X-Git-Url: https://git.distorted.org.uk/~mdw/fwd/blobdiff_plain/1c2054c7558f523dec9d7c1f243a2ceddd81c781..ee599f5566c155b4decd9c77bfa4d6212f20891e:/privconn.c diff --git a/privconn.c b/privconn.c new file mode 100644 index 0000000..fcd292b --- /dev/null +++ b/privconn.c @@ -0,0 +1,380 @@ +/* -*-c-*- + * + * $Id: privconn.c,v 1.1 2003/11/29 20:36:07 mdw Exp $ + * + * Making privileged connections + * + * (c) 2003 Straylight/Edgeware + */ + +/*----- Licensing notice --------------------------------------------------* + * + * This file is part of the `fw' port forwarder. + * + * `fw' is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * `fw' is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with `fw'; if not, write to the Free Software Foundation, + * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + */ + +/*----- Revision history --------------------------------------------------* + * + * $Log: privconn.c,v $ + * Revision 1.1 2003/11/29 20:36:07 mdw + * Privileged outgoing connections. + * + */ + +/*----- Header files ------------------------------------------------------*/ + +#include +#include +#include +#include + +#include +#include + +#include +#include +#include + +#include +#include +#include +#include +#include +#include + +#include "privconn.h" + +/*----- Data structures ---------------------------------------------------*/ + +typedef struct connrec { + struct in_addr peer; + unsigned port; +} connrec; + +typedef struct connrq { + int i; + struct in_addr bind; +} connrq; + +DA_DECL(connrec_v, connrec); + +/*----- Static variables --------------------------------------------------*/ + +static connrec_v cv = DA_INIT; +static conn *qhead = 0, **qtail = &qhead; +static int kidfd = -1; +static sel_file sf; + +/*----- Main code ---------------------------------------------------------*/ + +/* --- @doconn@ --- * + * + * Arguments: @const connrq *rq@ = index of connection record + * + * Returns: Connected file descriptor, or @-1@. + * + * Use: Main privileged connection thing. + */ + +static int doconn(const connrq *rq) +{ + struct sockaddr_in sin_bind; + struct sockaddr_in sin_peer; + int fd; + int i; + connrec *c; + + /* --- Check the argument --- */ + + if (rq->i < 0 || rq->i >= DA_LEN(&cv)) { + errno = EINVAL; + goto fail_0; + } + c = &DA(&cv)[rq->i]; + + /* --- Make a new socket --- */ + + if ((fd = socket(PF_INET, SOCK_STREAM, 0)) < 0) + goto fail_0; + + /* --- Bind it to a low-numbered port --- */ + + memset(&sin_bind, 0, sizeof(sin_bind)); + sin_bind.sin_family = AF_INET; + sin_bind.sin_addr = rq->bind; + for (i = 1023; i >= 512; i--) { + sin_bind.sin_port = htons(i); + if (!bind(fd, (struct sockaddr *)&sin_bind, sizeof(sin_bind))) + goto bound; + if (errno != EADDRINUSE) + goto fail_1; + } + goto fail_1; + + /* --- Connect to the peer --- * + * + * We can find out whether it's connected later, so there's no need to + * distinguish these cases. + */ + +bound: + memset(&sin_peer, 0, sizeof(sin_peer)); + sin_peer.sin_family = AF_INET; + sin_peer.sin_addr = c->peer; + sin_peer.sin_port = c->port; + fdflags(fd, O_NONBLOCK, O_NONBLOCK, 0, 0); + if (connect(fd, (struct sockaddr *)&sin_peer, sizeof(sin_peer)) < 0 && + errno != EINPROGRESS) + goto fail_1; + return (fd); + + /* --- Tidy up on errors --- */ + +fail_1: + close(fd); +fail_0: + return (-1); +} + +/* --- @dochild@ --- * + * + * Arguments: @int fd@ = my file descriptor + * + * Returns: Never. + * + * Use: Child process for making privileged connections, separated + * from main process after initialization. + */ + +static void dochild(int fd) +{ + int i; + connrq rq; + int nfd; + ssize_t sz; +#if defined(_SC_OPEN_MAX) + int maxfd = sysconf(_SC_OPEN_MAX); +#elif defined(OPEN_MAX) + int maxfd = OPEN_MAX; +#else + int maxfd = -1; +#endif + struct sigaction sa; + struct sigaction sa_dfl; + + /* --- Clear out unnecessary file descriptors --- */ + + if (maxfd < 0) + maxfd = 256; + for (i = 3; i < maxfd; i++) + if (i != fd) close(i); + + /* --- Close off signal handlers --- */ + + sa_dfl.sa_handler = SIG_DFL; + sigemptyset(&sa_dfl.sa_mask); + sa_dfl.sa_flags = 0; + for (i = 0; i < 256; i++) { + if (sigaction(i, 0, &sa)) + break; + if (sa.sa_handler != SIG_DFL && sa.sa_handler != SIG_IGN) + sigaction(i, &sa_dfl, 0); + } + + /* --- Main loop --- */ + + for (;;) { + sz = read(fd, &rq, sizeof(rq)); + if (!sz) + break; + if (sz < 0) + die(1, "read error in privconn child: %s", strerror(errno)); + if ((nfd = doconn(&rq)) < 0) + goto err; + i = 0; + sz = fdpass_send(fd, nfd, &i, sizeof(i)); + if (sz < 0) + goto err; + if (sz < sizeof(i)) + die(1, "short write in privconn child"); + continue; + + err: + if (write(fd, &errno, sizeof(errno)) < 0) + die(1, "write error in privconn child: %s", strerror(errno)); + } + _exit(0); +} + +/* --- @dorecvfd@ --- * + * + * Arguments: @int fd@ = file descriptor (@== kidfd@) + * @unsigned mode@ = what's happening (@== SEL_READ@) + * @void *p@ = uninteresting (@== 0@) + * + * Returns: --- + * + * Use: Receives a file descriptor from the privileged part. + */ + +void dorecvfd(int fd, unsigned mode, void *p) +{ + conn *c, *cc; + ssize_t n; + int e; + + n = fdpass_recv(kidfd, &fd, &e, sizeof(e)); + if (!n) + goto close; + assert(qhead); + c = qhead; + qhead = (conn *)c->writer.next; + if (!qhead) qtail = &qhead; + if (n < 0 || (errno = e) != 0) + goto fail; + if (fd == -1) { + errno = EIO; + goto fail; + } + conn_fd(c, c->writer.s, fd, c->func, c->p); + return; + +fail: + c->func(-1, c->p); + return; + +close: + close(kidfd); + kidfd = 0; + errno = EIO; + sel_rmfile(&sf); + for (c = qhead; c; c = cc) { + cc = (conn *)c->writer.next; + c->func(-1, c->p); + } + qhead = 0; + qtail = &qhead; + return; +} + +/* --- @privconn_split@ --- * + * + * Arguments: @sel_state *s@ = select state + * + * Returns: --- + * + * Use: Splits off the privileged binding code into a separate + * process. + */ + +void privconn_split(sel_state *s) +{ + pid_t kid; + int fd[2]; + + if (kidfd != -1) + return; + if (socketpair(PF_UNIX, SOCK_STREAM, 0, fd) < 0) + die(1, "couldn't create privconn socketpair: %s", strerror(errno)); + kidfd = fd[0]; + if ((kid = fork()) < 0) + die(1, "couldn't fork privconn child: %s", strerror(errno)); + if (!kid) { + close(kidfd); + dochild(fd[1]); + _exit(127); + } + close(fd[1]); + fdflags(kidfd, 0, 0, FD_CLOEXEC, FD_CLOEXEC); + sel_initfile(s, &sf, kidfd, SEL_READ, dorecvfd, 0); + sel_addfile(&sf); +} + +/* --- @privconn_adddest@ --- * + * + * Arguments: @struct in_addr peer@ = address to connect to + * @unsigned port@ = port to connect to + * + * Returns: Index for this destination address, or @-1@ if not + * available. + * + * Use: Adds a valid destination for a privileged connection. + */ + +int privconn_adddest(struct in_addr peer, unsigned port) +{ + int i; + struct connrec *c; + + if (kidfd != -1) + return (-1); + for (i = 0; i < DA_LEN(&cv); i++) { + c = &DA(&cv)[i]; + if (peer.s_addr == c->peer.s_addr && port == c->port) + return (i); + } + DA_ENSURE(&cv, 1); + DA_EXTEND(&cv, 1); + c = &DA(&cv)[i]; + c->peer = peer; + c->port = port; + return (i); +} + +/* --- @privconn_connect@ --- * + * + * Arguments: @conn *c@ = connection structure to fill in + * @sel_state *s@ = pointer to select state to attach to + * @int i@ = address index to connect to + * @struct in_addr bind@ = address to bind to + * @void (*func)(int, void *)@ = function to call on connect + * @void *p@ = argument for the function + * + * Returns: Zero on success, @-1@ on failure. + * + * Use: Sets up a privileged connection job. + */ + +int privconn_connect(conn *c, sel_state *s, int i, struct in_addr bind, + void (*func)(int, void *), void *p) +{ + int fd; + connrq rq; + ssize_t n; + + rq.i = i; + rq.bind = bind; + if (kidfd == -1) { + if ((fd = doconn(&rq)) < 0) + return (-1); + conn_fd(c, s, fd, func, p); + return (0); + } + + n = write(kidfd, &rq, sizeof(rq)); + if (n < 0) + return (-1); + c->writer.fd = -1; + c->writer.s = s; + c->writer.next = 0; + c->func = func; + c->p = p; + *qtail = c; + qtail = (conn **)&c->writer.next; + return (0); +} + +/*----- That's all, folks -------------------------------------------------*/