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It only takes a minute to sign up. I want to find out the base address and the imagesize of the program being debugged in gdb. As in, where it got loaded in memory. For shared libraries I can do "info sharedlibrary" and I get very nice output like so:. Background: I am using gdb's mi, and I can keep a basic overview of where things are by parsing sharedlibrary-load messages. But it never sends such a message for the main program, which is the most important thing.

You'll see something like this it's a result of a process named opt which I am debugging just now :. Sign up to join this community.

The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Find base address and memory size of program debugged in gdb Ask Question. Asked 1 year, 6 months ago. Active 8 months ago.

info address command

Viewed 7k times. Active Oldest Votes. If I understand your question correctly the line 8 r-x-- opt is what you need.

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I get that gdb isnt a rce tool, but it really bothers me that basic stuff like finding where your target is loaded in memory is so hard to come by. Another example is the starti command thatwas only added very recently. Anyways, thanks for solving this.

Entry point: 0x 0x - 0x is. ABI-tag 0x - 0x is.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Information Security Stack Exchange is a question and answer site for information security professionals. It only takes a minute to sign up. I have never worked with BoF before, and after reading lots of similar questions, posts, etc.

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I have this information correct me if it's wrong :. And here is where I don't know what to do. I have been reading gdb tutorials, but still nothing.

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Refer this blog. When the program pause on the breakpoint, you can search the environment address following command. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Finding environment variables with gdb, to exploit a buffer overflow Ask Question.

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Asked 8 years ago. Active 2 years, 11 months ago. Viewed 37k times. Gilles 'SO- stop being evil' Palantir Palantir 2 2 gold badges 2 2 silver badges 7 7 bronze badges. Active Oldest Votes. That's it!! I get "Cannot access memory at address Possible memory-read protection in RHEL 6 systems?? Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. The Overflow How many jobs can be done at home?

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The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I want to find the address of a string in memory.

Its an initialized variable, so its in the. So what do I do in GDB to find out its memory address? And I do not know the name of the variable its stored in. Use the find command. Search memory for the sequence of bytes specified by val1, val2, etc.

They may be specified in either order, apart or together. All values are interpreted in the current language. This is useful when one wants to specify the search pattern as a mixture of types. The default is to print all finds. You can use strings as search values. Quote them with double-quotes ". The string value is copied into the search pattern byte by byte, regardless of the endianness of the target and the size specification. Learn more.

How to find the address of a string in memory using GDB? Ask Question. Asked 8 years, 9 months ago. Active 1 year, 5 months ago. Viewed 36k times. Very related. Many "duplicate answers", different question. Active Oldest Votes. Using info proc map sounds like a better approach to me. Reza Hashemi Reza Hashemi 1, 11 11 silver badges 12 12 bronze badges. Karim Manaouil Karim Manaouil 5 5 silver badges 17 17 bronze badges.

You can refer to sourceware.The commands described in this chapter allow you to inquire about the symbols names of variables, functions and types defined in your program.

This information is inherent in the text of your program and does not change as your program executes. Occasionally, you may need to refer to symbols that contain unusual characters, which GDB ordinarily treats as word delimiters. The most frequent case is in referring to static variables in other source files see Program Variables.

File names are recorded in object files as debugging symbols, but GDB would ordinarily parse a typical file name, like foo. Normally, when GDB looks up symbols, it matches their names with case sensitivity determined by the current source language.

Occasionally, you may wish to control that. The command set case-sensitive lets you do that by specifying on for case-sensitive matches or off for case-insensitive ones. If you specify autocase sensitivity is reset to the default suitable for the source language. The default is case-sensitive matches for all languages except for Fortran, for which the default is case-insensitive matches.

Normally, when GDB prints a class, it displays any methods declared in that class. You can control this behavior either by passing the appropriate flag to ptypeor using set print type methods. Specifying on will cause GDB to display the methods; this is the default.

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Specifying off will cause GDB to omit the methods. Set the limit of displayed nested types that the type printer will show. A limit of unlimited or -1 will show all nested definitions. By default, the type printer will not show any nested types defined in classes. Normally, when GDB prints a class, it displays any typedefs defined in that class.

You can control this behavior either by passing the appropriate flag to ptypeor using set print type typedefs. Specifying on will cause GDB to display the typedef definitions; this is the default. Specifying off will cause GDB to omit the typedef definitions.

Note that this controls whether the typedef definition itself is printed, not whether typedef names are substituted when printing other types. Describe where the data for symbol is stored. For a register variable, this says which register it is kept in. For a non-register local variable, this prints the stack-frame offset at which the variable is always stored.

Print the name of a symbol which is stored at the address addr. If no symbol is stored exactly at addrGDB prints the nearest symbol and an offset from it:.

How to examine memory in GDB

This is the opposite of the info address command. You can use it to find out the name of a variable or a function given its address. For dynamically linked executables, the name of executable or shared library containing the symbol is also printed:. Demangle name. If language is provided it is the name of the language to demangle name in. Otherwise name is demangled in the current language.The precise semantics of threads differ from one operating system to another, but in general the threads of a single program are akin to multiple processes—except that they share one address space that is, they can all examine and modify the same variables.

