UTIL: allow to skip default options for child processes

Currently the SSSD default options like e.g. --debug-level are added
unconditionally to the command line options of a child process when
started with the child helper functions.

If a binary from a different source should be started as a child by SSSD
those options might not be known or used differently. This patch adds an
option to exec_child_ex() which allows to skip the default options and
only add specific options.

Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

6 files changed, 47 insertions, 38 deletions

diff --git a/src/providers/ad/ad_gpo.c b/src/providers/ad/ad_gpo.c
index cca5e5861..069196c3b 100644
--- a/src/providers/ad/ad_gpo.c
+++ b/src/providers/ad/ad_gpo.c
@@ -4144,7 +4144,7 @@ gpo_fork_child(struct tevent_req *req)
     if (pid == 0) { /* child */
         err = exec_child_ex(state,
                             pipefd_to_child, pipefd_from_child,
-                            GPO_CHILD, gpo_child_debug_fd, NULL,
+                            GPO_CHILD, gpo_child_debug_fd, NULL, false,
                             STDIN_FILENO, AD_GPO_CHILD_OUT_FILENO);
         DEBUG(SSSDBG_CRIT_FAILURE, "Could not exec gpo_child: [%d][%s].\n",
               err, strerror(err));
diff --git a/src/providers/krb5/krb5_child_handler.c b/src/providers/krb5/krb5_child_handler.c
index fa1055eb7..167a2b2ad 100644
--- a/src/providers/krb5/krb5_child_handler.c
+++ b/src/providers/krb5/krb5_child_handler.c
@@ -312,7 +312,7 @@ static errno_t fork_child(struct tevent_req *req)
         err = exec_child_ex(state,
                             pipefd_to_child, pipefd_from_child,
                             KRB5_CHILD, state->kr->krb5_ctx->child_debug_fd,
-                            k5c_extra_args, STDIN_FILENO, STDOUT_FILENO);
+                            k5c_extra_args, false, STDIN_FILENO, STDOUT_FILENO);
         if (err != EOK) {
             DEBUG(SSSDBG_CRIT_FAILURE, "Could not exec KRB5 child: [%d][%s].\n",
                       err, strerror(err));
diff --git a/src/responder/pam/pamsrv_p11.c b/src/responder/pam/pamsrv_p11.c
index 58310a253..ea428a6a3 100644
--- a/src/responder/pam/pamsrv_p11.c
+++ b/src/responder/pam/pamsrv_p11.c
@@ -322,7 +322,7 @@ struct tevent_req *pam_check_cert_send(TALLOC_CTX *mem_ctx,
     child_pid = fork();
     if (child_pid == 0) { /* child */
         ret = exec_child_ex(state, pipefd_to_child, pipefd_from_child,
-                            P11_CHILD_PATH, child_debug_fd, extra_args,
+                            P11_CHILD_PATH, child_debug_fd, extra_args, false,
                             STDIN_FILENO, STDOUT_FILENO);
         if (ret != EOK) {
             DEBUG(SSSDBG_CRIT_FAILURE, "Could not exec p11 child: [%d][%s].\n",
diff --git a/src/tests/cmocka/test_child_common.c b/src/tests/cmocka/test_child_common.c
index bf500fa5a..9ed9c1ae4 100644
--- a/src/tests/cmocka/test_child_common.c
+++ b/src/tests/cmocka/test_child_common.c
@@ -139,7 +139,7 @@ void test_exec_child_extra_args(void **state)
         ret = exec_child_ex(child_tctx,
                             child_tctx->pipefd_to_child,
                             child_tctx->pipefd_from_child,
-                            CHILD_DIR"/"TEST_BIN, 2, extra_args,
+                            CHILD_DIR"/"TEST_BIN, 2, extra_args, false,
                             STDIN_FILENO, STDOUT_FILENO);
         assert_int_equal(ret, EOK);
     } else {
@@ -287,7 +287,7 @@ void test_exec_child_echo(void **state)
         ret = exec_child_ex(child_tctx,
                             child_tctx->pipefd_to_child,
                             child_tctx->pipefd_from_child,
-                            CHILD_DIR"/"TEST_BIN, 2, NULL,
+                            CHILD_DIR"/"TEST_BIN, 2, NULL, false,
                             STDIN_FILENO, 3);
         assert_int_equal(ret, EOK);
     }
diff --git a/src/util/child_common.c b/src/util/child_common.c
index a6131cd20..60466c146 100644
--- a/src/util/child_common.c
+++ b/src/util/child_common.c
@@ -612,6 +612,7 @@ static errno_t prepare_child_argv(TALLOC_CTX *mem_ctx,
                                   int child_debug_fd,
                                   const char *binary,
                                   const char *extra_argv[],
+                                  bool extra_args_only,
                                   char ***_argv)
 {
     /*
@@ -619,18 +620,24 @@ static errno_t prepare_child_argv(TALLOC_CTX *mem_ctx,
      * debug_microseconds and NULL
      */
     uint_t argc = 5;
-    char ** argv;
+    char ** argv = NULL;
     errno_t ret = EINVAL;
     size_t i;
 
