1  /*
       2   * Check decoding of SCM_CREDENTIALS control messages.
       3   *
       4   * Copyright (c) 2023 Dmitry V. Levin <ldv@strace.io>
       5   * All rights reserved.
       6   *
       7   * SPDX-License-Identifier: GPL-2.0-or-later
       8   */
       9  
      10  #include "tests.h"
      11  #include <assert.h>
      12  #include <stdio.h>
      13  #include <string.h>
      14  #include <unistd.h>
      15  #include <sys/socket.h>
      16  
      17  static void
      18  print_ucred(const struct cmsghdr *c)
      19  {
      20  	const void *cmsg_header = c;
      21  	const void *cmsg_data = CMSG_DATA(c);
      22  	struct ucred uc;
      23  	const unsigned int expected_len = sizeof(uc);
      24  	const unsigned int data_len = c->cmsg_len - (cmsg_data - cmsg_header);
      25  
      26  	if (expected_len != data_len)
      27  		perror_msg_and_fail("sizeof(struct ucred) = %u"
      28  				    ", data_len = %u\n",
      29  				    expected_len, data_len);
      30  
      31  	memcpy(&uc, cmsg_data, sizeof(uc));
      32  	printf("{pid=%u, uid=%u, gid=%u}", uc.pid, uc.uid, uc.gid);
      33  }
      34  
      35  int
      36  main(void)
      37  {
      38  	skip_if_unavailable("/proc/self/fd/");
      39  
      40  	int sv[2];
      41  	if (socketpair(AF_UNIX, SOCK_STREAM, 0, sv))
      42                  perror_msg_and_skip("socketpair AF_UNIX SOCK_STREAM");
      43  
      44  	int one = 1;
      45  	if (setsockopt(sv[0], SOL_SOCKET, SO_PASSCRED, &one, sizeof(one)))
      46  		perror_msg_and_skip("setsockopt");
      47  
      48  	char sym = 'A';
      49  	if (send(sv[1], &sym, 1, 0) != 1)
      50  		perror_msg_and_fail("send");
      51  	if (close(sv[1]))
      52  		perror_msg_and_fail("close send");
      53  
      54  	struct ucred uc;
      55  	unsigned int cmsg_size = CMSG_SPACE(sizeof(uc));
      56  	struct cmsghdr *cmsg = tail_alloc(cmsg_size);
      57  	memset(cmsg, 0, cmsg_size);
      58  
      59  	struct iovec iov = {
      60  		.iov_base = &sym,
      61  		.iov_len = sizeof(sym)
      62  	};
      63  	struct msghdr mh = {
      64  		.msg_iov = &iov,
      65  		.msg_iovlen = 1,
      66  		.msg_control = cmsg,
      67  		.msg_controllen = cmsg_size
      68  	};
      69  
      70  	if (recvmsg(sv[0], &mh, 0) != 1)
      71  		perror_msg_and_fail("recvmsg");
      72  	if (close(sv[0]))
      73  		perror_msg_and_fail("close recv");
      74  
      75  	printf("recvmsg(%d, {msg_name=NULL, msg_namelen=0"
      76  	       ", msg_iov=[{iov_base=\"A\", iov_len=1}], msg_iovlen=1",
      77  	       sv[0]);
      78  
      79  	bool found = false;
      80  	if (mh.msg_controllen) {
      81  		printf(", msg_control=[");
      82  		for (struct cmsghdr *c = CMSG_FIRSTHDR(&mh); c;
      83  		     c = CMSG_NXTHDR(&mh, c)) {
      84  			printf("%s{cmsg_len=%lu, cmsg_level=",
      85  			       (c == cmsg ? "" : ", "),
      86  			       (unsigned long) c->cmsg_len);
      87  			if (c->cmsg_level == SOL_SOCKET) {
      88  				printf("SOL_SOCKET");
      89  			} else {
      90  				printf("%d /* expected SOL_SOCKET == %d */",
      91  				       c->cmsg_level, (int) SOL_SOCKET);
      92  			}
      93  			printf(", cmsg_type=");
      94  			if (c->cmsg_type == SCM_CREDENTIALS) {
      95  				printf("SCM_CREDENTIALS, cmsg_data=");
      96  				print_ucred(c);
      97  				found = true;
      98  			} else {
      99  				printf("%d /* expected SCM_CREDENTIALS == %d */",
     100  				       c->cmsg_type, (int) SCM_CREDENTIALS);
     101  			}
     102  			printf("}");
     103  		}
     104  		printf("]");
     105  	}
     106  	printf(", msg_controllen=%lu, msg_flags=0}, 0) = 1\n",
     107  	       (unsigned long) mh.msg_controllen);
     108  
     109  	if (!found)
     110  		error_msg_and_fail("SCM_CREDENTIALS not found");
     111  
     112  	puts("+++ exited with 0 +++");
     113  	return 0;
     114  }