Make handle_child_* request public

I took the opportunity to move everything related to the handling of the
krb5_child into a separate file and cleaned the interfaces and related
structures a bit.

4 files changed, 432 insertions, 326 deletions

diff --git a/Makefile.am b/Makefile.am
index c0dfb3711..c9fd0a165 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -824,6 +824,7 @@ libsss_krb5_la_SOURCES = \
     src/providers/krb5/krb5_delayed_online_authentication.c \
     src/providers/krb5/krb5_auth.c \
     src/providers/krb5/krb5_access.c \
+    src/providers/krb5/krb5_child_handler.c \
     src/providers/krb5/krb5_common.c \
     src/providers/krb5/krb5_init.c \
     src/util/sss_krb5.c
@@ -870,7 +871,8 @@ libsss_ipa_la_SOURCES = \
     src/providers/krb5/krb5_delayed_online_authentication.c \
     src/providers/krb5/krb5_common.c \
     src/providers/krb5/krb5_auth.c \
-    src/providers/krb5/krb5_access.c
+    src/providers/krb5/krb5_access.c \
+    src/providers/krb5/krb5_child_handler.c
 libsss_ipa_la_CFLAGS = \
     $(AM_CFLAGS) \
     $(LDAP_CFLAGS) \
diff --git a/src/providers/krb5/krb5_auth.c b/src/providers/krb5/krb5_auth.c
index 80d8734a7..9dc7a2c9e 100644
--- a/src/providers/krb5/krb5_auth.c
+++ b/src/providers/krb5/krb5_auth.c
@@ -39,12 +39,6 @@
 #include "providers/krb5/krb5_auth.h"
 #include "providers/krb5/krb5_utils.h"
 
-#ifndef SSSD_LIBEXEC_PATH
-#error "SSSD_LIBEXEC_PATH not defined"
-#else
-#define KRB5_CHILD SSSD_LIBEXEC_PATH"/krb5_child"
-#endif
-
 static errno_t safe_remove_old_ccache_file(const char *old_ccache_file,
                                            const char *new_ccache_file)
 {
@@ -205,72 +199,6 @@ done:
     return ret;
 }
 
-errno_t create_send_buffer(struct krb5child_req *kr, struct io_buffer **io_buf)
-{
-    struct io_buffer *buf;
-    size_t rp;
-    const char *keytab;
-    uint32_t validate;
-
-    keytab = dp_opt_get_cstring(kr->krb5_ctx->opts, KRB5_KEYTAB);
-    if (keytab == NULL) {
-        DEBUG(1, ("Missing keytab option.\n"));
-        return EINVAL;
-    }
-
-    validate = dp_opt_get_bool(kr->krb5_ctx->opts, KRB5_VALIDATE) ? 1 : 0;
-
-    buf = talloc(kr, struct io_buffer);
-    if (buf == NULL) {
-        DEBUG(1, ("talloc failed.\n"));
-        return ENOMEM;
-    }
-
-    buf->size = 9*sizeof(uint32_t) + strlen(kr->upn) + strlen(kr->ccname) +
-                strlen(keytab) +
-                kr->pd->authtok_size;
-    if (kr->pd->cmd == SSS_PAM_CHAUTHTOK) {
-        buf->size += sizeof(uint32_t) + kr->pd->newauthtok_size;
-    }
-
-    buf->data = talloc_size(kr, buf->size);
-    if (buf->data == NULL) {
-        DEBUG(1, ("talloc_size failed.\n"));
-        talloc_free(buf);
-        return ENOMEM;
-    }
-
-    rp = 0;
-    SAFEALIGN_COPY_UINT32(&buf->data[rp], &kr->pd->cmd, &rp);
-    SAFEALIGN_COPY_UINT32(&buf->data[rp], &kr->uid, &rp);
-    SAFEALIGN_COPY_UINT32(&buf->data[rp], &kr->gid, &rp);
-    SAFEALIGN_COPY_UINT32(&buf->data[rp], &validate, &rp);
-    SAFEALIGN_COPY_UINT32(&buf->data[rp], &kr->is_offline, &rp);
-
-    SAFEALIGN_SET_UINT32(&buf->data[rp], strlen(kr->upn), &rp);
-    safealign_memcpy(&buf->data[rp], kr->upn, strlen(kr->upn), &rp);
-
-    SAFEALIGN_SET_UINT32(&buf->data[rp], strlen(kr->ccname), &rp);
-    safealign_memcpy(&buf->data[rp], kr->ccname, strlen(kr->ccname), &rp);
-
-    SAFEALIGN_SET_UINT32(&buf->data[rp], strlen(keytab), &rp);
-    safealign_memcpy(&buf->data[rp], keytab, strlen(keytab), &rp);
-
-    SAFEALIGN_COPY_UINT32(&buf->data[rp], &kr->pd->authtok_size, &rp);
-    safealign_memcpy(&buf->data[rp], kr->pd->authtok,
-                     kr->pd->authtok_size, &rp);
-
-    if (kr->pd->cmd == SSS_PAM_CHAUTHTOK) {
-        SAFEALIGN_COPY_UINT32(&buf->data[rp], &kr->pd->newauthtok_size, &rp);
-        safealign_memcpy(&buf->data[rp], kr->pd->newauthtok,
-                         kr->pd->newauthtok_size, &rp);
-    }
-
-    *io_buf = buf;
-
-    return EOK;
-}
-
 static struct krb5_ctx *get_krb5_ctx(struct be_req *be_req)
 {
     struct pam_data *pd;
@@ -305,7 +233,6 @@ static int krb5_cleanup(void *ptr)
 
