src/auth/mech.c

	mech.c revision 5fb63932ddaa3a4043e33ccd5b2d50037448535f
/* Copyright (C) 2002 Timo Sirainen */

#include "common.h"
#include "ioloop.h"
#include "buffer.h"
#include "hash.h"
#include "mech.h"
#include "safe-memset.h"
#include "str.h"
#include "str-sanitize.h"
#include "var-expand.h"
#include "auth-client-connection.h"
#include "auth-master-connection.h"
#include "passdb.h"
#include "passdb-cache.h"

#include <stdlib.h>

struct auth_request_extra {
    struct auth_request *request;
    string_t *str;
    char *user_password, *password;
};

struct mech_module_list *mech_modules;
buffer_t *mech_handshake;

const char *const *auth_realms;
const char *default_realm;
const char *anonymous_username;
char username_chars[256], username_translation[256];
int ssl_require_client_cert;

static buffer_t *auth_failures_buf;
static struct timeout *to_auth_failures;

void mech_register_module(struct mech_module *module)
{
    struct mech_module_list *list;

    list = i_new(struct mech_module_list, 1);
    list->module = *module;

    str_printfa(mech_handshake, "MECH\t%s", module->mech_name);
    if ((module->flags & MECH_SEC_PRIVATE) != 0)
        str_append(mech_handshake, "\tprivate");
    if ((module->flags & MECH_SEC_ANONYMOUS) != 0)
        str_append(mech_handshake, "\tanonymous");
    if ((module->flags & MECH_SEC_PLAINTEXT) != 0)
        str_append(mech_handshake, "\tplaintext");
    if ((module->flags & MECH_SEC_DICTIONARY) != 0)
        str_append(mech_handshake, "\tdictionary");
    if ((module->flags & MECH_SEC_ACTIVE) != 0)
        str_append(mech_handshake, "\tactive");
    if ((module->flags & MECH_SEC_FORWARD_SECRECY) != 0)
        str_append(mech_handshake, "\tforward-secrecy");
    if ((module->flags & MECH_SEC_MUTUAL_AUTH) != 0)
        str_append(mech_handshake, "\tmutual-auth");
    str_append_c(mech_handshake, '\n');

    list->next = mech_modules;
    mech_modules = list;
}

void mech_unregister_module(struct mech_module *module)
{
    struct mech_module_list **pos, *list;

    for (pos = &mech_modules; *pos != NULL; pos = &(*pos)->next) {
        if (strcmp((*pos)->module.mech_name, module->mech_name) == 0) {
            list = *pos;
            *pos = (*pos)->next;
            i_free(list);
            break;
        }
    }
}

const string_t *auth_mechanisms_get_list(void)
{
    struct mech_module_list *list;
    string_t *str;

    str = t_str_new(128);
    for (list = mech_modules; list != NULL; list = list->next)
        str_append(str, list->module.mech_name);

    return str;
}

struct mech_module *mech_module_find(const char *name)
{
    struct mech_module_list *list;

    for (list = mech_modules; list != NULL; list = list->next) {
        if (strcasecmp(list->module.mech_name, name) == 0)
            return &list->module;
    }
    return NULL;
}

struct auth_request *auth_request_new(struct mech_module *mech)
{
    struct auth_request *request;

    request = mech->auth_new();
    if (request == NULL)
        return NULL;

    request->mech = mech;
    request->created = ioloop_time;
    return request;
}

void auth_request_destroy(struct auth_request *request)
{
    if (request->conn != NULL) {
        hash_remove(request->conn->auth_requests,
                POINTER_CAST(request->id));
    }
    auth_request_unref(request);
}

void mech_auth_finish(struct auth_request *request,
              const void *data, size_t data_size, int success)
{
    if (!success) {
        if (request->no_failure_delay) {
            /* passdb specifically requested to to delay the
               reply. */
            request->callback(request, AUTH_CLIENT_RESULT_FAILURE,
                      NULL, 0);
            auth_request_destroy(request);
            return;
        }

