Other than using the much safer snprintf that takes buffer length and does not write past that, you can also ask the compiler to add stack protectors, or memory sanitization to the compiled code. This will indeed result in stack smashing and opens doors for potential hacks or just leaving the application to an unpredictable state.įor C-developers, the underlying stack protector mechanism is well-known, but for Java developers, it might need a bit more explanation. With longer inputs the remaining characters will be written past its end. Sprintf(dst_filename, "%s.digested", src_filename) įrom the above it is clear that the buffer can only hold a fixed number characters. The underlying problem is not too complex and is probably immediately visible in the C code: char dst_filename
#Stack smashing detected mac os
You should be aware of the fact that I only tested the examples on Linux and Mac OS X, and it might behave differently on Windows. Instead, the JVM is crashed without so much as a crash log. So the native method finished its execution just fine, but the control was not returned to Java. *** stack smashing detected ***: java terminated The not-so straightforward part is exposed when you discover yourself staring at the output with a slightly different (longer) filename used for input: $ java -jar build/libs/checksum.jar 123456789012.txt Got checksum from native method: 1804289383 $ java -jar build/libs/checksum.jar 123.txtĮxiting native method with checksum: 1804289383 You would just need to clone the repository and launch it similar to the following example: $.
#Stack smashing detected code
The code is simple and straightforward and so is running it. To achieve Awesome Performance (TM), I decided to implement the checksum calculation part using native implementation. It consists of a simple Java class, calculating checksums for files. To walk you through the experience, I have created a small test case. Or in more detail, how using native methods can result in JVM crashing silently without any reasonable traces in log files. This post is about a recent experience with native methods. I am also sure that the surprise has later vanished over the years with coming to understand how the JVM handles calls to native implementations via JNI. Sorry.I bet every Java developer has been surprised at some point in the beginning of their career when they first encounter native methods in Java code. I would have liked to give more references and articles in english about this flaw but nobody seemed have write about this thing. _fortify_fail_abort is added to avoid backtrace from _libc_message is changed to acceptĮnum _libc_message_action and call BEFORE_ABORT only if action includesĭo_backtrace. _stack_chk_fail is called on corrupted stack. (need_backtrace & _libc_argv != NULLĪnd, here is the comment attached to the original commit introducing the patch:Īvoid backtrace from _stack_chk_fail _libc_message (need_backtrace ? (do_abort | do_backtrace) : do_abort, _libc_argv if we aren't doing backtrace since _libc_argv
![stack smashing detected stack smashing detected](https://images.sftcdn.net/images/t_app-cover-l,f_auto/p/daa04874-d796-420e-827c-2c02f0639faa/3134031126/stack-smash-ultimate-screenshot.jpg)
* The loop is added only to keep gcc happy. _fortify_fail_abort (_Bool need_backtrace, const char *msg) Here is an answer on Unix/Linux Stack-Exchange site that pinpoint the part of the code of glibc that is responsible for that. That is why, sometime last year, some developers decided to avoid to use argv when displaying information about the stack-smashing and replaced it by. If a secret key or some confidential data were stored in the stack, then an attacker can access it through this feature.
![stack smashing detected stack smashing detected](https://www.mysteinbach.ca/game-zone/wp-content/uploads/launch-stack-smash.jpg)
As fork() is cloning the memory of the initial process, the ASLR was useless because the same starting memory image was used and, then, the same memory mapping was used again and again. This technique was mainly used in servers where fork() was used to respawn an instance. Indeed, if you can control the address at argv and crash the application, you can leak the whole stack outside of the application. But, some attackers started to exploit the fact that you could overflow the stack, reach the argv and overwrite it with an address that you choose. The " " (which is a static string added by -fstack-protector) that you see was previously argv. In fact, this is a fairly recent mitigation mechanism introduced to avoid to leak information about the stack of the crashed application.