Buffer overflow strcpy

Buffer overflow strcpy. Let's say this buffer is allocated at 0xbfffecfc. // Assumption: `s1` points to a C string. Let us compile and run the program with the command: gcc bof. Right-click your C++ and chose the "Properties" item to get to the properties window. In C, strncpy has the advantage over strcpy that it does not overflow the buffer when the source is larger than the destination. strcpy writes to an existing buffer, it doesn't need to and shouldn't call malloc. I need to enter the value 1 ( 0x00000001) at this buffer address via the command line. Dec 8, 2019 · Note, however, in the case of strcpy(), strcpy_s() is actually more akin to strncpy() as strcpy() is just a bog-standard C string function that doesn't do bounds checking, but strncpy() is a perverse function in that it will completely fill its target buffer, starting with data from the source string, and filling the entire target buffer with Jul 29, 2017 · I'm trying to replicate a simple buffer overflow for which I have the following code (strcpy_ex. Dec 31, 2018 · It is found that the value of “saved frame/base pointer” will be overwritten if we write past 608 bytes. Apr 21, 2014 · Best to use type size_t as that is the type returned from strlen () and used by malloc () and memcpy (). – Xofo. After discovering overflow vulnerability, attackers will observe how the call obtains 4. This event launched cybersecurity to the forefront of computer science headlines for one of the first times in history. c -g. 0x04 Control RIP We have found a little problem but for every problem, there's a solution! We can overflow using a smaller buffer so the address pointed by rsp will looks like something like 0x0000414141414141. So I tried to use strncpy () and set the null terminating character. The correct way to declare MyData would be with a zero sized array. It is almost certainly not a bug in Ubuntu. With this observation, we establish a sufficient condition for preventing buffer-overflow attacks and prove that it creates a Jan 7, 2016 · In modern C++ there's really little reason to use pointers at all these days, least of all for strings. int is not the proper type for these operations. Jul 16, 2015 · strcpy isn't dangerous as far as you know that the destination buffer is large enough to hold the characters of the source string; otherwise strcpy will happily copy more characters than your target buffer can hold, which can lead to several unfortunate consequences (stack/other variables overwriting, which can result in crashes, stack smashing Jun 30, 2019 · So i went to make a way bigger input and have an Integer overflow so that the short where the length is saved to is too big and gets below 32700 But that didnt seem to work either. I found a very useful gadget at address 0x0000f26c so I am obliged to insert null bytes to the stack to override the return address of the vulnerable function. strncat This function is similar to strcat , but it allows the programmer to specify the maximum number of characters to be concatenated to the end of the Aug 23, 2011 · 3. (In your example it would return always the same number Apr 13, 2020 · 1、strcpy溢出原理简述. Mar 11, 2019 · Now let’s start debugging the application with a handy tool called “gdb” to see how we can analyze this application. In the examples of this section, we will use strcpy(), which is used to copy strings. Apr 10, 2015 · For a more detailed overview of the stack based overflow exploitation: page 32-bit Stack-based Buffer Overflow. So let’s take the following program as an example. What matters is that the destination buffer is large enough to accommodate the string. Weakness ID: 122. ) Future operations may expect conforming C nul-terminated strings between equally sized buffers and malfunction downstream when the result is copied to yet a third buffer. buffer overflow attacks—the oldest and most pervasive attack technique. It’s better explained using an example. In simple words, it occurs when more data is put into a fixed-length buffer than the buffer can handle. Aug 3, 2011 at 2:02. By ta Hackers have been trying to steal information since the beginning of the information age. The function copies the entire source string, including the null terminator Description. The sprintf () function facilitates unbounded copying of text, in turn leaving the buffer susceptible to overflow attack. CWE-122: Heap-based Buffer Overflow. The user is able to write to and modify this file. To see the effects of the overflow make sure you set the breakpoint after `strcpy` and let's change the args to go just past `buf` 4-byte boundary: ``` > b 17 > set args > set args "AAAABC" > r ``` If you print the local variable `c` before and after the `strcpy` you'll see that we've overflow from `buf` into `c May 28, 2018 · Dealing with NULL byte (0x00) in offsets. May 3, 2017 · This requires a human. 