path: root/src/mod_authn_ldap.c

#include "first.h"

#include <ldap.h>

#include "base.h"
#include "http_auth.h"
#include "log.h"
#include "plugin.h"

#include <errno.h>
#include <stdlib.h>
#include <string.h>

typedef struct {
    LDAP *ldap;
    server *srv;

    buffer *auth_ldap_hostname;
    buffer *auth_ldap_basedn;
    buffer *auth_ldap_binddn;
    buffer *auth_ldap_bindpw;
    buffer *auth_ldap_filter;
    buffer *auth_ldap_cafile;
    buffer *auth_ldap_groupmember;
    unsigned short auth_ldap_starttls;
    unsigned short auth_ldap_allow_empty_pw;
} plugin_config;

typedef struct {
    PLUGIN_DATA;
    plugin_config **config_storage;
    plugin_config conf, *anon_conf; /* this is only used as long as no handler_ctx is setup */

    buffer *ldap_filter;
} plugin_data;

static handler_t mod_authn_ldap_basic(server *srv, connection *con, void *p_d, const http_auth_require_t *require, const buffer *username, const char *pw);

INIT_FUNC(mod_authn_ldap_init) {
    static http_auth_backend_t http_auth_backend_ldap =
      { "ldap", mod_authn_ldap_basic, NULL, NULL };
    plugin_data *p = calloc(1, sizeof(*p));
    p->ldap_filter = buffer_init();

    /* register http_auth_backend_ldap */
    http_auth_backend_ldap.p_d = p;
    http_auth_backend_set(&http_auth_backend_ldap);

    return p;
}

FREE_FUNC(mod_authn_ldap_free) {
    plugin_data *p = p_d;

    UNUSED(srv);

    if (!p) return HANDLER_GO_ON;

    buffer_free(p->ldap_filter);

    if (p->config_storage) {
        size_t i;
        for (i = 0; i < srv->config_context->used; i++) {
            plugin_config *s = p->config_storage[i];

            if (NULL == s) continue;

            buffer_free(s->auth_ldap_hostname);
            buffer_free(s->auth_ldap_basedn);
            buffer_free(s->auth_ldap_binddn);
            buffer_free(s->auth_ldap_bindpw);
            buffer_free(s->auth_ldap_filter);
            buffer_free(s->auth_ldap_cafile);
            buffer_free(s->auth_ldap_groupmember);

            if (NULL != s->ldap) ldap_unbind_ext_s(s->ldap, NULL, NULL);
            free(s);
        }
        free(p->config_storage);
    }

    free(p);

    return HANDLER_GO_ON;
}

/*(copied from mod_vhostdb_ldap.c)*/
static void mod_authn_add_scheme (server *srv, buffer *host)
{
    if (!buffer_string_is_empty(host)) {
        /* reformat hostname(s) as LDAP URIs (scheme://host:port) */
        static const char *schemes[] = {
          "ldap://", "ldaps://", "ldapi://", "cldap://"
        };
        char *b, *e = host->ptr;
        buffer_clear(srv->tmp_buf);
        while (*(b = e)) {
            unsigned int j;
            while (*b==' '||*b=='\t'||*b=='\r'||*b=='\n'||*b==',') ++b;
            if (*b == '\0') break;
            e = b;
            while (*e!=' '&&*e!='\t'&&*e!='\r'&&*e!='\n'&&*e!=','&&*e!='\0')
                ++e;
            if (!buffer_string_is_empty(srv->tmp_buf))
                buffer_append_string_len(srv->tmp_buf, CONST_STR_LEN(","));
            for (j = 0; j < sizeof(schemes)/sizeof(char *); ++j) {
                if (0 == strncasecmp(b, schemes[j], strlen(schemes[j]))) {
                    break;
                }
            }
            if (j == sizeof(schemes)/sizeof(char *))
                buffer_append_string_len(srv->tmp_buf,
                                         CONST_STR_LEN("ldap://"));
            buffer_append_string_len(srv->tmp_buf, b, (size_t)(e - b));
        }
        buffer_copy_buffer(host, srv->tmp_buf);
    }
}

