folder.c

/*
 *  pop3d       - IP/TCP/POP3 server for UNIX 4.3BSD
 *            Post Office Protocol - Version 3 (RFC1225)
 *
 *      (C) Copyright 1991 Regents of the University of California
 *
 *      Permission to use, copy, modify, and distribute this program
 *      for any purpose and without fee is hereby granted, provided
 *      that this copyright and permission notice appear on all copies
 *      and supporting documentation, the name of University of California
 *      not be used in advertising or publicity pertaining to distribution
 *      of the program without specific prior permission, and notice be
 *      given in supporting documentation that copying and distribution is
 *      by permission of the University of California.
 *      The University of California makes no representations about
 *      the suitability of this software for any purpose.  It is provided
 *      "as is" without express or implied warranty.
 *
 *  Katie Stevens
 *  dkstevens@ucdavis.edu
 *  Information Technology -- Campus Access Point
 *  University of California, Davis
 *
 **************************************
 *
 *  folder.c
 *
 *  REVISIONS:
 *      02-27-90 [ks]   original implementation
 *  1.000   03-04-90 [ks]
 *  1.001   06-24-90 [ks]   allow TRANS state if 0 msgs in folder
 *              implement optional TOP command
 *  1.002   07-22-91 [ks]   reset index counter after folder rewind
 *              in fld_release (Thanks to John Briggs,
 *              vaxs09@vitro.com, Vitro Corporation,
 *              Silver Spring, MD for finding this bug!)
 *  1.004   11-13-91 [ks]   leave original mailbox intact during POP
 *              session (Thanks to Dave Cooley,
 *              dwcooley@colby.edu for suggesting this)
 *  1.005   01-04-96 [dts]  change mktemp to mkstemp to avoid security
 *              hole with mktemp (timing attack).
 */

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <syslog.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/file.h>
#include "pop3.h"

#ifdef QMAIL
# include <pwd.h>
#endif

#ifdef LINUX
# include <unistd.h>
#endif

#ifdef VIRTUAL
extern int virtual_mode;
extern char *virt_spooldir;
extern char *virt_workdir;
#endif

/* In main.c */
extern char *svr_hostname;
extern char svr_buf[];
extern char cli_user[];

/* In util.c */
extern char flash_buf[];

extern FILE *logfp;
extern int mypid;
extern int debug;

/* Constants used when closing a folder after POP session */
#define REMOVE_MBOX 1
#define SAVE_NEW    2
#define SAVE_ALL    3

static char *svr_nomsg = "-ERR no messages in mailbox\r\n";
static char *cli_mbox = NULL;       /* Filename of mailbox folder */

#define FNAME_SIZ 128
static char fld_fname[FNAME_SIZ];   /* Filename for working folder */
static FILE *fld_fp = NULL;     /* Stream pointer for mailbox */
static struct fld_item *fld_msg;    /* Struct for mailbox stats */
static int fld_max = -1;        /* Actual # msgs in mailbox */
static int fld_highest = -1;        /* Max msg accessed by client */
static long fld_orig_size;      /* [1.004] size of mbox when loaded */
static time_t fld_orig_mod_time;    /* [1.004] timestamp on mbox file */

#define isfromsp_start(buf) (strncmp(buf,"From ",5) == 0)

static int fld_select();
static void retr_fromsp();
static int msg_fromsp();

/**************************************************************************/

static void
delete_folder()
{
    unlink(fld_fname);
}

/**************************************************************************/

/* Open a FromSpace delimited mailbox */
int
fld_fromsp(fname)
char *fname;
{
    int cnt;
    static char buffer[256];    /* DTS 14Sep99 - try to speed up */

