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Diffstat (limited to 'winsup/cygwin/socket_tests/scm_cred_recv.c')
| -rw-r--r-- | winsup/cygwin/socket_tests/scm_cred_recv.c | 173 |
1 files changed, 173 insertions, 0 deletions
diff --git a/winsup/cygwin/socket_tests/scm_cred_recv.c b/winsup/cygwin/socket_tests/scm_cred_recv.c new file mode 100644 index 000000000..121b472a4 --- /dev/null +++ b/winsup/cygwin/socket_tests/scm_cred_recv.c @@ -0,0 +1,173 @@ +/*************************************************************************\ +* Copyright (C) Michael Kerrisk, 2018. * +* * +* This program is free software. You may use, modify, and redistribute it * +* under the terms of the GNU General Public License as published by the * +* Free Software Foundation, either version 3 or (at your option) any * +* later version. This program is distributed without any warranty. See * +* the file COPYING.gpl-v3 for details. * +\*************************************************************************/ + +/* Supplementary program for Chapter 61 */ + +/* scm_cred_recv.c + + Used in conjunction with scm_cred_send.c to demonstrate passing of + process credentials via a UNIX domain socket. + + This program receives credentials sent to a UNIX domain socket. + + Usage is as shown in the usageErr() call below. + + Credentials can be exchanged over stream or datagram sockets. This program + uses stream sockets by default; the "-d" command-line option specifies + that datagram sockets should be used instead. + + This program is Linux-specific. + + See also scm_multi_recv.c. +*/ +#include "scm_cred.h" + +int +main(int argc, char *argv[]) +{ + int data, lfd, sfd, optval, opt; + ssize_t nr; + Boolean useDatagramSocket; + struct msghdr msgh; + struct iovec iov; + struct ucred *ucredp, ucred; + + /* Allocate a char array of suitable size to hold the ancillary data. + However, since this buffer is in reality a 'struct cmsghdr', use a + union to ensure that it is aligned as required for that structure. + Alternatively, we could allocate the buffer using malloc(), which + returns a buffer that satisfies the strictest alignment + requirements of any type */ + + union { + char buf[CMSG_SPACE(sizeof(struct ucred))]; + /* Space large enough to hold a 'ucred' structure */ + struct cmsghdr align; + } controlMsg; + struct cmsghdr *cmsgp; /* Pointer used to iterate through + headers in ancillary data */ + socklen_t len; + + /* Parse command-line options */ + + useDatagramSocket = FALSE; + + while ((opt = getopt(argc, argv, "d")) != -1) { + switch (opt) { + case 'd': + useDatagramSocket = TRUE; + break; + + default: + usageErr("%s [-d]\n" + " -d use datagram socket\n", argv[0]); + } + } + + /* Create socket bound to a well-known address. In the case where + we are using stream sockets, also make the socket a listening + socket and accept a connection on the socket. */ + + if (remove(SOCK_PATH) == -1 && errno != ENOENT) + errExit("remove-%s", SOCK_PATH); + + if (useDatagramSocket) { + sfd = unixBind(SOCK_PATH, SOCK_DGRAM); + if (sfd == -1) + errExit("unixBind"); + + } else { + lfd = unixBind(SOCK_PATH, SOCK_STREAM); + if (lfd == -1) + errExit("unixBind"); + + if (listen(lfd, 5) == -1) + errExit("listen"); + + sfd = accept(lfd, NULL, NULL); + if (sfd == -1) + errExit("accept"); + } + + /* We must set the SO_PASSCRED socket option in order to receive + credentials */ + + optval = 1; + if (setsockopt(sfd, SOL_SOCKET, SO_PASSCRED, &optval, sizeof(optval)) == -1) + errExit("setsockopt"); + + /* The 'msg_name' field can be set to point to a buffer where the + kernel will place the address of the peer socket. However, we don't + need the address of the peer, so we set this field to NULL. */ + + msgh.msg_name = NULL; + msgh.msg_namelen = 0; + + /* Set fields of 'msgh' to point to buffer used to receive (real) + data read by recvmsg() */ + + msgh.msg_iov = &iov; + msgh.msg_iovlen = 1; + iov.iov_base = &data; + iov.iov_len = sizeof(int); + + /* Set 'msgh' fields to describe the ancillary data buffer */ + + msgh.msg_control = controlMsg.buf; + msgh.msg_controllen = sizeof(controlMsg.buf); + + /* Receive real plus ancillary data */ + + nr = recvmsg(sfd, &msgh, 0); + if (nr == -1) + errExit("recvmsg"); + printf("recvmsg() returned %ld\n", (long) nr); + + if (nr > 0) + printf("Received data = %d\n", data); + + /* Get the address of the first 'cmsghdr' in the received + ancillary data */ + + cmsgp = CMSG_FIRSTHDR(&msgh); + + /* Check the validity of the 'cmsghdr' */ + + if (cmsgp == NULL || cmsgp->cmsg_len != CMSG_LEN(sizeof(struct ucred))) + fatal("bad cmsg header / message length"); + if (cmsgp->cmsg_level != SOL_SOCKET) + fatal("cmsg_level != SOL_SOCKET"); + if (cmsgp->cmsg_type != SCM_CREDENTIALS) + fatal("cmsg_type != SCM_CREDENTIALS"); + + /* The data area of the 'cmsghdr' is a 'struct ucred', so assign + the address of the data area to a suitable pointer */ + + ucredp = (struct ucred *) CMSG_DATA(cmsgp); + + /* Display the credentials from the received data area */ + + printf("Received credentials pid=%ld, uid=%ld, gid=%ld\n", + (long) ucredp->pid, (long) ucredp->uid, (long) ucredp->gid); + + /* The Linux-specific, read-only SO_PEERCRED socket option returns + credential information about the peer, as described in socket(7). + This operation can be performed on UNIX domain stream sockets and on + UNIX domain sockets (stream or datagram) created with socketpair(). */ + + len = sizeof(struct ucred); + if (getsockopt(sfd, SOL_SOCKET, SO_PEERCRED, &ucred, &len) == -1) + errExit("getsockopt"); + + printf("Credentials from SO_PEERCRED: pid=%ld, euid=%ld, egid=%ld\n", + (long) ucred.pid, (long) ucred.uid, (long) ucred.gid); + + exit(EXIT_SUCCESS); +} |