SETDEFAULTS_FUNC(mod_authn_ldap_set_defaults) {
    plugin_data *p = p_d;
    size_t i;
config_values_t cv[] = {
        { "auth.backend.ldap.hostname",     NULL, T_CONFIG_STRING, T_CONFIG_SCOPE_CONNECTION }, /* 0 */
        { "auth.backend.ldap.base-dn",      NULL, T_CONFIG_STRING, T_CONFIG_SCOPE_CONNECTION }, /* 1 */
        { "auth.backend.ldap.filter",       NULL, T_CONFIG_STRING, T_CONFIG_SCOPE_CONNECTION }, /* 2 */
        { "auth.backend.ldap.ca-file",      NULL, T_CONFIG_STRING, T_CONFIG_SCOPE_CONNECTION }, /* 3 */
        { "auth.backend.ldap.starttls",     NULL, T_CONFIG_BOOLEAN, T_CONFIG_SCOPE_CONNECTION }, /* 4 */
        { "auth.backend.ldap.bind-dn",      NULL, T_CONFIG_STRING, T_CONFIG_SCOPE_CONNECTION }, /* 5 */
        { "auth.backend.ldap.bind-pw",      NULL, T_CONFIG_STRING, T_CONFIG_SCOPE_CONNECTION }, /* 6 */
        { "auth.backend.ldap.allow-empty-pw",     NULL, T_CONFIG_BOOLEAN, T_CONFIG_SCOPE_CONNECTION }, /* 7 */
        { "auth.backend.ldap.groupmember",  NULL, T_CONFIG_STRING, T_CONFIG_SCOPE_CONNECTION }, /* 8 */
        { NULL,                             NULL, T_CONFIG_UNSET, T_CONFIG_SCOPE_UNSET }
    };

    p->config_storage = calloc(srv->config_context->used, sizeof(plugin_config *));

    for (i = 0; i < srv->config_context->used; i++) {
        data_config const* config = (data_config const*)srv->config_context->data[i];
        plugin_config *s;

        s = calloc(1, sizeof(plugin_config));

        s->auth_ldap_hostname = buffer_init();
        s->auth_ldap_basedn = buffer_init();
        s->auth_ldap_binddn = buffer_init();
        s->auth_ldap_bindpw = buffer_init();
        s->auth_ldap_filter = buffer_init();
        s->auth_ldap_cafile = buffer_init();
        s->auth_ldap_groupmember = buffer_init_string("memberUid");
        s->auth_ldap_starttls = 0;
        s->ldap = NULL;

        cv[0].destination = s->auth_ldap_hostname;
        cv[1].destination = s->auth_ldap_basedn;
        cv[2].destination = s->auth_ldap_filter;
        cv[3].destination = s->auth_ldap_cafile;
        cv[4].destination = &(s->auth_ldap_starttls);
        cv[5].destination = s->auth_ldap_binddn;
        cv[6].destination = s->auth_ldap_bindpw;
        cv[7].destination = &(s->auth_ldap_allow_empty_pw);
        cv[8].destination = s->auth_ldap_groupmember;

        p->config_storage[i] = s;

        if (0 != config_insert_values_global(srv, config->value, cv, i == 0 ? T_CONFIG_SCOPE_SERVER : T_CONFIG_SCOPE_CONNECTION)) {
            return HANDLER_ERROR;
        }

        if (!buffer_string_is_empty(s->auth_ldap_filter)) {
            if (*s->auth_ldap_filter->ptr != ',') {
                /*(translate '$' to '?' for consistency with other modules)*/
                char *d = s->auth_ldap_filter->ptr;
                for (; NULL != (d = strchr(d, '$')); ++d) *d = '?';
                if (NULL == strchr(s->auth_ldap_filter->ptr, '?')) {
                    log_error_write(srv, __FILE__, __LINE__, "s", "ldap: auth.backend.ldap.filter is missing a replace-operator '?'");
                    return HANDLER_ERROR;
                }
            }
        }

        mod_authn_add_scheme(srv, s->auth_ldap_hostname);
    }

    return HANDLER_GO_ON;
}

#define PATCH(x) \
    p->conf.x = s->x;
static int mod_authn_ldap_patch_connection(server *srv, connection *con, plugin_data *p) {
    size_t i, j;
    plugin_config *s = p->config_storage[0];