    /* Release previously opened mailbox */
    if (fld_fp != NULL)
        fld_release();
    /* Construct filename for new mailbox */
    /* DTS 14Sep99 - added "if" to try to speed up (malloc slow?) */
    if ( strlen(fname) <= 255 ) {
        cli_mbox = buffer;
    } else {
        cli_mbox = malloc(strlen(fname)+1);
        if (cli_mbox == NULL)
            fail(FAIL_OUT_OF_MEMORY);
    }
/*  cli_mbox = malloc(strlen(fname)+1);
 *  if (cli_mbox == NULL)
 *      fail(FAIL_OUT_OF_MEMORY);
 */
    strcpy(cli_mbox,fname);
    /* Open mailbox */
    /* DTS 10Oct96 [ 1.005d ] added logic for "-2" return value */
    if ((cnt = fld_select(cli_mbox)) < 0) {
        if( cnt == -2 )
            sprintf(svr_buf,"-ERR being read already %s (stuck lock file in %s?)\r\n",
                cli_mbox,DEF_POP3_DIR);
        else
#ifdef QMAIL
            sprintf(svr_buf,
"-ERR cannot open mailbox %s or work file (disk space full?)\r\n",
                cli_mbox);
#else
            sprintf(svr_buf,
"-ERR cannot open mailbox %s or work file (disk space for %s?)\r\n",
                cli_mbox,DEF_POP3_DIR);
#endif
        free(cli_mbox);
        cli_mbox = NULL;
        return(SVR_FOLD_STATE);
    } else {
        sprintf(svr_buf,"+OK %d messages ready for %s in %s\r\n",
            cnt,cli_user,cli_mbox);
        return(SVR_TRANS_STATE);
    }
}

/**************************************************************************/

/* Mark a message for deletion */
void
fld_delete(msgnum)
int msgnum;
{
    if (fld_fp == NULL) {
        strcpy(svr_buf, svr_nomsg);
        return;
    }

    if ((msgnum < 1)||(msgnum > fld_max)) {
        sprintf(svr_buf,"-ERR invalid message; number out of range\r\n");
    } else {
        fld_msg[msgnum-1].status |= MSG_DELETED;
        sprintf(svr_buf,"+OK message %d marked for deletion\r\n",
            msgnum);
        if ((msgnum-1) > fld_highest)
            fld_highest =(msgnum-1);
    }
}

/* Report the highest access number for this mailbox */
void
fld_last()
{
    sprintf(svr_buf,"+OK %d\r\n",(fld_highest+1));
}

/* Give information about messages in mailbox folder */
void
fld_list(msgnum)
int msgnum;
{
    int i;

    if (fld_fp == NULL) {
        strcpy(svr_buf, svr_nomsg);
        return;
    }

    if (msgnum == -1) {
        sprintf(svr_buf,"+OK %d messages; msg# and size (in octets) for undeleted messages:\r\n",fld_max);
        svr_data_out(svr_buf);
        for (i=0; i<fld_max; ++i) {
            if ((fld_msg[i].status & MSG_DELETED) == 0) {
                sprintf(svr_buf,"%d %ld\r\n",
                    (i+1),fld_msg[i].bcount);
                svr_data_out(svr_buf);
            }
        }
        sprintf(svr_buf,".\r\n");
    } else {
        if ((msgnum < 1)||(msgnum > fld_max))
            sprintf(svr_buf,"-ERR invalid message; number out of range\r\n");
        else if (fld_msg[msgnum-1].status & MSG_DELETED)
            sprintf(svr_buf,"-ERR message %d has been marked for deletion\r\n",
                msgnum);
        else
            sprintf(svr_buf,"+OK %d %ld\r\n",
                msgnum,fld_msg[msgnum-1].bcount);
    }
}

/* Give id listing of messages in mailbox folder */
void
fld_uidl(msgnum)
int msgnum;
{
    static int uidl_ready = 0;
    int i;

    if (fld_fp == NULL) {
        strcpy(svr_buf, svr_nomsg);
        return;
    }

    if (!uidl_ready) {
        for (i=0; i<fld_max; ++i) {
            do_md5_file(fld_fp, fld_msg[i].fmsg_entry, fld_msg[i].count, svr_buf);
            if( fld_msg[i].id ) free(fld_msg[i].id);
            fld_msg[i].id = strdup(svr_buf);
        }
        uidl_ready = 1;
    }

    if (msgnum == -1) {
        sprintf(svr_buf,"+OK %d messages; msg# and id for undeleted messages:\r\n",fld_max);
        svr_data_out(svr_buf);
        for (i=0; i<fld_max; ++i) {
            if ((fld_msg[i].status & MSG_DELETED) == 0) {
                sprintf(svr_buf,"%d %s\r\n",
                    (i+1),fld_msg[i].id);
                svr_data_out(svr_buf);
            }
        }
        sprintf(svr_buf,".\r\n");
    } else {
        if ((msgnum < 1)||(msgnum > fld_max))
            sprintf(svr_buf,"-ERR invalid message; number out of range\r\n");
        else if (fld_msg[msgnum-1].status & MSG_DELETED)
            sprintf(svr_buf,"-ERR message %d has been marked for deletion\r\n",
                msgnum);
        else {
            sprintf(svr_buf,"+OK %d %s\r\n",
                msgnum,fld_msg[msgnum-1].id);
        }
    }
}