496180+0100 Assignment 3[38082:4064098] detected source and destination buffer overlap. This all happens when I use GetSting () (from cs50. Therefore, if zero appears in the middle of the payload, the content after the zero cannot be copied onto the stack. Oct 20, 2022 · I'm currently learning about a return-to-libc method to bypass the non-executable stack countermeasure. Sep 6, 2018 · The third argument of strncpy is meant to represent the size of the target buffer. 0x0000000000400516 in main (argc=Cannot access memory at address 0x414141414141412d Buffer overflow is a class of vulnerability that occurs due to the use of functions that do not perform bounds checking. The additional n is for additional (third) parameter, that is as the maximal number of characters to copy/concatenate/compare. An example is shown in the code below. Nearly three decades later in 2014, a buffer overflow vulnerability Apr 2, 2021 · char data[1]; }; MyData *d1 = malloc(1024); strcpy(d1->data, a_string); gcc sees a strcpy being called with a buffer of size 1 as its destination - because that is what you told the compiler in the field's declaration char data [1];. If you have sufficient space for the terminator and you insist on strncpy, just pass strlen(p) + 1 so it will not assume it exhausted the target buffer. I was looking the source for some 3rd Party Library that we link against in our code. There are two ways in which heap overflows are exploited: by modifying data and by modifying objects. That said, the code with strcat_s is better in two ways: This is no longer a buffer overflow vulnerability. This program gets its input from a file called "badfile". Consider this victim program with a buffer overflow weakness because of an unbounded strcpy: Feb 7, 2017 · In the late 1980s, a buffer overflow in UNIX’s fingerd program allowed Robert T. Buffer overflow attacks have been Aug 2, 2012 · Show us the code. And addresses are 8 bytes in a 64-bit machine. Dec 13, 2023 · A buffer overflow was introduced in this commit due to unmitigated usage of unsafe C functions and improper bounds checking. The C convention for strings is that they are terminated by null characters. Feb 22, 2009 · A buffer overflow is basically when a crafted section (or buffer) of memory is written outside of its intended bounds. It causes some of that data to leak out into other buffers, which can corrupt or overwrite whatever data they were holding. Not allocating space for the null character. Mar 21, 2013 · My buffer character length, in which I copy my input strings is [5]. Share. The problem is that strcpy assumes it is looking at strings. newArgv[i] = new char[strlen(argv[i]) + 1]; Dec 13, 2014 · To put it another way: strcpy doesn't exactly copy a string to a string. You must pass the size of your buffer as parameter. Vulnerability Mapping: ALLOWEDThis CWE ID may be used to map to real-world vulnerabilitiesAbstraction: VariantVariant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. Morris to create a worm which infected 10% of the Internet—in two days. You should always check buffer sizes, regardless of which string concatenation function you use. May 16, 2016 · 它的返回值其实为dest数组的收地址，保存在寄存器rax里，所以strcpy返回的地址就是函数evilfunction里的buffer的地址，也就是说rax寄存器里的地址就是evilfunction里的buffer的起始位置，而非常幸运的是在evilfunction函数中在strcpy后面并没有对rax寄存器做任何操作，而本身 Stack-based buffer overflows work like this: An attacker overwrites the return address on the stack, which causes the program to jump to shellcode elsewhere in address space. Roughly they contain code which replaces standard APIs (like strcpy) with their fortified analogs (like __strcpy_chk): $ cat /usr/include/string. Buffer overflow errors are characterized by the overwriting of memory fragments of the process, which should have never been modified intentionally or unintentionally. I don't understand how the strings can overlap. Since this program is a root-owned Set-UID program, if a normal user can exploit this buffer overflow vulnerability, the user might be able to get a root shell. The extra data can overflow into adjacent memory locations, potentially overwriting important data or executing malicious code. In programming and information security, a buffer overflow or buffer overrun is an anomaly whereby a program writes data to a buffer beyond the buffer's allocated memory, overwriting adjacent memory locations. The exact address is very difficult to predict, many of the exploits around strcpy overwrite the stack or static data areas, which is more predictable (although still not standard). Using strcpy () function to copy a large character array into a smaller one is dangerous, but if the string will fit, then it will not be worth the risk. You should be careful, as (for example) copying at most n Aug 13, 2020 · In the code in the question, the size of the string being copied is known, a buffer that's large enough has been allocated, and strcpy would do exactly what's needed. First problem: ASLR . This happens via the strcpy () function which writes directly to 0xbfffecfc. FORTIFY_SOURCE uses "safer" variants of high risk functions like memcpy, strcpy and gets. Buffer overflows on the stack can overwrite “interesting” data. But if the string is 12 (or more) characters long, you're right, there'll be a buffer overflow, because strcpy will also copy the 13th, terminating null character. Jun 2, 2014 · You want movies[j], which is a buffer of 150 chars. The RTSP URL string received from the game streaming server is copied into urlAddr, which is a static buffer of May 26, 2014 · 7. 