    PATCH(auth_ldap_hostname);
    PATCH(auth_ldap_basedn);
    PATCH(auth_ldap_binddn);
    PATCH(auth_ldap_bindpw);
    PATCH(auth_ldap_filter);
    PATCH(auth_ldap_cafile);
    PATCH(auth_ldap_starttls);
    PATCH(auth_ldap_allow_empty_pw);
    PATCH(auth_ldap_groupmember);
    p->anon_conf = s;

    /* skip the first, the global context */
    for (i = 1; i < srv->config_context->used; i++) {
        data_config *dc = (data_config *)srv->config_context->data[i];
        s = p->config_storage[i];

        /* condition didn't match */
        if (!config_check_cond(srv, con, dc)) continue;

        /* merge config */
        for (j = 0; j < dc->value->used; j++) {
            data_unset *du = dc->value->data[j];

            if (buffer_is_equal_string(du->key, CONST_STR_LEN("auth.backend.ldap.hostname"))) {
                PATCH(auth_ldap_hostname);
                p->anon_conf = s;
            } else if (buffer_is_equal_string(du->key, CONST_STR_LEN("auth.backend.ldap.base-dn"))) {
                PATCH(auth_ldap_basedn);
            } else if (buffer_is_equal_string(du->key, CONST_STR_LEN("auth.backend.ldap.filter"))) {
                PATCH(auth_ldap_filter);
            } else if (buffer_is_equal_string(du->key, CONST_STR_LEN("auth.backend.ldap.ca-file"))) {
                PATCH(auth_ldap_cafile);
            } else if (buffer_is_equal_string(du->key, CONST_STR_LEN("auth.backend.ldap.starttls"))) {
                PATCH(auth_ldap_starttls);
            } else if (buffer_is_equal_string(du->key, CONST_STR_LEN("auth.backend.ldap.bind-dn"))) {
                PATCH(auth_ldap_binddn);
            } else if (buffer_is_equal_string(du->key, CONST_STR_LEN("auth.backend.ldap.bind-pw"))) {
                PATCH(auth_ldap_bindpw);
            } else if (buffer_is_equal_string(du->key, CONST_STR_LEN("auth.backend.ldap.allow-empty-pw"))) {
                PATCH(auth_ldap_allow_empty_pw);
            } else if (buffer_is_equal_string(du->key, CONST_STR_LEN("auth.backend.ldap.groupmember"))) {
                PATCH(auth_ldap_groupmember);
            }
        }
    }

    return 0;
}
#undef PATCH

static void mod_authn_ldap_err(server *srv, const char *file, unsigned long line, const char *fn, int err)
{
    log_error_write(srv,file,line,"sSss","ldap:",fn,":",ldap_err2string(err));
}

static void mod_authn_ldap_opt_err(server *srv, const char *file, unsigned long line, const char *fn, LDAP *ld)
{
    int err;
    ldap_get_option(ld, LDAP_OPT_ERROR_NUMBER, &err);
    mod_authn_ldap_err(srv, file, line, fn, err);
}

static void mod_authn_append_ldap_dn_escape(buffer * const filter, const buffer * const raw) {
    /* [RFC4514] 2.4 Converting an AttributeValue from ASN.1 to a String
     *
     * https://www.ldap.com/ldap-dns-and-rdns
     * http://social.technet.microsoft.com/wiki/contents/articles/5312.active-directory-characters-to-escape.aspx
     */
    const char * const b = raw->ptr;
    const size_t rlen = buffer_string_length(raw);
    if (0 == rlen) return;

    if (b[0] == ' ') { /* || b[0] == '#' handled below for MS Active Directory*/
        /* escape leading ' ' */
        buffer_append_string_len(filter, CONST_STR_LEN("\\"));
    }