On the other hand, each thread has its own registers and execution stack, and perhaps private memory. The GDB thread debugging facility allows you to observe all threads while your program runs—but whenever GDB takes control, one thread in particular is always the focus of debugging. This thread is called the current thread.

Debugging commands show program information from the perspective of the current thread. For debugging purposes, GDB associates its own thread number —always a single integer—with each thread of an inferior. This number is unique between all threads of an inferior, but not unique between threads of different inferiors. You can refer to a given thread in an inferior using the qualified inferior-num. For example, thread 2. If you omit inferior-num e. Until you create a second inferior, GDB does not show the inferior-num part of thread IDs, even though you can always use the full inferior-num.

Some commands accept a space-separated thread ID list as argument.

gdb find address

A list element can be:. For example, if the current inferior is 1, and inferior 7 has one thread with ID 7. In addition to a per-inferior number, each thread is also assigned a unique global number, also known as global thread IDa single integer. You may find this useful in writing breakpoint conditional expressions, command scripts, and so forth. See Convenience Variablesfor general information on convenience variables. If GDB detects the program is multi-threaded, it augments the usual message about stopping at a breakpoint with the ID and name of the thread that hit the breakpoint.

Display information about one or more threads. With no arguments displays information about all threads. You can specify the list of threads that you want to display using the thread ID list syntax see thread ID lists. Otherwise, only thread-num is shown. Make thread ID thread-id the current thread. GDB responds by displaying the system identifier of the thread you selected, and its current stack frame summary:.

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The thread apply command allows you to apply the named command to one or more threads. Specify the threads that you want affected using the thread ID list syntax see thread ID listsor specify all to apply to all threads.

To apply a command to all threads in descending order, type thread apply all command. To apply a command to all threads in ascending order, type thread apply all -ascending command. The flag arguments control what output to produce and how to handle errors raised when applying command to a thread.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

Reverse Engineering Stack Exchange is a question and answer site for researchers and developers who explore the principles of a system through analysis of its structure, function, and operation.

It only takes a minute to sign up. What's the right way of deducing the return address? I've tried ESP - len shellcode but this doesn't seem to work. Nothing easier than that. So, if your shellcode starts at byte 0 of the buffer, you want to overwrite the saved EIP on the stack with 0xbffff In fact, to make your exploit independent from small changes in the program one more local variable, or one less This still leaves you with 32 bytes for the shellcode, which should be plenty.

Then, jump to 0xbffff which is 16 bytes into the nops, and shifting them around by a few bytes won't hurt you anymore. At the end, instead of calculating how many bytes between the end of the buffer and the saved EIPi'd just repeat the buffer address a few times, so you can be sure EIP gets overwritten; you don't really care about whatever else is there.

Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Problem finding return address for shellcode Ask Question.

Asked 5 years ago. Active 5 years ago. Viewed 12k times. How do you go about calculating the right return address the more precise the better? GDB related examples appreciated. This question might be better asked at security. Active Oldest Votes. So to sum it up, your input should be 0x90 32 times your shellcode as many 0x90's as you need to fill the buffer to 64 bytes 0x48 0xf8 0xff 0xbf repeated about 10 times.

Remember to swap the EIP bytes because we're on a little endian machine. Guntram Blohm How to make sure that each time you run program, you have the same return address? Does it change with each execution of program? Sign up or log in Sign up using Google. Sign up using Facebook.

gdb find address

Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog.

The Overflow How many jobs can be done at home? Featured on Meta. Community and Moderator guidelines for escalating issues via new response….By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Information Security Stack Exchange is a question and answer site for information security professionals. It only takes a minute to sign up. Please correct me if I'm wrong about the way I found the addresses, and I'd love to get help with finding the string's address :.

If they are different, your executable is probably running under ASLR. In order to find the base address of the executable module at runtime you can use use gdb or any other debugger and search for the entry point of the executable or just search for your string after the executable is loaded into memory Basically any program that will load your executable to memory and allow you to view the memory will do.

The address of an executable under linux is usually 0x for 64 bit executables and 0x for 32 bit executables as defined by the gnu linker.

Debugging using gdb: Find a segFault

But there's nothing stopping someone from changing the entry point to a different address. After you've figured out the memory mappings, you'll need to find gadgets in the code, I'll leave that for you to research Perhaps you can find more answers by looking at exercises at exploit-exercises. Here are two methods: 1.

Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Asked 2 years, 7 months ago. Active 9 days ago. Viewed 16k times. I was struggling with finding the address of "sh" in the fflush command in the program.

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Please correct me if I'm wrong about the way I found the addresses, and I'd love to get help with finding the string's address : Thank you in advance! Jonathan Jonathan 33 1 1 gold badge 2 2 silver badges 7 7 bronze badges. Are you still lost? Then go practice the Corelan tutorials.

gdb find address

This sounds more suited for Reverse Engineering Stack Exchangethough. Active Oldest Votes. When using "info proc mappings" I get 3 different addresses for libc, which one is the actual one? Heres a screenshot of the 3 libc addresses I get : prntscr.

Thank you lightnet for the help! Adding this technique to your solution since yours was useful! Arav Garg Arav Garg 21 1 1 bronze badge. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. The Overflow How many jobs can be done at home?

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