/* Reset deleted messages and highest access number */
void
fld_reset()
{
    int i;

    if (fld_fp == NULL) {
        strcpy(svr_buf, svr_nomsg);
        return;
    }
    /* Reset messages marked for deletion */
    for (i=0; i<fld_max; ++i) {
        fld_msg[i].status &= ~MSG_DELETED;
    }
    /* Reset highest access number for this mailbox */
    fld_highest = -1;
    sprintf(svr_buf,"+OK %d messages ready for %s in %s\r\n",
        fld_max,cli_user,cli_mbox);
}

/* Retrieve a message from mailbox */
void
fld_retr(msgnum,linecnt)
int msgnum;
int linecnt;
{
    if (fld_fp == NULL) {
        strcpy(svr_buf, svr_nomsg);
        return;
    }

    if ((msgnum < 1)||(msgnum > fld_max)) {
        sprintf(svr_buf,"-ERR invalid message; number out of range\r\n");
    } else if (fld_msg[msgnum-1].status & MSG_DELETED) {
        sprintf(svr_buf,"-ERR message %d has been marked for deletion\r\n",
            msgnum);
    } else {
        sprintf(svr_buf,"+OK message %d (%ld octets):\r\n",
            msgnum,fld_msg[msgnum-1].bcount);
        svr_data_out(svr_buf);
        retr_fromsp(--msgnum,linecnt);
        sprintf(svr_buf,".\r\n");
        if ((linecnt != -1)&&(msgnum > fld_highest))
            fld_highest = msgnum;
    }
}

/* Give message count and total size (in octets) of a mailbox folder */
void
fld_stat()
{
    int i;
    long total_cnt = 0L;

    if (fld_fp == NULL) {
        strcpy(svr_buf, "+OK 0 0\r\n");
        return;
    }
    for (i=0; i<fld_max; ++i) {
        total_cnt += fld_msg[i].bcount;
    }
    sprintf(svr_buf,"+OK %d %ld\r\n",fld_max,total_cnt);
}

/**************************************************************************/

/* Attempt to load a mailbox folder */
static int
fld_select(mbox)
char *mbox;
{
    int fd;         /* [1.005] DTS for mkstemp */
#ifdef QMAIL
    struct passwd *pwd;
#endif
    struct stat stat_buf;
    FILE *mboxfp;
    int lock;

    /* Reset folder variables */
    fld_fp = NULL;
    fld_highest = -1;

    /* Make sure mailbox is present and non-zero size */
    /* DTS 06Oct98 - added syslog below, rec'd by:  led@cyberdiner.com  */
    if (stat(mbox,&stat_buf) == -1) {
        if (errno == EACCES)
            syslog(SYSLOGPRI,
                "Permission denied on mailbox for %s",mbox);
        return 0;
    }

    if (stat_buf.st_size == 0L)
        return 0;

    /* Save current mailbox size and last-modified-timestamp */
    fld_orig_size = stat_buf.st_size;   /* [1.004] */
    fld_orig_mod_time = stat_buf.st_mtime;  /* [1.004] */

    /* [1.005d] DTS 20Oct96 re-wrote to use named temp file
     *  (checking for prior existance for security reasons).
     */
#ifdef VIRTUAL
    if(virtual_mode)
        snprintf(fld_fname,FNAME_SIZ,"%s",virt_workdir);
    else {
#  ifdef QMAIL
        pwd=getpwnam(cli_user);
        snprintf(fld_fname,FNAME_SIZ,"%s/.pop-",pwd->pw_dir);
#  else
        strncpy(fld_fname, DEF_POP3_DIR, FNAME_SIZ-1);
#  endif
    }

