If msg_control is not present in struct msghdr use msg_accrights instead.

Fixes building on Solaris and probably others.  It is possible to
expose msg_control on Solaris but this requires a specific set of
feature flag defines which can cause other complications.

config.h.in

@@ -824,6 +824,9 @@
 /* Define to 1 if the system has the type `struct in6_addr'. */
 #undef HAVE_STRUCT_IN6_ADDR
 
+/* Define to 1 if `msg_control' is a member of `struct msghdr'. */
+#undef HAVE_STRUCT_MSGHDR_MSG_CONTROL
+
 /* Define to 1 if `pr_ttydev' is a member of `struct psinfo'. */
 #undef HAVE_STRUCT_PSINFO_PR_TTYDEV
 

configure

@@ -21970,6 +21970,19 @@ then :
 printf "%s\n" "#define HAVE_STRUCT_DIRENT_D_NAMLEN 1" >>confdefs.h
 
 
+fi
+
+ac_fn_c_check_member "$LINENO" "struct msghdr" "msg_control" "ac_cv_member_struct_msghdr_msg_control" "
+$ac_includes_default
+#include <sys/socket.h>
+
+"
+if test "x$ac_cv_member_struct_msghdr_msg_control" = xyes
+then :
+
+printf "%s\n" "#define HAVE_STRUCT_MSGHDR_MSG_CONTROL 1" >>confdefs.h
+
+
 fi
 
 openssl_missing=no

configure.ac

@@ -2913,6 +2913,13 @@ AC_INCLUDES_DEFAULT
 #include <$ac_header_dirent>
 ])
 dnl
+dnl Check for POSIX sendmsg() ancillary data support.
+dnl
+AC_CHECK_MEMBERS(struct msghdr.msg_control, [], [], [
+AC_INCLUDES_DEFAULT
+#include <sys/socket.h>
+])
+dnl
 dnl Check for functions only present in OpenSSL 1.1 and above
 dnl
 openssl_missing=no

src/exec.c

@@ -978,11 +978,13 @@ intercept_fd_cb(int fd, int what, void *v)
     struct intercept_closure *closure = NULL;
     struct intercept_fd_closure *fdc = v;
     struct msghdr msg;
+#if defined(HAVE_STRUCT_MSGHDR_MSG_CONTROL) && HAVE_STRUCT_MSGHDR_MSG_CONTROL == 1
     union {
 	struct cmsghdr hdr;
 	char buf[CMSG_SPACE(sizeof(int))];
     } cmsgbuf;
     struct cmsghdr *cmsg;
+#endif
     struct iovec iov[1];
     int newfd = -1;
     char ch;
@@ -1003,11 +1005,16 @@ intercept_fd_cb(int fd, int what, void *v)
     iov[0].iov_base = &ch;
     iov[0].iov_len = 1;
     memset(&msg, 0, sizeof(msg));
-    memset(&cmsgbuf, 0, sizeof(cmsgbuf));
     msg.msg_iov = iov;
     msg.msg_iovlen = 1;
+#if defined(HAVE_STRUCT_MSGHDR_MSG_CONTROL) && HAVE_STRUCT_MSGHDR_MSG_CONTROL == 1
+    memset(&cmsgbuf, 0, sizeof(cmsgbuf));
     msg.msg_control = &cmsgbuf.buf;
     msg.msg_controllen = sizeof(cmsgbuf.buf);
+#else
+    msg.msg_accrights = (caddr_t)&fd;
+    msg.msg_accrightslen = sizeof(fd);
+#endif /* HAVE_STRUCT_MSGHDR_MSG_CONTROL */
 
     switch (recvmsg(fd, &msg, 0)) {
     case -1:
@@ -1021,6 +1028,7 @@ intercept_fd_cb(int fd, int what, void *v)
 	break;
     }
 
+#if defined(HAVE_STRUCT_MSGHDR_MSG_CONTROL) && HAVE_STRUCT_MSGHDR_MSG_CONTROL == 1
     cmsg = CMSG_FIRSTHDR(&msg);
     if (cmsg == NULL) {
 	sudo_warnx(U_("%s: missing message header"), __func__);
@@ -1032,8 +1040,14 @@ intercept_fd_cb(int fd, int what, void *v)
 	    SCM_RIGHTS, cmsg->cmsg_type);
 	goto bad;
     }
+    memcpy(&newfd, CMSG_DATA(cmsg), sizeof(newfd));
+#else
+    if (msg.msg_accrightslen != sizeof(fd)) {
+	sudo_warnx(U_("%s: missing message header"), __func__);
+	goto bad;
+    }
+#endif /* HAVE_STRUCT_MSGHDR_MSG_CONTROL */
 
-    newfd = (*(int *)CMSG_DATA(cmsg));
     if (sudo_ev_set(&closure->ev, newfd, SUDO_EV_READ, intercept_cb, closure) == -1) {
 	sudo_warn("%s", U_("unable to add event to queue"));
 	goto bad;

src/sudo_intercept_common.c

@@ -153,11 +153,13 @@ static bool
 intercept_send_fd(int sock, int fd)
 {
     struct msghdr msg;
+#if defined(HAVE_STRUCT_MSGHDR_MSG_CONTROL) && HAVE_STRUCT_MSGHDR_MSG_CONTROL == 1
     union {
 	struct cmsghdr hdr;
 	char buf[CMSG_SPACE(sizeof(int))];
     } cmsgbuf;
     struct cmsghdr *cmsg;
+#endif
     struct iovec iov[1];
     char ch = '\0';
     ssize_t nsent;
@@ -171,17 +173,21 @@ intercept_send_fd(int sock, int fd)
     iov[0].iov_base = &ch;
     iov[0].iov_len = 1;
     memset(&msg, 0, sizeof(msg));
-    memset(&cmsgbuf, 0, sizeof(cmsgbuf));
     msg.msg_iov = iov;
     msg.msg_iovlen = 1;
+#if defined(HAVE_STRUCT_MSGHDR_MSG_CONTROL) && HAVE_STRUCT_MSGHDR_MSG_CONTROL == 1
+    memset(&cmsgbuf, 0, sizeof(cmsgbuf));
     msg.msg_control = &cmsgbuf.buf;
     msg.msg_controllen = sizeof(cmsgbuf.buf);
-
     cmsg = CMSG_FIRSTHDR(&msg);
     cmsg->cmsg_len = CMSG_LEN(sizeof(int));
     cmsg->cmsg_level = SOL_SOCKET;
     cmsg->cmsg_type = SCM_RIGHTS;
-    *(int *)CMSG_DATA(cmsg) = fd;
+    memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));
+#else
+    msg.msg_accrights = (caddr_t)&fd;
+    msg.msg_accrightslen = sizeof(fd);
+#endif /* HAVE_STRUCT_MSGHDR_MSG_CONTROL */
 
     for (;;) {
 	nsent = sendmsg(sock, &msg, 0);