    for (size_t i = 0; i < rlen; ++i) {
        size_t len = i;
        int bs = 0;
        do {
            /* encode all UTF-8 chars with high bit set
             * (instead of validating UTF-8 and escaping only invalid UTF-8) */
            if (((unsigned char *)b)[len] > 0x7f)
                break;
            switch (b[len]) {
              default:
                continue;
              case '"': case '+': case ',': case ';': case '\\':
              case '<': case '>':
              case '=': case '#': /* (for MS Active Directory) */
                bs = 1;
                break;
              case '\0':
                break;
            }
            break;
        } while (++len < rlen);
        len -= i;

        if (len) {
            buffer_append_string_len(filter, b+i, len);
            if ((i += len) == rlen) break;
        }

        if (bs) {
            buffer_append_string_len(filter, CONST_STR_LEN("\\"));
            buffer_append_string_len(filter, b+i, 1);
        }
        else {
            /* escape NUL ('\0') (and all UTF-8 chars with high bit set) */
            char *f;
            buffer_string_prepare_append(filter, 3);
            f = filter->ptr + buffer_string_length(filter);
            f[0] = '\\';
            f[1] = "0123456789abcdef"[(((unsigned char *)b)[i] >> 4) & 0xf];
            f[2] = "0123456789abcdef"[(((unsigned char *)b)[i]     ) & 0xf];
            buffer_commit(filter, 3);
        }
    }

    if (rlen > 1 && b[rlen-1] == ' ') {
        /* escape trailing ' ' */
        filter->ptr[buffer_string_length(filter)-1] = '\\';
        buffer_append_string_len(filter, CONST_STR_LEN(" "));
    }
}

static void mod_authn_append_ldap_filter_escape(buffer * const filter, const buffer * const raw) {
    /* [RFC4515] 3. String Search Filter Definition
     *
     * [...]
     *
     * The <valueencoding> rule ensures that the entire filter string is a
     * valid UTF-8 string and provides that the octets that represent the
     * ASCII characters "*" (ASCII 0x2a), "(" (ASCII 0x28), ")" (ASCII
     * 0x29), "\" (ASCII 0x5c), and NUL (ASCII 0x00) are represented as a
     * backslash "\" (ASCII 0x5c) followed by the two hexadecimal digits
     * representing the value of the encoded octet.
     *
     * [...]
     *
     * As indicated by the <valueencoding> rule, implementations MUST escape
     * all octets greater than 0x7F that are not part of a valid UTF-8
     * encoding sequence when they generate a string representation of a
     * search filter.  Implementations SHOULD accept as input strings that
     * are not valid UTF-8 strings.  This is necessary because RFC 2254 did
     * not clearly define the term "string representation" (and in
     * particular did not mention that the string representation of an LDAP
     * search filter is a string of UTF-8-encoded Unicode characters).
     *
     *
     * https://www.ldap.com/ldap-filters
     * Although not required, you may escape any other characters that you want
     * in the assertion value (or substring component) of a filter. This may be
     * accomplished by prefixing the hexadecimal representation of each byte of
     * the UTF-8 encoding of the character to escape with a backslash character.
     */
    const char * const b = raw->ptr;
    const size_t rlen = buffer_string_length(raw);
    for (size_t i = 0; i < rlen; ++i) {
        size_t len = i;
        char *f;
        do {
            /* encode all UTF-8 chars with high bit set
             * (instead of validating UTF-8 and escaping only invalid UTF-8) */
            if (((unsigned char *)b)[len] > 0x7f)
                break;
            switch (b[len]) {
              default:
                continue;
              case '\0': case '(': case ')': case '*': case '\\':
                break;
            }
            break;
        } while (++len < rlen);
        len -= i;

        if (len) {
            buffer_append_string_len(filter, b+i, len);
            if ((i += len) == rlen) break;
        }