#else
#  ifdef QMAIL
    pwd=getpwnam(cli_user);
    snprintf(fld_fname,FNAME_SIZ,"%s/.pop-",pwd->pw_dir);
#  else
    strncpy(fld_fname, DEF_POP3_DIR, FNAME_SIZ-1);
#  endif
#endif
    strncat(fld_fname, (const char *) basename(mbox),
            FNAME_SIZ-strlen(fld_fname)-1);
    if ((fd=open(fld_fname, O_CREAT|O_EXCL|O_RDWR, 0600)) < 0)
        return -2;

    atexit(delete_folder);

    /* [1.005] DTS Convert from fd to fp to be compat. with existing code */
    if ((fld_fp = fdopen(fd,"w")) == NULL) {
        close(fd);
        unlink(fld_fname);
        return -1;
    }

    /* Secure mailbox for POP3 session; copy to temporary file */
    if ((mboxfp = fopen(mbox, "r")) == NULL) {
        fclose(fld_fp);
        unlink(fld_fname);
        return -1;
    }
    if ((lock = dup(fileno(mboxfp))) == -1) {
        fclose(fld_fp);
        fclose(mboxfp);
        unlink(fld_fname);
        return -1;
    }
    if (flock(lock, LOCK_EX) == -1) {
        fclose(fld_fp);
        fclose(mboxfp);
        close(lock);
        unlink(fld_fname);
        return -1;
    }

    /* Load messages from folder */
    fld_max = msg_fromsp(mboxfp, fld_fp);
    if (fclose(mboxfp) == EOF)
        fld_max = -1;
    if (fclose(fld_fp) == EOF)
        fld_max = -1;

    /* Unlock mailbox */
    flock(lock, LOCK_UN);
    close(lock);

    /* Prepare to use temporary file for POP3 session */
    if (fld_max > 0) {
        if ((fld_fp = fopen(fld_fname,"r")) == NULL) {
            unlink(fld_fname);
            fld_max = -1;
        }
    } else {
        /* Either zero messages or error */
        unlink(fld_fname);
        fld_fp = NULL;
    }
    return(fld_max);
}

/* Close a mailbox folder; remove messages marked for deletion */
void
fld_release()
{
    char temp_fname[FNAME_SIZ];
    int fd;         /* [1.005] DTS for mkstemp */
    FILE *mboxfp;
    FILE *tempfp;
    int lock;
    int i = 0;
    int savemsg = 1;
    int zap_orig_mbox;
    struct stat stat_buf;

    /* If no messages in folder, just free memory for filename */
    if (fld_fp == NULL) {
        if (cli_mbox != NULL) {
            free(cli_mbox);
            cli_mbox = NULL;
        }
        return;
    }

    /* [1.004] Check size and timestamp on the original mailbox file */
    if (stat(cli_mbox, &stat_buf) == -1) {
        /* Another user agent removed it while we were working */
        zap_orig_mbox = REMOVE_MBOX;
    } else {
        if ((stat_buf.st_mtime == fld_orig_mod_time) &&
            (stat_buf.st_size  == fld_orig_size)) {
            /* Nothing added to mailbox while we were working */
            zap_orig_mbox = REMOVE_MBOX;
        } else {
            if (stat_buf.st_size > fld_orig_size) {
                /* More messages were added to end of mbox */
                zap_orig_mbox = SAVE_NEW;

                /* If no messages were deleted, just remove */
                /* the working mailbox file.                */
                for (i=0; i<fld_max; ++i) {
                    if ((fld_msg[i].status & MSG_DELETED) != 0)
                        break;
                }
                if (i == fld_max)
                    goto cleanup;
            } else {
                /* Another user agent made changes while
                 * we were working; save it all to be safe
                 */
                zap_orig_mbox = SAVE_ALL;
            }
        }
    }

    /* Save changes made to original mailbox folder during
     * this POP3 session
     */
    if (zap_orig_mbox == REMOVE_MBOX) {
        /* No changes to save */
        if ((mboxfp = fopen(cli_mbox, "w")) == NULL)
            fail(FAIL_FILE_ERROR);
    } else { /* SAVE_NEW or SAVE_ALL */
        /* Save parts of this mailbox */
        if ((mboxfp = fopen(cli_mbox, "r")) == NULL)
            fail(FAIL_FILE_ERROR);
    }
    /* Lock original mailbox folder */
    if ((lock = dup(fileno(mboxfp))) == -1)
        fail(FAIL_FILE_ERROR);
    if (flock(lock, LOCK_EX) == -1)
        fail(FAIL_FILE_ERROR);