4. Simplest form (sometimes called “stack smashing”) Unchecked length on string input into bounded array causes overwriting of stack data. L15: Buffer Overflows CSE351, Autumn 2021. strcat has an implicit search for the NULL terminator. Given the code Aug 26, 2022 · C++ coverity issue STRING_OVERFLOW. memcpy () is rarely slower than strcpy () or strncpy () and often significantly faster. " How should I replace the above "strcpy" and "strncpy" to resolve the warning. Second exploit. There is strength in this answer. My code is identical to the reading and I don't understand CWE Glossary Definition. My inputs are constructed as follow: . The heap will contain areas of unused or defunct memory, which is less likely on the stack. Using strncpy(3) is better than strcpy(3) but things like strlcpy(3) are better still. h header file. In Strcpy if a null character is seen then it will stop copying. Nov 17, 2020 · The c code contains a strcpy () statement, so I can overwrite a struct with the memory address of a certain buffer. strncpy(ret, arg1, strlen(arg1)) does not null character terminate ret, so the next strncat(ret, is undefined behavior as ret needs to point to a string. More specific than a Base weakness. h> int main( int argc, char** argv ) { char buffer[500]; Stack Exchange Network Stack Exchange network consists of 183 Q&A communities including Stack Overflow , the largest, most trusted online community for developers to learn Aug 18, 2014 · Functions like strcpy operate on pointers, and though pointers point to buffers, there is no way for strcpy implementation to know how long a buffer is. This may result in a buffer overflow condition if an attacker can influence the contents of the string parameter. For more information about the stack memory layout and calling convention for 64-bit Linux programs: page Linux x64 Calling Convention: Stack Frame 4. So, 608+8=616 bytes need to be written A quick fix is to add the _CRT_SECURE_NO_WARNINGS definition to your project's settings. Microsoft, in an effort to promote safer coding in C and C++ has provided a suite of replacement functions for the dangerous string methods. Oct 23, 2009 · Strncpy will surely not overruns a buffer if you a) have the proper space for the "String" b) you get it right with the length. Jan 26, 2017 · It also always includes the null terminator \0, unless the buffer size is 0. c. Another strange thing is that printf before the strcpy does not print out anything We can do this by storing the compiled code to run a shell as a string (Google for "buffer overflow shellcode") and then overwriting the return address such that it points to our controlled string. The first index points to your string/film title in the string array, the second index points to characters in that string. The stacktrace show you are using strcpy somewhere in your code, and it's in there the overflow happens. Jul 24, 2014 · I examine the memory with x/200x and get a nice overview which I have omitted here because of its size, but I can clearly see the 0x42 that denote the legal size of the buffer, and the return address. Apr 24, 2023 · The buffer overflow vulnerability occurs whenever data written to a buffer exceeds its size. That dance of strncpy with a length that's smaller than the actual buffer followed by filling in the nul terminator (even if the code was corrected to put it in the correct Apr 24, 2014 · Before any call to strcpy(), you need to know the size of the data to be copied. When more data (than was originally allocated to be stored) gets placed by a program or system process, the extra data overflows. NOTE: default value on my machine was 2, note yours before changing this. However, many successful exploits have involved heap overflows. If the destination string is not large enough to store the Dec 1, 2016 · If I use strcpy () again to copy the value of argv [1] to k one more time, I get buffer overflow in encMsg concatenating both strings. It is not. I'm trying to exploit a strcpy () buffer overflow vulnerability to test ROP attack. May 2, 2022 · "This call to strcpy() and strncpy() contains a buffer overflow. GNU gdb (Debian 8. char call [64] = {'\0'} /* clean buffer */ strncpy (call, info. Now if we try and overflow the buffer in a way This is because strcpy_s() is expecting the source string to be a null terminated C-String. Push the return address on the stack. 