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MDEV-26212 PAM authentication fails with ENOMEM

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use posix_spawn(), not fork() - it's better for systems that don't
overcommit memory
This commit is contained in:
Sergei Golubchik 2022-04-25 18:13:13 +02:00
parent d45841b9be
commit e6bbc83d5e
1 changed files with 32 additions and 45 deletions
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65
plugin/auth_pam/auth_pam.c
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@ -20,6 +20,7 @@
#include <string.h> #include <string.h>
#include <sys/types.h> #include <sys/types.h>
#include <sys/wait.h> #include <sys/wait.h>
#include <spawn.h>
#include <mysql/plugin_auth.h> #include <mysql/plugin_auth.h>
#include "auth_pam_tool.h" #include "auth_pam_tool.h"
#include <my_global.h> #include <my_global.h>
@ -51,44 +52,25 @@ static int pam_auth(MYSQL_PLUGIN_VIO *vio, MYSQL_SERVER_AUTH_INFO *info)
unsigned char field, *pkt; unsigned char field, *pkt;
unsigned int n_sleep= 0; unsigned int n_sleep= 0;
useconds_t sleep_time= 100; useconds_t sleep_time= 100;
posix_spawn_file_actions_t file_actions;
char toolpath[FN_REFLEN];
size_t plugin_dir_len= strlen(opt_plugin_dir);
char *const argv[2]= {toolpath, 0};
int res;
PAM_DEBUG((stderr, "PAM: opening pipes.\n")); PAM_DEBUG((stderr, "PAM: opening pipes.\n"));
if (pipe(p_to_c) < 0 || pipe(c_to_p) < 0) if (pipe(p_to_c) < 0 || pipe(c_to_p) < 0)
{ {
/* Error creating pipes. */ my_printf_error(ENOEXEC, "pam: cannot create pipes (errno: %M)",
ME_ERROR_LOG_ONLY, errno);
return CR_ERROR; return CR_ERROR;
} }
PAM_DEBUG((stderr, "PAM: forking.\n"));
if ((proc_id= fork()) < 0)
{
/* Error forking. */
close(p_to_c[0]);
close(c_to_p[1]);
goto error_ret;
}
if (proc_id == 0)
{
/* The 'sandbox' process started. */
char toolpath[FN_REFLEN];
size_t plugin_dir_len= strlen(opt_plugin_dir);
PAM_DEBUG((stderr, "PAM: Child process prepares pipes.\n"));
if (close(p_to_c[1]) < 0 ||
close(c_to_p[0]) < 0 ||
dup2(p_to_c[0], 0) < 0 || /* Parent's pipe to STDIN. */
dup2(c_to_p[1], 1) < 0) /* Sandbox's pipe to STDOUT. */
{
exit(-1);
}
PAM_DEBUG((stderr, "PAM: check tool directory: %s, %s.\n",
opt_plugin_dir, tool_name));
if (plugin_dir_len + tool_name_len + 2 > sizeof(toolpath)) if (plugin_dir_len + tool_name_len + 2 > sizeof(toolpath))
{ {
/* Tool path too long. */ my_printf_error(ENOEXEC, "pam: too long path to <plugindir>/%s",
exit(-1); ME_ERROR_LOG_ONLY, tool_name);
return CR_ERROR;
} }
memcpy(toolpath, opt_plugin_dir, plugin_dir_len); memcpy(toolpath, opt_plugin_dir, plugin_dir_len);
@ -96,20 +78,25 @@ static int pam_auth(MYSQL_PLUGIN_VIO *vio, MYSQL_SERVER_AUTH_INFO *info)
toolpath[plugin_dir_len++]= FN_LIBCHAR; toolpath[plugin_dir_len++]= FN_LIBCHAR;
memcpy(toolpath+plugin_dir_len, tool_name, tool_name_len+1); memcpy(toolpath+plugin_dir_len, tool_name, tool_name_len+1);
PAM_DEBUG((stderr, "PAM: execute pam sandbox [%s].\n", toolpath)); PAM_DEBUG((stderr, "PAM: forking %s\n", toolpath));
(void) execl(toolpath, toolpath, NULL); res= posix_spawn_file_actions_init(&file_actions) ||
PAM_DEBUG((stderr, "PAM: exec() failed.\n")); posix_spawn_file_actions_addclose(&file_actions, p_to_c[1]) ||
my_printf_error(1, "PAM: Cannot execute %s (errno: %M)", ME_ERROR_LOG_ONLY, posix_spawn_file_actions_addclose(&file_actions, c_to_p[0]) ||
toolpath, errno); posix_spawn_file_actions_adddup2(&file_actions, p_to_c[0], 0) ||
exit(-1); posix_spawn_file_actions_adddup2(&file_actions, c_to_p[1], 1) ||
} posix_spawn(&proc_id, toolpath, &file_actions, NULL, argv, NULL);
/* Parent process continues. */ /* Parent process continues. */
posix_spawn_file_actions_destroy(&file_actions);
close(p_to_c[0]);
close(c_to_p[1]);
PAM_DEBUG((stderr, "PAM: parent continues.\n")); if (res)
if (close(p_to_c[0]) < 0 || {
close(c_to_p[1]) < 0) my_printf_error(ENOEXEC, "pam: cannot exec %s (errno: %M)",
ME_ERROR_LOG_ONLY, toolpath, errno);
goto error_ret; goto error_ret;
}
/* no user name yet ? read the client handshake packet with the user name */ /* no user name yet ? read the client handshake packet with the user name */
if (info->user_name == 0) if (info->user_name == 0)