     if (kr == NULL) return EOK;
 
-    child_cleanup(kr->read_from_child_fd, kr->write_to_child_fd);
     memset(kr, 0, sizeof(struct krb5child_req));
 
     return EOK;
@@ -321,10 +248,9 @@ errno_t krb5_setup(TALLOC_CTX *mem_ctx, struct pam_data *pd,
         DEBUG(1, ("talloc failed.\n"));
         return ENOMEM;
     }
-    kr->read_from_child_fd = -1;
-    kr->write_to_child_fd = -1;
     kr->is_offline = false;
     kr->active_ccache_present = true;
+    kr->run_as_user = true;
     talloc_set_destructor((TALLOC_CTX *) kr, krb5_cleanup);
 
     kr->pd = pd;
@@ -335,249 +261,6 @@ errno_t krb5_setup(TALLOC_CTX *mem_ctx, struct pam_data *pd,
     return EOK;
 }
 
-struct handle_child_state {
-    struct tevent_context *ev;
-    struct krb5child_req *kr;
-    uint8_t *buf;
-    ssize_t len;
-};
-
-static void krb5_child_timeout(struct tevent_context *ev,
-                               struct tevent_timer *te,
-                               struct timeval tv, void *pvt)
-{
-    struct tevent_req *req = talloc_get_type(pvt, struct tevent_req);
-    struct handle_child_state *state = tevent_req_data(req,
-                                                     struct handle_child_state);
-    struct krb5child_req *kr = state->kr;
-    int ret;
-
-    if (kr->timeout_handler == NULL) {
-        return;
-    }
-
-    DEBUG(9, ("timeout for child [%d] reached.\n", kr->child_pid));
-
-    ret = kill(kr->child_pid, SIGKILL);
-    if (ret == -1) {
-        DEBUG(1, ("kill failed [%d][%s].\n", errno, strerror(errno)));
-    }
-
-    tevent_req_error(req, ETIMEDOUT);
-}
-
-static errno_t activate_child_timeout_handler(struct tevent_req *req,
-                                              struct tevent_context *ev,
-                                              struct krb5child_req *kr)
-{
-    struct timeval tv;
-    struct handle_child_state *state = tevent_req_data(req,
-                                                     struct handle_child_state);
-
-    tv = tevent_timeval_current();
-    tv = tevent_timeval_add(&tv,
-                            dp_opt_get_int(kr->krb5_ctx->opts,
-                                           KRB5_AUTH_TIMEOUT),
-                            0);
-    kr->timeout_handler = tevent_add_timer(ev, state, tv,
-                                           krb5_child_timeout, req);
-    if (kr->timeout_handler == NULL) {
-        DEBUG(1, ("tevent_add_timer failed.\n"));
-        return ENOMEM;
-    }
-
-    return EOK;
-}
-
-static errno_t fork_child(struct tevent_req *req, struct tevent_context *ev,
-                          struct krb5child_req *kr)
-{
-    int pipefd_to_child[2];
-    int pipefd_from_child[2];
-    pid_t pid;
-    int ret;
-    errno_t err;
-
-    ret = pipe(pipefd_from_child);
-    if (ret == -1) {
-        err = errno;
-        DEBUG(1, ("pipe failed [%d][%s].\n", errno, strerror(errno)));
-        return err;
-    }
-    ret = pipe(pipefd_to_child);
-    if (ret == -1) {
-        err = errno;
-        DEBUG(1, ("pipe failed [%d][%s].\n", errno, strerror(errno)));
-        return err;
-    }
-
-    pid = fork();
-
-    if (pid == 0) { /* child */
-        /* We need to keep the root privileges to read the keytab file if
-         * validation is enabled, otherwise we can drop them here and run
-         * krb5_child with user privileges.
-         * If we are offline and want to create an empty ccache file. In this
-         * case we can drop the privileges, too. */
-        if (!dp_opt_get_bool(kr->krb5_ctx->opts, KRB5_VALIDATE) ||
-            kr->is_offline) {
-            ret = become_user(kr->uid, kr->gid);
-            if (ret != EOK) {
-                DEBUG(1, ("become_user failed.\n"));
-                return ret;
-            }
-        }
-
-        err = exec_child(kr,
-                         pipefd_to_child, pipefd_from_child,
-                         KRB5_CHILD, kr->krb5_ctx->child_debug_fd);
-        if (err != EOK) {
-            DEBUG(1, ("Could not exec LDAP child: [%d][%s].\n",
-                      err, strerror(err)));
-            return err;
-        }
-    } else if (pid > 0) { /* parent */
-        kr->child_pid = pid;
-        kr->read_from_child_fd = pipefd_from_child[0];
-        close(pipefd_from_child[1]);