    /* Adjust position in original mailbox file */
    if (zap_orig_mbox == SAVE_NEW) {
        /* Save only the messages added while we were working */
        if (fseek(mboxfp, fld_orig_size, 0) == -1)
            fail(FAIL_FILE_ERROR);
    }

    /* Transfer messages we want to save */
    if (zap_orig_mbox == REMOVE_MBOX) {
        /* Nothing to save, close file we just openned for write */
        if (fclose(mboxfp) == EOF)
            fail(FAIL_FILE_ERROR);
        temp_fname[0] = '\0';
    } else {         /* SAVE_NEW or SAVE_ALL */
        /* Copy from the original mailbox to a temp file */
        /* [1.005d] DTS 20Oct96 re-wrote to use named temp file
         *  (checking for prior existance for security reasons).
         */
        strncpy(temp_fname, fld_fname, FNAME_SIZ-1);
        strncat(temp_fname, ".tmp", FNAME_SIZ-strlen(temp_fname)-1);
        if ((fd=open(temp_fname, O_CREAT|O_EXCL|O_RDWR, 0600)) < 0)
            fail(FAIL_DUP_READ);

        if ((tempfp = fdopen(fd,"w")) == NULL)
            fail(FAIL_FILE_ERROR);

        while (fgetl(svr_buf,SVR_BUFSIZ,mboxfp) != NULL) {
            fputs(svr_buf,tempfp);
            if (ferror(tempfp))
                fail(FAIL_FILE_ERROR);
        }
        if (ferror(mboxfp))
            fail(FAIL_FILE_ERROR);
        if (fclose(mboxfp) == EOF)
            fail(FAIL_FILE_ERROR);
        if (fclose(tempfp) == EOF)
            fail(FAIL_FILE_ERROR);
    }

    /* Transfer contents of working folder to original */
    /* mailbox folder; dont copy deleted messages.     */
    if ((mboxfp = fopen(cli_mbox,"w")) == NULL)
        fail(FAIL_FILE_ERROR);

    /* If all messages were deleted, we don't need to look */
    /* through the working mailbox file.                   */
    for (i=0; i<fld_max; ++i) {
        if ((fld_msg[i].status & MSG_DELETED) == 0)
            break;
    }
    if (i == fld_max)
        goto addnew;

    /* Transfer undeleted messages from the working mailbox */
    rewind(fld_fp);
    i = 0;              /* [1.002] reset index counter */
    while (fgetl(svr_buf,SVR_BUFSIZ,fld_fp) != NULL) {
        if (isfromsp_start(svr_buf)) {
            /* FromSPACE delimited mailbox */
            /* Transfer next msg, unless deleted */
            savemsg = !(fld_msg[i++].status & MSG_DELETED);
        }
        if (savemsg) {
            fputs(svr_buf,mboxfp);
            if (ferror(mboxfp))
                fail(FAIL_FILE_ERROR);
        }
    }
    if (ferror(fld_fp))
        fail(FAIL_FILE_ERROR);

    if (temp_fname[0] == '\0') {
        /* Nothing more to add, close the original mailbox file */
        if (fclose(mboxfp) == EOF)
            fail(FAIL_FILE_ERROR);
    }

addnew:
    if (temp_fname[0] != '\0') {
        /* There were changes to the original mailbox file
         * while we were working. Save the messages that
         * changed in the original mailbox file.
         */
        /* Transfer contents of temp file (messages added */
        /* to original mailbox during this POP3 session)  */
        /* back to mailbox folder                         */
        if ((tempfp = fopen(temp_fname,"r")) == NULL)
            fail(FAIL_FILE_ERROR);
        while (fgets(svr_buf,SVR_BUFSIZ,tempfp) != NULL) {
            fputs(svr_buf,mboxfp);
            if (ferror(mboxfp))
                fail(FAIL_FILE_ERROR);
        }
        if (ferror(tempfp))
            fail(FAIL_FILE_ERROR);
        if (fclose(tempfp) == EOF)
            fail(FAIL_FILE_ERROR);
        unlink(temp_fname);
        if (fclose(mboxfp) == EOF)
            fail(FAIL_FILE_ERROR);
    }

