src/auth/mech-winbind.c

	mech-winbind.c revision 49fc09f995183d44e004bbc3eb9b6c6c7b6cae7f
/*
 * NTLM and Negotiate authentication mechanisms,
 * using Samba winbind daemon
 *
 * Copyright (c) 2007 Dmitry Butskoy <dmitry@butskoy.name>
 *
 * This software is released under the MIT license.
 */

#include "auth-common.h"
#include "lib-signals.h"
#include "mech.h"
#include "str.h"
#include "buffer.h"
#include "base64.h"
#include "execv-const.h"
#include "istream.h"
#include "ostream.h"

#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>

#define DEFAULT_WINBIND_HELPER_PATH "/usr/bin/ntlm_auth"

enum helper_result {
    HR_OK   = 0,    /* OK or continue */
    HR_FAIL = -1,   /* authentication failed */
    HR_RESTART = -2 /* FAIL + try to restart helper */
};

struct winbind_helper {
    const char *param;
    pid_t pid;

    struct istream *in_pipe;
    struct ostream *out_pipe;
};

struct winbind_auth_request {
    struct auth_request auth_request;

    struct winbind_helper *winbind;
    bool continued;
};

static struct winbind_helper winbind_ntlm_context = {
    "--helper-protocol=squid-2.5-ntlmssp", -1, NULL, NULL
};
static struct winbind_helper winbind_spnego_context = {
    "--helper-protocol=gss-spnego", -1, NULL, NULL
};

static bool sigchld_handler_set = FALSE;

static void winbind_helper_disconnect(struct winbind_helper *winbind)
{
    if (winbind->in_pipe != NULL)
        i_stream_destroy(&winbind->in_pipe);
    if (winbind->out_pipe != NULL)
        o_stream_destroy(&winbind->out_pipe);
}

static void winbind_wait_pid(struct winbind_helper *winbind)
{
    int status, ret;

    if (winbind->pid == -1)
        return;

    /* FIXME: use child-wait.h API */
    if ((ret = waitpid(winbind->pid, &status, WNOHANG)) <= 0) {
        if (ret < 0 && errno != ECHILD && errno != EINTR)
            i_error("waitpid() failed: %m");
        return;
    }

    if (WIFSIGNALED(status)) {
        i_error("winbind: ntlm_auth died with signal %d",
            WTERMSIG(status));
    } else if (WIFEXITED(status)) {
        i_error("winbind: ntlm_auth exited with exit code %d",
            WEXITSTATUS(status));
    } else {
        /* shouldn't happen */
        i_error("winbind: ntlm_auth exited with status %d",
            status);
    }
    winbind->pid = -1;
}

static void sigchld_handler(const siginfo_t *si ATTR_UNUSED,
                void *context ATTR_UNUSED)
{
    winbind_wait_pid(&winbind_ntlm_context);
    winbind_wait_pid(&winbind_spnego_context);
}

static void
winbind_helper_connect(const struct auth_settings *set,
               struct winbind_helper *winbind)
{
    int infd[2], outfd[2];
    pid_t pid;

    if (winbind->in_pipe != NULL || winbind->pid != -1)
        return;

    if (pipe(infd) < 0) {
        i_error("pipe() failed: %m");
        return;
    }
    if (pipe(outfd) < 0) {
        i_close_fd(&infd[0]); i_close_fd(&infd[1]);
        return;
    }

    pid = fork();
    if (pid < 0) {
        i_error("fork() failed: %m");
        i_close_fd(&infd[0]); i_close_fd(&infd[1]);
        i_close_fd(&outfd[0]); i_close_fd(&outfd[1]);
        return;
    }

    if (pid == 0) {
        /* child */
        const char *args[3];

        i_close_fd(&infd[0]);
        i_close_fd(&outfd[1]);

        if (dup2(outfd[0], STDIN_FILENO) < 0 ||
            dup2(infd[1], STDOUT_FILENO) < 0)
            i_fatal("dup2() failed: %m");

        args[0] = set->winbind_helper_path;
        args[1] = winbind->param;
        args[2] = NULL;
        execv_const(args[0], args);
    }

    /* parent */
    i_close_fd(&infd[1]);
    i_close_fd(&outfd[0]);

    winbind->pid = pid;
    winbind->in_pipe =
        i_stream_create_fd(infd[0], AUTH_CLIENT_MAX_LINE_LENGTH, TRUE);
    winbind->out_pipe =
        o_stream_create_fd(outfd[1], (size_t)-1, TRUE);

    if (!sigchld_handler_set) {
        sigchld_handler_set = TRUE;
        lib_signals_set_handler(SIGCHLD, LIBSIG_FLAGS_SAFE,
                    sigchld_handler, NULL);
    }
}

static enum helper_result
do_auth_continue(struct auth_request *auth_request,
         const unsigned char *data, size_t data_size)
{
    struct winbind_auth_request *request =
        (struct winbind_auth_request *)auth_request;
    struct istream *in_pipe = request->winbind->in_pipe;
    string_t *str;
    char *answer;
    const char **token;
    bool gss_spnego = request->winbind == &winbind_spnego_context;

    if (request->winbind->in_pipe == NULL)
        return HR_RESTART;

    str = t_str_new(MAX_BASE64_ENCODED_SIZE(data_size + 1) + 4);
    str_printfa(str, "%s ", request->continued ? "KK" : "YR");
    base64_encode(data, data_size, str);
    str_append_c(str, '\n');