-        kr->write_to_child_fd = pipefd_to_child[1];
-        close(pipefd_to_child[0]);
-        fd_nonblocking(kr->read_from_child_fd);
-        fd_nonblocking(kr->write_to_child_fd);
-
-        ret = child_handler_setup(ev, pid, NULL, NULL);
-        if (ret != EOK) {
-            DEBUG(1, ("Could not set up child signal handler\n"));
-            return ret;
-        }
-
-        err = activate_child_timeout_handler(req, ev, kr);
-        if (err != EOK) {
-            DEBUG(1, ("activate_child_timeout_handler failed.\n"));
-        }
-
-    } else { /* error */
-        err = errno;
-        DEBUG(1, ("fork failed [%d][%s].\n", errno, strerror(errno)));
-        return err;
-    }
-
-    return EOK;
-}
-
-static void handle_child_step(struct tevent_req *subreq);
-static void handle_child_done(struct tevent_req *subreq);
-
-static struct tevent_req *handle_child_send(TALLOC_CTX *mem_ctx,
-                                            struct tevent_context *ev,
-                                            struct krb5child_req *kr)
-{
-    struct tevent_req *req, *subreq;
-    struct handle_child_state *state;
-    struct io_buffer *buf;
-    int ret;
-
-    req = tevent_req_create(mem_ctx, &state, struct handle_child_state);
-    if (req == NULL) {
-        return NULL;
-    }
-
-    state->ev = ev;
-    state->kr = kr;
-    state->buf = NULL;
-    state->len = 0;
-
-    ret = create_send_buffer(kr, &buf);
-    if (ret != EOK) {
-        DEBUG(1, ("create_send_buffer failed.\n"));
-        goto fail;
-    }
-
-    ret = fork_child(req, ev, kr);
-    if (ret != EOK) {
-        DEBUG(1, ("fork_child failed.\n"));
-        goto fail;
-    }
-
-    subreq = write_pipe_send(state, ev, buf->data, buf->size,
-                             kr->write_to_child_fd);
-    if (!subreq) {
-        ret = ENOMEM;
-        goto fail;
-    }
-    tevent_req_set_callback(subreq, handle_child_step, req);
-
-    return req;
-
-fail:
-    tevent_req_error(req, ret);
-    tevent_req_post(req, ev);
-    return req;
-}
-
-static void handle_child_step(struct tevent_req *subreq)
-{
-    struct tevent_req *req = tevent_req_callback_data(subreq,
-                                                      struct tevent_req);
-    struct handle_child_state *state = tevent_req_data(req,
-                                                    struct handle_child_state);
-    int ret;
-
-    ret = write_pipe_recv(subreq);
-    talloc_zfree(subreq);
-    if (ret != EOK) {
-        tevent_req_error(req, ret);
-        return;
-    }
-
-    close(state->kr->write_to_child_fd);
-    state->kr->write_to_child_fd = -1;
-
-    subreq = read_pipe_send(state, state->ev, state->kr->read_from_child_fd);
-    if (!subreq) {
-        tevent_req_error(req, ENOMEM);
-        return;
-    }
-    tevent_req_set_callback(subreq, handle_child_done, req);
-}
-
-static void handle_child_done(struct tevent_req *subreq)
-{
-    struct tevent_req *req = tevent_req_callback_data(subreq,
-                                                      struct tevent_req);
-    struct handle_child_state *state = tevent_req_data(req,
-                                                    struct handle_child_state);
-    int ret;
-
-    ret = read_pipe_recv(subreq, state, &state->buf, &state->len);
-    talloc_zfree(subreq);
-    if (ret != EOK) {
-        tevent_req_error(req, ret);
-        return;
-    }
-
-    close(state->kr->read_from_child_fd);
-    state->kr->read_from_child_fd = -1;
-
-    tevent_req_done(req);
-    return;
-}
-
-static int handle_child_recv(struct tevent_req *req,
-                             TALLOC_CTX *mem_ctx,
-                             uint8_t **buf, ssize_t *len)
-{
-    struct handle_child_state *state = tevent_req_data(req,
-                                                    struct handle_child_state);
-
-    TEVENT_REQ_RETURN_ON_ERROR(req);
-
-    *buf = talloc_move(mem_ctx, &state->buf);
-    *len = state->len;
-
-    return EOK;
-}
-
 static void krb5_resolve_kdc_done(struct tevent_req *subreq);
 static void krb5_resolve_kpasswd_done(struct tevent_req *subreq);
 static void krb5_find_ccache_step(struct tevent_req *req);
@@ -957,6 +640,17 @@ static void krb5_find_ccache_step(struct tevent_req *req)
         }
     }
 
