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  • Illustration of buffer overflows for students (linux, C)

    - by osgx
    Hello My friend is teacher of first-year CS students. We want to show them buffer overflow exploitation. But modern distribs are protected from simples buffer overflows: HOME=`perl -e "print 'A'x269"` one_widely_used_utility_is_here --help on debian (blame it) Caught signal 11, on modern commercial redhat *** buffer overflow detected ***: /usr/bin/one_widely_used_utility_is_here terminated ======= Backtrace: ========= /lib/libc.so.6(__chk_fail+0x41)[0xc321c1] /lib/libc.so.6(__strcpy_chk+0x43)[0xc315e3] /usr/bin/one_widely_used_utility_is_here[0x805xxxc] /usr/bin/one_widely_used_utility_is_here[0x804xxxc] /lib/libc.so.6(__libc_start_main+0xdc)[0xb61e9c] /usr/bin/one_widely_used_utility_is_here[0x804xxx1] ======= Memory map: ======== 00336000-00341000 r-xp 00000000 08:02 2751047 /lib/libgcc_s-4.1.2-20080825.so.1 00341000-00342000 rwxp 0000a000 08:02 2751047 /lib/libgcc_s-4.1.2-20080825.so.1 008f3000-008f4000 r-xp 008f3000 00:00 0 [vdso] The same detector fails for more synthetic examples from the internet. How can we demonstrate buffer overflow with modern non-GPL distribs (there is no debian in classes) How can we DISABLE canary word checking in stack ? DISABLE checking variants of strcpy/strcat ? write an example (in plain C) with working buffer overrun ?

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  • Stack Overflow problem in a recursive program in C

    - by Adi
    Hi all, I am getting a stack overflow in one of the recursive functions i am running.. Here is the code.. void* buddyMalloc(int req_size) { // Do something here return buddy_findout(original_index,req_size); // This is the recursive call } void *buddy_findout(int current_index,int req_size) { char *selected = NULL; if(front!=NULL) { if(current_index==original_index) { // Do something here return selected; } else { // Do Something here return buddy_findout(current_index+1,req_size); } } else { return buddy_findout(current_index-1,req_size); } } Consider the initial value of index to be 4. and it first do index-1 till it reaches 0 index. and then it comes back to index 4 by incrementing..This is wht i want to implement. But it gives a stack overflow with memory map in the command prompt : Here is the output from my shell : * glibc detected * ./473_mem: free(): invalid pointer: 0x00c274c0 * ======= Backtrace: ========= /lib/tls/i686/cmov/libc.so.6[0xb50ff1] /lib/tls/i686/cmov/libc.so.6[0xb526f2] /lib/tls/i686/cmov/libc.so.6(cfree+0x6d)[0xb557cd] ./473_mem[0x8048b44] ./473_mem[0x8048b74] ./473_mem[0x8048b74] ./473_mem[0x8048944] ./473_mem[0x8048c87] ./473_mem[0x8048d31] ./473_mem[0x8048f79] /lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xe6)[0xafcb56] ./473_mem[0x8048671] ======= Memory map: ======== 0017c000-00198000 r-xp 00000000 08:01 5224 /lib/libgcc_s.so.1 00198000-00199000 r--p 0001b000 08:01 5224 /lib/libgcc_s.so.1 00199000-0019a000 rw-p 0001c000 08:01 5224 /lib/libgcc_s.so.1 00260000-00284000 r-xp 00000000 08:01 1927 /lib/tls/i686/cmov/libm-2.10.1.so 00284000-00285000 r--p 00023000 08:01 1927 /lib/tls/i686/cmov/libm-2.10.1.so 00285000-00286000 rw-p 00024000 08:01 1927 /lib/tls/i686/cmov/libm-2.10.1.so 006cd000-006e8000 r-xp 00000000 08:01 6662 /lib/ld-2.10.1.so 006e8000-006e9000 r--p 0001a000 08:01 6662 /lib/ld-2.10.1.so 006e9000-006ea000 rw-p 0001b000 08:01 6662 /lib/ld-2.10.1.so 00aa9000-00aaa000 r-xp 00000000 00:00 0 [vdso] 00ae6000-00c24000 r-xp 00000000 08:01 1900 /lib/tls/i686/cmov/libc-2.10.1.so 00c24000-00c25000 ---p 0013e000 08:01 1900 /lib/tls/i686/cmov/libc-2.10.1.so 00c25000-00c27000 r--p 0013e000 08:01 1900 /lib/tls/i686/cmov/libc-2.10.1.so 00c27000-00c28000 rw-p 00140000 08:01 1900 /lib/tls/i686/cmov/libc-2.10.1.so 00c28000-00c2b000 rw-p 00000000 00:00 0 08048000-0804a000 r-xp 00000000 00:14 2176 /media/windows-share/OS/Project2/473_mem 0804a000-0804b000 r--p 00001000 00:14 2176 /media/windows-share/OS/Project2/473_mem 0804b000-0804c000 rw-p 00002000 00:14 2176 /media/windows-share/OS/Project2/473_mem 08483000-084a4000 rw-p 00000000 00:00 0 [heap] b7600000-b7621000 rw-p 00000000 00:00 0 b7621000-b7700000 ---p 00000000 00:00 0 b7716000-b7819000 rw-p 00000000 00:00 0 b7827000-b782a000 rw-p 00000000 00:00 0 bfb96000-bfbab000 rw-p 00000000 00:00 0 [stack] Aborted Thanks in advance adi

