nscd_query.c raw

   1  #include <sys/socket.h>
   2  #include <byteswap.h>
   3  #include <unistd.h>
   4  #include <stdio.h>
   5  #include <string.h>
   6  #include <errno.h>
   7  #include <limits.h>
   8  #include "nscd.h"
   9  
  10  static const struct {
  11  	short sun_family;
  12  	char sun_path[21];
  13  } addr = {
  14  	AF_UNIX,
  15  	"/var/run/nscd/socket"
  16  };
  17  
  18  FILE *__nscd_query(int32_t req, const char *key, int32_t *buf, size_t len, int *swap)
  19  {
  20  	size_t i;
  21  	int fd;
  22  	FILE *f = 0;
  23  	int32_t req_buf[REQ_LEN] = {
  24  		NSCDVERSION,
  25  		req,
  26  		strnlen(key,LOGIN_NAME_MAX)+1
  27  	};
  28  	struct msghdr msg = {
  29  		.msg_iov = (struct iovec[]){
  30  			{&req_buf, sizeof(req_buf)},
  31  			{(char*)key, strlen(key)+1}
  32  		},
  33  		.msg_iovlen = 2
  34  	};
  35  	int errno_save = errno;
  36  
  37  	*swap = 0;
  38  retry:
  39  	memset(buf, 0, len);
  40  	buf[0] = NSCDVERSION;
  41  
  42  	fd = socket(PF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
  43  	if (fd < 0) {
  44  		if (errno == EAFNOSUPPORT) {
  45  			f = fopen("/dev/null", "re");
  46  			if (f)
  47  				errno = errno_save;
  48  			return f;
  49  		}
  50  		return 0;
  51  	}
  52  
  53  	if(!(f = fdopen(fd, "r"))) {
  54  		close(fd);
  55  		return 0;
  56  	}
  57  
  58  	if (req_buf[2] > LOGIN_NAME_MAX)
  59  		return f;
  60  
  61  	if (connect(fd, (struct sockaddr*)&addr, sizeof(addr)) < 0) {
  62  		/* If there isn't a running nscd we simulate a "not found"
  63  		 * result and the caller is responsible for calling
  64  		 * fclose on the (unconnected) socket. The value of
  65  		 * errno must be left unchanged in this case.  */
  66  		if (errno == EACCES || errno == ECONNREFUSED || errno == ENOENT) {
  67  			errno = errno_save;
  68  			return f;
  69  		}
  70  		goto error;
  71  	}
  72  
  73  	if (sendmsg(fd, &msg, MSG_NOSIGNAL) < 0)
  74  		goto error;
  75  
  76  	if (!fread(buf, len, 1, f)) {
  77  		/* If the VERSION entry mismatches nscd will disconnect. The
  78  		 * most likely cause is that the endianness mismatched. So, we
  79  		 * byteswap and try once more. (if we already swapped, just
  80  		 * fail out)
  81  		 */
  82  		if (ferror(f)) goto error;
  83  		if (!*swap) {
  84  			fclose(f);
  85  			for (i = 0; i < sizeof(req_buf)/sizeof(req_buf[0]); i++) {
  86  				req_buf[i] = bswap_32(req_buf[i]);
  87  			}
  88  			*swap = 1;
  89  			goto retry;
  90  		} else {
  91  			errno = EIO;
  92  			goto error;
  93  		}
  94  	}
  95  
  96  	if (*swap) {
  97  		for (i = 0; i < len/sizeof(buf[0]); i++) {
  98  			buf[i] = bswap_32(buf[i]);
  99  		}
 100  	}
 101  
 102  	/* The first entry in every nscd response is the version number. This
 103  	 * really shouldn't happen, and is evidence of some form of malformed
 104  	 * response.
 105  	 */
 106  	if(buf[0] != NSCDVERSION) {
 107  		errno = EIO;
 108  		goto error;
 109  	}
 110  
 111  	return f;
 112  error:
 113  	fclose(f);
 114  	return 0;
 115  }
 116