+    /* We need to keep the root privileges to read the keytab file if
+     * validation is enabled, otherwise we can drop them and run krb5_child
+     * with user privileges.
+     * If we are offline we want to create an empty ccache file. In this
+     * case we can drop the privileges, too. */
+    if (!dp_opt_get_bool(kr->krb5_ctx->opts, KRB5_VALIDATE) || kr->is_offline) {
+        kr->run_as_user = true;
+    } else {
+        kr->run_as_user = false;
+    }
+
     subreq = handle_child_send(state, state->ev, kr);
     if (subreq == NULL) {
         DEBUG(1, ("handle_child_send failed.\n"));
@@ -996,7 +690,6 @@ static void krb5_child_done(struct tevent_req *subreq)
     int32_t msg_len;
 
     ret = handle_child_recv(subreq, pd, &buf, &len);
-    talloc_zfree(kr->timeout_handler);
     talloc_zfree(subreq);
     if (ret != EOK) {
         DEBUG(1, ("child failed (%d [%s])\n", ret, strerror(ret)));
diff --git a/src/providers/krb5/krb5_auth.h b/src/providers/krb5/krb5_auth.h
index a54058645..130e85db9 100644
--- a/src/providers/krb5/krb5_auth.h
+++ b/src/providers/krb5/krb5_auth.h
@@ -30,6 +30,7 @@
 