        /* failure. don't announce it immediately to avoid
           a) timing attacks, b) flooding */
        if (auth_failures_buf->used > 0) {
            const struct auth_request *const *requests;

            requests = auth_failures_buf->data;
            requests += auth_failures_buf->used/sizeof(*requests)-1;
            i_assert(*requests != request);
        }
        buffer_append(auth_failures_buf, &request, sizeof(request));
        return;
    }

    if (request->conn != NULL) {
        request->callback(request, AUTH_CLIENT_RESULT_SUCCESS,
                  data, data_size);
    }

    if (request->no_login || request->conn == NULL ||
        AUTH_MASTER_IS_DUMMY(request->conn->master)) {
        /* we don't have master process, the request is no longer
           needed */
        auth_request_destroy(request);
    }
}

int mech_fix_username(char *username, const char **error_r)
{
    unsigned char *p;

    if (*username == '\0') {
        /* Some PAM plugins go nuts with empty usernames */
        *error_r = "Empty username";
        return FALSE;
    }

    for (p = (unsigned char *)username; *p != '\0'; p++) {
        if (username_translation[*p & 0xff] != 0)
            *p = username_translation[*p & 0xff];
        if (username_chars[*p & 0xff] == 0) {
            *error_r = "Username contains disallowed characters";
            return FALSE;
        }
    }

    return TRUE;
}

void auth_request_ref(struct auth_request *request)
{
    request->refcount++;
}

int auth_request_unref(struct auth_request *request)
{
    if (--request->refcount > 0)
        return TRUE;

    request->mech->auth_free(request);
    return FALSE;
}

struct auth_request_extra *
auth_request_extra_begin(struct auth_request *request,
             const char *user_password)
{
    struct auth_request_extra *extra;

    extra = i_new(struct auth_request_extra, 1);
    extra->request = request;
    extra->user_password = i_strdup(user_password);
    return extra;
}

void auth_request_extra_next(struct auth_request_extra *extra,
                 const char *name, const char *value)
{
    string_t *str;

    i_assert(value != NULL);

    if (strcmp(name, "password") == 0) {
        i_assert(extra->password == NULL);
        extra->password = i_strdup(value);
        return;
    }

    if (strcmp(name, "nodelay") == 0) {
        /* don't delay replying to client of the failure */
        extra->request->no_failure_delay = TRUE;
        return;
    }

    str = extra->str;
    if (str == NULL)
        extra->str = str = str_new(extra->request->pool, 64);

    if (strcmp(name, "nologin") == 0) {
        /* user can't actually login - don't keep this
           reply for master */
        extra->request->no_login = TRUE;
        if (str_len(str) > 0)
            str_append_c(str, '\t');
        str_append(str, name);
    } else if (strcmp(name, "proxy") == 0) {
        /* we're proxying authentication for this user. send
           password back if using plaintext authentication. */
        extra->request->proxy = TRUE;
        if (str_len(str) > 0)
            str_append_c(str, '\t');
        str_append(str, name);
    } else {
        if (str_len(str) > 0)
            str_append_c(str, '\t');
        str_printfa(str, "%s=%s", name, value);
    }
}

void auth_request_extra_finish(struct auth_request_extra *extra,
                   const char *cache_key)
{
    string_t *str;

    if (passdb_cache != NULL && cache_key != NULL) {
        str = t_str_new(64);
        if (extra->str != NULL)
            str_append_str(str, extra->str);
        if (extra->request->no_failure_delay) {
            if (str_len(str) > 0)
                str_append_c(str, '\t');
            str_append(str, "nodelay");
        }
        auth_cache_insert(passdb_cache, extra->request, cache_key,
                  t_strconcat(extra->password == NULL ? "" :
                          extra->password,
                          str_len(str) > 0 ? "\t" : "",
                          str_c(str), NULL));
    }

