commit 9acdf15bf1bc7de354dff59c611c44d58cfc83c3 Author: David Goulet dgoulet@ev0ke.net Date: Thu Jun 6 20:37:55 2013 -0400

Add basic interface for libc overload

Signed-off-by: David Goulet dgoulet@ev0ke.net --- src/common/compat.h | 6 ++++++ src/lib/Makefile.am | 6 +++--- src/lib/torsocks.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++ src/lib/torsocks.h | 14 ++++++++++++++ 4 files changed, 73 insertions(+), 3 deletions(-)

diff --git a/src/common/compat.h b/src/common/compat.h index 3ac4941..020fe8e 100644 --- a/src/common/compat.h +++ b/src/common/compat.h @@ -18,6 +18,12 @@ #ifndef TORSOCKS_COMPAT_H #define TORSOCKS_COMPAT_H

+#if (defined(__linux__) || defined(__FreeBSD__) || defined(__darwin__)) + +#define RTLD_NEXT ((void *) -1) + +#endif /* __linux__, __FreeBSD__, __darwin__ */ + #ifdef __linux__

#include <pthread.h> diff --git a/src/lib/Makefile.am b/src/lib/Makefile.am index f578d3f..7a1586d 100644 --- a/src/lib/Makefile.am +++ b/src/lib/Makefile.am @@ -1,4 +1,5 @@ AM_CPPFLAGS = -I$(top_srcdir)/include -I$(top_srcdir)/src -I$(builddir) +AM_CFLAGS = -fno-strict-aliasing

libdir = @libdir@/torsocks

@@ -11,7 +12,6 @@ lib_LTLIBRARIES = libtorsocks.la

libtorsocks_la_SOURCES = torsocks.c torsocks.h

-libtorsocks_la_LDFLAGS = $(TORSOCKSLDFLAGS) - libtorsocks_la_LIBADD = \ - $(top_builddir)/src/common/libcommon.la + $(top_builddir)/src/common/libcommon.la \ + -ldl diff --git a/src/lib/torsocks.c b/src/lib/torsocks.c index c0450ad..f5029e7 100644 --- a/src/lib/torsocks.c +++ b/src/lib/torsocks.c @@ -17,6 +17,8 @@ * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */

+#include <assert.h> +#include <dlfcn.h> #include <stdlib.h>

#include <common/defaults.h> @@ -31,6 +33,27 @@ static int is_suid;

/* + * Lookup symbol in the loaded libraries of the binary. + * + * Return the function pointer or NULL on error. + */ +static void *find_libc_symbol(const char *symbol) +{ + void *fct_ptr = NULL; + + assert(symbol); + + fct_ptr = dlsym(RTLD_NEXT, symbol); + if (!fct_ptr) { + ERR("Unable to find %s", symbol); + goto end; + } + +end: + return fct_ptr; +} + +/* * Initialize logging subsytem using either the default values or the one given * by the environment variables. */ @@ -85,3 +108,30 @@ static void __attribute__((constructor)) init()

init_logging(); } + +/* + * Cleanup and exit with the given status. + */ +static void clean_exit(int status) +{ + exit(status); +} + +/* + * Libc hijacked symbol connect(2). + */ +int connect(LIBC_CONNECT_SIG) +{ + static int (*libc_connect)(LIBC_CONNECT_SIG) = NULL; + + /* Find symbol if not already set. */ + if (!libc_connect) { + libc_connect = find_libc_symbol("connect"); + if (!libc_connect) { + ERR("This is critical for torsocks. Exiting"); + clean_exit(EXIT_FAILURE); + } + } + + return libc_connect(_sockfd, _addr, _addrlen); +} diff --git a/src/lib/torsocks.h b/src/lib/torsocks.h index 7e6eec1..122d711 100644 --- a/src/lib/torsocks.h +++ b/src/lib/torsocks.h @@ -22,4 +22,18 @@

#include <common/compat.h>

+#if (defined(__linux__) || defined(__FreeBSD__) || defined(__darwin__)) + +#include <sys/types.h> +#include <sys/socket.h> + +#ifndef LIBC_CONNECT_SIG +#define LIBC_CONNECT_SIG \ + int _sockfd, const struct sockaddr *_addr, socklen_t _addrlen +#endif /* LIBC_CONNECT_SIG */ + +#else +#error "OS not supported." +#endif /* __linux__ , __FreeBSD__, __darwin__ */ + #endif /* TORSOCKS_H */