From 7ab83f97e1cbefb78ece17232185bdd2985f0bbe Mon Sep 17 00:00:00 2001
From: Alexey Tikhonov <atikhono@redhat.com>
Date: Fri, 18 Jun 2021 13:17:19 +0200
Subject: [PATCH] TOOLS: replace system() with execvp() to avoid execution of
user supplied command
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:relnote: A flaw was found in SSSD, where the sssctl command was
vulnerable to shell command injection via the logs-fetch and
cache-expire subcommands. This flaw allows an attacker to trick
the root user into running a specially crafted sssctl command,
such as via sudo, to gain root access. The highest threat from this
vulnerability is to confidentiality, integrity, as well as system
availability.
This patch fixes a flaw by replacing system() with execvp().
:fixes: CVE-2021-3621
Reviewed-by: Pavel Březina <pbrezina@redhat.com>
---
src/tools/sssctl/sssctl.c | 39 ++++++++++++++++-------
src/tools/sssctl/sssctl.h | 2 +-
src/tools/sssctl/sssctl_data.c | 57 +++++++++++-----------------------
src/tools/sssctl/sssctl_logs.c | 32 +++++++++++++++----
4 files changed, 73 insertions(+), 57 deletions(-)
diff --git a/src/tools/sssctl/sssctl.c b/src/tools/sssctl/sssctl.c
index 2997dbf96..8adaf3091 100644
--- a/src/tools/sssctl/sssctl.c
+++ b/src/tools/sssctl/sssctl.c
@@ -97,22 +97,36 @@ sssctl_prompt(const char *message,
return SSSCTL_PROMPT_ERROR;
}
-errno_t sssctl_run_command(const char *command)
+errno_t sssctl_run_command(const char *const argv[])
{
int ret;
+ int wstatus;
- DEBUG(SSSDBG_TRACE_FUNC, "Running %s\n", command);
+ DEBUG(SSSDBG_TRACE_FUNC, "Running '%s'\n", argv[0]);
- ret = system(command);
+ ret = fork();
if (ret == -1) {
- DEBUG(SSSDBG_CRIT_FAILURE, "Unable to execute %s\n", command);
ERROR("Error while executing external command\n");
return EFAULT;
- } else if (WEXITSTATUS(ret) != 0) {
- DEBUG(SSSDBG_CRIT_FAILURE, "Command %s failed with [%d]\n",
- command, WEXITSTATUS(ret));
+ }
+
+ if (ret == 0) {
+ /* cast is safe - see
+ https://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html
+ "The statement about argv[] and envp[] being constants ... "
+ */
+ execvp(argv[0], discard_const_p(char * const, argv));
ERROR("Error while executing external command\n");
- return EIO;
+ _exit(1);
+ } else {
+ if (waitpid(ret, &wstatus, 0) == -1) {
+ ERROR("Error while executing external command '%s'\n", argv[0]);
+ return EFAULT;
+ } else if (WEXITSTATUS(wstatus) != 0) {
+ ERROR("Command '%s' failed with [%d]\n",
+ argv[0], WEXITSTATUS(wstatus));
+ return EIO;
+ }
}
return EOK;
@@ -132,11 +146,14 @@ static errno_t sssctl_manage_service(enum sssctl_svc_action action)
#elif defined(HAVE_SERVICE)
switch (action) {
case SSSCTL_SVC_START:
- return sssctl_run_command(SERVICE_PATH" sssd start");
+ return sssctl_run_command(
+ (const char *[]){SERVICE_PATH, "sssd", "start", NULL});
case SSSCTL_SVC_STOP:
- return sssctl_run_command(SERVICE_PATH" sssd stop");
+ return sssctl_run_command(