        /* escape * ( ) \ NUL ('\0') (and all UTF-8 chars with high bit set) */
        buffer_string_prepare_append(filter, 3);
        f = filter->ptr + buffer_string_length(filter);
        f[0] = '\\';
        f[1] = "0123456789abcdef"[(((unsigned char *)b)[i] >> 4) & 0xf];
        f[2] = "0123456789abcdef"[(((unsigned char *)b)[i]     ) & 0xf];
        buffer_commit(filter, 3);
    }
}

static LDAP * mod_authn_ldap_host_init(server *srv, plugin_config *s) {
    LDAP *ld;
    int ret;

    if (buffer_string_is_empty(s->auth_ldap_hostname)) return NULL;

    if (LDAP_SUCCESS != ldap_initialize(&ld, s->auth_ldap_hostname->ptr)) {
        log_error_write(srv, __FILE__, __LINE__, "sss", "ldap:",
                        "ldap_initialize():", strerror(errno));
        return NULL;
    }

    ret = LDAP_VERSION3;
    ret = ldap_set_option(ld, LDAP_OPT_PROTOCOL_VERSION, &ret);
    if (LDAP_OPT_SUCCESS != ret) {
        mod_authn_ldap_err(srv, __FILE__, __LINE__, "ldap_set_option()", ret);
        ldap_destroy(ld);
        return NULL;
    }

    if (s->auth_ldap_starttls) {
        /* if no CA file is given, it is ok, as we will use encryption
         * if the server requires a CAfile it will tell us */
        if (!buffer_string_is_empty(s->auth_ldap_cafile)) {
            ret = ldap_set_option(NULL, LDAP_OPT_X_TLS_CACERTFILE,
                                  s->auth_ldap_cafile->ptr);
            if (LDAP_OPT_SUCCESS != ret) {
                mod_authn_ldap_err(srv, __FILE__, __LINE__,
                                   "ldap_set_option(LDAP_OPT_X_TLS_CACERTFILE)",
                                   ret);
                ldap_destroy(ld);
                return NULL;
            }
        }

        ret = ldap_start_tls_s(ld, NULL,  NULL);
        if (LDAP_OPT_SUCCESS != ret) {
            mod_authn_ldap_err(srv,__FILE__,__LINE__,"ldap_start_tls_s()",ret);
            ldap_destroy(ld);
            return NULL;
        }
    }

    return ld;
}

static int mod_authn_ldap_bind(server *srv, LDAP *ld, const char *dn, const char *pw) {
    struct berval creds;
    int ret;

    if (NULL != pw) {
        *((const char **)&creds.bv_val) = pw; /*(cast away const)*/
        creds.bv_len = strlen(pw);
    } else {
        creds.bv_val = NULL;
        creds.bv_len = 0;
    }

    /* RFE: add functionality: LDAP_SASL_EXTERNAL (or GSS-SPNEGO, etc.) */

    ret = ldap_sasl_bind_s(ld,dn,LDAP_SASL_SIMPLE,&creds,NULL,NULL,NULL);
    if (ret != LDAP_SUCCESS) {
        mod_authn_ldap_err(srv, __FILE__, __LINE__, "ldap_sasl_bind_s()", ret);
    }

    return ret;
}

static int mod_authn_ldap_rebind_proc (LDAP *ld, LDAP_CONST char *url, ber_tag_t ldap_request, ber_int_t msgid, void *params) {
    plugin_config *s = (plugin_config *)params;
    UNUSED(url);
    UNUSED(ldap_request);
    UNUSED(msgid);
    return !buffer_string_is_empty(s->auth_ldap_binddn)
      ? mod_authn_ldap_bind(s->srv, ld,
                            s->auth_ldap_binddn->ptr,
                            s->auth_ldap_bindpw->ptr)
      : mod_authn_ldap_bind(s->srv, ld, NULL, NULL);
}

static LDAPMessage * mod_authn_ldap_search(server *srv, plugin_config *s, char *base, char *filter) {
    LDAPMessage *lm = NULL;
    char *attrs[] = { LDAP_NO_ATTRS, NULL };
    int ret;

