commit 3c5ba7b51aafe3e590a4383116477d9b4d40875c Author: David Goulet dgoulet@ev0ke.net Date: Thu Feb 20 12:00:19 2014 +0000

Deny libc function accept()/accept4()

Inbound connection to an application handled by torsocks should not be allowed since we can't make them nor make sure that it goes/come through the Tor network.

Signed-off-by: David Goulet dgoulet@ev0ke.net --- src/lib/Makefile.am | 2 +- src/lib/accept.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++ src/lib/torsocks.h | 28 +++++++++++++++++++ 3 files changed, 104 insertions(+), 1 deletion(-)

diff --git a/src/lib/Makefile.am b/src/lib/Makefile.am index ad25f8c..c508733 100644 --- a/src/lib/Makefile.am +++ b/src/lib/Makefile.am @@ -9,6 +9,6 @@ lib_LTLIBRARIES = libtorsocks.la libtorsocks_la_SOURCES = torsocks.c torsocks.h \ connect.c gethostbyname.c getaddrinfo.c close.c \ getpeername.c socket.c syscall.c socketpair.c recv.c \ - exit.c + exit.c accept.c

libtorsocks_la_LIBADD = $(top_builddir)/src/common/libcommon.la diff --git a/src/lib/accept.c b/src/lib/accept.c new file mode 100644 index 0000000..3dd7617 --- /dev/null +++ b/src/lib/accept.c @@ -0,0 +1,75 @@ +/* + * Copyright (C) 2014 - David Goulet dgoulet@ev0ke.net + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License, version 2 only, as + * published by the Free Software Foundation. + * + * This program 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 + * this program; if not, write to the Free Software Foundation, Inc., 51 + * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#include <assert.h> + +#include "torsocks.h" + +TSOCKS_LIBC_DECL(accept, LIBC_ACCEPT_RET_TYPE, LIBC_ACCEPT_SIG) + +/* + * Torsocks call for accept(2). + */ +LIBC_ACCEPT_RET_TYPE tsocks_accept(LIBC_ACCEPT_SIG) +{ + DBG("[accept] Syscall denied since inbound connection are not allowed."); + + /* + * Accept is completely denied here since this means that the application + * can accept inbound connections that are obviously NOT handled by the Tor + * network thus reject this call. + */ + errno = EPERM; + return -1; +} + +/* + * Libc hijacked symbol accept(2). + */ +LIBC_ACCEPT_DECL +{ + return tsocks_accept(LIBC_ACCEPT_ARGS); +} + +#if (defined(__linux__)) + +TSOCKS_LIBC_DECL(accept4, LIBC_ACCEPT4_RET_TYPE, LIBC_ACCEPT4_SIG) + +/* + * Torsocks call for accept4(2). + */ +LIBC_ACCEPT4_RET_TYPE tsocks_accept4(LIBC_ACCEPT4_SIG) +{ + DBG("[accept] Syscall denied since inbound connection are not allowed."); + + /* + * Accept is completely denied here since this means that the application + * can accept inbound connections that are obviously NOT handled by the Tor + * network thus reject this call. + */ + errno = EPERM; + return -1; +} + +/* + * Libc hijacked symbol accept4(2). + */ +LIBC_ACCEPT4_DECL +{ + return tsocks_accept4(LIBC_ACCEPT4_ARGS); +} +#endif diff --git a/src/lib/torsocks.h b/src/lib/torsocks.h index 454ad1c..369652c 100644 --- a/src/lib/torsocks.h +++ b/src/lib/torsocks.h @@ -169,6 +169,14 @@ struct hostent **result, int *h_errnop #define LIBC_RECVMSG_ARGS \ sockfd, msg, flags

+/* accept(2) */ +#define LIBC_ACCEPT_NAME accept +#define LIBC_ACCEPT_NAME_STR XSTR(LIBC_ACCEPT_NAME) +#define LIBC_ACCEPT_RET_TYPE int +#define LIBC_ACCEPT_SIG \ + int sockfd, struct sockaddr *addr, socklen_t *addrlen +#define LIBC_ACCEPT_ARGS sockfd, addr, addrlen + #else #error "OS not supported." #endif /* __GLIBC__ , __FreeBSD__, __darwin__, __NetBSD__ */ @@ -184,6 +192,14 @@ struct hostent **result, int *h_errnop #define LIBC_SYSCALL_SIG long int number, ... #define LIBC_SYSCALL_ARGS number

+/* accept4(2) */ +#define LIBC_ACCEPT4_NAME accept4 +#define LIBC_ACCEPT4_NAME_STR XSTR(LIBC_ACCEPT4_NAME) +#define LIBC_ACCEPT4_RET_TYPE int +#define LIBC_ACCEPT4_SIG \ + int sockfd, struct sockaddr *addr, socklen_t *addrlen, int flags +#define LIBC_ACCEPT4_ARGS sockfd, addr, addrlen, flags + #endif /* __linux__ */

#if (defined(__FreeBSD__) || defined(__darwin__) || defined(__NetBSD__)) @@ -321,6 +337,18 @@ extern TSOCKS_LIBC_DECL(getpeername, LIBC_GETPEERNAME_RET_TYPE, #define LIBC_GETPEERNAME_DECL LIBC_GETPEERNAME_RET_TYPE \ LIBC_GETPEERNAME_NAME(LIBC_GETPEERNAME_SIG)

+/* accept(2) */ +extern TSOCKS_LIBC_DECL(accept, LIBC_ACCEPT_RET_TYPE, LIBC_ACCEPT_SIG) +#define LIBC_ACCEPT_DECL LIBC_ACCEPT_RET_TYPE \ + LIBC_ACCEPT_NAME(LIBC_ACCEPT_SIG) + +/* accept4(2) */ +#if (defined(__linux__)) +extern TSOCKS_LIBC_DECL(accept4, LIBC_ACCEPT4_RET_TYPE, LIBC_ACCEPT4_SIG) +#define LIBC_ACCEPT4_DECL LIBC_ACCEPT4_RET_TYPE \ + LIBC_ACCEPT4_NAME(LIBC_ACCEPT4_SIG) +#endif + /* * Those are actions to do during the lookup process of libc symbols. For * instance the connect(2) syscall is essential to Torsocks so the function