即如果将长度较大的值 b 赋值给 较短的值 a（b>a），那么strcpy之后，b多出来将一部分将会覆盖原来的内存单元。. c to call myname. When the program reaches a ret instruction, the program will jump to an attacker controlled location. Overwriting values of the IP (Instruction Pointer), BP (Base Pointer) and other registers causes exceptions, segmentation faults, and other errors to occur. A memory corruption exists within the parseUrlAddrFromRtspUrlString function in RtspConnection. I see that since str is char* its length cannot be predicted (although as per my code it will always be 32). h #ifdef _FORTIFY_SOURCE #define strcpy __strcpy_chk #endif Sep 12, 2014 · Add a comment. You can pass in a pointer to null, but you can not copy string from pointer to null. A buffer is a temporary area for data storage. The reason is probably that the destination buffer you copy to is to small, so you copy outside of allocated memory. 0x00007fffffffffff and we try to overflow using 0x4141414141414141. In general, exploiting a buffer overflow on the heap is more challenging than exploiting an overflow on the stack. So every call of strncpy must be followed with a statement terminating the buffer, such as Feb 10, 2013 · While strcpy is a common string function, it has a history of being the source of many bugs and security holes in software (due to the ease of buffer overflows). On Linux, your fourth choice is to use FORTIFY_SOURCE. I have checked other tutorials in which the next step is to show how to spawn a shell, but I want testme. Jul 1, 2022 · Buffer Overflow Attack with Example. Use strncpy instead of strcpy, strncat instead of strcat, strncmp instead of strcmp, and so on. The function takes two arguments: a destination buffer where the copied string will be stored, and a source string that will be copied. c -o bof -fno-stack-protector -m32 -z execstack. Attackers just choose the right inputs. The function strcpy_s is similar to the BSD function strlcpy, except that. Details. Feb 20, 2014 · The safer way to detect buffer overflows is by providing your own implementation of calloc instead. Sep 24, 2015 · Using strcpy & buffer overflow to execute shell code. This would be a alternative to strncpy () or strcpy (), if you really don't want to use it. May 23, 2010 · (Imagine a source string longer than the destination buffer. The function char* strcpy (char* dest, const char* src) is copy string from address src to address dest, your dest is null. It copies a string to a buffer. The malicious nature of buffer-overflow attacks is the use of external data (input) as addresses (or control data). The functions strlcpy and strlcat are not standard. There are many functions in C that can be used to copy data, including strcpy(), strcat(), memcpy(), etc. Here is what I did in gdb. Dec 8, 2011 · 4. Feb 4, 2014 · Firstly I'd like to say that I've looked online and have yet to find anything of value. If the copy would exceed the destination buffer size, then the program calls abort(). Allocate space on stack for 10*8 bytes. I've compiled it in 64 bit mode: #include &lt;s Jan 9, 2012 · Proposed solution to detect NULL pointer and buffer overflow in memcpy, memset, strcpy before hand and print out the location (file:line) where the problem occurs Nov 17, 2021 · In our buffer-overflow attacks, we need to store at least one address in the payload, and the payload will be copied onto the stack via strcpy(), which will stop copying when it sees a zero. 以下为strcpy（）函数溢出的示意图：. You are passing it an array of char. For that all you probably best use the following code (pseudo-C, partly taken from Code Complete II) char buf [MAX_LEN+1]; strncpy (buf, src, MAX_LEN); In that case strncpy is safer then strcpy. gcc is being exactly as smart as it should be. Often a call like strcpy (dest, src); can be transformed into strcpy_s (dest, sizeof dest, src);, but if dest is heap-allocated this will just be the size of the pointer rather than the pointed-at buffer which of course is wrong. strncpy has the disadvantage that, when the source is larger than the destination, it does not terminate the buffer with a \0. h); Overview. I have allocated enough memory for the May 24, 2020 · I was expecting a segmentation fault at the end of the mainit instead happens at the end of the strcpyactually what happens (by looking with gdb) is that at the end of the strcpy the ESP points to 0x6361616e which is part of the input string. 当溢出的值刚好覆盖了 函数结束后 ret 返回的地址时，那么函数 ret后将会执行 溢出的值 However, the programmer does not ensure that the size of the data pointed to by string will fit in the local buffer and copies the data with the potentially dangerous strcpy() function. Provide a few bytes padding before and after the returned block, set them to a known value (NOT 0 or 255), and when calling free check that they're untouched. Buffer overflows have been a major security concern for decades and are a common target for attackers. 