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  • Creating a Stack Overflow notifier

    - by Trey
    I could not find a Stack Overflow notifier Android app so I am planning on making one. I hope that my app will serve a similar purpose as the Stack Overflow Notifier Chrome extension. This will be my first Android app so I am still unfamiliar with the platform. My main concern when creating this app is, what is the proper way to access the user's Recent Activity page? I thought of two different approaches but I'm not sure how to implement either one: Make the user login to Stack Overflow through the Browser application or an embedded browser and scrape their recent activity page occasionally for updates. Ask the user for their username and password and forward this information to Stack Overflow for authentication, storing cookies somehow to keep the session active. I think Astrid uses something similar to the first approach, but I haven't been able to figure it out yet from skimming their code. What is the correct way to handle a notification application like this that requires session management?

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  • What is the difference between a segmentation fault and a stack overflow?

    - by AruniRC
    For example when we call say, a recursive function, the successive calls are stored in the stack. However, due to an error if it goes on infinitely the error is 'Segmentation fault' (as seen on GCC). Shouldn't it have been 'stack-overflow'? What then is the basic difference between the two? Btw, an explanation would be more helpful than wikipedia links (gone through that, but no answer to specific query).

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  • View Latest Comments Made

    - by Abs
    Hello all, I hope I can give feedback like this. It may be just me and others may have already suggested this but is there a way to view our recent comments in our account profiles? I mean I can see questions asked, questions answered etc. But there are loads of questions where I add a comment to the question asker and when I leave the site, I either have to remember what the question was to go back and check if anyone has posted anything. Simply, I think having a place where we can view our latest comments if not all our comments in the control panel/user area would be great! Thanks all

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  • Stack Overflow on Marshal.PtrToStructure reading wmv files

    - by Nick Udell
    Hi, I'm using a frame grabber class in order to capture and process each frame in a video. The class can be found here: http://www.codeproject.com/KB/graphics/FrameGrabber.aspx I'm having issues with running it, however. When loading the file, it attempts to marshal a video format pointer into a VideoInfoHeader (I'm using DirectShow.Net). The code that does this is as follows: videoInfo = (VideoInfoHeader)Marshal.PtrToStructure(mediaType.formatPtr, typeof(VideoInfoHeader)); When I run this it immediately crashes out of the debugging environment, probably with a stack overflow. When stepping through I can see that the formatPtr always equals 93, though I do not know what to make of this as I am fairly new to marshalling. I have checked that the video runs fine in Windows Media Player. This is essential in finding the dimensions of the video and also the size of the header, which needs to be skipped before the frames can be read. I am running Windows 7 x64. Any help on this would be much appreciated, I must've tried fifteen different frame grabbing techniques.

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  • [Java] Flood fill using a stack

    - by dafero
    Hello to everyone :), I am using the recursive Flood fill algorithm in Java to fill some areas of a image. With very small images it works fine, but when de image becomes larger the JVM gives me a Stack Over Flow Error. That's the reason why I have to reimplement the method using a Flood Fill with my own stack. (I read that's the best way to do it in these kind of cases) Can anyone explain me how to code it? (if you don't have the code at hand, with the pseudo-code of the algorithm will be fine) I've read a lot in the Internet but I haven't understood it very well. Thanks!

