Proxy provider PAM handling in child process

This patch adds a new tevent_req to the proxy provider, which will
spawn short-lived child processes to handle PAM requests. These
processes then call the proxied PAM stack and return the results
via SBUS method reply. Once it is returned, the parent process
kills the child.

There is a maximum of ten child processes running simultaneously,
after which requests will be queued for sending once a child slot
frees up. The maximum processes will be made configurable at a
later date (as this would violate string freeze).

4 files changed, 1561 insertions, 148 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index cb0685cd7..b83523255 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -62,7 +62,8 @@ sssdlibexec_PROGRAMS = \
     krb5_child \
     ldap_child \
     $(sssd_pk) \
-    $(sssd_info)
+    $(sssd_info) \
+    proxy_child
 
 dist_sssdlibexec_SCRIPTS = \
     config/upgrade_config.py
@@ -356,6 +357,7 @@ dist_noinst_HEADERS = \
     providers/ipa/ipa_timerules.h \
     providers/ipa/ipa_auth.h \
     providers/ipa/ipa_dyndns.h \
+    providers/proxy/proxy.h \
     tools/tools_util.h \
     tools/sss_sync_ops.h \
     resolv/async_resolv.h \
@@ -753,7 +755,7 @@ libsss_ldap_la_LDFLAGS = \
     -module
 
 libsss_proxy_la_SOURCES = \
-    providers/proxy.c
+    providers/proxy/proxy.c
 libsss_proxy_la_CFLAGS = \
     $(AM_CFLAGS)
 libsss_proxy_la_LIBADD = \
@@ -870,6 +872,16 @@ ldap_child_LDADD = \
     $(OPENLDAP_LIBS) \
     $(KRB5_LIBS)
 
+proxy_child_SOURCES = \
+    $(SSSD_UTIL_OBJ) \
+    providers/proxy/proxy_child.c
+proxy_child_CFLAGS = \
+    $(AM_CFLAGS) \
+    $(POPT_CFLAGS)
+proxy_child_LDADD = \
+    $(PAM_LIBS) \
+    $(SSSD_LIBS)
+
 memberof_la_SOURCES = \
     ldb_modules/memberof.c
 memberof_la_CFLAGS = \
diff --git a/src/providers/proxy.c b/src/providers/proxy/proxy.c
index d3ec7ef35..ac2a7dffc 100644
--- a/src/providers/proxy.c
+++ b/src/providers/proxy/proxy.c
@@ -24,6 +24,8 @@
 #include <pwd.h>
 #include <grp.h>
 #include <dlfcn.h>
+#include <sys/types.h>
+#include <sys/wait.h>
 
 #include <security/pam_appl.h>
 #include <security/pam_modules.h>
@@ -31,6 +33,8 @@
 #include "util/util.h"
 #include "providers/dp_backend.h"
 #include "db/sysdb.h"
+#include "proxy.h"
+#include <dhash.h>
 
 struct proxy_nss_ops {
     enum nss_status (*getpwnam_r)(const char *name, struct passwd *result,
@@ -65,69 +69,54 @@ struct proxy_ctx {
 struct proxy_auth_ctx {
     struct be_ctx *be;
     char *pam_target;
-};
 
-struct authtok_conv {
-    uint32_t authtok_size;
-    uint8_t *authtok;
+    uint32_t max_children;
+    uint32_t running;
+    uint32_t next_id;
+    hash_table_t *request_table;
+    struct sbus_connection *sbus_srv;
+    int timeout_ms;
 };
 
-static int proxy_internal_conv(int num_msg, const struct pam_message **msgm,
-                            struct pam_response **response,
-                            void *appdata_ptr) {
-    int i;
-    struct pam_response *reply;
-    struct authtok_conv *auth_data;
-
-    auth_data = talloc_get_type(appdata_ptr, struct authtok_conv);
-
-    if (num_msg <= 0) return PAM_CONV_ERR;
+static int client_registration(DBusMessage *message,
+                               struct sbus_connection *conn);
 
-    reply = (struct pam_response *) calloc(num_msg,
-                                           sizeof(struct pam_response));
-    if (reply == NULL) return PAM_CONV_ERR;
-
-    for (i=0; i < num_msg; i++) {
-        switch( msgm[i]->msg_style ) {
-            case PAM_PROMPT_ECHO_OFF:
-                DEBUG(4, ("Conversation message: [%s]\n", msgm[i]->msg));
-                reply[i].resp_retcode = 0;
-                reply[i].resp = calloc(auth_data->authtok_size + 1,
-                                       sizeof(char));
-                if (reply[i].resp == NULL) goto failed;
-                memcpy(reply[i].resp, auth_data->authtok, auth_data->authtok_size);
-
-                break;
-            default:
-                DEBUG(1, ("Conversation style %d not supported.\n",
-                           msgm[i]->msg_style));
-                goto failed;
-        }
-    }
+static struct sbus_method proxy_methods[] = {
+    { DP_METHOD_REGISTER, client_registration },
+    { NULL, NULL }
+};
 
-    *response = reply;
-    reply = NULL;
+struct sbus_interface proxy_interface = {
+    DP_INTERFACE,
+    DP_PATH,
+    SBUS_DEFAULT_VTABLE,
+    proxy_methods,
+    NULL
+};
 
-    return PAM_SUCCESS;
+struct authtok_conv {
+    uint32_t authtok_size;
+    uint8_t *authtok;
+};
 
-failed:
-    free(reply);
-    return PAM_CONV_ERR;
-}
+struct proxy_client_ctx {
+    struct be_req *be_req;
+    struct proxy_auth_ctx *auth_ctx;
+};
 
 static void proxy_pam_handler_cache_done(struct tevent_req *treq);
 static void proxy_reply(struct be_req *req, int dp_err,
                         int error, const char *errstr);
 
+static struct tevent_req *proxy_child_send(TALLOC_CTX *mem_ctx,
+                                           struct proxy_auth_ctx *ctx,
+                                           struct be_req *be_req);
+static void proxy_child_done(struct tevent_req *child_req);
 static void proxy_pam_handler(struct be_req *req) {
-    int ret;
-    int pam_status;
-    pam_handle_t *pamh=NULL;
-    struct authtok_conv *auth_data;
-    struct pam_conv conv;
     struct pam_data *pd;
-    struct proxy_auth_ctx *ctx;;
-    bool cache_auth_data = false;
+    struct proxy_auth_ctx *ctx;
+    struct tevent_req *child_req = NULL;
+    struct proxy_client_ctx *client_ctx;
 
     pd = talloc_get_type(req->req_data, struct pam_data);
 
@@ -158,139 +147,793 @@ static void proxy_pam_handler(struct be_req *req) {
             return;
     }
 