 #include "util/sss_krb5.h"
 #include "providers/dp_backend.h"
+#include "providers/child_common.h"
 #include "providers/krb5/krb5_common.h"
 
 #define CCACHE_ENV_NAME "KRB5CCNAME"
@@ -37,15 +38,9 @@
 #define ILLEGAL_PATH_PATTERN "//|/\\./|/\\.\\./"
 
 struct krb5child_req {
-    pid_t child_pid;
-    int read_from_child_fd;
-    int write_to_child_fd;
-
     struct pam_data *pd;
     struct krb5_ctx *krb5_ctx;
 
-    struct tevent_timer *timeout_handler;
-
     const char *ccname;
     const char *old_ccname;
     const char *homedir;
@@ -57,6 +52,7 @@ struct krb5child_req {
     struct fo_server *kpasswd_srv;
     bool active_ccache_present;
     bool valid_tgt_present;
+    bool run_as_user;
 };
 
 errno_t krb5_setup(TALLOC_CTX *mem_ctx, struct pam_data *pd,
@@ -71,6 +67,12 @@ struct tevent_req *krb5_auth_send(TALLOC_CTX *mem_ctx,
                                   struct krb5_ctx *krb5_ctx);
 int krb5_auth_recv(struct tevent_req *req, int *pam_status, int *dp_err);
 