+ (const char *[]){SERVICE_PATH, "sssd", "stop", NULL});
case SSSCTL_SVC_RESTART:
- return sssctl_run_command(SERVICE_PATH" sssd restart");
+ return sssctl_run_command(
+ (const char *[]){SERVICE_PATH, "sssd", "restart", NULL});
}
#endif
diff --git a/src/tools/sssctl/sssctl.h b/src/tools/sssctl/sssctl.h
index 0115b2457..599ef6519 100644
--- a/src/tools/sssctl/sssctl.h
+++ b/src/tools/sssctl/sssctl.h
@@ -47,7 +47,7 @@ enum sssctl_prompt_result
sssctl_prompt(const char *message,
enum sssctl_prompt_result defval);
-errno_t sssctl_run_command(const char *command);
+errno_t sssctl_run_command(const char *const argv[]); /* argv[0] - command */
bool sssctl_start_sssd(bool force);
bool sssctl_stop_sssd(bool force);
bool sssctl_restart_sssd(bool force);
diff --git a/src/tools/sssctl/sssctl_data.c b/src/tools/sssctl/sssctl_data.c
index 8d79b977f..bf2291341 100644
--- a/src/tools/sssctl/sssctl_data.c
+++ b/src/tools/sssctl/sssctl_data.c
@@ -105,15 +105,15 @@ static errno_t sssctl_backup(bool force)
}
}
- ret = sssctl_run_command("sss_override user-export "
- SSS_BACKUP_USER_OVERRIDES);
+ ret = sssctl_run_command((const char *[]){"sss_override", "user-export",
+ SSS_BACKUP_USER_OVERRIDES, NULL});
if (ret != EOK) {
ERROR("Unable to export user overrides\n");
return ret;
}
- ret = sssctl_run_command("sss_override group-export "
- SSS_BACKUP_GROUP_OVERRIDES);
+ ret = sssctl_run_command((const char *[]){"sss_override", "group-export",
+ SSS_BACKUP_GROUP_OVERRIDES, NULL});
if (ret != EOK) {
ERROR("Unable to export group overrides\n");
return ret;
@@ -158,8 +158,8 @@ static errno_t sssctl_restore(bool force_start, bool force_restart)
}
if (sssctl_backup_file_exists(SSS_BACKUP_USER_OVERRIDES)) {
- ret = sssctl_run_command("sss_override user-import "
- SSS_BACKUP_USER_OVERRIDES);
+ ret = sssctl_run_command((const char *[]){"sss_override", "user-import",
+ SSS_BACKUP_USER_OVERRIDES, NULL});
if (ret != EOK) {
ERROR("Unable to import user overrides\n");
return ret;
@@ -167,8 +167,8 @@ static errno_t sssctl_restore(bool force_start, bool force_restart)
}
if (sssctl_backup_file_exists(SSS_BACKUP_USER_OVERRIDES)) {
- ret = sssctl_run_command("sss_override group-import "
- SSS_BACKUP_GROUP_OVERRIDES);
+ ret = sssctl_run_command((const char *[]){"sss_override", "group-import",
+ SSS_BACKUP_GROUP_OVERRIDES, NULL});
if (ret != EOK) {
ERROR("Unable to import group overrides\n");
return ret;
@@ -296,40 +296,19 @@ errno_t sssctl_cache_expire(struct sss_cmdline *cmdline,
void *pvt)
{
errno_t ret;
- char *cmd_args = NULL;
- const char *cachecmd = SSS_CACHE;
- char *cmd = NULL;
- int i;
-
- if (cmdline->argc == 0) {
- ret = sssctl_run_command(cachecmd);
- goto done;
- }
- cmd_args = talloc_strdup(tool_ctx, "");
- if (cmd_args == NULL) {
- ret = ENOMEM;
- goto done;
+ const char **args = talloc_array_size(tool_ctx,
+ sizeof(char *),
+ cmdline->argc + 2);
+ if (!args) {
+ return ENOMEM;
}
+ memcpy(&args[1], cmdline->argv, sizeof(char *) * cmdline->argc);
