InfoMagic Internet Tools 1993 July/Internet Tools.iso/RockRidge/mail/sendmail/sendmail-5.65c+IDA-1.4.4.1/support/fakename.c

C/C++ Source or Header | 1990-11-08 | 4.1 KB | 148 lines

/*
** fakemail - a SysV /bin/mail preprocessor for sendmail
**
** Standard AT&T /bin/mail adds it's own From_ line specifying the
** identity of the sender (commenting out any previously existing
** From_ lines in the process).  While this behavior might be
** consistent with RFC-976, it only serves to confuse mailers such
** as mailx which use the From_ line to determine reply addresses.
**
** To determine the sender identity (placed in the generated From_
** line), /bin/mail uses $LOGNAME of the user/program invoking it.
** For local mail this is moderately acceptable (the user could fake
** the sender by changing $LOGNAME), but for use with sendmail this
** behavior is unreasonable since the invocation of /bin/mail is
** done by root.  As a result, mailx reports all external mail as
** "From root", and the actual identity of the sender is obscured.
**
** `fakemail' is designed as a replacement for the sendmail local
** delivery program.  It preprocesses mail messages (read from
** stdin) and changes $LOGNAME before calling the regular /bin/mail.
** The new $LOGNAME is derived from the address portion of the From_
** line, which is found in the first line of the header.
**
**    From user@site Fri Jun 15 13:18:09 1990
**
** If no From_ line is found, $LOGNAME defaults to the user of the
** program, as with normal /bin/mail.
**
** Technically, `fakemail' could be considered a slightly better
** mechanism than direct /bin/mail since you cannot spoof the
** program by changing $LOGNAME.  An argument against this, however,
** is the fact that you *can* trick `fakemail' by supplying a bogus
** From_ line as the first line of the header.
**
** To use:
**
**    1) Compile and install this program
**        make fakemail
**        cpset fakemail /usr/bin
**
**    2) Edit /usr/lib/sendmail.cf
**        change the 'Mlocal' mailer to use /usr/bin/fakemail
**
**    3) Restart sendmail
**        ps -eaf; kill -9 <sendmail_pid>
**        /usr/lib/sendmail -bd -q30m
**
** NOTE: This is simply a hack for sendmail+mailx.  Use of another
** MTA (ie, smail) or MUA (ie, Elm) would eliminate any need for this
** program.
**
** --
** Bill Houle                       [e-mail]
** NCR SE-San Diego                 [phone]
*/

#include <stdio.h>
#include <string.h>

/*#define DEBUG    "/bin/cat"        /* comment this out for installation */
#define    BINMAIL    "/bin/mail"
#define    TRUE    1
#define    FALSE    0

char    line[255], env[255];
void    exit(), perror();

void syserr(str)
char *str;
{
    perror(str);
    exit(1);
}

main(argc, argv)
int argc;
char **argv;
{
    int fd[2], from_found=TRUE;

    if (gets(line) != NULL) {            /* read first line    *
/
        strcpy(env, "LOGNAME=");
        if (strncmp(line, "From ", 5) == 0) {    /* From_ line?        *
/
            (void) strtok(line, " \t\n\r");    /* get address token  *
/
            strcat(env, strtok(NULL, " \t\n\r"));
        }
        else {
            from_found=FALSE;        /* no From_ line      *
/
            strcat(env, cuserid(NULL));    /* default to user-id *
/
        }
        (void) putenv(env);            /* change $LOGNAME    *
/
    }

    if (pipe(fd) < 0) syserr("pipe");        /* prepare pipe       *
/
    switch (fork()) {                /* fork to /bin/mail  *
/
    case -1:
        syserr("fork to /bin/mail");
    case 0:
        if (close(0) < 0)            /* close stdin        *
/
            syserr("close child stdin");
        if (dup(fd[0]) != 0)            /* stdin from pipe    *
/
            syserr("dup pipe to stdin");
        if (close(fd[0]) < 0 || close(fd[1]) < 0)
            syserr("close child pipe");
#ifdef DEBUG
        (void) fprintf(stderr, "[set %s and exec %s]\n", env, BINMAIL);
        (void) fprintf(stderr, "Debugging through %s.\n", DEBUG);
        (void) execl(DEBUG, DEBUG, 0);
        (void) fprintf(stderr, "Cannot exec %s from %s.\n",
          DEBUG, argv[0]);
        exit(0);
#else
        (void) execv(BINMAIL, argv);
        (void) fprintf(stderr, "Cannot exec %s from %s.\n",
          BINMAIL, argv[0]);
        exit(1);
#endif
    }

    if (close(1) < 0)                /* close stdout       *
/
        syserr("close parent stdout");
    if (dup(fd[1]) != 1)                /* stdout to pipe     *
/
        syserr("dup pipe to stdout");
    if (close(fd[0]) < 0 || close(fd[1]) < 0)
        syserr("close parent pipe");

    if (!from_found) (void) puts(line);        /* 1st line not From_ *
/
    while (gets(line) != NULL)            /* send rest of msg   *
/
        (void) puts(line);
    exit(0);
    return(0);                    /* make lint happy    *
/
}