+struct tevent_req *handle_child_send(TALLOC_CTX *mem_ctx,
+                                     struct tevent_context *ev,
+                                     struct krb5child_req *kr);
+int handle_child_recv(struct tevent_req *req, TALLOC_CTX *mem_ctx,
+                      uint8_t **buf, ssize_t *len);
+
 errno_t add_user_to_delayed_online_authentication(struct krb5_ctx *krb5_ctx,
                                                   struct pam_data *pd,
                                                   uid_t uid);
diff --git a/src/providers/krb5/krb5_child_handler.c b/src/providers/krb5/krb5_child_handler.c
new file mode 100644
index 000000000..e708c50cc
--- /dev/null
+++ b/src/providers/krb5/krb5_child_handler.c
@@ -0,0 +1,409 @@
+/*
+    SSSD
+
+    Kerberos 5 Backend Module - Manage krb5_child
+
+    Authors:
+        Sumit Bose <sbose@redhat.com>
+
+    Copyright (C) 2010 Red Hat
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "util/util.h"
+#include "providers/child_common.h"
+#include "providers/krb5/krb5_common.h"
+#include "providers/krb5/krb5_auth.h"
+#include "src/providers/krb5/krb5_utils.h"
+
+#ifndef SSSD_LIBEXEC_PATH
+#error "SSSD_LIBEXEC_PATH not defined"
+#else
+#define KRB5_CHILD SSSD_LIBEXEC_PATH"/krb5_child"
+#endif
+
+struct io {
+    int read_from_child_fd;
+    int write_to_child_fd;
+};
+
+struct handle_child_state {
+    struct tevent_context *ev;
+    struct krb5child_req *kr;
+    uint8_t *buf;
+    ssize_t len;
+
+    struct tevent_timer *timeout_handler;
+    pid_t child_pid;
+
+    struct io *io;
+};
+
+static int child_io_destructor(void *ptr)
+{
+    int ret;
+    struct io *io = talloc_get_type(ptr, struct io);
+    if (io == NULL) return EOK;
+
+    if (io->write_to_child_fd != -1) {
+        ret = close(io->write_to_child_fd);
+        io->write_to_child_fd = -1;
+        if (ret != EOK) {
+            ret = errno;
+            DEBUG(1, ("close failed [%d][%s].\n", ret, strerror(ret)));
+        }
+    }
+
+    if (io->read_from_child_fd != -1) {
+        ret = close(io->read_from_child_fd);
+        io->read_from_child_fd = -1;
+        if (ret != EOK) {
+            ret = errno;
+            DEBUG(1, ("close failed [%d][%s].\n", ret, strerror(ret)));
+        }
+    }
+
+    return EOK;
+}
+
+static errno_t create_send_buffer(struct krb5child_req *kr,
+                                  struct io_buffer **io_buf)
+{
+    struct io_buffer *buf;
+    size_t rp;
+    const char *keytab;
+    uint32_t validate;
+    size_t username_len;
+
+    keytab = dp_opt_get_cstring(kr->krb5_ctx->opts, KRB5_KEYTAB);
+    if (keytab == NULL) {
+        DEBUG(1, ("Missing keytab option.\n"));
+        return EINVAL;
+    }
+
+    validate = dp_opt_get_bool(kr->krb5_ctx->opts, KRB5_VALIDATE) ? 1 : 0;
+
+    buf = talloc(kr, struct io_buffer);
+    if (buf == NULL) {
+        DEBUG(1, ("talloc failed.\n"));
+        return ENOMEM;
+    }
+
+    buf->size = 6*sizeof(uint32_t) + strlen(kr->upn);
+
+    if (kr->pd->cmd == SSS_PAM_AUTHENTICATE ||
+        kr->pd->cmd == SSS_PAM_CHAUTHTOK_PRELIM ||
+        kr->pd->cmd == SSS_PAM_CHAUTHTOK) {
+        buf->size += 3*sizeof(uint32_t) + strlen(kr->ccname) + strlen(keytab) +
+                     kr->pd->authtok_size;
+    }
+
+    if (kr->pd->cmd == SSS_PAM_CHAUTHTOK) {
+        buf->size += sizeof(uint32_t) + kr->pd->newauthtok_size;
+    }
+
+    if (kr->pd->cmd == SSS_PAM_ACCT_MGMT) {
+        username_len = strlen(kr->pd->user);
+        buf->size += sizeof(uint32_t) + username_len;
+    }
+
+    buf->data = talloc_size(kr, buf->size);
+    if (buf->data == NULL) {
+        DEBUG(1, ("talloc_size failed.\n"));
+        talloc_free(buf);
+        return ENOMEM;
+    }
+
+    rp = 0;
+    SAFEALIGN_COPY_UINT32(&buf->data[rp], &kr->pd->cmd, &rp);
+    SAFEALIGN_COPY_UINT32(&buf->data[rp], &kr->uid, &rp);
+    SAFEALIGN_COPY_UINT32(&buf->data[rp], &kr->gid, &rp);
+    SAFEALIGN_COPY_UINT32(&buf->data[rp], &validate, &rp);
+    SAFEALIGN_COPY_UINT32(&buf->data[rp], &kr->is_offline, &rp);
+
+    SAFEALIGN_SET_UINT32(&buf->data[rp], strlen(kr->upn), &rp);
+    safealign_memcpy(&buf->data[rp], kr->upn, strlen(kr->upn), &rp);
+
+    if (kr->pd->cmd == SSS_PAM_AUTHENTICATE ||
+        kr->pd->cmd == SSS_PAM_CHAUTHTOK_PRELIM ||
