printf-hook-builtin: Fix invalid memory access

When precision is given for a string, we must not run unbounded
strlen() as it will read beyond the given length. It might even cause
a crash if the given pointer is near end of heap or mapping.

Fixes numerous valgrind errors such as:

==19215== Invalid read of size 1
==19215==    at 0x52D36C6: builtin_vsnprintf (printf_hook_builtin.c:853)
==19215==    by 0x52D40A8: builtin_snprintf (printf_hook_builtin.c:1084)
==19215==    by 0x52CE464: dntoa (identification.c:337)
==19215==    by 0x52CE464: identification_printf_hook (identification.c:837)
==19215==    by 0x52D3DAA: builtin_vsnprintf (printf_hook_builtin.c:1010)
==19215==    by 0x57040EB: vlog (bus.c:388)
==19215==    by 0x570427D: log_ (bus.c:430)
==19215==    by 0xA8445D3: load_x509_ca (stroke_cred.c:416)
==19215==    by 0xA8445D3: load_certdir (stroke_cred.c:537)
==19215==    by 0xA846A95: load_certs (stroke_cred.c:1353)
==19215==    by 0xA846A95: stroke_cred_create (stroke_cred.c:1475)
==19215==    by 0xA84073E: stroke_socket_create (stroke_socket.c:782)
==19215==    by 0xA83F27C: register_stroke (stroke_plugin.c:53)
==19215==    by 0x52C3125: load_feature (plugin_loader.c:716)
==19215==    by 0x52C3125: load_provided (plugin_loader.c:778)
==19215==    by 0x52C3A20: load_features (plugin_loader.c:799)
==19215==    by 0x52C3A20: load_plugins (plugin_loader.c:1159)
==19215==  Address 0x50cdb42 is 0 bytes after a block of size 2 alloc'd
==19215==    at 0x4C919FE: malloc (vg_replace_malloc.c:296)
==19215==    by 0x52CD198: chunk_printable (chunk.c:759)
==19215==    by 0x52CE442: dntoa (identification.c:334)
==19215==    by 0x52CE442: identification_printf_hook (identification.c:837)
==19215==    by 0x52D3DAA: builtin_vsnprintf (printf_hook_builtin.c:1010)
==19215==    by 0x57040EB: vlog (bus.c:388)
==19215==    by 0x570427D: log_ (bus.c:430)
==19215==    by 0xA8445D3: load_x509_ca (stroke_cred.c:416)
==19215==    by 0xA8445D3: load_certdir (stroke_cred.c:537)
==19215==    by 0xA846A95: load_certs (stroke_cred.c:1353)
==19215==    by 0xA846A95: stroke_cred_create (stroke_cred.c:1475)
==19215==    by 0xA84073E: stroke_socket_create (stroke_socket.c:782)
==19215==    by 0xA83F27C: register_stroke (stroke_plugin.c:53)
==19215==    by 0x52C3125: load_feature (plugin_loader.c:716)
==19215==    by 0x52C3125: load_provided (plugin_loader.c:778)
==19215==    by 0x52C3A20: load_features (plugin_loader.c:799)
==19215==    by 0x52C3A20: load_plugins (plugin_loader.c:1159)

diff --git a/src/libstrongswan/utils/printf_hook/printf_hook_builtin.c b/src/libstrongswan/utils/printf_hook/printf_hook_builtin.c
index 466c673..af54940 100644 (file)
--- a/src/libstrongswan/utils/printf_hook/printf_hook_builtin.c
+++ b/src/libstrongswan/utils/printf_hook/printf_hook_builtin.c
@@ -843,7 +843,8 @@ int builtin_vsnprintf(char *buffer, size_t n, const char *format, va_list ap)
                                                                /* String */
                                                                sarg = va_arg(ap, const char *);
                                                                sarg = sarg ? sarg : "(null)";
-                                                               slen = strlen(sarg);
+                                                               slen = prec != -1 ? strnlen(sarg, prec)
+                                                                                                 : strlen(sarg);
                                                                goto is_string;
                                                        }
                                                        case 'm':