-    conv.conv=proxy_internal_conv;
-    auth_data = talloc_zero(req, struct authtok_conv);
-    conv.appdata_ptr=auth_data;
-
-    ret = pam_start(ctx->pam_target, pd->user, &conv, &pamh);
-    if (ret == PAM_SUCCESS) {
-        DEBUG(1, ("Pam transaction started.\n"));
-        ret = pam_set_item(pamh, PAM_TTY, pd->tty);
-        if (ret != PAM_SUCCESS) {
-            DEBUG(1, ("Setting PAM_TTY failed: %s.\n", pam_strerror(pamh, ret)));
-        }
-        ret = pam_set_item(pamh, PAM_RUSER, pd->ruser);
-        if (ret != PAM_SUCCESS) {
-            DEBUG(1, ("Setting PAM_RUSER failed: %s.\n", pam_strerror(pamh, ret)));
-        }
-        ret = pam_set_item(pamh, PAM_RHOST, pd->rhost);
-        if (ret != PAM_SUCCESS) {
-            DEBUG(1, ("Setting PAM_RHOST failed: %s.\n", pam_strerror(pamh, ret)));
-        }
-        switch (pd->cmd) {
-            case SSS_PAM_AUTHENTICATE:
-                auth_data->authtok_size = pd->authtok_size;
-                auth_data->authtok = pd->authtok;
-                pam_status = pam_authenticate(pamh, 0);
-                if ((pam_status == PAM_SUCCESS) &&
-                    (req->be_ctx->domain->cache_credentials)) {
-                    cache_auth_data = true;
-                }
-                break;
-            case SSS_PAM_SETCRED:
-                pam_status=pam_setcred(pamh, 0);
-                break;
-            case SSS_PAM_ACCT_MGMT:
-                pam_status=pam_acct_mgmt(pamh, 0);
-                break;
-            case SSS_PAM_OPEN_SESSION:
-                pam_status=pam_open_session(pamh, 0);
-                break;
-            case SSS_PAM_CLOSE_SESSION:
-                pam_status=pam_close_session(pamh, 0);
-                break;
-            case SSS_PAM_CHAUTHTOK:
-                if (pd->priv != 1) {
-                    auth_data->authtok_size = pd->authtok_size;
-                    auth_data->authtok = pd->authtok;
-                    pam_status = pam_authenticate(pamh, 0);
-                    if (pam_status != PAM_SUCCESS) break;
-                }
-                auth_data->authtok_size = pd->newauthtok_size;
-                auth_data->authtok = pd->newauthtok;
-                pam_status = pam_chauthtok(pamh, 0);
-                if ((pam_status == PAM_SUCCESS) &&
-                    (req->be_ctx->domain->cache_credentials)) {
-                    cache_auth_data = true;
-                }
-                break;
-            case SSS_PAM_CHAUTHTOK_PRELIM:
-                if (pd->priv != 1) {
-                    auth_data->authtok_size = pd->authtok_size;
-                    auth_data->authtok = pd->authtok;
-                    pam_status = pam_authenticate(pamh, 0);
-                } else {
-                    pam_status = PAM_SUCCESS;
-                }
-                break;
-            default:
-                DEBUG(1, ("unknown PAM call\n"));
-                pam_status=PAM_ABORT;
+    client_ctx = talloc(req, struct proxy_client_ctx);
+    if (client_ctx == NULL) {
+        proxy_reply(req, DP_ERR_FATAL, ENOMEM, NULL);
+        return;
+    }
+    client_ctx->auth_ctx = ctx;
+    client_ctx->be_req = req;
+
+    /* Queue the request and spawn a child if there
+     * is an available slot.
+     */
+    child_req = proxy_child_send(req, ctx, req);
+    if (child_req == NULL) {
+        /* Could not queue request
+         * Return an error
+         */
+        proxy_reply(req, DP_ERR_FATAL, EINVAL, "Could not queue request\n");
+        return;
+    }
+    tevent_req_set_callback(child_req, proxy_child_done, client_ctx);
+    return;
+}
+
+struct pc_init_ctx;
+struct proxy_child_ctx {
+    struct proxy_auth_ctx *auth_ctx;
+    struct be_req *be_req;
+    struct pam_data *pd;
+
+    uint32_t id;
+    pid_t pid;
+    bool running;
+
+    struct sbus_connection *conn;
+    struct tevent_timer *timer;
+
+    struct tevent_req *init_req;
+};
+
+static int proxy_child_destructor(TALLOC_CTX *ctx)
+{
+    struct proxy_child_ctx *child_ctx =
+            talloc_get_type(ctx, struct proxy_child_ctx);
+    hash_key_t key;
+
+    DEBUG(8, ("Removing proxy child id [%d]\n", child_ctx->id));
+    key.type = HASH_KEY_ULONG;
+    key.ul = child_ctx->id;
+    hash_delete(child_ctx->auth_ctx->request_table, &key);
+    return 0;
+}
+
+static struct tevent_req *proxy_child_init_send(TALLOC_CTX *mem_ctx,
+                                              struct proxy_child_ctx *child_ctx,
+                                              struct proxy_auth_ctx *auth_ctx);
+static void proxy_child_init_done(struct tevent_req *subreq);
+static struct tevent_req *proxy_child_send(TALLOC_CTX *mem_ctx,
+                                           struct proxy_auth_ctx *auth_ctx,
+                                           struct be_req *be_req)
+{
+    struct tevent_req *req;
+    struct tevent_req *subreq;
+    struct proxy_child_ctx *state;
+    int hret;
+    hash_key_t key;
+    hash_value_t value;
+    uint32_t first;
+
+    req = tevent_req_create(mem_ctx, &state, struct proxy_child_ctx);
+    if (req == NULL) {
+        DEBUG(1, ("Could not send PAM request to child\n"));
+        return NULL;
+    }
+
+    state->be_req = be_req;
+    state->auth_ctx = auth_ctx;
+    state->pd = talloc_get_type(be_req->req_data, struct pam_data);
+
+    /* Find an available key */
+    key.type = HASH_KEY_ULONG;
+    key.ul = auth_ctx->next_id;
+
+    first = auth_ctx->next_id;
+    while (auth_ctx->next_id == 0 ||
+            hash_has_key(auth_ctx->request_table, &key)) {
+        /* Handle overflow, zero is a reserved value
+         * Also handle the unlikely case where the next ID
+         * is still awaiting being run
+         */
+        auth_ctx->next_id++;
+        key.ul = auth_ctx->next_id;
+
+        if (auth_ctx->next_id == first) {
+            /* We've looped through all possible integers! */
+            DEBUG(0, ("Serious error: queue is too long!\n"));
+            talloc_zfree(req);
+            return NULL;
         }
+    }
 
-        DEBUG(4, ("Pam result: [%d][%s]\n", pam_status,
-                  pam_strerror(pamh, pam_status)));
+    state->id = auth_ctx->next_id;
+    auth_ctx->next_id++;
 
-        if (pam_status == PAM_AUTHINFO_UNAVAIL) {
-            be_mark_offline(req->be_ctx);
+    value.type = HASH_VALUE_PTR;
+    value.ptr = req;
+    DEBUG(8, ("Queueing request [%d]\n", key.ul));
+    hret = hash_enter(auth_ctx->request_table,
+                      &key, &value);
+    if (hret != HASH_SUCCESS) {
+        DEBUG(1, ("Could not add request to the queue\n"));
+        talloc_zfree(req);
+        return NULL;
+    }
+
+    talloc_set_destructor((TALLOC_CTX *) state,
+                          proxy_child_destructor);
+
+    if (auth_ctx->running < auth_ctx->max_children) {
+        /* There's an available slot; start a child
+         * to handle the request
+         */
+
+        auth_ctx->running++;
+        subreq = proxy_child_init_send(auth_ctx, state, auth_ctx);
+        if (!subreq) {
+            DEBUG(1, ("Could not fork child process\n"));
+            auth_ctx->running--;
+            talloc_zfree(req);
+            return NULL;
         }
+        tevent_req_set_callback(subreq, proxy_child_init_done, req);
+
+        state->running = true;
+    }
+
+    /* If there was no available slot, it will be queued
+     * until a slot is available
+     */
+    return req;
+}
+
+struct pc_init_ctx {
+    char *command;
+    pid_t pid;
+    struct tevent_timer *timeout;
+    struct tevent_signal *sige;
+    struct proxy_child_ctx *child_ctx;
+    struct sbus_connection *conn;
+};
+
+static int pc_init_destructor (TALLOC_CTX *ctx)
+{
+    struct pc_init_ctx *init_ctx =
+            talloc_get_type(ctx, struct pc_init_ctx);
+
+    /* If the init request has died, forcibly kill the child */
+    kill(init_ctx->pid, SIGKILL);
+    return 0;
+}
+
+static void pc_init_sig_handler(struct tevent_context *ev,
+                           struct tevent_signal *sige, int signum,
+                           int count, void *__siginfo, void *pvt);
+static void pc_init_timeout(struct tevent_context *ev,
+                            struct tevent_timer *te,
+                            struct timeval t, void *ptr);
+static struct tevent_req *proxy_child_init_send(TALLOC_CTX *mem_ctx,
+                                              struct proxy_child_ctx *child_ctx,
+                                              struct proxy_auth_ctx *auth_ctx)
+{
+    struct tevent_req *req;
+    struct pc_init_ctx *state;
+    char **proxy_child_args;
+    struct timeval tv;
+    errno_t ret;
+    pid_t pid;
+
+    req = tevent_req_create(mem_ctx, &state, struct pc_init_ctx);
+    if (req == NULL) {
+        DEBUG(1, ("Could not create tevent_req\n"));
+        return NULL;
+    }
+
+    state->child_ctx = child_ctx;
+
+    state->command = talloc_asprintf(req,
+            "%s/proxy_child -d %d%s%s --domain %s --id %d",
+            SSSD_LIBEXEC_PATH, debug_level,
+            (debug_timestamps ? "" : " --debug-timestamps=0"),
+            (debug_to_file ? " --debug-to-files" : ""),
+            auth_ctx->be->domain->name,
+            child_ctx->id);
+    if (state->command == NULL) {
+        DEBUG(1, ("talloc_asprintf failed.\n"));
+        return NULL;
+    }
+
+    DEBUG(7, ("Starting proxy child with args [%s]\n", state->command));
+
+    pid = fork();
+    if (pid < 0) {
+        ret = errno;
+        DEBUG(1, ("fork failed [%d][%s].\n", ret, strerror(ret)));
+        talloc_zfree(req);
+        return NULL;
+    }
+
+    if (pid == 0) { /* child */
+        proxy_child_args = parse_args(state->command);
+        execvp(proxy_child_args[0], proxy_child_args);
+
+        ret = errno;
+        DEBUG(0, ("Could not start proxy child [%s]: [%d][%s].\n",
+                  state->command, ret, strerror(ret)));
 