+ args[0] = SSS_CACHE;
+ args[cmdline->argc + 1] = NULL;
- for (i = 0; i < cmdline->argc; i++) {
- cmd_args = talloc_strdup_append(cmd_args, cmdline->argv[i]);
- if (i != cmdline->argc - 1) {
- cmd_args = talloc_strdup_append(cmd_args, " ");
- }
- }
-
- cmd = talloc_asprintf(tool_ctx, "%s %s", cachecmd, cmd_args);
- if (cmd == NULL) {
- ret = ENOMEM;
- goto done;
- }
-
- ret = sssctl_run_command(cmd);
-
-done:
- talloc_free(cmd_args);
- talloc_free(cmd);
+ ret = sssctl_run_command(args);
+ talloc_free(args);
return ret;
}
diff --git a/src/tools/sssctl/sssctl_logs.c b/src/tools/sssctl/sssctl_logs.c
index 9ff2be05b..ebb2c4571 100644
--- a/src/tools/sssctl/sssctl_logs.c
+++ b/src/tools/sssctl/sssctl_logs.c
@@ -31,6 +31,7 @@
#include <ldb.h>
#include <popt.h>
#include <stdio.h>
+#include <glob.h>
#include "util/util.h"
#include "tools/common/sss_process.h"
@@ -230,6 +231,7 @@ errno_t sssctl_logs_remove(struct sss_cmdline *cmdline,
{
struct sssctl_logs_opts opts = {0};
errno_t ret;
+ glob_t globbuf;
/* Parse command line. */
struct poptOption options[] = {
@@ -253,8 +255,20 @@ errno_t sssctl_logs_remove(struct sss_cmdline *cmdline,
sss_signal(SIGHUP);
} else {
+ globbuf.gl_offs = 4;
+ ret = glob(LOG_PATH"/*.log", GLOB_ERR|GLOB_DOOFFS, NULL, &globbuf);
+ if (ret != 0) {
+ DEBUG(SSSDBG_CRIT_FAILURE, "Unable to expand log files list\n");
+ return ret;
+ }
+ globbuf.gl_pathv[0] = discard_const_p(char, "truncate");
+ globbuf.gl_pathv[1] = discard_const_p(char, "--no-create");
+ globbuf.gl_pathv[2] = discard_const_p(char, "--size");
+ globbuf.gl_pathv[3] = discard_const_p(char, "0");
+
PRINT("Truncating log files...\n");
- ret = sssctl_run_command("truncate --no-create --size 0 " LOG_FILES);
+ ret = sssctl_run_command((const char * const*)globbuf.gl_pathv);
+ globfree(&globbuf);
if (ret != EOK) {
ERROR("Unable to truncate log files\n");
return ret;
@@ -269,8 +283,8 @@ errno_t sssctl_logs_fetch(struct sss_cmdline *cmdline,
void *pvt)
{
const char *file;
- const char *cmd;
errno_t ret;
+ glob_t globbuf;
/* Parse command line. */
ret = sss_tool_popt_ex(cmdline, NULL, SSS_TOOL_OPT_OPTIONAL, NULL, NULL,
@@ -280,13 +294,19 @@ errno_t sssctl_logs_fetch(struct sss_cmdline *cmdline,
return ret;
}
- cmd = talloc_asprintf(tool_ctx, "tar -czf %s %s", file, LOG_FILES);
- if (cmd == NULL) {
- ERROR("Out of memory!");
+ globbuf.gl_offs = 3;
+ ret = glob(LOG_PATH"/*.log", GLOB_ERR|GLOB_DOOFFS, NULL, &globbuf);
+ if (ret != 0) {
+ DEBUG(SSSDBG_CRIT_FAILURE, "Unable to expand log files list\n");
+ return ret;
}
+ globbuf.gl_pathv[0] = discard_const_p(char, "tar");
+ globbuf.gl_pathv[1] = discard_const_p(char, "-czf");
+ globbuf.gl_pathv[2] = discard_const_p(char, file);
PRINT("Archiving log files into %s...\n", file);
- ret = sssctl_run_command(cmd);
+ ret = sssctl_run_command((const char * const*)globbuf.gl_pathv);
+ globfree(&globbuf);
if (ret != EOK) {
ERROR("Unable to archive log files\n");
return ret;
--
2.26.3