150 lines
3.3 KiB
C
150 lines
3.3 KiB
C
/* getgrent(), getgrgid(), getgrnam() - group file routines
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*
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* Author: Kees J. Bot
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* 31 Jan 1994
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*/
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#define open _open
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#define fcntl _fcntl
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#define read _read
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#define close _close
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#include <sys/types.h>
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#include <grp.h>
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#include <string.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <fcntl.h>
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#define arraysize(a) (sizeof(a) / sizeof((a)[0]))
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#define arraylimit(a) ((a) + arraysize(a))
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static char GROUP[]= "/etc/group"; /* The group file. */
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static const char *grfile; /* Current group file. */
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static char buf[1024]; /* Read buffer. */
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static char grline[512]; /* One line from the group file. */
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static struct group entry; /* Entry to fill and return. */
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static char *members[64]; /* Group members with the entry. */
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static int grfd= -1; /* Filedescriptor to the file. */
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static char *bufptr; /* Place in buf. */
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static ssize_t buflen= 0; /* Remaining characters in buf. */
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static char *lineptr; /* Place in the line. */
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void endgrent(void)
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/* Close the group file. */
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{
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if (grfd >= 0) {
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(void) close(grfd);
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grfd= -1;
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buflen= 0;
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}
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}
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int setgrent(void)
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/* Open the group file. */
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{
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if (grfd >= 0) endgrent();
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if (grfile == NULL) grfile= GROUP;
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if ((grfd= open(grfile, O_RDONLY)) < 0) return -1;
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(void) fcntl(grfd, F_SETFD, fcntl(grfd, F_GETFD) | FD_CLOEXEC);
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return 0;
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}
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void setgrfile(const char *file)
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/* Prepare for reading an alternate group file. */
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{
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endgrent();
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grfile= file;
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}
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static int getline(void)
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/* Get one line from the group file, return 0 if bad or EOF. */
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{
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lineptr= grline;
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do {
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if (buflen == 0) {
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if ((buflen= read(grfd, buf, sizeof(buf))) <= 0)
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return 0;
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bufptr= buf;
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}
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if (lineptr == arraylimit(grline)) return 0;
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buflen--;
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} while ((*lineptr++ = *bufptr++) != '\n');
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lineptr= grline;
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return 1;
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}
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static char *scan_punct(int punct)
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/* Scan for a field separator in a line, return the start of the field. */
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{
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char *field= lineptr;
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char *last;
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for (;;) {
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last= lineptr;
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if (*lineptr == 0) return NULL;
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if (*lineptr == '\n') break;
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if (*lineptr++ == punct) break;
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if (lineptr[-1] == ':') return NULL; /* :::,,,:,,,? */
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}
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*last= 0;
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return field;
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}
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struct group *getgrent(void)
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/* Read one entry from the group file. */
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{
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char *p;
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char **mem;
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/* Open the file if not yet open. */
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if (grfd < 0 && setgrent() < 0) return NULL;
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/* Until a good line is read. */
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for (;;) {
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if (!getline()) return NULL; /* EOF or corrupt. */
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if ((entry.gr_name= scan_punct(':')) == NULL) continue;
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if ((entry.gr_passwd= scan_punct(':')) == NULL) continue;
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if ((p= scan_punct(':')) == NULL) continue;
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entry.gr_gid= strtol(p, NULL, 0);
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entry.gr_mem= mem= members;
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if (*lineptr != '\n') {
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do {
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if ((*mem= scan_punct(',')) == NULL) goto again;
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if (mem < arraylimit(members) - 1) mem++;
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} while (*lineptr != 0);
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}
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*mem= NULL;
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return &entry;
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again:;
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}
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}
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struct group *getgrgid(gid_t gid)
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/* Return the group file entry belonging to the user-id. */
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{
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struct group *gr;
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endgrent();
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while ((gr= getgrent()) != NULL && gr->gr_gid != gid) {}
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endgrent();
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return gr;
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}
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struct group *getgrnam(const char *name)
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/* Return the group file entry belonging to the user name. */
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{
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struct group *gr;
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endgrent();
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while ((gr= getgrent()) != NULL && strcmp(gr->gr_name, name) != 0) {}
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endgrent();
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return gr;
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}
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