-        ret = pam_end(pamh, pam_status);
-        if (ret != PAM_SUCCESS) {
-            pamh=NULL;
-            DEBUG(1, ("Cannot terminate pam transaction.\n"));
+        _exit(1);
+    }
+
+    else { /* parent */
+        state->pid = pid;
+        /* Make sure to kill the child process if we abort */
+        talloc_set_destructor((TALLOC_CTX *)state, pc_init_destructor);
+
+        state->sige = tevent_add_signal(auth_ctx->be->ev, req,
+                                        SIGCHLD, SA_SIGINFO,
+                                        pc_init_sig_handler, req);
+        if (state->sige == NULL) {
+            DEBUG(1, ("tevent_add_signal failed.\n"));
+            talloc_zfree(req);
+            return NULL;
+        }
+
+        /* Save the init request to the child context.
+         * This is technically a layering violation,
+         * but it's the only sane way to be able to
+         * identify which client is which when it
+         * connects to the backend in
+         * client_registration()
+         */
+        child_ctx->init_req = req;
+
+        /* Wait six seconds for the child to connect
+         * This is because the connection handler will add
+         * its own five-second timeout, and we don't want to
+         * be faster here.
+         */
+        tv = tevent_timeval_current_ofs(6, 0);
+        state->timeout = tevent_add_timer(auth_ctx->be->ev, req,
+                                          tv, pc_init_timeout, req);
+
+        /* processing will continue once the connection is received
+         * in proxy_client_init()
+         */
+        return req;
+    }
+}
+
+static void pc_init_sig_handler(struct tevent_context *ev,
+                                struct tevent_signal *sige, int signum,
+                                int count, void *__siginfo, void *pvt)
+{
+    int ret;
+    int child_status;
+    struct tevent_req *req;
+    struct pc_init_ctx *init_ctx;
+
+    if (count <= 0) {
+        DEBUG(0, ("SIGCHLD handler called with invalid child count\n"));
+        return;
+    }
+
+    req = talloc_get_type(pvt, struct tevent_req);
+    init_ctx = tevent_req_data(req, struct pc_init_ctx);
+
+    DEBUG(7, ("Waiting for child [%d].\n", init_ctx->pid));
+
+    errno = 0;
+    ret = waitpid(init_ctx->pid, &child_status, WNOHANG);
+
+    if (ret == -1) {
+        ret = errno;
+        DEBUG(1, ("waitpid failed [%d][%s].\n", ret, strerror(ret)));
+    } else if (ret == 0) {
+        DEBUG(1, ("waitpid did not find a child with changed status.\n"));
+    } else {
+        if (WIFEXITED(child_status)) {
+            DEBUG(4, ("child [%d] exited with status [%d].\n", ret,
+                      WEXITSTATUS(child_status)));
+            tevent_req_error(req, EIO);
+        } else if (WIFSIGNALED(child_status)) {
+            DEBUG(4, ("child [%d] was terminate by signal [%d].\n", ret,
+                      WTERMSIG(child_status)));
+            tevent_req_error(req, EIO);
+        } else {
+            if (WIFSTOPPED(child_status)) {
+                DEBUG(1, ("child [%d] was stopped by signal [%d].\n", ret,
+                          WSTOPSIG(child_status)));
+            }
+            if (WIFCONTINUED(child_status)) {
+                DEBUG(1, ("child [%d] was resumed by delivery of SIGCONT.\n",
+                          ret));
+            }
+            DEBUG(1, ("Child is still running, no new child is started.\n"));
+            return;
         }
+    }
+}
+
+static void pc_init_timeout(struct tevent_context *ev,
+                            struct tevent_timer *te,
+                            struct timeval t, void *ptr)
+{
+    struct tevent_req *req;
+    struct pc_init_ctx *state;
+
+    DEBUG(2, ("Client timed out before Identification!\n"));
+
+    req = talloc_get_type(ptr, struct tevent_req);
+    state = tevent_req_data(req, struct pc_init_ctx);
+
+    tevent_req_error(req, ETIMEDOUT);
+}
+
+static errno_t proxy_child_init_recv(struct tevent_req *req,
+                                   pid_t *pid,
+                                   struct sbus_connection **conn)
+{
+    struct pc_init_ctx *state;
+
+    TEVENT_REQ_RETURN_ON_ERROR(req);
+
+    state = tevent_req_data(req, struct pc_init_ctx);
+
+    /* Unset the destructor since we initialized successfully.
+     * We don't want to kill the child now that it's properly
+     * set up.
+     */
+    talloc_set_destructor((TALLOC_CTX *)state, NULL);
+
+    *pid = state->pid;
+    *conn = state->conn;
 