    /* Unlock original mailbox folder */
    flock(lock, LOCK_UN);
    close(lock);


cleanup:
    /* Close and remove working copy of mailbox folder */
    fclose(fld_fp);
    fld_fp = NULL;
    unlink(fld_fname);
    for (i=0; i<fld_max; ++i) {
        if (fld_msg[i].pop_hdr != NULL)
            free(fld_msg[i].pop_hdr);
    }
    free( (char *)fld_msg );
    free(cli_mbox);
    cli_mbox = NULL;
}

/********************************************/

/* Send a FromSP delimited message to the POP3 client */
static void
retr_fromsp(msgnum,linecnt)
int msgnum;
int linecnt;
{
    char *cp, *tp;
    int msgbody = 0;

    /* Locate start of message in mailbox file */
    if (fseek(fld_fp, fld_msg[msgnum].fmsg_entry, 0) == -1)
        return;

    /* Setup for byte-stuff on lines that start with '.' */
    cp = svr_buf;
    *cp = DOT_CHAR;
    ++cp;
    /* Display message for the client */
    if (fld_msg[msgnum].pop_hdr != NULL)
        svr_data_out(fld_msg[msgnum].pop_hdr);
    while (fgetl(cp,SVR_BUFSIZ,fld_fp) != NULL) {
        if (isfromsp_start(cp))
            break;
        /* Use CR-LF line terminator */
        tp = strchr(cp,LF_CHAR);
        if (tp != NULL)
            strcpy(tp,"\r\n");
        /* Byte-stuff lines that start with '.' */
        if (*cp == DOT_CHAR)
            svr_data_out(svr_buf);
        else
            svr_data_out(cp);
        if ((msgbody)&&(--linecnt == 0)) {
            break;
        } else {
            if (*cp == CR_CHAR) {
                msgbody = 1;
                if (linecnt == 0)
                    break;
            }
        }
    }
}

/**************************************************************************/

/* Load messages from a mailbox delimited by FromSPACE */
static int
msg_fromsp(infp, outfp)
FILE *infp;
FILE *outfp;
{
    int i = 0;
    register struct fld_item *mp;

    /* Get an array for storing info about messages in folder */
    get_e_array(fld_msg, FLD_ENTRY_BLOCK);
    if (fld_msg == NULL)
        fail(FAIL_OUT_OF_MEMORY);
    mp = &fld_msg[0];
    /* Load messages from mailbox folder to temporary folder */
    while (fgetl(svr_buf,SVR_BUFSIZ,infp) != NULL) {
        fputs(svr_buf, outfp);
        if (ferror(outfp))
            return -1;
        if (isfromsp_start(svr_buf)) {
            /* Make sure there is room in array for this entry */
            chk_e_size(fld_msg, FLD_ENTRY_BLOCK, i);
            if (fld_msg == NULL)
                fail(FAIL_OUT_OF_MEMORY);
            /* Reset stats for this message */
            mp = &fld_msg[i];
            mp->fmsg_entry = ftell(outfp);
            mp->status = 0;
            sprintf(flash_buf,"%s %s@%s\r\n",POP3_RCPT_HDR,
                    cli_user,svr_hostname);
            mp->pop_hdr = malloc(strlen(flash_buf)+1);
            if (mp->pop_hdr == NULL)
                fail(FAIL_OUT_OF_MEMORY);
            strcpy(mp->pop_hdr,flash_buf);
            mp->bcount = strlen(mp->pop_hdr);
            mp->count = 0;
                        /* patch: wlad, 06/14/98,  UIDL crash on line 224, free(id) */
            mp->id = (char *)NULL;
            /* patch: end */

            ++i;
        } else {
            int len = strlen(svr_buf);
            mp->bcount += len + 1L;
            mp->count += len;
        }
    }
    if (ferror(infp))
        return -1;
    if (i == 0)
        free((char *)fld_msg);
    return(i);
}

/************************************************/