0x7fffffffda90: 0xffffdab0 0x00007fff 0x00400610 0x00000000 New breakpoint just after strcpy(): Jul 30, 2023 · strcpy_s is allowed to clobber the destination array from the last character written up to destsz in order to improve efficiency: it may copy in multibyte blocks and then check for null bytes. If you do know the size, strcpy() is however perfectly safe to use. size_t size = strlen(s1) + 1; Morris Worm and Buffer Overflow One of the wormʼs propagation techniques was a buffer overflow attack against a vulnerable version of fingerd on VAX systems • By sending special string to finger daemon, worm caused it to execute code creating a new worm copy • Unable to determine remote OS version, worm also Jul 18, 2017 · But in the push_list () function, there is an error: 2017-07-18 13:26:32. Your suggestion of using sizeof does not work, since sizeof returns the object size, not the size of the buffer a pointer points to. Apr 20, 2015 · It's a general misconception that strncpy is safer than strcpy. A buffer overflow condition exists when a program attempts to put more data in a buffer than it can hold or when a program attempts to put data in a memory area past a buffer. First we load the bof application into the debugger “gdb” using “gdb bof”. Buffers are areas of memory set aside to hold data, often while moving it from one section of a program to another, or between programs. So, let's overflow the buffer. strlcpy truncates the source string to fit in the destination (which is a Nov 14, 2013 · We all know that strcpy is unsafe because it leaves a program vulnerable to buffer overflow issues. The return address I'm trying to overflow on the stack is the libc system() function's address but it contains a Null Termination byte at the end which stop the strcpy() function from copying any further into a buffer. It's easy to calculate the size of our buffer with simple mathematics. Let's say I want to replace all calls to strcpy with calls to strncpy. Now let’s execute this command with an argument. The compiler uses the safer variants when it can deduce the destination buffer size. This can result in dangerous bugs and exploits. See full list on thegeekstuff. Like many already noted by now. The big problem with strncpy is that using it may produce non-null terminated char buffers. 1. In this case, a buffer is a sequential section of memory allocated to contain anything from a character string to an array of integers. Feb 3, 2022 · I know how to overflow the buffer variable in the exploitable function by giving a long enough string input to get a segmentation fault, but I cannot proceed any further than this. After the copy, that buffer contains a string. c): #include <string. Jun 28, 2016 · 0. The source string has an allocated size of (unavailable) bytes, and the destination buffer is 64 bytes. You'd have to be sure dest was declared an array! Mar 26, 2021 · Same applies when I try to use strcpy or strcpy_s, instead of memcpy. A technique for replacing all calls to strcpy (dest, src) would involve calling strncpy with the parameters (dest, src, length of dest - 1) and then terminating dest with \0. A buffer overflow occurs when a process attemps to store more data than the boundaries allow in the fixe-length buffer. 2. So catString is the total length of all the strings + 1 (for null terminator). (for \xXX my desired inputs) Mar 27, 2023 · Like strcpy, it does not perform any size checking, so it can be used to append a string that is larger than the buffer to the buffer, potentially leading to a buffer overflow vulnerability. Oct 1, 2022 · All fortification logic is implemented in Glibc headers. The desired functionality of push_list is described in a comment by the function initialization. A buffer overflow vulnerability occurs when an attacker is able to supply a piece of data that is too long, and that data then overwrites Nov 28, 2015 · When I perform a strcpy to a char[]: char buf[100]; strcpy(buf[], largeInput); If largeInput is longer than 100 bytes we have a buffer overflow. Running on Linux, Ubuntu 32bit via VirtualBox gcc compiler with -fno-stack-protector -ggdb -g tags. It is defined in the string. I am doing Mar 18, 2021 · Problems. To fix this, either add a 4th null character or use strncpy. BUFFER buf; strcpy((char*)buf, str); The issue says - "Copy into fixed size buffer (STRING_OVERFLOW)" for the strcpy () line. com May 30, 2021 · There are several inbuilt functions in C which are vulnerable to Buffer Overflow attack such as gets (), strcpy (). If you can't wait, snprintf returns the number of characters written, so you can store the buffer offset, allowing offset+=snprintf (buf+offset, (sizeof buf)-offset, "%s", "String2") – Dave. Mar 3, 2023 · strcpy is a C standard library function that copies a string from one location to another. Jan 14, 2014 · 1 Answer. But you have not null terminated the array (so it does not act like a C-String). Using pointers just creates problems like the one you have, and more. ASLR prevents us from using static addresses. Jan 8, 2018 · Will return catString lead to a buffer overflow? Strlen will calculate all the strings until it reaches a null terminator. Jan 20, 2018 · I want to get a root shell by exploiting strcpy() or strchr(). If I use strccpy (), it won't get the content of k erased, but it will overflow and