    if (extra->user_password != NULL) {
        if (extra->request->proxy) {
            /* we're proxying - send back the password that was
               sent by user (not the password in passdb). */
            str_printfa(extra->str, "\tpass=%s",
                    extra->user_password);
        }
        safe_memset(extra->user_password, 0,
                strlen(extra->user_password));
        i_free(extra->user_password);
    }

    if (extra->str != NULL)
        extra->request->extra_fields = str_c(extra->str);

    if (extra->password != NULL) {
        safe_memset(extra->password, 0, strlen(extra->password));
        i_free(extra->password);
    }
    i_free(extra);
}

static const char *escape_none(const char *str)
{
    return str;
}

const struct var_expand_table *
auth_request_get_var_expand_table(const struct auth_request *auth_request,
                  const char *(*escape_func)(const char *))
{
    static struct var_expand_table static_tab[] = {
        { 'u', NULL },
        { 'n', NULL },
        { 'd', NULL },
        { 's', NULL },
        { 'h', NULL },
        { 'l', NULL },
        { 'r', NULL },
        { 'p', NULL },
        { '\0', NULL }
    };
    struct var_expand_table *tab;

    if (escape_func == NULL)
        escape_func = escape_none;

    tab = t_malloc(sizeof(static_tab));
    memcpy(tab, static_tab, sizeof(static_tab));

    tab[0].value = escape_func(auth_request->user);
    tab[1].value = escape_func(t_strcut(auth_request->user, '@'));
    tab[2].value = strchr(auth_request->user, '@');
    if (tab[2].value != NULL)
        tab[2].value = escape_func(tab[2].value+1);
    tab[3].value = auth_request->service;
    /* tab[4] = we have no home dir */
    if (auth_request->local_ip.family != 0)
        tab[5].value = net_ip2addr(&auth_request->local_ip);
    if (auth_request->remote_ip.family != 0)
        tab[6].value = net_ip2addr(&auth_request->remote_ip);
    tab[7].value = dec2str(auth_request->conn->pid);
    return tab;
}

const char *get_log_prefix(const struct auth_request *auth_request)
{
#define MAX_LOG_USERNAME_LEN 64
    const char *ip;
    string_t *str;

    str = t_str_new(64);

    if (auth_request->user == NULL)
        str_append(str, "?");
    else {
        str_sanitize_append(str, auth_request->user,
                    MAX_LOG_USERNAME_LEN);
    }

    ip = net_ip2addr(&auth_request->remote_ip);
    if (ip != NULL) {
        str_append_c(str, ',');
        str_append(str, ip);
    }
    return str_c(str);
}

void auth_failure_buf_flush(void)
{
    struct auth_request **auth_request;
    size_t i, size;

    auth_request = buffer_get_modifyable_data(auth_failures_buf, &size);
    size /= sizeof(*auth_request);

    for (i = 0; i < size; i++) {
        if (auth_request[i]->conn != NULL) {
            auth_request[i]->callback(auth_request[i],
                          AUTH_CLIENT_RESULT_FAILURE,
                          NULL, 0);
        }
        auth_request_destroy(auth_request[i]);
    }
    buffer_set_used_size(auth_failures_buf, 0);
}

static void auth_failure_timeout(void *context __attr_unused__)
{
    auth_failure_buf_flush();
}

static void mech_list_verify_passdb(struct passdb_module *passdb)
{
    struct mech_module_list *list;

    for (list = mech_modules; list != NULL; list = list->next) {
        if (list->module.passdb_need_plain &&
            passdb->verify_plain == NULL)
            break;
        if (list->module.passdb_need_credentials &&
            passdb->lookup_credentials == NULL)
            break;
    }

    if (list != NULL) {
        i_fatal("Passdb %s doesn't support %s method",
            passdb->name, list->module.mech_name);
    }
}
extern struct mech_module mech_plain;
extern struct mech_module mech_login;
extern struct mech_module mech_apop;
extern struct mech_module mech_cram_md5;
extern struct mech_module mech_digest_md5;
extern struct mech_module mech_ntlm;
extern struct mech_module mech_rpa;
extern struct mech_module mech_anonymous;

void mech_init(void)
{
    const char *const *mechanisms;
    const char *env;

    mech_modules = NULL;
    mech_handshake = str_new(default_pool, 512);

    anonymous_username = getenv("ANONYMOUS_USERNAME");
    if (anonymous_username != NULL && *anonymous_username == '\0')
                anonymous_username = NULL;