+    return EOK;
+}
+
+struct proxy_child_sig_ctx {
+    struct proxy_auth_ctx *auth_ctx;
+    pid_t pid;
+};
+static void proxy_child_sig_handler(struct tevent_context *ev,
+                                    struct tevent_signal *sige, int signum,
+                                    int count, void *__siginfo, void *pvt);
+static struct tevent_req *proxy_pam_conv_send(TALLOC_CTX *mem_ctx,
+                                              struct proxy_auth_ctx *auth_ctx,
+                                              struct sbus_connection *conn,
+                                              struct pam_data *pd,
+                                              pid_t pid);
+static void proxy_pam_conv_done(struct tevent_req *subreq);
+static void proxy_child_init_done(struct tevent_req *subreq) {
+    int ret;
+    struct tevent_signal *sige;
+    struct tevent_req *req =
+            tevent_req_callback_data(subreq, struct tevent_req);
+    struct proxy_child_ctx *child_ctx =
+            tevent_req_data(req, struct proxy_child_ctx);
+    struct proxy_child_sig_ctx *sig_ctx;
+
+    ret = proxy_child_init_recv(subreq, &child_ctx->pid, &child_ctx->conn);
+    talloc_zfree(subreq);
+    if (ret != EOK) {
+        DEBUG(6, ("Proxy child init failed [%d]\n", ret));
+        tevent_req_error(req, ret);
+        return;
+    }
+
+    /* An initialized child is available, awaiting the PAM command */
+    subreq = proxy_pam_conv_send(req, child_ctx->auth_ctx,
+                                 child_ctx->conn, child_ctx->pd,
+                                 child_ctx->pid);
+    if (!subreq) {
+        DEBUG(1,("Could not start PAM conversation\n"));
+        tevent_req_error(req, EIO);
+        return;
+    }
+    tevent_req_set_callback(subreq, proxy_pam_conv_done, req);
+
+    /* Add a signal handler for the child under the auth_ctx,
+     * that way if the child exits after completion of the
+     * request, it will still be handled.
+     */
+    sig_ctx = talloc_zero(child_ctx->auth_ctx, struct proxy_child_sig_ctx);
+    if(sig_ctx == NULL) {
+        DEBUG(1, ("tevent_add_signal failed.\n"));
+        tevent_req_error(req, ENOMEM);
+        return;
+    }
+    sig_ctx->auth_ctx = child_ctx->auth_ctx;
+    sig_ctx->pid = child_ctx->pid;
+
+    sige = tevent_add_signal(child_ctx->auth_ctx->be->ev,
+                             child_ctx->auth_ctx,
+                             SIGCHLD, SA_SIGINFO,
+                             proxy_child_sig_handler,
+                             sig_ctx);
+    if (sige == NULL) {
+        DEBUG(1, ("tevent_add_signal failed.\n"));
+        tevent_req_error(req, ENOMEM);
+        return;
+    }
+
+    /* Steal the signal context onto the signal event
+     * so that when the signal is freed, the context
+     * will go with it.
+     */
+    talloc_steal(sige, sig_ctx);
+}
+
+static void remove_sige(struct tevent_context *ev,
+                        struct tevent_immediate *imm,
+                        void *pvt);
+static void run_proxy_child_queue(struct tevent_context *ev,
+                                  struct tevent_immediate *imm,
+                                  void *pvt);
+static void proxy_child_sig_handler(struct tevent_context *ev,
+                                    struct tevent_signal *sige, int signum,
+                                    int count, void *__siginfo, void *pvt)
+{
+    int ret;
+    int child_status;
+    struct proxy_child_sig_ctx *sig_ctx;
+    struct tevent_immediate *imm;
+    struct tevent_immediate *imm2;
+
+    if (count <= 0) {
+        DEBUG(0, ("SIGCHLD handler called with invalid child count\n"));
+        return;
+    }
+
+    sig_ctx = talloc_get_type(pvt, struct proxy_child_sig_ctx);
+    DEBUG(7, ("Waiting for child [%d].\n", sig_ctx->pid));
+
+    errno = 0;
+    ret = waitpid(sig_ctx->pid, &child_status, WNOHANG);
+
+    if (ret == -1) {
+        ret = errno;
+        DEBUG(1, ("waitpid failed [%d][%s].\n", ret, strerror(ret)));
+    } else if (ret == 0) {
+        DEBUG(1, ("waitpid did not found a child with changed status.\n"));
     } else {
-        DEBUG(1, ("Failed to initialize pam transaction.\n"));
-        pam_status = PAM_SYSTEM_ERR;
+        if (WIFEXITED(child_status)) {
+            DEBUG(4, ("child [%d] exited with status [%d].\n", ret,
+                      WEXITSTATUS(child_status)));
+        } else if (WIFSIGNALED(child_status)) {
+            DEBUG(4, ("child [%d] was terminated by signal [%d].\n", ret,
+                      WTERMSIG(child_status)));
+        } else {
+            if (WIFSTOPPED(child_status)) {
+                DEBUG(1, ("child [%d] was stopped by signal [%d].\n", ret,
+                          WSTOPSIG(child_status)));
+            }
+            if (WIFCONTINUED(child_status)) {
+                DEBUG(1, ("child [%d] was resumed by delivery of SIGCONT.\n",
+                          ret));
+            }
+            DEBUG(1, ("Child is still running, no new child is started.\n"));
+            return;
+        }
+
+        imm = tevent_create_immediate(ev);
+        if (imm == NULL) {
+            DEBUG(1, ("tevent_create_immediate failed.\n"));
+            return;
+        }
+
+        tevent_schedule_immediate(imm, ev, run_proxy_child_queue,
+                                  sig_ctx->auth_ctx);
+
+        /* schedule another immediate timer to delete the sigchld handler */
+        imm2 = tevent_create_immediate(ev);
+        if (imm == NULL) {
+            DEBUG(1, ("tevent_create_immediate failed.\n"));
+            return;
+        }
+
+        tevent_schedule_immediate(imm2, ev, remove_sige, sige);
+    }
+
+    return;
+}
+
+static void remove_sige(struct tevent_context *ev,
+                        struct tevent_immediate *imm,
+                        void *pvt)
+{
+    talloc_free(pvt);
+}
+
+struct proxy_conv_ctx {
+    struct proxy_auth_ctx *auth_ctx;
+    struct sbus_connection *conn;
+    struct pam_data *pd;
+    pid_t pid;
+};
+static void proxy_pam_conv_reply(DBusPendingCall *pending, void *ptr);
+static struct tevent_req *proxy_pam_conv_send(TALLOC_CTX *mem_ctx,
+                                              struct proxy_auth_ctx *auth_ctx,
+                                              struct sbus_connection *conn,
+                                              struct pam_data *pd,
+                                              pid_t pid)
+{
+    errno_t ret;
+    bool dp_ret;
+    DBusMessage *msg;
+    struct tevent_req *req;
+    struct proxy_conv_ctx *state;
+
+    req = tevent_req_create(mem_ctx, &state, struct proxy_conv_ctx);
+    if (req == NULL) {
+        return NULL;
     }
 
-    pd->pam_status = pam_status;
+    state->auth_ctx = auth_ctx;
+    state->conn = conn;
+    state->pd = pd;
+    state->pid = pid;
 
-    if (cache_auth_data) {
-        struct tevent_req *subreq;
-        char *password;
+    msg = dbus_message_new_method_call(NULL,
+                                       DP_PATH,
+                                       DP_INTERFACE,
+                                       DP_METHOD_PAMHANDLER);
+    if (msg == NULL) {
+        DEBUG(1, ("dbus_message_new_method_call failed.\n"));
+        talloc_zfree(req);
+        return NULL;
+    }
+
+    DEBUG(4, ("Sending request with the following data:\n"));
+    DEBUG_PAM_DATA(4, pd);
 
-        password = talloc_size(req, auth_data->authtok_size + 1);
+    dp_ret = dp_pack_pam_request(msg, pd);
+    if (!dp_ret) {
+        DEBUG(1, ("Failed to build message\n"));
+        dbus_message_unref(msg);
+        talloc_zfree(req);
+        return NULL;
+    }
+
+    ret = sbus_conn_send(state->conn, msg, state->auth_ctx->timeout_ms,
+                         proxy_pam_conv_reply, req, NULL);
+    if (ret != EOK) {
+        dbus_message_unref(msg);
+        talloc_zfree(req);
+        return NULL;
+    }
+
+    dbus_message_unref(msg);
+    return req;
+}
+
+static void proxy_pam_conv_reply(DBusPendingCall *pending, void *ptr)
+{
+    struct tevent_req *req;
+    struct proxy_conv_ctx *state;
+    DBusError dbus_error;
+    DBusMessage *reply;
+    int type;
+    int ret;
+
+    DEBUG(8, ("Handling pam conversation reply\n"));
+
+    req = talloc_get_type(ptr, struct tevent_req);
+    state = tevent_req_data(req, struct proxy_conv_ctx);
+
+    dbus_error_init(&dbus_error);
+
+    reply = dbus_pending_call_steal_reply(pending);
+    dbus_pending_call_unref(pending);
+    if (reply == NULL) {
+        DEBUG(0, ("Severe error. A reply callback was called but no reply was"
+                  "received and no timeout occurred\n"));
+        state->pd->pam_status = PAM_SYSTEM_ERR;
+        tevent_req_error(req, EIO);
+    }
+
+    type = dbus_message_get_type(reply);
+    switch (type) {
+        case DBUS_MESSAGE_TYPE_METHOD_RETURN:
+            ret = dp_unpack_pam_response(reply, state->pd, &dbus_error);
+            if (!ret) {
+                DEBUG(0, ("Failed to parse reply.\n"));
+                state->pd->pam_status = PAM_SYSTEM_ERR;
+                dbus_message_unref(reply);
+                tevent_req_error(req, EIO);
+                return;
+            }
+            DEBUG(4, ("received: [%d][%s]\n",
+                      state->pd->pam_status,
+                      state->pd->domain));
+            break;
+        case DBUS_MESSAGE_TYPE_ERROR:
+            DEBUG(0, ("Reply error [%s].\n",
+                    dbus_message_get_error_name(reply)));
+            state->pd->pam_status = PAM_SYSTEM_ERR;
+            break;
+        default:
+            DEBUG(0, ("Default... what now?.\n"));
+            state->pd->pam_status = PAM_SYSTEM_ERR;
+    }
+    dbus_message_unref(reply);
+
+    /* Kill the child */
+    kill(state->pid, SIGKILL);
+
+    /* Conversation is finished */
+    tevent_req_done(req);
+}
+
+static errno_t proxy_pam_conv_recv(struct tevent_req *req)
+{
+    TEVENT_REQ_RETURN_ON_ERROR(req);
+
+    return EOK;
+}
+
+static void proxy_pam_conv_done(struct tevent_req *subreq)
+{
+    struct tevent_req *req;
+    int ret;
+
+    req = tevent_req_callback_data(subreq, struct tevent_req);
+
+    ret = proxy_pam_conv_recv(subreq);
+    talloc_zfree(subreq);
+    if (ret != EOK) {
+        DEBUG(6, ("Proxy PAM conversation failed [%d]\n", ret));
+        tevent_req_error(req, ret);
+        return;
+    }
+
+    tevent_req_done(req);
+}
+
+static int proxy_child_recv(struct tevent_req *req,
+                          TALLOC_CTX *mem_ctx,
+                          struct pam_data **pd)
+{
+    struct proxy_child_ctx *ctx;
+
+    TEVENT_REQ_RETURN_ON_ERROR(req);
+
+    ctx = tevent_req_data(req, struct proxy_child_ctx);
+    *pd = talloc_steal(mem_ctx, ctx->pd);
+
+    return EOK;
+}
+
+static void proxy_child_done(struct tevent_req *req)
+{
+    struct proxy_client_ctx *client_ctx =
+            tevent_req_callback_data(req, struct proxy_client_ctx);
+    struct pam_data *pd;
+    char *password;
+    int ret;
+    struct tevent_immediate *imm;
+
+    ret = proxy_child_recv(req, client_ctx, &pd);
+    talloc_zfree(req);
+    if (ret != EOK) {
+        /* Pam child failed */
+        client_ctx->auth_ctx->running--;
+        proxy_reply(client_ctx->be_req, DP_ERR_FATAL, ret,
+                    "PAM child failed");
+
+        /* Start the next auth in the queue, if any */
+        imm = tevent_create_immediate(client_ctx->be_req->be_ctx->ev);
+        if (imm == NULL) {
+            DEBUG(1, ("tevent_create_immediate failed.\n"));
+            return;
+        }
+
+        tevent_schedule_immediate(imm,
+                                  client_ctx->be_req->be_ctx->ev,
+                                  run_proxy_child_queue,
+                                  client_ctx->auth_ctx);
+        return;
+    }
+
+    /* Check if we need to save the cached credentials */
+    if ((pd->cmd == SSS_PAM_AUTHENTICATE || pd->cmd == SSS_PAM_CHAUTHTOK) &&
+            pd->pam_status == PAM_SUCCESS &&
+            client_ctx->be_req->be_ctx->domain->cache_credentials) {
+        password = talloc_strndup(client_ctx->be_req,
+                                  (char *) pd->authtok,
+                                  pd->authtok_size);
         if (!password) {
             /* password caching failures are not fatal errors */
-            return proxy_reply(req, DP_ERR_OK, EOK, NULL);
+            DEBUG(2, ("Failed to cache password\n"));
+            goto done;
         }
-        memcpy(password, auth_data->authtok, auth_data->authtok_size);
-        password[auth_data->authtok_size] = '\0';
         talloc_set_destructor((TALLOC_CTX *)password, password_destructor);
 