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  • Grails - Recursive computing call "StackOverflowError" and don't update on show

    - by Kedare
    Hello, I have a little problem, I have made a Category domain on Grails, but I want to "cache" the string representation on the database by generating it when the representation field is empty or NULL (to avoid recursive queries at each toString), here is the code : package devkedare class Category { String title; String description; String representation; Date dateCreated; Date lastUpdate; Category parent; static constraints = { title(blank:false, nullable:false, size:2..100); description(blank:true, nullable:false); dateCreated(nullable:true); lastUpdate(nullable:true); autoTimestamp: true; } static hasMany = [childs:Category] @Override String toString() { if((!this.representation) || (this.representation == "")) { this.computeRepresentation(true) } return this.representation; } String computeRepresentation(boolean updateChilds) { if(updateChilds) { for(child in this.childs) { child.representation = child.computeRepresentation(true); } } if(this.parent) { this.representation = "${this.parent.computeRepresentation(false)}/${this.title}"; } else { this.representation = this.title } return this.representation; } void beforeUpdate() { this.computeRepresentation(true); } } There is 2 problems : It don't update the representation when the representation if NULL or empty and toString id called, it only update it on save, how to fix that ? On some category, updating it throw a StackOverflowError, here is an example of my actual category table as CSV : Uploaded the csv file here, pasting csv looks buggy: http://kedare.free.fr/Dist/01.csv Updating the representation works everywhere except on "IT" that throw a StackOverlowError (this is the only category that has many childs). Any idea of how can I fix those 2 problems ? Thank you !

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  • Stack overflow error after creating a instance using 'new'