    /*
     * 1. connect anonymously (if not already connected)
     *    (ldap connection is kept open unless connection-level error occurs)
     * 2. issue search using filter
     */

    if (s->ldap != NULL) {
        ret = ldap_search_ext_s(s->ldap, base, LDAP_SCOPE_SUBTREE, filter,
                                attrs, 0, NULL, NULL, NULL, 0, &lm);
        if (LDAP_SUCCESS == ret) {
            return lm;
        } else if (LDAP_SERVER_DOWN != ret) {
            /* try again (or initial request);
             * ldap lib sometimes fails for the first call but reconnects */
            ret = ldap_search_ext_s(s->ldap, base, LDAP_SCOPE_SUBTREE, filter,
                                    attrs, 0, NULL, NULL, NULL, 0, &lm);
            if (LDAP_SUCCESS == ret) {
                return lm;
            }
        }

        ldap_unbind_ext_s(s->ldap, NULL, NULL);
    }

    s->ldap = mod_authn_ldap_host_init(srv, s);
    if (NULL == s->ldap) {
        return NULL;
    }

    ldap_set_rebind_proc(s->ldap, mod_authn_ldap_rebind_proc, s);
    ret = mod_authn_ldap_rebind_proc(s->ldap, NULL, 0, 0, s);
    if (LDAP_SUCCESS != ret) {
        ldap_destroy(s->ldap);
        s->ldap = NULL;
        return NULL;
    }

    ret = ldap_search_ext_s(s->ldap, base, LDAP_SCOPE_SUBTREE, filter,
                            attrs, 0, NULL, NULL, NULL, 0, &lm);
    if (LDAP_SUCCESS != ret) {
        log_error_write(srv, __FILE__, __LINE__, "sSss",
                        "ldap:", ldap_err2string(ret), "; filter:", filter);
        ldap_unbind_ext_s(s->ldap, NULL, NULL);
        s->ldap = NULL;
        return NULL;
    }

    return lm;
}

static char * mod_authn_ldap_get_dn(server *srv, plugin_config *s, char *base, char *filter) {
    LDAP *ld;
    LDAPMessage *lm, *first;
    char *dn;
    int count;

    lm = mod_authn_ldap_search(srv, s, base, filter);
    if (NULL == lm) {
        return NULL;
    }

    ld = s->ldap; /*(must be after mod_authn_ldap_search(); might reconnect)*/

    count = ldap_count_entries(ld, lm);
    if (0 == count) { /*(no entires found)*/
        ldap_msgfree(lm);
        return NULL;
    } else if (count > 1) {
        log_error_write(srv, __FILE__, __LINE__, "sss",
                        "ldap:", "more than one record returned.  "
                        "you might have to refine the filter:", filter);
    }

    if (NULL == (first = ldap_first_entry(ld, lm))) {
        mod_authn_ldap_opt_err(srv,__FILE__,__LINE__,"ldap_first_entry()",ld);
        ldap_msgfree(lm);
        return NULL;
    }

    if (NULL == (dn = ldap_get_dn(ld, first))) {
        mod_authn_ldap_opt_err(srv,__FILE__,__LINE__,"ldap_get_dn()",ld);
        ldap_msgfree(lm);
        return NULL;
    }

    ldap_msgfree(lm);
    return dn;
}

static handler_t mod_authn_ldap_memberOf(server *srv, plugin_config *s, const http_auth_require_t *require, const buffer *username, const char *userdn) {
    array *groups = require->group;
    buffer *filter = buffer_init();
    handler_t rc = HANDLER_ERROR;

    buffer_copy_string_len(filter, CONST_STR_LEN("("));
    buffer_append_string_buffer(filter, s->auth_ldap_groupmember);
    buffer_append_string_len(filter, CONST_STR_LEN("="));
    if (buffer_is_equal_string(s->auth_ldap_groupmember,
                               CONST_STR_LEN("member"))) {
        buffer_append_string(filter, userdn);
    } else { /*(assume "memberUid"; consider validating in SETDEFAULTS_FUNC)*/
        mod_authn_append_ldap_filter_escape(filter, username);
    }
    buffer_append_string_len(filter, CONST_STR_LEN(")"));

    for (size_t i = 0; i < groups->used; ++i) {
        char *base = groups->data[i]->key->ptr;
        LDAPMessage *lm = mod_authn_ldap_search(srv, s, base, filter->ptr);
        if (NULL != lm) {
            int count = ldap_count_entries(s->ldap, lm);
            ldap_msgfree(lm);
            if (count > 0) {
                rc = HANDLER_GO_ON;
                break;
            }
        }
    }