-        subreq = sysdb_cache_password_send(req, req->be_ctx->ev,
-                                           req->be_ctx->sysdb, NULL,
-                                           req->be_ctx->domain,
-                                           pd->user, password);
-        if (!subreq) {
+        DEBUG(6, ("Caching the password\n"));
+        req = sysdb_cache_password_send(client_ctx,
+                                        client_ctx->be_req->be_ctx->ev,
+                                        client_ctx->be_req->be_ctx->sysdb,
+                                        NULL,
+                                        client_ctx->be_req->be_ctx->domain,
+                                        pd->user, password);
+        if (!req) {
             /* password caching failures are not fatal errors */
-            return proxy_reply(req, DP_ERR_OK, EOK, NULL);
+            DEBUG(2, ("Failed to cache password\n"));
+            goto done;
         }
-        tevent_req_set_callback(subreq, proxy_pam_handler_cache_done, req);
+        tevent_req_set_callback(req, proxy_pam_handler_cache_done,
+                                client_ctx->be_req);
+        return;
+    }
+
+done:
+    proxy_reply(client_ctx->be_req, DP_ERR_OK, EOK, NULL);
+}
+
+static void run_proxy_child_queue(struct tevent_context *ev,
+                                  struct tevent_immediate *imm,
+                                  void *pvt)
+{
+    struct proxy_auth_ctx *auth_ctx;
+    struct hash_iter_context_t *iter;
+    struct hash_entry_t *entry;
+    struct tevent_req *req;
+    struct tevent_req *subreq;
+    struct proxy_child_ctx *state;
+
+    auth_ctx = talloc_get_type(pvt, struct proxy_auth_ctx);
+
+    /* Launch next queued request */
+    iter = new_hash_iter_context(auth_ctx->request_table);
+    while ((entry = iter->next(iter)) != NULL) {
+        req = talloc_get_type(entry->value.ptr, struct tevent_req);
+        state = tevent_req_data(req, struct proxy_child_ctx);
+        if (!state->running) {
+            break;
+        }
+    }
+
+    if (!entry) {
+        /* Nothing pending on the queue */
+        return;
     }
 
-    proxy_reply(req, DP_ERR_OK, EOK, NULL);
+    if (auth_ctx->running < auth_ctx->max_children) {
+        /* There's an available slot; start a child
+         * to handle the request
+         */
+        auth_ctx->running++;
+        subreq = proxy_child_init_send(auth_ctx, state, auth_ctx);
+        if (!subreq) {
+            DEBUG(1, ("Could not fork child process\n"));
+            auth_ctx->running--;
+            talloc_zfree(req);
+            return;
+        }
+        tevent_req_set_callback(subreq, proxy_child_init_done, req);
+
+        state->running = true;
+    }
 }
 
 static void proxy_pam_handler_cache_done(struct tevent_req *subreq)
 {
-    struct be_req *req = tevent_req_callback_data(subreq, struct be_req);
+    struct be_req *be_req = tevent_req_callback_data(subreq, struct be_req);
     int ret;
 
     /* password caching failures are not fatal errors */
     ret = sysdb_cache_password_recv(subreq);
     talloc_zfree(subreq);
 
-    /* so we just log it any return */
+    /* so we just log it and return */
     if (ret) {
         DEBUG(2, ("Failed to cache password (%d)[%s]!?\n",
                   ret, strerror(ret)));
     }
 
-    return proxy_reply(req, DP_ERR_OK, EOK, NULL);
+    proxy_reply(be_req, DP_ERR_OK, EOK, NULL);
+
+    return;
 }
 
 static void proxy_reply(struct be_req *req, int dp_err,
@@ -2480,17 +3123,203 @@ done:
     return ret;
 }
 