    - by Justin
    EDIT - The code looks strange here, so I suggest viewing the files directly in the link given. While working on my engine, I came across a issue that I'm unable to resolve. Hoping to fix this without any heavy modification, the code is below. void Block::DoCollision(GameObject* obj){ obj->DoCollision(this); } That is where the stack overflow occurs. This application works perfectly fine until I create two instances of the class using the new keyword. If I only had 1 instance of the class, it worked fine. Block* a = new Block(0, 0, 0, 5); AddGameObject(a); a = new Block(30, 0, 0, 5); AddGameObject(a); Those parameters are just x,y,z and size. The code is checked before hand. Only a object with a matching Collisonflag and collision type will trigger the DoCollision(); function. ((*list1)->m_collisionFlag & (*list2)->m_type) Maybe my check is messed up though. I attached the files concerned here http://celestialcoding.com/index.php?topic=1465.msg9913;topicseen#new. You can download them without having to sign up. The main suspects, I also pasted the code for below. From GameManager.cpp void GameManager::Update(float dt){ GameList::iterator list1; for(list1=m_gameObjectList.begin(); list1 != m_gameObjectList.end(); ++list1){ GameObject* temp = *list1; // Update logic and positions if((*list1)->m_active){ (*list1)->Update(dt); // Clip((*list1)->m_position); // Modify for bounce affect } else continue; // Check for collisions if((*list1)->m_collisionFlag != GameObject::TYPE_NONE){ GameList::iterator list2; for(list2=m_gameObjectList.begin(); list2 != m_gameObjectList.end(); ++list2){ if(!(*list2)->m_active) continue; if(list1 == list2) continue; if( (*list2)->m_active && ((*list1)->m_collisionFlag & (*list2)->m_type) && (*list1)->IsColliding(*list2)){ (*list1)->DoCollision((*list2)); } } } if(list1==m_gameObjectList.end()) break; } GameList::iterator end    = m_gameObjectList.end(); GameList::iterator newEnd = remove_if(m_gameObjectList.begin(),m_gameObjectList.end(),RemoveNotActive); if(newEnd != end)        m_gameObjectList.erase(newEnd,end); } void GameManager::LoadAllFiles(){ LoadSkin(m_gameTextureList, "Models/Skybox/Images/Top.bmp", GetNextFreeID()); LoadSkin(m_gameTextureList, "Models/Skybox/Images/Right.bmp", GetNextFreeID()); LoadSkin(m_gameTextureList, "Models/Skybox/Images/Back.bmp", GetNextFreeID()); LoadSkin(m_gameTextureList, "Models/Skybox/Images/Left.bmp", GetNextFreeID()); LoadSkin(m_gameTextureList, "Models/Skybox/Images/Front.bmp", GetNextFreeID()); LoadSkin(m_gameTextureList, "Models/Skybox/Images/Bottom.bmp", GetNextFreeID()); LoadSkin(m_gameTextureList, "Terrain/Textures/Terrain1.bmp", GetNextFreeID()); LoadSkin(m_gameTextureList, "Terrain/Textures/Terrain2.bmp", GetNextFreeID()); LoadSkin(m_gameTextureList, "Terrain/Details/TerrainDetails.bmp", GetNextFreeID()); LoadSkin(m_gameTextureList, "Terrain/Textures/Water1.bmp", GetNextFreeID()); Block* a = new Block(0, 0, 0, 5); AddGameObject(a); a = new Block(30, 0, 0, 5); AddGameObject(a); Player* d = new Player(0, 100,0); AddGameObject(d); } void Block::Draw(){ glPushMatrix(); glTranslatef(m_position.x(), m_position.y(), m_position.z()); glRotatef(m_facingAngle, 0, 1, 0); glScalef(m_size, m_size, m_size); glBegin(GL_LINES); glColor3f(255, 255, 255); glVertex3f(m_boundingRect.left, m_boundingRect.top, m_position.z()); glVertex3f(m_boundingRect.right, m_boundingRect.top, m_position.z()); glVertex3f(m_boundingRect.left, m_boundingRect.bottom, m_position.z()); glVertex3f(m_boundingRect.right, m_boundingRect.bottom, m_position.z()); glVertex3f(m_boundingRect.left, m_boundingRect.top, m_position.z()); glVertex3f(m_boundingRect.left, m_boundingRect.bottom, m_position.z()); glVertex3f(m_boundingRect.right, m_boundingRect.top, m_position.z()); glVertex3f(m_boundingRect.right, m_boundingRect.bottom, m_position.z()); glEnd(); // DrawBox(m_position.x(), m_position.y(), m_position.z(), m_size, m_size, m_size, 8); glPopMatrix(); } void Block::DoCollision(GameObject* obj){ GameObject* t = this;   // I modified this to see for sure that it was causing the mistake. // obj->DoCollision(NULL); // Just revert it back to /* void Block::DoCollision(GameObject* obj){     obj->DoCollision(this);   }   */ }

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  • Stack Overflow Exploit in C

    - by Fernando Gonzalez
    Hey there guys, the question is actually about stack overflows in C. I have an assigment that I can not get done for the life of me, i've looked at everything in the gdb and I just cant figure it. The question is the following: int i,n; void confused() { printf("who called me"); exit(0); } void shell_call(char *c) { printf(" ***Now calling \"%s\" shell command *** \n",c); system(c); exit(0); } void victim_func() { int a[4]; printf("[8]:%x\n", &a[8]); printf("Enter n: "); scanf("%d",&n); printf("Enter %d HEX Values \n",n); for(i=0;i<n;i++) scanf("%x",&a[i]); printf("Done reading junk numbers\n"); } int main() { printf("ls=736c --- ps = 7370 --- cal = 6c6163\n"); printf("location of confused %x \n", confused); printf("location of shell_call %x \n", shell_call); victim_func(); printf("Done, thank you\n"); } Ok, so I managed to get the first question correctly, which is to arbitrarily call one of the two functions not explicitly called in the main path. By the way, this has to be done while running the program without any modifications. I did this by running the program, setting N to 7, which gets me to the Function Pointer of the victim_func frame, I write a[7] with the memory address of confused or shell_call, and it works. (I have a 64 bit machine, thats why I have to get it to 7, since the EBI pointer is 2 ints wide, instead of 1) My question is the following, how could I control which argument gets passed to the shell_code funcion? ie. how do i write a string to char* c. The whole point is executing unix commands like "ps" etc, by running only the program. I figured writing the EBI pointer with the hex representation of "ps" and setting the arg list of shell_call to that, but that didn't work. I also tried inputing argsv arguments and setting the arg list of shell_call to the arg_list of main, but didnt work either. I think the second version should work, but i believe im not setting the arg list of the new stack frame correctly ( I did it by writing a[8] to 0, since its the first part of the functin pointer, and writing a[9]=736c and a[10]=0000, but its probably not right since those are the parameters of victim_func. So how do i access the parameters of shell_call?

