commit c7d9b5c8f53f42b424ad0d3ee1e5256932a66357 Author: David Goulet dgoulet@ev0ke.net Date: Sun Jun 9 11:35:27 2013 -0400

Improve libc symbol interface and add destructor

This commit adds a *_DECL macro which builds the libc call declaration using the returned type and signature defined on a per OS basis.

Signed-off-by: David Goulet dgoulet@ev0ke.net --- src/lib/torsocks.c | 54 +++++++++++++++++++++++++++++++++------------------- src/lib/torsocks.h | 26 ++++++++++++++++++++++--- 2 files changed, 57 insertions(+), 23 deletions(-)

diff --git a/src/lib/torsocks.c b/src/lib/torsocks.c index f5029e7..b927201 100644 --- a/src/lib/torsocks.c +++ b/src/lib/torsocks.c @@ -33,11 +33,21 @@ static int is_suid;

/* + * Cleanup and exit with the given status. Note that the lib destructor will be + * called after this call. + */ +static void clean_exit(int status) +{ + exit(status); +} + +/* * 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) +static void *find_libc_symbol(const char *symbol, + enum tsocks_sym_action action) { void *fct_ptr = NULL;

@@ -46,10 +56,12 @@ static void *find_libc_symbol(const char *symbol) fct_ptr = dlsym(RTLD_NEXT, symbol); if (!fct_ptr) { ERR("Unable to find %s", symbol); - goto end; + if (action == TSOCKS_SYM_EXIT_NOT_FOUND) { + ERR("This is critical for torsocks. Exiting"); + clean_exit(EXIT_FAILURE); + } }

-end: return fct_ptr; }

@@ -101,7 +113,7 @@ static void init_logging(void) * Lib constructor. Initialize torsocks here before the main execution of the * binary we are preloading. */ -static void __attribute__((constructor)) init() +static void __attribute__((constructor)) tsocks_init(void) { /* UID and effective UID MUST be the same or else we are SUID. */ is_suid = (getuid() != geteuid()); @@ -110,28 +122,30 @@ static void __attribute__((constructor)) init() }

/* - * Cleanup and exit with the given status. + * Lib destructor. */ -static void clean_exit(int status) +static void __attribute__((destructor)) tsocks_exit(void) { - exit(status); + /* Clean up logging. */ + log_destroy(); }

/* - * Libc hijacked symbol connect(2). + * Torsocks call for connect(2). */ -int connect(LIBC_CONNECT_SIG) +LIBC_CONNECT_RET_TYPE tsocks_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); - } - } + DBG("Connect catched on fd %d", __sockfd); + return tsocks_libc_connect(LIBC_CONNECT_ARGS); +}

- return libc_connect(_sockfd, _addr, _addrlen); +/* + * Libc hijacked symbol connect(2). + */ +LIBC_CONNECT_DECL +{ + /* Find symbol if not already set. Exit if not found. */ + tsocks_libc_connect = find_libc_symbol(LIBC_CONNECT_NAME_STR, + TSOCKS_SYM_EXIT_NOT_FOUND); + return tsocks_connect(LIBC_CONNECT_ARGS); } diff --git a/src/lib/torsocks.h b/src/lib/torsocks.h index 122d711..3d0b1b6 100644 --- a/src/lib/torsocks.h +++ b/src/lib/torsocks.h @@ -22,18 +22,38 @@

#include <common/compat.h>

+#define TSOCKS_LIBC_DECL(name, type, sig) \ + type (*tsocks_libc_##name)(sig); + #if (defined(__linux__) || defined(__FreeBSD__) || defined(__darwin__))

#include <sys/types.h> #include <sys/socket.h>

-#ifndef LIBC_CONNECT_SIG +#define LIBC_CONNECT_NAME connect +#define LIBC_CONNECT_NAME_STR XSTR(LIBC_CONNECT_NAME) +#define LIBC_CONNECT_RET_TYPE int #define LIBC_CONNECT_SIG \ - int _sockfd, const struct sockaddr *_addr, socklen_t _addrlen -#endif /* LIBC_CONNECT_SIG */ + int __sockfd, const struct sockaddr *__addr, socklen_t __addrlen +#define LIBC_CONNECT_ARGS \ + __sockfd, __addr, __addrlen

#else #error "OS not supported." #endif /* __linux__ , __FreeBSD__, __darwin__ */

+/* + * The following defines are libc function declarations using the macros + * defined above on a per OS basis. + */ + +/* connect(2) */ +TSOCKS_LIBC_DECL(connect, LIBC_CONNECT_RET_TYPE, LIBC_CONNECT_SIG) +#define LIBC_CONNECT_DECL \ + LIBC_CONNECT_RET_TYPE LIBC_CONNECT_NAME(LIBC_CONNECT_SIG) + +enum tsocks_sym_action { + TSOCKS_SYM_EXIT_NOT_FOUND = 1, +}; + #endif /* TORSOCKS_H */