Avoid string overflow for mode strings of size at most 10 chars plus one byte

string termination (`\0`). Dumb down the sharelink mode iterator to keep it
simple.
Adjust prefix for shared PAM and NSS log line helper to clarify that. Otherwise
we get `pam_mig` log entries even for key login, which never hits PAM.

Author: jonasbardino

mig/src/include/auth/migauth.h

@@ -170,7 +170,7 @@
     fprintf(stderr, #priority ": " __FILE__"("TOSTRING(__LINE__)"): " format, ##__VA_ARGS__)
 #else                           /* DEBUG_LOG_STDERR */
 #define WRITELOGMESSAGE(priority, format, ...) \
-    openlog("pam_mig", LOG_PID, LOG_AUTHPRIV); \
+    openlog("nss-pam_mig", LOG_PID, LOG_AUTHPRIV); \
     syslog(priority, #priority ": " __FILE__"("TOSTRING(__LINE__)"): " format, ##__VA_ARGS__);
 #endif                          /* DEBUG_LOG_STDERR */
 #else                           /* DEBUG || DEBUG_LOG_STDERR */
@@ -186,7 +186,7 @@
 */
 #define WRITELOGMESSAGE(priority, ...) \
     if (priority != LOG_DEBUG) { \
-        openlog("pam_mig", LOG_PID, LOG_AUTHPRIV); \
+        openlog("nss-pam_mig", LOG_PID, LOG_AUTHPRIV); \
         syslog(priority, ##__VA_ARGS__); \
     }
 #endif                          /* DEBUG || DEBUG_LOG_STDERR */

mig/src/libnss-mig/libnss_mig.c

@@ -183,8 +183,8 @@ _nss_mig_getpwnam_r(const char *name,
     if (keep_trying && name_len == get_sharelink_length()) {
         WRITELOGMESSAGE(LOG_DEBUG, "Checking for sharelink: %s\n", name);
 
-        char sharelink_modes[][10] = { SHARELINK_RW_DIR, SHARELINK_RO_DIR, SHARELINK_WO_DIR };
-        for (size_t i = 0; i < sizeof(sharelink_modes) / sizeof(sharelink_modes[0]); i++)
+        char sharelink_modes[3][11] = { SHARELINK_RW_DIR, SHARELINK_RO_DIR, SHARELINK_WO_DIR };
+        for (uint i = 0; i < 3; i++)
         {
 
         memset(pathbuf, 0, PATH_BUF_LEN);

mig/src/libpam-mig/libpam_mig.c

@@ -715,8 +715,8 @@ PAM_EXTERN int pam_sm_authenticate(pam_handle_t * pamh, int flags,
     if (strlen(pUsername) == get_sharelink_length()) {
         char share_path[MAX_PATH_LENGTH];
 
-        char sharelink_modes[][10] = { SHARELINK_RW_DIR, SHARELINK_RO_DIR, SHARELINK_WO_DIR };
-        for (size_t i = 0; i < sizeof(sharelink_modes) / sizeof(sharelink_modes[0]); i++)
+        char sharelink_modes[3][11] = { SHARELINK_RW_DIR, SHARELINK_RO_DIR, SHARELINK_WO_DIR };
+        for (uint i = 0; i < 3; i++)
         {
 
         memset(share_path, 0, MAX_PATH_LENGTH);