    buffer_free(filter);
    return rc;
}

static handler_t mod_authn_ldap_basic(server *srv, connection *con, void *p_d, const http_auth_require_t *require, const buffer *username, const char *pw) {
    plugin_data *p = (plugin_data *)p_d;
    LDAP *ld;
    char *dn;
    buffer *template;
    handler_t rc;

    mod_authn_ldap_patch_connection(srv, con, p);
    p->anon_conf->srv = srv;
    p->conf.srv = srv;

    if (pw[0] == '\0' && !p->conf.auth_ldap_allow_empty_pw)
        return HANDLER_ERROR;

    template = p->conf.auth_ldap_filter;
    if (buffer_string_is_empty(template)) {
        return HANDLER_ERROR;
    }

    /* build filter to get DN for uid = username */
    buffer_clear(p->ldap_filter);
    if (*template->ptr == ',') {
        /* special-case filter template beginning with ',' to be explicit DN */
        buffer_append_string_len(p->ldap_filter, CONST_STR_LEN("uid="));
        mod_authn_append_ldap_dn_escape(p->ldap_filter, username);
        buffer_append_string_buffer(p->ldap_filter, template);
        dn = p->ldap_filter->ptr;
    } else {
        for (char *b = template->ptr, *d; *b; b = d+1) {
            if (NULL != (d = strchr(b, '?'))) {
                buffer_append_string_len(p->ldap_filter, b, (size_t)(d - b));
                mod_authn_append_ldap_filter_escape(p->ldap_filter, username);
            } else {
                d = template->ptr + buffer_string_length(template);
                buffer_append_string_len(p->ldap_filter, b, (size_t)(d - b));
                break;
            }
        }

        /* ldap_search for DN (synchronous; blocking) */
        dn = mod_authn_ldap_get_dn(srv, p->anon_conf,
                                   p->conf.auth_ldap_basedn->ptr,
                                   p->ldap_filter->ptr);
        if (NULL == dn) {
            return HANDLER_ERROR;
        }
    }

    /* auth against LDAP server (synchronous; blocking) */

    ld = mod_authn_ldap_host_init(srv, &p->conf);
    if (NULL == ld) {
        if (dn != p->ldap_filter->ptr) ldap_memfree(dn);
        return HANDLER_ERROR;
    }

    /* Disable referral tracking.  Target user should be in provided scope */
    {
        int ret = ldap_set_option(ld, LDAP_OPT_REFERRALS, LDAP_OPT_OFF);
        if (LDAP_OPT_SUCCESS != ret) {
            mod_authn_ldap_err(srv,__FILE__,__LINE__,"ldap_set_option()",ret);
            ldap_destroy(ld);
            if (dn != p->ldap_filter->ptr) ldap_memfree(dn);
            return HANDLER_ERROR;
        }
    }

    if (LDAP_SUCCESS != mod_authn_ldap_bind(srv, ld, dn, pw)) {
        ldap_destroy(ld);
        if (dn != p->ldap_filter->ptr) ldap_memfree(dn);
        return HANDLER_ERROR;
    }

    ldap_unbind_ext_s(ld, NULL, NULL); /* disconnect */

    if (http_auth_match_rules(require, username->ptr, NULL, NULL)) {
        rc = HANDLER_GO_ON; /* access granted */
    } else {
        rc = HANDLER_ERROR;
        if (require->group->used) {
            /*(must not re-use p->ldap_filter, since it might be used for dn)*/
            rc = mod_authn_ldap_memberOf(srv, &p->conf, require, username, dn);
        }
    }

    if (dn != p->ldap_filter->ptr) ldap_memfree(dn);
    return rc;
}

int mod_authn_ldap_plugin_init(plugin *p);
int mod_authn_ldap_plugin_init(plugin *p) {
    p->version     = LIGHTTPD_VERSION_ID;
    p->name        = buffer_init_string("authn_ldap");
    p->init        = mod_authn_ldap_init;
    p->set_defaults = mod_authn_ldap_set_defaults;
    p->cleanup     = mod_authn_ldap_free;

    p->data        = NULL;

    return 0;
}