mate-about-me: interact with passwd via /dev/ptmx

[pyhalov]

No description provided.

[lukefromdc]

I got these warnings ending in a build error on Debian Unstable:

mate-about-me-password.c: In function ‘spawn_passwd’:
mate-about-me-password.c:193:10: warning: implicit declaration of function ‘ptsname’; did you mean ‘ttyname’? [-Wimplicit-function-declaration]
   name = ptsname(pdialog->pty_m);
          ^~~~~~~
          ttyname
mate-about-me-password.c:193:8: warning: assignment to ‘char *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
   name = ptsname(pdialog->pty_m);
        ^
mate-about-me-password.c:195:4: warning: implicit declaration of function ‘strlcpy’; did you mean ‘strncpy’? [-Wimplicit-function-declaration]
    strlcpy(slave_name, name, PTY_MAX_NAME);
    ^~~~~~~
    strncpy
mate-about-me-password.c:205:6: warning: implicit declaration of function ‘grantpt’ [-Wimplicit-function-declaration]
  if (grantpt(pdialog->pty_m) < 0) {
      ^~~~~~~
mate-about-me-password.c:210:6: warning: implicit declaration of function ‘unlockpt’; did you mean ‘unlinkat’? [-Wimplicit-function-declaration]
  if (unlockpt(pdialog->pty_m) < 0) {
      ^~~~~~~~
      unlinkat
mate-about-me-password.c:232:7: warning: implicit declaration of function ‘ioctl’ [-Wimplicit-function-declaration]
   if (ioctl(pdialog->pty_s,TIOCSCTTY, NULL) < 0) {
       ^~~~~
mate-about-me-password.c:232:28: error: ‘TIOCSCTTY’ undeclared (first use in this function)
   if (ioctl(pdialog->pty_s,TIOCSCTTY, NULL) < 0) {

[pyhalov]

@lukefromdc tried to follow linux man pages, however don't have a system to check compilation

[lukefromdc]

Got another build error, this time

mate-about-me-password.c: In function ‘spawn_passwd’:
mate-about-me-password.c:240:28: error: ‘TIOCSCTTY’ undeclared (first use in this function)
   if (ioctl(pdialog->pty_s,TIOCSCTTY, NULL) < 0) {

[lukefromdc]

Got another build error, maybe from a typo ?

mate-about-me-password.c: In function ‘spawn_passwd’:
mate-about-me-password.c:239:6: warning: implicit declaration of function ‘pipe2’; did you mean ‘pipe’? [-Wimplicit-function-declaration]
  if (pipe2(err_pipe, O_CLOEXEC) < 0) {
      ^~~~~
      pipe
mate-about-me-password.c:239:22: error: ‘O_CLOEXEC’ undeclared (first use in this function); did you mean ‘FD_CLOEXEC’?
  if (pipe2(err_pipe, O_CLOEXEC) < 0) {
                      ^~~~~~~~~
                      FD_CLOEXEC

[lukefromdc]

With the last change, this now builds and runs on Debian Unstable, and I had no trouble changing a user password and changing it back

[lukefromdc]

Note that I don't know enough about the handling of the *name variable set in line 196 and then initialized with name = ptsname(pty_m); to evaluate the memory handling here.

[pyhalov]

ptsname(3C) on OpenIndiana says:

      Upon successful completion, the function ptsname() returns a pointer to
       a string which is the name of the pseudo-terminal slave device. This
       value points to a static data area that is overwritten by each call to
       ptsname(). Upon failure, ptsname() returns NULL.

ptsname(3) on Linux says:

On success, ptsname() returns a pointer to a string in static storage which will be overwritten by subsequent calls.  This pointer must not be freed.  On failure, NULL is returned

[lukefromdc]

OK, that part is probably the same everywhere, good to to

[pyhalov]

Note, that last change (s/return/exit/) will fail unless #387 is also applied. I was a bit puzzled, why we can't exit() from child on error, when we should (we don't want to run duplicate process). Now we know the reason :)

[lukefromdc]

Any more updates on this?