+struct proxy_client {
+    struct proxy_auth_ctx *proxy_auth_ctx;
+    struct sbus_connection *conn;
+    struct tevent_timer *timeout;
+    bool initialized;
+};
+
+static void init_timeout(struct tevent_context *ev,
+                         struct tevent_timer *te,
+                         struct timeval t, void *ptr);
+static int proxy_client_init(struct sbus_connection *conn, void *data)
+{
+    struct proxy_auth_ctx *proxy_auth_ctx;
+    struct proxy_client *proxy_cli;
+    struct timeval tv;
+
+    proxy_auth_ctx = talloc_get_type(data, struct proxy_auth_ctx);
+
+    /* hang off this memory to the connection so that when the connection
+     * is freed we can potentially call a destructor */
+
+    proxy_cli = talloc_zero(conn, struct proxy_client);
+    if (!proxy_cli) {
+        DEBUG(0,("Out of memory?!\n"));
+        talloc_zfree(conn);
+        return ENOMEM;
+    }
+    proxy_cli->proxy_auth_ctx = proxy_auth_ctx;
+    proxy_cli->conn = conn;
+    proxy_cli->initialized = false;
+
+    /* 5 seconds should be plenty */
+    tv = tevent_timeval_current_ofs(5, 0);
+
+    proxy_cli->timeout = tevent_add_timer(proxy_auth_ctx->be->ev, proxy_cli,
+                                          tv, init_timeout, proxy_cli);
+    if (!proxy_cli->timeout) {
+        DEBUG(0,("Out of memory?!\n"));
+        talloc_zfree(conn);
+        return ENOMEM;
+    }
+    DEBUG(4, ("Set-up proxy client ID timeout [%p]\n", proxy_cli->timeout));
+
+    /* Attach the client context to the connection context, so that it is
+     * always available when we need to manage the connection. */
+    sbus_conn_set_private_data(conn, proxy_cli);
+
+    return EOK;
+}
+
+static void init_timeout(struct tevent_context *ev,
+                         struct tevent_timer *te,
+                         struct timeval t, void *ptr)
+{
+    struct proxy_client *proxy_cli;
+
+    DEBUG(2, ("Client timed out before Identification [%p]!\n", te));
+
+    proxy_cli = talloc_get_type(ptr, struct proxy_client);
+
+    sbus_disconnect(proxy_cli->conn);
+    talloc_zfree(proxy_cli);
+
+    /* If we time out here, we will also time out to
+     * pc_init_timeout(), so we'll finish the request
+     * there.
+     */
+}
+
+static int client_registration(DBusMessage *message,
+                               struct sbus_connection *conn)
+{
+    dbus_uint16_t version = DATA_PROVIDER_VERSION;
+    struct proxy_client *proxy_cli;
+    DBusMessage *reply;
+    DBusError dbus_error;
+    dbus_uint16_t cli_ver;
+    uint32_t cli_id;
+    dbus_bool_t dbret;
+    void *data;
+    int hret;
+    hash_key_t key;
+    hash_value_t value;
+    struct tevent_req *req;
+    struct proxy_child_ctx *child_ctx;
+    struct pc_init_ctx *init_ctx;
+
+    data = sbus_conn_get_private_data(conn);
+    proxy_cli = talloc_get_type(data, struct proxy_client);
+    if (!proxy_cli) {
+        DEBUG(0, ("Connection holds no valid init data\n"));
+        return EINVAL;
+    }
+
+    /* First thing, cancel the timeout */
+    DEBUG(4, ("Cancel proxy client ID timeout [%p]\n", proxy_cli->timeout));
+    talloc_zfree(proxy_cli->timeout);
+
+    dbus_error_init(&dbus_error);
+
+    dbret = dbus_message_get_args(message, &dbus_error,
+                                  DBUS_TYPE_UINT16, &cli_ver,
+                                  DBUS_TYPE_UINT32, &cli_id,
+                                  DBUS_TYPE_INVALID);
+    if (!dbret) {
+        DEBUG(1, ("Failed to parse message, killing connection\n"));
+        if (dbus_error_is_set(&dbus_error)) dbus_error_free(&dbus_error);
+        sbus_disconnect(conn);
+        /* FIXME: should we just talloc_zfree(conn) ? */
+        return EIO;
+    }
+
+    DEBUG(4, ("Proxy client [%ld] connected\n", cli_id));
+
+    /* Check the hash table */
+    key.type = HASH_KEY_ULONG;
+    key.ul = cli_id;
+    if (!hash_has_key(proxy_cli->proxy_auth_ctx->request_table, &key)) {
+        DEBUG(1, ("Unknown child ID. Killing the connection\n"));
+        sbus_disconnect(proxy_cli->conn);
+        return EIO;
+    }
+
+    /* reply that all is ok */
+    reply = dbus_message_new_method_return(message);
+    if (!reply) {
+        DEBUG(0, ("Dbus Out of memory!\n"));
+        return ENOMEM;
+    }
+
+    dbret = dbus_message_append_args(reply,
+                                     DBUS_TYPE_UINT16, &version,
+                                     DBUS_TYPE_INVALID);
+    if (!dbret) {
+        DEBUG(0, ("Failed to build dbus reply\n"));
+        dbus_message_unref(reply);
+        sbus_disconnect(conn);
+        return EIO;
+    }
+
+    /* send reply back */
+    sbus_conn_send_reply(conn, reply);
+    dbus_message_unref(reply);
+
+    hret = hash_lookup(proxy_cli->proxy_auth_ctx->request_table, &key, &value);
+    if (hret != HASH_SUCCESS) {
+        DEBUG(1, ("Hash error [%d][%s]\n", hret, hash_error_string(hret)));
+        sbus_disconnect(conn);
+    }
+
+    /* Signal that the child is up and ready to receive the request */
+    req = talloc_get_type(value.ptr, struct tevent_req);
+    child_ctx = tevent_req_data(req, struct proxy_child_ctx);
+
+    if (!child_ctx->running) {
+        /* This should hopefully be impossible, but protect
+         * against it anyway. If we're not marked running, then
+         * the init_req will be NULL below and things will
+         * break.
+         */
+        DEBUG(1, ("Client connection from a request "
+                  "that's not marked as running\n"));
+        return EIO;
+    }
+
+    init_ctx = tevent_req_data(child_ctx->init_req, struct pc_init_ctx);
+    init_ctx->conn = conn;
+    tevent_req_done(child_ctx->init_req);
+    child_ctx->init_req = NULL;
+
+    return EOK;
+}
+
 int sssm_proxy_auth_init(struct be_ctx *bectx,
                          struct bet_ops **ops, void **pvt_data)
 {
     struct proxy_auth_ctx *ctx;
     int ret;
+    int hret;
+    char *sbus_address;
+
+    /* If we're already set up, just return that */
+    if(bectx->bet_info[BET_AUTH].mod_name &&
+       strcmp("proxy", bectx->bet_info[BET_AUTH].mod_name) == 0) {
+        DEBUG(8, ("Re-using proxy_auth_ctx for this provider\n"));
+        *ops = bectx->bet_info[BET_AUTH].bet_ops;
+        *pvt_data = bectx->bet_info[BET_AUTH].pvt_bet_data;
+        return EOK;
+    }
 
     ctx = talloc(bectx, struct proxy_auth_ctx);
     if (!ctx) {
         return ENOMEM;
     }
     ctx->be = bectx;
+    ctx->timeout_ms = SSS_CLI_SOCKET_TIMEOUT/4;
+    ctx->next_id = 1;
 
     ret = confdb_get_string(bectx->cdb, ctx, bectx->conf_path,
                             CONFDB_PROXY_PAM_TARGET, NULL,
@@ -2502,6 +3331,33 @@ int sssm_proxy_auth_init(struct be_ctx *bectx,
         goto done;
     }
 
+    sbus_address = talloc_asprintf(ctx, "unix:path=%s/%s_%s", PIPE_PATH,
+                                   PROXY_CHILD_PIPE, bectx->domain->name);
+    if (sbus_address == NULL) {
+        DEBUG(1, ("talloc_asprintf failed.\n"));
+        ret = ENOMEM;
+        goto done;
+    }
+
+    ret = sbus_new_server(ctx, bectx->ev, sbus_address, &proxy_interface,
+                          &ctx->sbus_srv, proxy_client_init, ctx);
+    if (ret != EOK) {
+        DEBUG(0, ("Could not set up sbus server.\n"));
+        goto done;
+    }
+
+    /* Set up request hash table */
+    /* FIXME: get max_children from configuration file */
+    ctx->max_children = 10;
+
+    hret = hash_create(ctx->max_children * 2, &ctx->request_table,
+                       NULL, NULL);
+    if (hret != HASH_SUCCESS) {
+        DEBUG(0, ("Could not initialize request table\n"));
+        ret = EIO;
+        goto done;
+    }
+
     *ops = &proxy_auth_ops;
     *pvt_data = ctx;
 