+        kr->pd->cmd == SSS_PAM_CHAUTHTOK) {
+        SAFEALIGN_SET_UINT32(&buf->data[rp], strlen(kr->ccname), &rp);
+        safealign_memcpy(&buf->data[rp], kr->ccname, strlen(kr->ccname), &rp);
+
+        SAFEALIGN_SET_UINT32(&buf->data[rp], strlen(keytab), &rp);
+        safealign_memcpy(&buf->data[rp], keytab, strlen(keytab), &rp);
+
+        SAFEALIGN_COPY_UINT32(&buf->data[rp], &kr->pd->authtok_size, &rp);
+        safealign_memcpy(&buf->data[rp], kr->pd->authtok,
+                         kr->pd->authtok_size, &rp);
+    }
+
+    if (kr->pd->cmd == SSS_PAM_CHAUTHTOK) {
+        SAFEALIGN_COPY_UINT32(&buf->data[rp], &kr->pd->newauthtok_size, &rp);
+        safealign_memcpy(&buf->data[rp], kr->pd->newauthtok,
+                         kr->pd->newauthtok_size, &rp);
+    }
+
+    if (kr->pd->cmd == SSS_PAM_ACCT_MGMT) {
+        SAFEALIGN_SET_UINT32(&buf->data[rp], username_len, &rp);
+        safealign_memcpy(&buf->data[rp], kr->pd->user, username_len, &rp);
+    }
+
+    *io_buf = buf;
+
+    return EOK;
+}
+
+
+static void krb5_child_timeout(struct tevent_context *ev,
+                               struct tevent_timer *te,
+                               struct timeval tv, void *pvt)
+{
+    struct tevent_req *req = talloc_get_type(pvt, struct tevent_req);
+    struct handle_child_state *state = tevent_req_data(req,
+                                                     struct handle_child_state);
+    int ret;
+
+    if (state->timeout_handler == NULL) {
+        return;
+    }
+
+    DEBUG(9, ("timeout for child [%d] reached.\n", state->child_pid));
+
+    ret = kill(state->child_pid, SIGKILL);
+    if (ret == -1) {
+        DEBUG(1, ("kill failed [%d][%s].\n", errno, strerror(errno)));
+    }
+
+    tevent_req_error(req, ETIMEDOUT);
+}
+
+static errno_t activate_child_timeout_handler(struct tevent_req *req,
+                                              struct tevent_context *ev,
+                                              const uint32_t timeout_seconds)
+{
+    struct timeval tv;
+    struct handle_child_state *state = tevent_req_data(req,
+                                                     struct handle_child_state);
+
+    tv = tevent_timeval_current();
+    tv = tevent_timeval_add(&tv, timeout_seconds, 0);
+    state->timeout_handler = tevent_add_timer(ev, state, tv,
+                                           krb5_child_timeout, req);
+    if (state->timeout_handler == NULL) {
+        DEBUG(1, ("tevent_add_timer failed.\n"));
+        return ENOMEM;
+    }
+
+    return EOK;
+}
+
+static errno_t fork_child(struct tevent_req *req)
+{
+    int pipefd_to_child[2];
+    int pipefd_from_child[2];
+    pid_t pid;
+    int ret;
+    errno_t err;
+    struct handle_child_state *state = tevent_req_data(req,
+                                                     struct handle_child_state);
+
+    ret = pipe(pipefd_from_child);
+    if (ret == -1) {
+        err = errno;
+        DEBUG(1, ("pipe failed [%d][%s].\n", errno, strerror(errno)));
+        return err;
+    }
+    ret = pipe(pipefd_to_child);
+    if (ret == -1) {
+        err = errno;
+        DEBUG(1, ("pipe failed [%d][%s].\n", errno, strerror(errno)));
+        return err;
+    }
+
+    pid = fork();
+
+    if (pid == 0) { /* child */
+        if (state->kr->run_as_user) {
+            ret = become_user(state->kr->uid, state->kr->gid);
+            if (ret != EOK) {
+                DEBUG(1, ("become_user failed.\n"));
+                return ret;
+            }
+        }
+
+        err = exec_child(state,
+                         pipefd_to_child, pipefd_from_child,
+                         KRB5_CHILD, state->kr->krb5_ctx->child_debug_fd);
+        if (err != EOK) {
+            DEBUG(1, ("Could not exec KRB5 child: [%d][%s].\n",
+                      err, strerror(err)));
+            return err;
+        }
+    } else if (pid > 0) { /* parent */
+        state->child_pid = pid;
+        state->io->read_from_child_fd = pipefd_from_child[0];
+        close(pipefd_from_child[1]);
+        state->io->write_to_child_fd = pipefd_to_child[1];
+        close(pipefd_to_child[0]);
+        fd_nonblocking(state->io->read_from_child_fd);
+        fd_nonblocking(state->io->write_to_child_fd);
