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Diffstat (limited to 'src/util/unix_send_fd.c')
| -rw-r--r-- | src/util/unix_send_fd.c | 193 |
1 files changed, 193 insertions, 0 deletions
diff --git a/src/util/unix_send_fd.c b/src/util/unix_send_fd.c new file mode 100644 index 0000000..1998a7c --- /dev/null +++ b/src/util/unix_send_fd.c @@ -0,0 +1,193 @@ +/*++ +/* NAME +/* unix_send_fd 3 +/* SUMMARY +/* send file descriptor +/* SYNOPSIS +/* #include <iostuff.h> +/* +/* int unix_send_fd(fd, sendfd) +/* int fd; +/* int sendfd; +/* DESCRIPTION +/* unix_send_fd() sends a file descriptor over the specified +/* UNIX-domain socket. +/* +/* Arguments: +/* .IP fd +/* File descriptor that connects the sending and receiving processes. +/* .IP sendfd +/* The file descriptor to be sent. +/* DIAGNOSTICS +/* unix_send_fd() returns -1 upon failure. +/* LICENSE +/* .ad +/* .fi +/* The Secure Mailer license must be distributed with this software. +/* AUTHOR(S) +/* Wietse Venema +/* IBM T.J. Watson Research +/* P.O. Box 704 +/* Yorktown Heights, NY 10598, USA +/*--*/ + +/* System library. */ + +#include <sys_defs.h> /* includes <sys/types.h> */ +#include <sys/socket.h> +#include <sys/uio.h> +#include <string.h> + +/* Utility library. */ + +#include <msg.h> +#include <iostuff.h> + +/* unix_send_fd - send file descriptor */ + +int unix_send_fd(int fd, int sendfd) +{ + + /* + * This code does not work with version <2.2 Linux kernels, and it does + * not compile with version <2 Linux libraries. + */ +#ifdef CANT_USE_SEND_RECV_MSG + const char *myname = "unix_send_fd"; + + msg_warn("%s: your system has no support for file descriptor passing", + myname); + return (-1); +#else + struct msghdr msg; + struct iovec iov[1]; + + /* + * Adapted from: W. Richard Stevens, UNIX Network Programming, Volume 1, + * Second edition. Except that we use CMSG_LEN instead of CMSG_SPACE, for + * portability to some LP64 environments. See also unix_recv_fd.c. + */ +#if defined(CMSG_SPACE) && !defined(NO_MSGHDR_MSG_CONTROL) + union { + struct cmsghdr just_for_alignment; + char control[CMSG_SPACE(sizeof(sendfd))]; + } control_un; + struct cmsghdr *cmptr; + + memset((void *) &msg, 0, sizeof(msg)); /* Fix 200512 */ + msg.msg_control = control_un.control; + if (unix_pass_fd_fix & UNIX_PASS_FD_FIX_CMSG_LEN) { + msg.msg_controllen = CMSG_LEN(sizeof(sendfd)); /* Fix 200506 */ + } else { + msg.msg_controllen = sizeof(control_un.control); /* normal */ + } + cmptr = CMSG_FIRSTHDR(&msg); + cmptr->cmsg_len = CMSG_LEN(sizeof(sendfd)); + cmptr->cmsg_level = SOL_SOCKET; + cmptr->cmsg_type = SCM_RIGHTS; + *(int *) CMSG_DATA(cmptr) = sendfd; +#else + msg.msg_accrights = (char *) &sendfd; + msg.msg_accrightslen = sizeof(sendfd); +#endif + + msg.msg_name = 0; + msg.msg_namelen = 0; + + /* + * XXX We don't want to pass any data, just a file descriptor. However, + * setting msg.msg_iov = 0 and msg.msg_iovlen = 0 causes trouble. See the + * comments in the unix_recv_fd() routine. + */ + iov->iov_base = ""; + iov->iov_len = 1; + msg.msg_iov = iov; + msg.msg_iovlen = 1; + + /* + * The CMSG_LEN send/receive workaround was originally developed for + * OpenBSD 3.6 on SPARC64. After the workaround was verified to not break + * Solaris 8 on SPARC64, it was hard-coded with Postfix 2.3 for all + * platforms because of increasing pressure to work on other things. The + * workaround does nothing for 32-bit systems. + * + * The investigation was reopened with Postfix 2.7 because the workaround + * broke with NetBSD 5.0 on 64-bit architectures. This time it was found + * that OpenBSD <= 4.3 on AMD64 and SPARC64 needed the workaround for + * sending only. The following platforms worked with and without the + * workaround: OpenBSD 4.5 on AMD64 and SPARC64, FreeBSD 7.2 on AMD64, + * Solaris 8 on SPARC64, and Linux 2.6-11 on x86_64. + * + * As this appears to have been an OpenBSD-specific problem, we revert to + * the Postfix 2.2 behavior. Instead of hard-coding the workaround for + * all platforms, we now detect sendmsg() errors at run time and turn on + * the workaround dynamically. + * + * The workaround was made run-time configurable to investigate the problem + * on multiple platforms. Though set_unix_pass_fd_fix() is over-kill for + * this specific problem, it is left in place so that it can serve as an + * example of how to add run-time configurable workarounds to Postfix. + */ + if (sendmsg(fd, &msg, 0) >= 0) + return (0); + if (unix_pass_fd_fix == 0) { + if (msg_verbose) + msg_info("sendmsg error (%m). Trying CMSG_LEN workaround."); + unix_pass_fd_fix = UNIX_PASS_FD_FIX_CMSG_LEN; + return (unix_send_fd(fd, sendfd)); + } else { + return (-1); + } +#endif +} + +#ifdef TEST + + /* + * Proof-of-concept program. Open a file and send the descriptor, presumably + * to the unix_recv_fd test program. + */ +#include <unistd.h> +#include <string.h> +#include <stdlib.h> +#include <fcntl.h> +#include <split_at.h> +#include <connect.h> + +int main(int argc, char **argv) +{ + char *transport; + char *endpoint; + char *path; + int server_sock; + int client_fd; + + msg_verbose = 1; + + if (argc < 3 + || (endpoint = split_at(transport = argv[1], ':')) == 0 + || *endpoint == 0 || *transport == 0) + msg_fatal("usage: %s transport:endpoint file...", argv[0]); + + if (strcmp(transport, "unix") == 0) { + server_sock = unix_connect(endpoint, BLOCKING, 0); + } else { + msg_fatal("invalid transport name: %s", transport); + } + if (server_sock < 0) + msg_fatal("connect %s:%s: %m", transport, endpoint); + + argv += 2; + while ((path = *argv++) != 0) { + if ((client_fd = open(path, O_RDONLY, 0)) < 0) + msg_fatal("open %s: %m", path); + msg_info("path=%s fd=%d", path, client_fd); + if (unix_send_fd(server_sock, client_fd) < 0) + msg_fatal("send file descriptor: %m"); + if (close(client_fd) != 0) + msg_fatal("close(%d): %m", client_fd); + } + exit(0); +} + +#endif |