    if (o_stream_send(request->winbind->out_pipe,
              str_data(str), str_len(str)) < 0 ||
        o_stream_flush(request->winbind->out_pipe) < 0) {
        auth_request_log_error(auth_request, "winbind",
                       "write(out_pipe) failed: %m");
        return HR_RESTART;
    }
    request->continued = FALSE;

    while ((answer = i_stream_read_next_line(in_pipe)) == NULL) {
        if (in_pipe->stream_errno != 0)
            break;
    }
    if (answer == NULL) {
        auth_request_log_error(auth_request, "winbind",
                       "read(in_pipe) failed: %m");
        return HR_RESTART;
    }

    token = t_strsplit_spaces(answer, " ");
    if (token[0] == NULL ||
        (token[1] == NULL && strcmp(token[0], "BH") != 0) ||
        (gss_spnego && (token[1] == NULL || token[2] == NULL))) {
        auth_request_log_error(auth_request, "winbind",
                       "Invalid input from helper: %s", answer);
        return HR_RESTART;
    }

    /*
     *  NTLM:
     *  The child's reply contains 2 parts:
     *   - The code: TT, AF or NA
     *   - The argument:
     *        For TT it's the blob to send to the client, coded in base64
     *        For AF it's user or DOMAIN\user
     *        For NA it's the NT error code
     *
     *  GSS-SPNEGO:
     *  The child's reply contains 3 parts:
     *   - The code: TT, AF or NA
     *   - The blob to send to the client, coded in base64
     *   - The argument:
     *        For TT it's a dummy '*'
     *        For AF it's DOMAIN\user
     *        For NA it's the NT error code
     */

    if (strcmp(token[0], "TT") == 0) {
        buffer_t *buf;

        buf = t_base64_decode_str(token[1]);
        auth_request_handler_reply_continue(auth_request, buf->data,
                            buf->used);
        request->continued = TRUE;
        return HR_OK;
    } else if (strcmp(token[0], "NA") == 0) {
        const char *error = gss_spnego ? token[2] : token[1];

        auth_request_log_info(auth_request, "winbind",
                      "user not authenticated: %s", error);
        return HR_FAIL;
    } else if (strcmp(token[0], "AF") == 0) {
        const char *user, *p, *error;

        user = t_strarray_join(gss_spnego ? token+2 : token+1, " ");
        i_assert(user != NULL);

        p = strchr(user, '\\');
        if (p != NULL) {
            /* change "DOMAIN\user" to uniform style
               "user@DOMAIN" */
            user = t_strconcat(p+1, "@",
                       t_strdup_until(user, p), NULL);
        }

        if (!auth_request_set_username(auth_request, user, &error)) {
            auth_request_log_info(auth_request, "winbind",
                          "%s", error);
            return HR_FAIL;
        }

        request->auth_request.passdb_success = TRUE;
        if (gss_spnego && strcmp(token[1], "*") != 0) {
            buffer_t *buf;

            buf = t_base64_decode_str(token[1]);
            auth_request_success(&request->auth_request,
                         buf->data, buf->used);
        } else {
            auth_request_success(&request->auth_request, "", 0);
        }
        return HR_OK;
    } else if (strcmp(token[0], "BH") == 0) {
        auth_request_log_info(auth_request, "winbind",
                      "ntlm_auth reports broken helper: %s",
                      token[1] != NULL ? token[1] : "");
        return HR_RESTART;
    } else {
        auth_request_log_error(auth_request, "winbind",
                       "Invalid input from helper: %s", answer);
        return HR_RESTART;
    }
}

static void
mech_winbind_auth_initial(struct auth_request *auth_request,
              const unsigned char *data, size_t data_size)
{
    struct winbind_auth_request *request =
        (struct winbind_auth_request *)auth_request;

    winbind_helper_connect(auth_request->set, request->winbind);
    mech_generic_auth_initial(auth_request, data, data_size);
}

static void
mech_winbind_auth_continue(struct auth_request *auth_request,
               const unsigned char *data, size_t data_size)
{
    struct winbind_auth_request *request =
        (struct winbind_auth_request *)auth_request;
    enum helper_result res;

    res = do_auth_continue(auth_request, data, data_size);
    if (res != HR_OK) {
        if (res == HR_RESTART)
            winbind_helper_disconnect(request->winbind);
        auth_request_fail(auth_request);
    }
}

static struct auth_request *do_auth_new(struct winbind_helper *winbind)
{
    struct winbind_auth_request *request;
    pool_t pool;

    pool = pool_alloconly_create("winbind_auth_request", 1024);
    request = p_new(pool, struct winbind_auth_request, 1);
    request->auth_request.pool = pool;

    request->winbind = winbind;
    return &request->auth_request;
}

static struct auth_request *mech_winbind_ntlm_auth_new(void)
{
    return do_auth_new(&winbind_ntlm_context);
}

static struct auth_request *mech_winbind_spnego_auth_new(void)
{
    return do_auth_new(&winbind_spnego_context);
}

const struct mech_module mech_winbind_ntlm = {
    "NTLM",

    .flags = MECH_SEC_DICTIONARY | MECH_SEC_ACTIVE,
    .passdb_need = MECH_PASSDB_NEED_NOTHING,

    mech_winbind_ntlm_auth_new,
    mech_winbind_auth_initial,
    mech_winbind_auth_continue,
    mech_generic_auth_free
};

const struct mech_module mech_winbind_spnego = {
    "GSS-SPNEGO",

    .flags = 0,
    .passdb_need = MECH_PASSDB_NEED_NOTHING,

    mech_winbind_spnego_auth_new,
    mech_winbind_auth_initial,
    mech_winbind_auth_continue,
    mech_generic_auth_free
};