c sshfs automatic connection thru bash using libexpect - c

Question

I want to automate the mounting of a sshfs connection inside my C program (meant for linux) using only password for ssh. (I don't want to use public/private keys.)
It seems i could do it with libexpect. Based on this thread it seems possible to use libexpect to give the password when required. For example, i made a successful test program that creates a dir with sudo mkdir test and then provide the user password with libexpect. So that pipe seems really to be bidirectional. Thou, with sshfs and my simple function below, it doesn't work: i do have a sshfs mount produced by it, but it doesn't work and i can't see the files.
enum{ASKCONTINUE,ASKPWD};
int sshfs_connect (char data[10][200], char ip[]) {
char commandline[300];
sprintf(commandline,"sshfs %s#%s:%s %s -p %s -o ServerAliveInterval=15",
data[4],ip,data[6],data[5],data[7]);
bool shouldBreak = false;
FILE* fp = exp_popen(commandline);
while(shouldBreak == false)
{
switch(exp_fexpectl(fp,
//if asked for continuing (authenticity can't be established)
exp_glob, "ontinue connecting (yes/no)?", ASKCONTINUE,
//if asked for pwd
exp_glob, "s password:", ASKPWD,
exp_end)) //
{
case ASKCONTINUE:
printf("asked continue? !\n");
fprintf(fp,"%s\n","yes");
break;
case ASKPWD:
printf("asked pwd ! sending pwd: %s\n",data[8]);
fprintf(fp,"%s\n",data[8]);
shouldBreak = true;
break;
case EXP_TIMEOUT:
shouldBreak = true;
break;
case EXP_EOF:
shouldBreak = true;
break;
}
}
fclose(fp);
return 0;
}

Answer 1

It seems that expect (even the tcl version) cannot be used with sshfs, probably because the spawned process does not have a controlling tty and so the command tries to get the password from the user by other means, e.g. using a gui popup.
What works is adding the option -o password_stdin to ask sshfs to read the password from stdin. It does this without writing a prompt, so libexpect is a bit heavyweight, but nonetheless this should work for you: send the password and wait for eof (which would probably be within the default timeout of 10 seconds).
ssh = exp_popen("sshfs -o password_stdin user#host:/dir /mntpoint");
if(ssh==NULL)fatal("fail to spawn");
fprintf(ssh, "%s\n", password);
switch(exp_fexpectl(ssh,exp_end)) {
case EXP_EOF:
break; // ok
case EXP_TIMEOUT:
break; // fail
default:
break; // fail
}