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