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Replace g_strncpy() with str2memcpy()

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g_strncpy() is the wrong function for copying strings in struct utmp[x]
as it always terminates strings.

strncpy() itself would be a good choice, but is marked by many compilers
as being unsafe to use.

str2memcpy() is taken from util-linux, and is exactly right for this
application.
This commit is contained in:
matt335672 2023-06-30 10:09:49 +01:00
parent b53c683edf
commit 8cea9b03ab
1 changed files with 67 additions and 14 deletions
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81
sesman/sesexec/sessionrecord.c
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@ -14,6 +14,12 @@
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* str2memcpy() is taken from util-linux/include/strutils.h v2.39 which
* has the following header:-
*
* No copyright is claimed. This code is in the public domain; do with
* it what you wish.
*/
/**
@ -31,7 +37,6 @@
#include <config_ac.h>
#endif
#include "sessionrecord.h"
#include "login_info.h"
#include "log.h"
@ -49,6 +54,7 @@ enum add_xtmp_mode
#ifdef USE_UTMP
#include <sys/time.h>
#include <string.h>
#include <unistd.h>
#ifdef HAVE_UTMPX_H
@ -59,8 +65,6 @@ typedef struct utmpx _utmp;
typedef struct utmp _utmp;
#endif
#endif // USE_UTMP
#include "os_calls.h"
#include "string_calls.h"
@ -69,16 +73,50 @@ typedef struct utmp _utmp;
// number in hex
#define XRDP_ID_FORMAT ":%x"
/*
/******************************************************************************/
/**
* utmp-specific strncpy() replacement
*
* @param dest Destination pointer
* @param src Source pointer
* @param n bytes to copy
*
* This is like strncpy(), but based on memcpy(), so compilers and static
* analyzers do not complain when sizeof(destination) is the same as 'n' and
* result is not terminated by zero.
*
* ONLY use this function to copy string to logs with fixed sizes
* (wtmp/utmp. ...) where string terminator is optional.
*/
static inline void *__attribute__((nonnull (1)))
str2memcpy(void *dest, const char *src, size_t n)
{
size_t bytes = strlen(src) + 1;
if (bytes > n)
{
bytes = n;
}
memcpy(dest, src, bytes);
return dest;
}
/******************************************************************************/
/**
* Prepare the utmp struct and write it.
* this can handle login and logout at once with the 'mode' parameter
*
* @param pid PID of session manager
* @param display Display number of session
* @param login_info Login info (NULL for MODE_LOGOUT)
* @param mode see enum add_xtmp_mode
* @param e Exit status (NULL unless MODE_LOGOUT)
*/
static void
add_xtmp_entry(int pid, int display, const struct login_info *login_info,
enum add_xtmp_mode mode, const struct proc_exit_status *e)
{
#if USE_UTMP
char idbuff[16];
char str_display[16];
@ -92,16 +130,22 @@ add_xtmp_entry(int pid, int display, const struct login_info *login_info,
ut.ut_type = (mode == MODE_LOGIN) ? USER_PROCESS : DEAD_PROCESS;
ut.ut_pid = pid;
ut.ut_tv.tv_sec = tv.tv_sec;
ut.ut_tv.tv_usec = tv.tv_usec;
g_strncpy(ut.ut_line, str_display, sizeof(ut.ut_line));
g_strncpy(ut.ut_id, idbuff, sizeof(ut.ut_id));
if (login_info != NULL)
str2memcpy(ut.ut_id, idbuff, sizeof(ut.ut_id));
// Linux utmp(5) suggests ut_line, ut_time, ut_user, and ut_host
// are not set for a DEAD_PROCESS
if (ut.ut_type != DEAD_PROCESS)
{
g_strncpy(ut.ut_user, login_info->username, sizeof(ut.ut_user));
ut.ut_tv.tv_sec = tv.tv_sec;
ut.ut_tv.tv_usec = tv.tv_usec;
str2memcpy(ut.ut_line, str_display, sizeof(ut.ut_line));
if (login_info != NULL)
{
str2memcpy(ut.ut_user, login_info->username, sizeof(ut.ut_user));
#ifdef HAVE_UTMPX_UT_HOST
g_strncpy(ut.ut_host, login_info->ip_addr, sizeof(ut.ut_host));
str2memcpy(ut.ut_host, login_info->ip_addr, sizeof(ut.ut_host));
#endif
}
}
#ifdef HAVE_UTMPX_UT_EXIT
@ -123,9 +167,17 @@ add_xtmp_entry(int pid, int display, const struct login_info *login_info,
/* closes utmp */
endutxent();
#endif // USE_UTMP
}
#else // USE_UTMP
static void
add_xtmp_entry(int pid, int display, const struct login_info *login_info,
short state, const struct proc_exit_status *e)
{
}
#endif
/******************************************************************************/
void
utmp_login(int pid, int display, const struct login_info *login_info)
{
@ -136,6 +188,7 @@ utmp_login(int pid, int display, const struct login_info *login_info)
add_xtmp_entry(pid, display, login_info, MODE_LOGIN, NULL);
}
/******************************************************************************/
void
utmp_logout(int pid, int display, const struct proc_exit_status *exit_status)
{