diff --git a/src/providers/proxy/proxy.h b/src/providers/proxy/proxy.h
new file mode 100644
index 000000000..d95e50efe
--- /dev/null
+++ b/src/providers/proxy/proxy.h
@@ -0,0 +1,30 @@
+/*
+    SSSD
+
+    Proxy provider, private header file
+
+    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/>.
+*/
+
+#ifndef __PROXY_H__
+#define __PROXY_H__
+
+#define PROXY_CHILD_PIPE "private/proxy_child"
+
+#endif /* __PROXY_H__ */
diff --git a/src/providers/proxy/proxy_child.c b/src/providers/proxy/proxy_child.c
new file mode 100644
index 000000000..a5f85bcc5
--- /dev/null
+++ b/src/providers/proxy/proxy_child.c
@@ -0,0 +1,515 @@
+/*
+    SSSD
+
+    Pam Proxy 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 <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <string.h>
+#include <sys/time.h>
+#include <errno.h>
+#include <dlfcn.h>
+
+#include <security/pam_appl.h>
+#include <security/pam_modules.h>
+
+#include "popt.h"
+#include "util/util.h"
+#include "confdb/confdb.h"
+#include "db/sysdb.h"
+#include "dbus/dbus.h"
+#include "sbus/sssd_dbus.h"
+#include "providers/proxy/proxy.h"
+
+#include "providers/dp_backend.h"
+
+static int pc_pam_handler(DBusMessage *message, struct sbus_connection *conn);
+
+struct sbus_method pc_methods[] = {
+    { DP_METHOD_PAMHANDLER, pc_pam_handler },
+    { NULL, NULL }
+};
+
+struct sbus_interface pc_interface = {
+    DP_INTERFACE,
+    DP_PATH,
+    SBUS_DEFAULT_VTABLE,
+    pc_methods,
+    NULL
+};
+
+struct pc_ctx {
+    struct tevent_context *ev;
+    struct confdb_ctx *cdb;
+    struct sysdb_ctx *sysdb;
+    struct sss_domain_info *domain;
+    const char *identity;
+    const char *conf_path;
+    struct sbus_connection *mon_conn;
+    struct sbus_connection *conn;
+    const char *pam_target;
+    uint32_t id;
+};
+
+struct authtok_conv {
+    uint32_t authtok_size;
+    uint8_t *authtok;
+};
+
+static int proxy_internal_conv(int num_msg, const struct pam_message **msgm,
+                            struct pam_response **response,
+                            void *appdata_ptr) {
+    int i;
+    struct pam_response *reply;
+    struct authtok_conv *auth_data;
+
+    auth_data = talloc_get_type(appdata_ptr, struct authtok_conv);
+
+    if (num_msg <= 0) return PAM_CONV_ERR;
+
+    reply = (struct pam_response *) calloc(num_msg,
+                                           sizeof(struct pam_response));
+    if (reply == NULL) return PAM_CONV_ERR;
+
+    for (i=0; i < num_msg; i++) {
+        switch( msgm[i]->msg_style ) {
+            case PAM_PROMPT_ECHO_OFF:
+                DEBUG(4, ("Conversation message: [%s]\n", msgm[i]->msg));
+                reply[i].resp_retcode = 0;
+                reply[i].resp = calloc(auth_data->authtok_size + 1,
+                                       sizeof(char));
+                if (reply[i].resp == NULL) goto failed;
+                memcpy(reply[i].resp, auth_data->authtok,
+                       auth_data->authtok_size);
+
+                break;
+            default:
+                DEBUG(1, ("Conversation style %d not supported.\n",
+                           msgm[i]->msg_style));
+                goto failed;
+        }
+    }
+
+    *response = reply;
+    reply = NULL;
+
+    return PAM_SUCCESS;
+
+failed:
+    free(reply);
+    return PAM_CONV_ERR;
+}
+
+static errno_t call_pam_stack(const char *pam_target, struct pam_data *pd)
+{
+    int ret;
+    int pam_status;
+    pam_handle_t *pamh=NULL;
+    struct authtok_conv *auth_data;
+    struct pam_conv conv;
+
+    conv.conv=proxy_internal_conv;
+    auth_data = talloc_zero(pd, struct authtok_conv);
+    conv.appdata_ptr=auth_data;
+
+    ret = pam_start(pam_target, pd->user, &conv, &pamh);
+    if (ret == PAM_SUCCESS) {
+        DEBUG(7, ("Pam transaction started with service name [%s].\n",
+                  pam_target));
+        ret = pam_set_item(pamh, PAM_TTY, pd->tty);
+        if (ret != PAM_SUCCESS) {
+            DEBUG(1, ("Setting PAM_TTY failed: %s.\n",
+                      pam_strerror(pamh, ret)));
+        }
+        ret = pam_set_item(pamh, PAM_RUSER, pd->ruser);
+        if (ret != PAM_SUCCESS) {
+            DEBUG(1, ("Setting PAM_RUSER failed: %s.\n",
+                      pam_strerror(pamh, ret)));
+        }
+        ret = pam_set_item(pamh, PAM_RHOST, pd->rhost);
+        if (ret != PAM_SUCCESS) {
+            DEBUG(1, ("Setting PAM_RHOST failed: %s.\n",
+                      pam_strerror(pamh, ret)));
+        }
+        switch (pd->cmd) {
+            case SSS_PAM_AUTHENTICATE:
+                auth_data->authtok_size = pd->authtok_size;
+                auth_data->authtok = pd->authtok;
+                pam_status = pam_authenticate(pamh, 0);
+                break;
+            case SSS_PAM_SETCRED:
+                pam_status=pam_setcred(pamh, 0);
+                break;
+            case SSS_PAM_ACCT_MGMT:
+                pam_status=pam_acct_mgmt(pamh, 0);
+                break;
+            case SSS_PAM_OPEN_SESSION:
+                pam_status=pam_open_session(pamh, 0);
+                break;
+            case SSS_PAM_CLOSE_SESSION:
+                pam_status=pam_close_session(pamh, 0);
+                break;
+            case SSS_PAM_CHAUTHTOK:
+                if (pd->priv != 1) {
+                    auth_data->authtok_size = pd->authtok_size;
+                    auth_data->authtok = pd->authtok;
+                    pam_status = pam_authenticate(pamh, 0);
+                    if (pam_status != PAM_SUCCESS) break;
+                }
+                auth_data->authtok_size = pd->newauthtok_size;
+                auth_data->authtok = pd->newauthtok;
+                pam_status = pam_chauthtok(pamh, 0);
+                break;
+            case SSS_PAM_CHAUTHTOK_PRELIM:
+                if (pd->priv != 1) {
+                    auth_data->authtok_size = pd->authtok_size;
+                    auth_data->authtok = pd->authtok;
+                    pam_status = pam_authenticate(pamh, 0);
+                } else {
+                    pam_status = PAM_SUCCESS;
+                }
+                break;
+            default:
+                DEBUG(1, ("unknown PAM call\n"));
+                pam_status=PAM_ABORT;
+        }
+
+        DEBUG(4, ("Pam result: [%d][%s]\n", pam_status,
+                  pam_strerror(pamh, pam_status)));
+
+        ret = pam_end(pamh, pam_status);
+        if (ret != PAM_SUCCESS) {
+            pamh=NULL;
+            DEBUG(1, ("Cannot terminate pam transaction.\n"));
+        }
+
+    } else {
+        DEBUG(1, ("Failed to initialize pam transaction.\n"));
+        pam_status = PAM_SYSTEM_ERR;
+    }
+
+    pd->pam_status = pam_status;
+
+    return EOK;
+}
+
+static int pc_pam_handler(DBusMessage *message, struct sbus_connection *conn)
+{
+    DBusError dbus_error;
+    DBusMessage *reply;
+    struct pc_ctx *pc_ctx;
+    errno_t ret;
+    void *user_data;
+    struct pam_data *pd = NULL;
+
+    user_data = sbus_conn_get_private_data(conn);
+    if (!user_data) {
+        ret = EINVAL;
+        goto done;
+    }
+    pc_ctx = talloc_get_type(user_data, struct pc_ctx);
+    if (!pc_ctx) {
+        ret = EINVAL;
+        goto done;
+    }
+
+    reply = dbus_message_new_method_return(message);
+    if (!reply) {
+        DEBUG(1, ("dbus_message_new_method_return failed, "
+                  "cannot send reply.\n"));
+        ret = ENOMEM;
+        goto done;
+    }
+
+    dbus_error_init(&dbus_error);
+
+    ret = dp_unpack_pam_request(message, pc_ctx, &pd, &dbus_error);
+    if (!ret) {
+        DEBUG(1,("Failed, to parse message!\n"));