+
+        ret = child_handler_setup(state->ev, pid, NULL, NULL);
+        if (ret != EOK) {
+            DEBUG(1, ("Could not set up child signal handler\n"));
+            return ret;
+        }
+
+        err = activate_child_timeout_handler(req, state->ev,
+                  dp_opt_get_int(state->kr->krb5_ctx->opts, KRB5_AUTH_TIMEOUT));
+        if (err != EOK) {
+            DEBUG(1, ("activate_child_timeout_handler failed.\n"));
+        }
+
+    } else { /* error */
+        err = errno;
+        DEBUG(1, ("fork failed [%d][%s].\n", errno, strerror(errno)));
+        return err;
+    }
+
+    return EOK;
+}
+
+static void handle_child_step(struct tevent_req *subreq);
+static void handle_child_done(struct tevent_req *subreq);
+
+struct tevent_req *handle_child_send(TALLOC_CTX *mem_ctx,
+                                     struct tevent_context *ev,
+                                     struct krb5child_req *kr)
+{
+    struct tevent_req *req, *subreq;
+    struct handle_child_state *state;
+    int ret;
+    struct io_buffer *buf;
+
+    req = tevent_req_create(mem_ctx, &state, struct handle_child_state);
+    if (req == NULL) {
+        return NULL;
+    }
+
+    state->ev = ev;
+    state->kr = kr;
+    state->buf = NULL;
+    state->len = 0;
+    state->child_pid = -1;
+    state->timeout_handler = NULL;
+
+    state->io = talloc(state, struct io);
+    if (state->io == NULL) {
+        DEBUG(1, ("talloc failed.\n"));
+        ret = ENOMEM;
+        goto fail;
+    }
+    state->io->write_to_child_fd = -1;
+    state->io->read_from_child_fd = -1;
+    talloc_set_destructor((void *) state->io, child_io_destructor);
+
+    ret = create_send_buffer(kr, &buf);
+    if (ret != EOK) {
+        DEBUG(1, ("create_send_buffer failed.\n"));
+        goto fail;
+    }
+
+    ret = fork_child(req);
+    if (ret != EOK) {
+        DEBUG(1, ("fork_child failed.\n"));
+        goto fail;
+    }
+
+    subreq = write_pipe_send(state, ev, buf->data, buf->size,
+                             state->io->write_to_child_fd);
+    if (!subreq) {
+        ret = ENOMEM;
+        goto fail;
+    }
+    tevent_req_set_callback(subreq, handle_child_step, req);
+
+    return req;
+
+fail:
+    tevent_req_error(req, ret);
+    tevent_req_post(req, ev);
+    return req;
+}
+
+static void handle_child_step(struct tevent_req *subreq)
+{
+    struct tevent_req *req = tevent_req_callback_data(subreq,
+                                                      struct tevent_req);
+    struct handle_child_state *state = tevent_req_data(req,
+                                                    struct handle_child_state);
+    int ret;
+
+    ret = write_pipe_recv(subreq);
+    talloc_zfree(subreq);
+    if (ret != EOK) {
+        tevent_req_error(req, ret);
+        return;
+    }
+
+    close(state->io->write_to_child_fd);
+    state->io->write_to_child_fd = -1;
+
+    subreq = read_pipe_send(state, state->ev, state->io->read_from_child_fd);
+    if (!subreq) {
+        tevent_req_error(req, ENOMEM);
+        return;
+    }
+    tevent_req_set_callback(subreq, handle_child_done, req);
+}
+
+static void handle_child_done(struct tevent_req *subreq)
+{
+    struct tevent_req *req = tevent_req_callback_data(subreq,
+                                                      struct tevent_req);
+    struct handle_child_state *state = tevent_req_data(req,
+                                                    struct handle_child_state);
+    int ret;
+
+    talloc_zfree(state->timeout_handler);
+
+    ret = read_pipe_recv(subreq, state, &state->buf, &state->len);
+    talloc_zfree(subreq);
+    if (ret != EOK) {
+        tevent_req_error(req, ret);
+        return;
+    }
+
+    close(state->io->read_from_child_fd);
+    state->io->read_from_child_fd = -1;
+
+    tevent_req_done(req);
+    return;
+}
+
+int handle_child_recv(struct tevent_req *req, TALLOC_CTX *mem_ctx,
+                      uint8_t **buf, ssize_t *len)
+{
+    struct handle_child_state *state = tevent_req_data(req,
+                                                    struct handle_child_state);
+
+    TEVENT_REQ_RETURN_ON_ERROR(req);
+
+    *buf = talloc_move(mem_ctx, &state->buf);
+    *len = state->len;
+
+    return EOK;
+}