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122 lines
2.4 KiB
C
122 lines
2.4 KiB
C
/* pklock.c -- implements pklock.h */
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#include "estruct.h"
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#include "pklock.h"
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/* PKLOCK.C
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*
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* locking routines as modified by Petri Kutvonen
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*/
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#if (FILOCK && BSD) || SVR4
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <fcntl.h>
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#ifdef SVR4
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#include <string.h>
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#else
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#include <strings.h>
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#endif
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#include <errno.h>
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#define MAXLOCK 512
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#define MAXNAME 128
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#if defined(SVR4) && ! defined(__linux__)
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#include <sys/systeminfo.h>
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int gethostname(char *name, int namelen)
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{
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return sysinfo(SI_HOSTNAME, name, namelen);
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}
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#endif
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/**********************
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*
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* if successful, returns NULL
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* if file locked, returns username of person locking the file
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* if other error, returns "LOCK ERROR: explanation"
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*
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*********************/
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char *dolock( const char *fname)
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{
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int fd, n;
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static char lname[MAXLOCK], locker[MAXNAME + 1];
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int mask;
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struct stat sbuf;
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strcat(strcpy(lname, fname), ".lock~");
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/* check that we are not being cheated, qname must point to */
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/* a regular file - even this code leaves a small window of */
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/* vulnerability but it is rather hard to exploit it */
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#if defined(S_IFLNK)
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if (lstat(lname, &sbuf) == 0)
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#else
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if (stat(lname, &sbuf) == 0)
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#endif
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#if defined(S_ISREG)
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if (!S_ISREG(sbuf.st_mode))
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#else
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if (!(((sbuf.st_mode) & 070000) == 0)) /* SysV R2 */
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#endif
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return "LOCK ERROR: not a regular file";
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mask = umask(0);
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fd = open(lname, O_RDWR | O_CREAT, 0666);
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umask(mask);
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if (fd < 0) {
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if (errno == EACCES)
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return NULL;
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#ifdef EROFS
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if (errno == EROFS)
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return NULL;
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#endif
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return "LOCK ERROR: cannot access lock file";
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}
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if ((n = read(fd, locker, MAXNAME)) < 1) {
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lseek(fd, 0, SEEK_SET);
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/* strcpy(locker, getlogin()); */
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cuserid(locker);
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strcat(locker + strlen(locker), "@");
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gethostname(locker + strlen(locker), 64);
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write(fd, locker, strlen(locker));
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close(fd);
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return NULL;
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}
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locker[n > MAXNAME ? MAXNAME : n] = 0;
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return locker;
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}
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/*********************
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*
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* undolock -- unlock the file fname
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*
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* if successful, returns NULL
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* if other error, returns "LOCK ERROR: explanation"
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*
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*********************/
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char *undolock( const char *fname)
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{
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static char lname[MAXLOCK];
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strcat(strcpy(lname, fname), ".lock~");
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if (unlink(lname) != 0) {
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if (errno == EACCES || errno == ENOENT)
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return NULL;
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#ifdef EROFS
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if (errno == EROFS)
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return NULL;
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#endif
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return "LOCK ERROR: cannot remove lock file";
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}
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return NULL;
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}
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#endif
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