+        ret = EIO;
+        goto done;
+    }
+
+    pd->pam_status = PAM_SYSTEM_ERR;
+    pd->domain = talloc_strdup(pd, pc_ctx->domain->name);
+    if (pd->domain == NULL) {
+        talloc_free(pd);
+        ret = ENOMEM;
+        goto done;
+    }
+
+    DEBUG(4, ("Got request with the following data\n"));
+    DEBUG_PAM_DATA(4, pd);
+
+    ret = call_pam_stack(pc_ctx->pam_target, pd);
+    if (ret != EOK) {
+        DEBUG(1, ("call_pam_stack failed.\n"));
+    }
+
+    DEBUG(4, ("Sending result [%d][%s]\n",
+              pd->pam_status, pd->domain));
+
+    ret = dp_pack_pam_response(reply, pd);
+    if (!ret) {
+        DEBUG(1, ("Failed to generate dbus reply\n"));
+        talloc_free(pd);
+        dbus_message_unref(reply);
+        ret = EIO;
+        goto done;
+    }
+
+    sbus_conn_send_reply(conn, reply);
+    dbus_message_unref(reply);
+    talloc_free(pd);
+
+    /* We'll return the message and let the
+     * parent process kill us.
+     */
+    return EOK;
+
+done:
+    exit(ret);
+}
+
+int proxy_child_send_id(struct sbus_connection *conn,
+                        uint16_t version,
+                        uint32_t id);
+static int proxy_cli_init(struct pc_ctx *ctx)
+{
+    char *sbus_address;
+    int ret;
+
+    sbus_address = talloc_asprintf(ctx, "unix:path=%s/%s_%s",
+                                      PIPE_PATH, PROXY_CHILD_PIPE,
+                                      ctx->domain->name);
+    if (sbus_address == NULL) {
+        DEBUG(1, ("talloc_asprintf failed.\n"));
+        return ENOMEM;
+    }
+
+    ret = sbus_client_init(ctx, ctx->ev, sbus_address,
+                           &pc_interface, &ctx->conn,
+                           NULL, ctx);
+    if (ret != EOK) {
+        DEBUG(1, ("sbus_client_init failed.\n"));
+        return ret;
+    }
+
+    ret = proxy_child_send_id(ctx->conn, DATA_PROVIDER_VERSION, ctx->id);
+    if (ret != EOK) {
+        DEBUG(0, ("dp_common_send_id failed.\n"));
+        return ret;
+    }
+
+    return EOK;
+}
+
+int proxy_child_send_id(struct sbus_connection *conn,
+                        uint16_t version,
+                        uint32_t id)
+{
+    DBusMessage *msg;
+    dbus_bool_t ret;
+    int retval;
+
+    /* create the message */
+    msg = dbus_message_new_method_call(NULL,
+                                       DP_PATH,
+                                       DP_INTERFACE,
+                                       DP_METHOD_REGISTER);
+    if (msg == NULL) {
+        DEBUG(0, ("Out of memory?!\n"));
+        return ENOMEM;
+    }
+
+    DEBUG(4, ("Sending ID to Proxy Backend: (%d,%ld)\n",
+              version, id));
+
+    ret = dbus_message_append_args(msg,
+                                   DBUS_TYPE_UINT16, &version,
+                                   DBUS_TYPE_UINT32, &id,
+                                   DBUS_TYPE_INVALID);
+    if (!ret) {
+        DEBUG(1, ("Failed to build message\n"));
+        return EIO;
+    }
+
+    retval = sbus_conn_send(conn, msg, 30000, dp_id_callback, NULL, NULL);
+
+    dbus_message_unref(msg);
+    return retval;
+}
+
+int proxy_child_process_init(TALLOC_CTX *mem_ctx, const char *domain,
+                             struct tevent_context *ev, struct confdb_ctx *cdb,
+                             const char *pam_target, uint32_t id)
+{
+    struct pc_ctx *ctx;
+    int ret;
+
+    ctx = talloc_zero(mem_ctx, struct pc_ctx);
+    if (!ctx) {
+        DEBUG(0, ("fatal error initializing pc_ctx\n"));
+        return ENOMEM;
+    }
+    ctx->ev = ev;
+    ctx->cdb = cdb;
+    ctx->pam_target = talloc_steal(ctx, pam_target);
+    ctx->id = id;
+    ctx->conf_path = talloc_asprintf(ctx, CONFDB_DOMAIN_PATH_TMPL, domain);
+    if (!ctx->conf_path) {
+        DEBUG(0, ("Out of memory!?\n"));
+        return ENOMEM;
+    }
+
+    ret = confdb_get_domain(cdb, domain, &ctx->domain);
+    if (ret != EOK) {
+        DEBUG(0, ("fatal error retrieving domain configuration\n"));
+        return ret;
+    }
+
+    ret = sysdb_domain_init(ctx, ev, ctx->domain, DB_PATH, &ctx->sysdb);
+    if (ret != EOK) {
+        DEBUG(0, ("fatal error opening cache database\n"));
+        return ret;
+    }
+
+    ret = proxy_cli_init(ctx);
+    if (ret != EOK) {
+        DEBUG(0, ("fatal error setting up server bus\n"));
+        return ret;
+    }
+
+    return EOK;
+}
+
+int main(int argc, const char *argv[])
+{
+    int opt;
+    poptContext pc;
+    char *domain = NULL;
+    char *srv_name = NULL;
+    char *conf_entry = NULL;
+    struct main_context *main_ctx;
+    int ret;
+    long id;
+    char *pam_target = NULL;
+
+    struct poptOption long_options[] = {
+        POPT_AUTOHELP
+        SSSD_MAIN_OPTS
+        {"domain", 0, POPT_ARG_STRING, &domain, 0,
+         _("Domain of the information provider (mandatory)"), NULL },
+        {"id", 0, POPT_ARG_LONG, &id, 0,
+         _("Child identifier (mandatory)"), NULL },
+        POPT_TABLEEND
+    };
+
+    pc = poptGetContext(argv[0], argc, argv, long_options, 0);
+    while((opt = poptGetNextOpt(pc)) != -1) {
+        switch(opt) {
+        default:
+        fprintf(stderr, "\nInvalid option %s: %s\n\n",
+                  poptBadOption(pc, 0), poptStrerror(opt));
+            poptPrintUsage(pc, stderr, 0);
+            return 1;
+        }
+    }
+
+    if (domain == NULL) {
+        fprintf(stderr, "\nMissing option, "
+                        "--domain is a mandatory option.\n\n");
+            poptPrintUsage(pc, stderr, 0);
+            return 1;
+    }
+
+    if (id == 0) {
+        fprintf(stderr, "\nMissing option, "
+                        "--id is a mandatory option.\n\n");
+            poptPrintUsage(pc, stderr, 0);
+            return 1;
+    }
+
+    poptFreeContext(pc);
+
+
+    /* set up things like debug , signals, daemonization, etc... */
+    debug_log_file = talloc_asprintf(NULL, "proxy_child_%s", domain);
+    if (!debug_log_file) return 2;
+
+    srv_name = talloc_asprintf(NULL, "sssd[proxy_child[%s]]", domain);
+    if (!srv_name) return 2;
+
+    conf_entry = talloc_asprintf(NULL, CONFDB_DOMAIN_PATH_TMPL, domain);
+    if (!conf_entry) return 2;
+
+    ret = server_setup(srv_name, 0, conf_entry, &main_ctx);
+    if (ret != EOK) {
+        DEBUG(0, ("Could not set up mainloop [%d]\n", ret));
+        return 2;
+    }
+
+    ret = unsetenv("_SSS_LOOPS");
+    if (ret != EOK) {
+        DEBUG(1, ("Failed to unset _SSS_LOOPS, "
+                  "pam modules might not work as expected.\n"));
+    }
+
+    ret = confdb_get_string(main_ctx->confdb_ctx, main_ctx, conf_entry,
+                            CONFDB_PROXY_PAM_TARGET, NULL, &pam_target);
+    if (ret != EOK) {
+        DEBUG(0, ("Error reading from confdb (%d) [%s]\n",
+                  ret, strerror(ret)));
+        return 4;
+    }
+    if (pam_target == NULL) {
+        DEBUG(1, ("Missing option proxy_pam_target.\n"));
+        return 4;
+    }
+
+    ret = die_if_parent_died();
+    if (ret != EOK) {
+        /* This is not fatal, don't return */
+        DEBUG(2, ("Could not set up to exit when parent process does\n"));
+    }
+
+    ret = proxy_child_process_init(main_ctx, domain, main_ctx->event_ctx,
+                                   main_ctx->confdb_ctx, pam_target,
+                                   (uint32_t)id);
+    if (ret != EOK) {
+        DEBUG(0, ("Could not initialize proxy child [%d].\n", ret));
+        return 3;
+    }
+
+    DEBUG(1, ("Proxy child for domain [%s] started!\n", domain));
+
+    /* loop on main */
+    server_loop(main_ctx);
+
+    return 0;
+}