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/* * This is a sample filter program, for use with pam_filter (a module * provided with Linux-PAM). This filter simply transposes upper and * lower case letters, it is intended for demonstration purposes and * it serves no purpose other than to annoy the user... */ #include "config.h" #include <ctype.h> #include <stdio.h> #include <stdlib.h> #include <syslog.h> #include <sys/time.h> #include <sys/types.h> #include <unistd.h> #include "pam_filter.h" #include <security/pam_modutil.h> /* ---------------------------------------------------------------- */ static void do_transpose(char *buffer,int len) { int i; for (i=0; i<len; ++i) { if (islower(buffer[i])) { buffer[i] = toupper(buffer[i]); } else { buffer[i] = tolower(buffer[i]); } } } extern char **environ; int main(int argc, char **argv UNUSED) { char buffer[BUFSIZ]; fd_set readers; void (*before_user)(char *,int); void (*before_app)(char *,int); openlog("upperLOWER", LOG_CONS|LOG_PID, LOG_AUTHPRIV); #ifdef DEBUG { int i; fprintf(stderr,"environment :[\r\n"); for (i=0; environ[i]; ++i) { fprintf(stderr,"-> %s\r\n",environ[i]); } fprintf(stderr,"]: end\r\n"); } #endif if (argc != 1) { #ifdef DEBUG fprintf(stderr,"filter invoked as conventional executable\n"); #else syslog(LOG_ERR, "filter invoked as conventional executable"); #endif exit(1); } before_user = before_app = do_transpose; /* assign filter functions */ /* enter a loop that deals with the input and output of the user.. passing it to and from the application */ FD_ZERO(&readers); /* initialize reading mask */ for (;;) { FD_SET(APPOUT_FILENO, &readers); /* wake for output */ FD_SET(APPERR_FILENO, &readers); /* wake for error */ FD_SET(STDIN_FILENO, &readers); /* wake for input */ if ( select(APPTOP_FILE,&readers,NULL,NULL,NULL) < 0 ) { #ifdef DEBUG fprintf(stderr,"select failed\n"); #else syslog(LOG_WARNING,"select failed"); #endif break; } /* application errors */ if ( FD_ISSET(APPERR_FILENO,&readers) ) { int got = read(APPERR_FILENO, buffer, BUFSIZ); if (got <= 0) { break; } else { /* translate to give to real terminal */ if (before_user != NULL) before_user(buffer, got); if (pam_modutil_write(STDERR_FILENO, buffer, got) != got ) { syslog(LOG_WARNING,"couldn't write %d bytes?!",got); break; } } } else if ( FD_ISSET(APPOUT_FILENO,&readers) ) { /* app output */ int got = read(APPOUT_FILENO, buffer, BUFSIZ); if (got <= 0) { break; } else { /* translate to give to real terminal */ if (before_user != NULL) before_user(buffer, got); if (pam_modutil_write(STDOUT_FILENO, buffer, got) != got ) { syslog(LOG_WARNING,"couldn't write %d bytes!?",got); break; } } } if ( FD_ISSET(STDIN_FILENO, &readers) ) { /* user input */ int got = read(STDIN_FILENO, buffer, BUFSIZ); if (got < 0) { syslog(LOG_WARNING,"user input junked"); break; } else if (got) { /* translate to give to application */ if (before_app != NULL) before_app(buffer, got); if (pam_modutil_write(APPIN_FILENO, buffer, got) != got ) { syslog(LOG_WARNING,"couldn't pass %d bytes!?",got); break; } } else { /* nothing received -- an error? */ syslog(LOG_WARNING,"user input null?"); break; } } } exit(0); }