    /* register wanted mechanisms */
    env = getenv("MECHANISMS");
    if (env == NULL || *env == '\0')
        i_fatal("MECHANISMS environment is unset");

    mechanisms = t_strsplit_spaces(env, " ");
    while (*mechanisms != NULL) {
        if (strcasecmp(*mechanisms, "PLAIN") == 0)
            mech_register_module(&mech_plain);
        else if (strcasecmp(*mechanisms, "LOGIN") == 0)
            mech_register_module(&mech_login);
        else if (strcasecmp(*mechanisms, "APOP") == 0)
            mech_register_module(&mech_apop);
        else if (strcasecmp(*mechanisms, "CRAM-MD5") == 0)
            mech_register_module(&mech_cram_md5);
        else if (strcasecmp(*mechanisms, "DIGEST-MD5") == 0)
            mech_register_module(&mech_digest_md5);
        else if (strcasecmp(*mechanisms, "NTLM") == 0)
            mech_register_module(&mech_ntlm);
        else if (strcasecmp(*mechanisms, "RPA") == 0)
            mech_register_module(&mech_rpa);
        else if (strcasecmp(*mechanisms, "ANONYMOUS") == 0) {
            if (anonymous_username == NULL) {
                i_fatal("ANONYMOUS listed in mechanisms, "
                    "but anonymous_username not given");
            }
            mech_register_module(&mech_anonymous);
        } else {
            i_fatal("Unknown authentication mechanism '%s'",
                *mechanisms);
        }

        mechanisms++;
    }

    if (mech_modules == NULL)
        i_fatal("No authentication mechanisms configured");
    mech_list_verify_passdb(passdb);

    /* get our realm - note that we allocate from data stack so
       this function should never be called inside I/O loop or anywhere
       else where t_pop() is called */
    env = getenv("REALMS");
    if (env == NULL)
        env = "";
    auth_realms = t_strsplit_spaces(env, " ");

    default_realm = getenv("DEFAULT_REALM");
    if (default_realm != NULL && *default_realm == '\0')
        default_realm = NULL;

    env = getenv("USERNAME_CHARS");
    if (env == NULL || *env == '\0') {
        /* all chars are allowed */
        memset(username_chars, 1, sizeof(username_chars));
    } else {
        memset(username_chars, 0, sizeof(username_chars));
        for (; *env != '\0'; env++)
            username_chars[((unsigned char)*env) & 0xff] = 1;
    }

    env = getenv("USERNAME_TRANSLATION");
    memset(username_translation, 0, sizeof(username_translation));
    if (env != NULL) {
        for (; *env != '\0' && env[1] != '\0'; env += 2) {
            username_translation[((unsigned char)*env) & 0xff] =
                env[1];
        }
    }

    ssl_require_client_cert = getenv("SSL_REQUIRE_CLIENT_CERT") != NULL;

    auth_failures_buf = buffer_create_dynamic(default_pool, 1024);
        to_auth_failures = timeout_add(2000, auth_failure_timeout, NULL);
}

void mech_deinit(void)
{
    timeout_remove(to_auth_failures);

    mech_unregister_module(&mech_plain);
    mech_unregister_module(&mech_login);
    mech_unregister_module(&mech_apop);
    mech_unregister_module(&mech_cram_md5);
    mech_unregister_module(&mech_digest_md5);
    mech_unregister_module(&mech_ntlm);
    mech_unregister_module(&mech_rpa);
    mech_unregister_module(&mech_anonymous);

    str_free(mech_handshake);
}