src/passwd/nscd_query.c

#include <sys/socket.h>
#include <byteswap.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <limits.h>
#include "nscd.h"

static const struct {
	short sun_family;
	char sun_path[21];
} addr = {
	AF_UNIX,
	"/var/run/nscd/socket"
};

FILE *__nscd_query(int32_t req, const char *key, int32_t *buf, size_t len, int *swap)
{
	size_t i;
	int fd;
	FILE *f = 0;
	int32_t req_buf[REQ_LEN] = {
		NSCDVERSION,
		req,
		strnlen(key,LOGIN_NAME_MAX)+1
	};
	struct msghdr msg = {
		.msg_iov = (struct iovec[]){
			{&req_buf, sizeof(req_buf)},
			{(char*)key, strlen(key)+1}
		},
		.msg_iovlen = 2
	};
	int errno_save = errno;

	*swap = 0;
retry:
	memset(buf, 0, len);
	buf[0] = NSCDVERSION;

	fd = socket(PF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
	if (fd < 0) {
		if (errno == EAFNOSUPPORT) {
			f = fopen("/dev/null", "re");
			if (f)
				errno = errno_save;
			return f;
		}
		return 0;
	}

	if(!(f = fdopen(fd, "r"))) {
		close(fd);
		return 0;
	}

	if (req_buf[2] > LOGIN_NAME_MAX)
		return f;

	if (connect(fd, (struct sockaddr*)&addr, sizeof(addr)) < 0) {
		/* If there isn't a running nscd we simulate a "not found"
		 * result and the caller is responsible for calling
		 * fclose on the (unconnected) socket. The value of
		 * errno must be left unchanged in this case.  */
		if (errno == EACCES || errno == ECONNREFUSED || errno == ENOENT) {
			errno = errno_save;
			return f;
		}
		goto error;
	}

	if (sendmsg(fd, &msg, MSG_NOSIGNAL) < 0)
		goto error;

	if (!fread(buf, len, 1, f)) {
		/* If the VERSION entry mismatches nscd will disconnect. The
		 * most likely cause is that the endianness mismatched. So, we
		 * byteswap and try once more. (if we already swapped, just
		 * fail out)
		 */
		if (ferror(f)) goto error;
		if (!*swap) {
			fclose(f);
			for (i = 0; i < sizeof(req_buf)/sizeof(req_buf[0]); i++) {
				req_buf[i] = bswap_32(req_buf[i]);
			}
			*swap = 1;
			goto retry;
		} else {
			errno = EIO;
			goto error;
		}
	}

	if (*swap) {
		for (i = 0; i < len/sizeof(buf[0]); i++) {
			buf[i] = bswap_32(buf[i]);
		}
	}

	/* The first entry in every nscd response is the version number. This
	 * really shouldn't happen, and is evidence of some form of malformed
	 * response.
	 */
	if(buf[0] != NSCDVERSION) {
		errno = EIO;
		goto error;
	}

	return f;
error:
	fclose(f);
	return 0;
}