+    if (extra_args_only) {
+        argc = 2; /* program name and NULL */
+    }
+
     /* Save the current state in case an interrupt changes it */
     bool child_debug_to_file = debug_to_file;
     bool child_debug_timestamps = debug_timestamps;
     bool child_debug_microseconds = debug_microseconds;
     bool child_debug_stderr = debug_to_stderr;
 
-    if (child_debug_to_file) argc++;
-    if (child_debug_stderr) argc++;
+    if (!extra_args_only) {
+        if (child_debug_to_file) argc++;
+        if (child_debug_stderr) argc++;
+    }
 
     if (extra_argv) {
         for (i = 0; extra_argv[i]; i++) argc++;
@@ -659,42 +666,44 @@ static errno_t prepare_child_argv(TALLOC_CTX *mem_ctx,
         }
     }
 
-    argv[--argc] = talloc_asprintf(argv, "--debug-level=%#.4x",
-                              debug_level);
-    if (argv[argc] == NULL) {
-        ret = ENOMEM;
-        goto fail;
-    }
-
-    if (child_debug_stderr) {
-        argv[--argc] = talloc_strdup(argv, "--debug-to-stderr");
+    if (!extra_args_only) {
+        argv[--argc] = talloc_asprintf(argv, "--debug-level=%#.4x",
+                                  debug_level);
         if (argv[argc] == NULL) {
             ret = ENOMEM;
             goto fail;
         }
-    }
 
-    if (child_debug_to_file) {
-        argv[--argc] = talloc_asprintf(argv, "--debug-fd=%d",
-                                       child_debug_fd);
+        if (child_debug_stderr) {
+            argv[--argc] = talloc_strdup(argv, "--debug-to-stderr");
+            if (argv[argc] == NULL) {
+                ret = ENOMEM;
+                goto fail;
+            }
+        }
+
+        if (child_debug_to_file) {
+            argv[--argc] = talloc_asprintf(argv, "--debug-fd=%d",
+                                           child_debug_fd);
+            if (argv[argc] == NULL) {
+                ret = ENOMEM;
+                goto fail;
+            }
+        }
+
+        argv[--argc] = talloc_asprintf(argv, "--debug-timestamps=%d",
+                                       child_debug_timestamps);
         if (argv[argc] == NULL) {
             ret = ENOMEM;
             goto fail;
         }
-    }
 
-    argv[--argc] = talloc_asprintf(argv, "--debug-timestamps=%d",
-                                   child_debug_timestamps);
-    if (argv[argc] == NULL) {
-        ret = ENOMEM;
-        goto fail;
-    }
-
-    argv[--argc] = talloc_asprintf(argv, "--debug-microseconds=%d",
-                                       child_debug_microseconds);
-    if (argv[argc] == NULL) {
-        ret = ENOMEM;
-        goto fail;
+        argv[--argc] = talloc_asprintf(argv, "--debug-microseconds=%d",
+                                           child_debug_microseconds);
+        if (argv[argc] == NULL) {
+            ret = ENOMEM;
+            goto fail;
+        }
     }
 
     argv[--argc] = talloc_strdup(argv, binary);
@@ -720,7 +729,7 @@ fail:
 errno_t exec_child_ex(TALLOC_CTX *mem_ctx,
                       int *pipefd_to_child, int *pipefd_from_child,
                       const char *binary, int debug_fd,
-                      const char *extra_argv[],
+                      const char *extra_argv[], bool extra_args_only,
                       int child_in_fd, int child_out_fd)
 {
     int ret;
@@ -746,7 +755,7 @@ errno_t exec_child_ex(TALLOC_CTX *mem_ctx,
     }
 
     ret = prepare_child_argv(mem_ctx, debug_fd,
-                             binary, extra_argv,
+                             binary, extra_argv, extra_args_only,
                              &argv);
     if (ret != EOK) {
         DEBUG(SSSDBG_CRIT_FAILURE, "prepare_child_argv.\n");
@@ -764,7 +773,7 @@ errno_t exec_child(TALLOC_CTX *mem_ctx,
                    const char *binary, int debug_fd)
 {
     return exec_child_ex(mem_ctx, pipefd_to_child, pipefd_from_child,
-                         binary, debug_fd, NULL,
+                         binary, debug_fd, NULL, false,
                          STDIN_FILENO, STDOUT_FILENO);
 }
 
diff --git a/src/util/child_common.h b/src/util/child_common.h
index b93991832..0111f2cdb 100644
--- a/src/util/child_common.h
+++ b/src/util/child_common.h
@@ -104,7 +104,7 @@ void fd_nonblocking(int fd);
 errno_t exec_child_ex(TALLOC_CTX *mem_ctx,
                       int *pipefd_to_child, int *pipefd_from_child,
                       const char *binary, int debug_fd,
-                      const char *extra_argv[],
+                      const char *extra_argv[], bool extra_args_only,
                       int child_in_fd, int child_out_fd);
 
 /* Same as exec_child_ex() except child_in_fd is set to STDIN_FILENO and