
    return NULL;
}

static const char *set_uri_list(cmd_parms *cmd, void *config, const char *uri)
{
    digest_config_rec *c = (digest_config_rec *) config;
    if (c->uri_list) {
        c->uri_list[strlen(c->uri_list)-1] = '\0';
        c->uri_list = apr_pstrcat(cmd->pool, c->uri_list, " ", uri, "\"", NULL);
    }
    else {
        c->uri_list = apr_pstrcat(cmd->pool, ", domain=\"", uri, "\"", NULL);
    }
    return NULL;
}

static const char *set_shmem_size(cmd_parms *cmd, void *config,
                                  const char *size_str)
{
    char *endptr;
    long  size, min;

    size = strtol(size_str, &endptr, 10);
    while (apr_isspace(*endptr)) endptr++;
    if (*endptr == '\0' || *endptr == 'b' || *endptr == 'B') {
        ;
    }
    else if (*endptr == 'k' || *endptr == 'K') {
        size *= 1024;
    }
    else if (*endptr == 'm' || *endptr == 'M') {
        size *= 1048576;
    }
    else {
        return apr_pstrcat(cmd->pool, "Invalid size in AuthDigestShmemSize: ",
                          size_str, NULL);
    }

    min = sizeof(*client_list) + sizeof(client_entry*) + sizeof(client_entry);
    if (size < min) {
        return apr_psprintf(cmd->pool, "size in AuthDigestShmemSize too small: "
                           "%ld < %ld", size, min);
    }

    shmem_size  = size;
    num_buckets = (size - sizeof(*client_list)) /
                  (sizeof(client_entry*) + HASH_DEPTH * sizeof(client_entry));
    if (num_buckets == 0) {
        num_buckets = 1;
    }
    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, cmd->server,
                 "Digest: Set shmem-size: %ld, num-buckets: %ld", shmem_size,
                 num_buckets);

    return NULL;
}

static const command_rec digest_cmds[] =
{
    AP_INIT_TAKE1("AuthName", set_realm, NULL, OR_AUTHCFG,
     "The authentication realm (e.g. \"Members Only\")"),
    AP_INIT_ITERATE("AuthDigestProvider", add_authn_provider, NULL, OR_AUTHCFG,
                     "specify the auth providers for a directory or location"),
    AP_INIT_ITERATE("AuthDigestQop", set_qop, NULL, OR_AUTHCFG,
     "A list of quality-of-protection options"),
    AP_INIT_TAKE1("AuthDigestNonceLifetime", set_nonce_lifetime, NULL, OR_AUTHCFG,
     "Maximum lifetime of the server nonce (seconds)"),
    AP_INIT_TAKE1("AuthDigestNonceFormat", set_nonce_format, NULL, OR_AUTHCFG,
     "The format to use when generating the server nonce"),
    AP_INIT_FLAG("AuthDigestNcCheck", set_nc_check, NULL, OR_AUTHCFG,
     "Whether or not to check the nonce-count sent by the client"),
    AP_INIT_TAKE1("AuthDigestAlgorithm", set_algorithm, NULL, OR_AUTHCFG,
     "The algorithm used for the hash calculation"),
    AP_INIT_ITERATE("AuthDigestDomain", set_uri_list, NULL, OR_AUTHCFG,
     "A list of URI's which belong to the same protection space as the current URI"),
    AP_INIT_TAKE1("AuthDigestShmemSize", set_shmem_size, NULL, RSRC_CONF,
     "The amount of shared memory to allocate for keeping track of clients"),
    {NULL}
};


/*
 * client list code
 *
 * Each client is assigned a number, which is transferred in the opaque
 * field of the WWW-Authenticate and Authorization headers. The number
 * is just a simple counter which is incremented for each new client.
 * Clients can't forge this number because it is hashed up into the
 * server nonce, and that is checked.
 *
 * The clients are kept in a simple hash table, which consists of an
 * array of client_entry's, each with a linked list of entries hanging
 * off it. The client's number modulo the size of the array gives the
 * bucket number.
 *
 * The clients are garbage collected whenever a new client is allocated
 * but there is not enough space left in the shared memory segment. A
 * simple semi-LRU is used for this: whenever a client entry is accessed
 * it is moved to the beginning of the linked list in its bucket (this
 * also makes for faster lookups for current clients). The garbage
 * collecter then just removes the oldest entry (i.e. the one at the
 * end of the list) in each bucket.
 *
 * The main advantages of the above scheme are that it's easy to implement
 * and it keeps the hash table evenly balanced (i.e. same number of entries
 * in each bucket). The major disadvantage is that you may be throwing
 * entries out which are in active use. This is not tragic, as these
 * clients will just be sent a new client id (opaque field) and nonce
 * with a stale=true (i.e. it will just look like the nonce expired,
 * thereby forcing an extra round trip). If the shared memory segment
 * has enough headroom over the current client set size then this should
 * not occur too often.
 *
 * To help tune the size of the shared memory segment (and see if the
 * above algorithm is really sufficient) a set of counters is kept
 * indicating the number of clients held, the number of garbage collected
 * clients, and the number of erroneously purged clients. These are printed
 * out at each garbage collection run. Note that access to the counters is
 * not synchronized because they are just indicaters, and whether they are
 * off by a few doesn't matter; and for the same reason no attempt is made
 * to guarantee the num_renewed is correct in the face of clients spoofing
 * the opaque field.
 */

/*
 * Get the client given its client number (the key). Returns the entry,
 * or NULL if it's not found.
 *
 * Access to the list itself is synchronized via locks. However, access
 * to the entry returned by get_client() is NOT synchronized. This means
 * that there are potentially problems if a client uses multiple,
 * simultaneous connections to access url's within the same protection
 * space. However, these problems are not new: when using multiple
 * connections you have no guarantee of the order the requests are
 * processed anyway, so you have problems with the nonce-count and
 * one-time nonces anyway.
 */
static client_entry *get_client(unsigned long key, const request_rec *r)
{
    int bucket;
    client_entry *entry, *prev = NULL;


    if (!key || !client_shm)  return NULL;

    bucket = key % client_list->tbl_len;
    entry  = client_list->table[bucket];

    apr_global_mutex_lock(client_lock);

    while (entry && key != entry->key) {
        prev  = entry;
        entry = entry->next;
    }

    if (entry && prev) {                /* move entry to front of list */
        prev->next  = entry->next;
        entry->next = client_list->table[bucket];
        client_list->table[bucket] = entry;
    }

    apr_global_mutex_unlock(client_lock);

    if (entry) {
        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r,
                      "get_client(): client %lu found", key);
    }
    else {
        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r,
                      "get_client(): client %lu not found", key);
    }

    return entry;
}


/* A simple garbage-collecter to remove unused clients. It removes the
 * last entry in each bucket and updates the counters. Returns the
 * number of removed entries.
 */
static long gc(void)
{
    client_entry *entry, *prev;
    unsigned long num_removed = 0, idx;

    /* garbage collect all last entries */

    for (idx = 0; idx < client_list->tbl_len; idx++) {
        entry = client_list->table[idx];
        prev  = NULL;
        while (entry->next) {   /* find last entry */
            prev  = entry;
            entry = entry->next;
        }
        if (prev) {
            prev->next = NULL;   /* cut list */
        }
        else {
            client_list->table[idx] = NULL;
        }
        if (entry) {                    /* remove entry */
            apr_rmm_free(client_rmm, (apr_rmm_off_t)entry);
            num_removed++;
        }
    }

    /* update counters and log */

    client_list->num_entries -= num_removed;
    client_list->num_removed += num_removed;