concatenate both strings on encMsg. If an attacker can manage to make this happen from outside of a program it can cause security problems as it could potentially allow them to manipulate arbitrary memory locations, although many modern operating systems protect against the worst cases of this. If the compiler cannot deduce Here is a straightforward way of running your program with identical stacks in the terminal and in gdb: First, make sure your program is compiled without stack protection, gcc -m32 -fno-stack-protector -z execstack -o shelltest shelltest. called, sizeof (call)); I always use the sizeof for the destination for protecting a overflow, incase source is greater than the destination. Otherwise your program is vulnerable to buffer overflows. Earlier you asked about strncpy. However, manually adding a null terminator at the end of your string with strcpy () is always a simple, efficient approach. I have some troubles exploiting this with C, though it's got a strcpy() and strchr() inside it, because this is my first buffer overflow exploitation. If you pass the size of the string to copy you could as well use strcpy because it would do the same. Any ideas or any alternatives? How do I skip this unsafe use of of strcpy/memcpy (prevent buffer overflow)? C4496 and C6387 for using strcpy and strcat didn't help much :/ . /challenge `python -c "print 'A'*30000 + '\x00' + 'A'*10000" + '\xXX\xXX\xXX\xXX'`. gets () is used to take user inputs and strcpy () is used to copy one Morris Worm and Buffer Overflow One of the wormʼs propagation techniques was a buffer overflow attack against a vulnerable version of fingerd on VAX systems • By sending special string to finger daemon, worm caused it to execute code creating a new worm copy • Unable to determine remote OS version, worm also Nov 17, 2016 · I'm basically trying to run a buffer overflow attack. Buffer Overflow in a Nutshell. For the moment I failed doing this because strcpy () uses Jan 24, 2016 · Python (and other dynamic languages) usually use the heap to store values. 1 Copy Data to Buffer. Sep 13, 2016 · Figure 2-3 Heap overflow. Because strcpy() does not check boundaries, a buffer overflow will occur. Jul 2, 2018 · 1. run $(perl -e 'print "A"x32 ; ') Program received signal SIGSEGV, Segmentation fault. Jun 30, 2017 · if the passed-in bar points to a string of 11 or fewer characters, a valid string will be copied to MyArray, with no buffer overflow. I am using the code below. Feb 26, 2012 · We would like to show you a description here but the site won’t allow us. Feb 3, 2023 · Problem with strcpy (): The strcpy () function does not specify the size of the destination array, so buffer overrun is often a risk. Push the ebp on the stack (this is pointing to the main frame) 3. Google "strncpy unsafe". And using std::string also means you won't have the risk of a buffer overflow if the user inputs a string longer than 19 characters. Oct 24, 2020 · Unfortunately, a number of commonly used library functions, including strcpy, strcat, and sprintf, have the property that they can generate a byte sequence without being given any indication of the size of the destination buffer [97]. 3. 2. And when it fills it up, it doesn't add a null terminating character by design. I've been going through "Smashing the stack for fun and profit" and am having issues executing shell code through a buffer overflow. strcpy will copy echo|set /p password=" + null terminator. Your arrays are not, so strcpy doesn't know when to stop. Then we can disassemble the “main” function by typing “disassemble main. Feb 15, 2015 · And indeed, as copying "hello" would take 6 bytes (5 plus a nul byte), the buffer is assumed to be too small. However I have a question, if buf, instead of being a char[] is a char pointer, would there be a buffer overflow as well? Dec 21, 2020 · This program takes input from the program argument and tries to store it into the buffer of size 5. Buffer overflow attacks have been one of the ways they do it. Plain old strcpy is prohibited in its use in our company's coding standard because of its potential for buffer overflows. This way I can prevent a buffer overflow as it will only copy as much as the destination can handle. c through a buffer overflow. If you don't know this in advance, you must call strlen() to find out, before calling strcpy(). It just trades one problem (buffer overflow) for another (non-null terminated strings). The library source code has a use of strcpy like this: for (int i = 0; i < newArgc; i++) {. Such conditions can lead to vulnerabilities to buffer overflow. 1-1) 8. Based on what I understand we need 3 parts: A nope sled; Shell Code to execute; Return address; The problem I'm having is in 64 bit linux the return address is something like 0x00007fffffffdcf2. root@kali:~/bof# gdb bof. Off by 1. Passing the size of your string to copy invalidates the whole use of the function. I have here a very VERY simple, standard BOF file to attack. ba za nz jy kw nv il mk il bt