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  • Can I post a guide on SO as a question?

    - by Sahat
    I want to post a guide or a collection of learning resources on how to get started with developing for Windows Phone 7. Is it okay to start a guide by clicking ASK QUESTION button even though it's not really a question? Will I get down-ranked for that?

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  • Authenticating stackoveflow programatically - OpenID

    - by Ben Reeves
    I would like to add up and down voting to my iPhone appilcation - MyStacks, for this I need the to be able to authenticate the user with SO. I'm look at adapting the Twitter-OAuth-iPhone library. However The problem I have is obtaining the consumer and secret key. to use OAuth, do I need to obtain a different key for each provider? In order to obtain a consumer key from google the application needs to have a domain name, but this being an iPhone app of course i don't have one, does this mean that I can't use OAuth? Is there any other way to programatically authenticate SO? Thanks, Ben

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  • stack overflow problem in program

    - by Jay
    So I am currently getting a strange stack overflow exception when i try to run this program, which reads numbers from a list in a data/text file and inserts it into a binary search tree. The weird thing is that when the program works when I have a list of 4095 numbers in random order. However when i have a list of 4095 numbers in increasing order (so it makes a linear search tree), it throws a stack overflow message. The problem is not the static count variable because even when i removed it, and put t=new BinaryNode(x,1) it still gave a stack overflow exception. I tried debugging it, and it broke at if (t == NULL){ t = new BinaryNode(x,count); Here is the insert function. BinaryNode *BinarySearchTree::insert(int x, BinaryNode *t) { static long count=0; count++; if (t == NULL){ t = new BinaryNode(x,count); count=0; } else if (x < t->key){ t->left = insert(x, t->left); } else if (x > t->key){ t->right = insert(x, t->right); } else throw DuplicateItem(); return t; }

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  • Should a Stack have a maximum size?

    - by Sotirios Delimanolis
    I'm practicing my knowledge of ADTs by implementing some data structures, even if most already exist. With Stacks, a lot of books and other documentation I've read talk about the stack throwing an error when you try to add an element but the stack is full. In a java implementation (or any other), should I specifically keep track of a maximum stack size (from constructor), check to see if that size is reached, and throw an overflow exception if it is? Or is not such a big deal?

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  • Stack Overflow when debugging application in iPhone simulator

    - by mjdth
    I'm getting this every time I attempt to debug my app in the simulator: [Session started at 2010-05-11 16:16:52 -0500.] GNU gdb 6.3.50-20050815 (Apple version gdb-1467) (Wed Apr 21 06:57:21 UTC 2010) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "x86_64-apple-darwin".sharedlibrary apply-load-rules all Attaching to process 51573. Program received signal: “EXC_BAD_ACCESS”. Data Formatters temporarily unavailable, will re-try after a 'continue'. (Cannot call into the loader at present, it is locked.) I've looked around and found a few similar cases, but they all seem to be related to a missing file and an extra necessary build phase. I'm getting no notification of a missing file here so I'm not sure where to start to fix this and get the app running again. Thanks for any insight!

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  • StackOverflowError being caused by a TableModelListener

    - by me_here
    I'm not sure why this is recursing. jTable1.getModel().addTableModelListener(new TableModelListener() { public void tableChanged(TableModelEvent evt) { int sum = 0; int i=0; for (i =0 ; i<2; i++){ sum = sum + Integer.parseInt(jTable1.getValueAt(0, i).toString()); } jTable1.setValueAt(sum, 0, 2); } }); The exception is: (it keeps repeating) Exception in thread "AWT-EventQueue-0" java.lang.StackOverflowError at javax.swing.table.DefaultTableColumnModel.getColumn(DefaultTableColumnModel.java:277) at javax.swing.JTable.convertColumnIndexToModel(JTable.java:2553) at javax.swing.JTable.getValueAt(JTable.java:2695) at testprogram.guitest.TestTableModel$1.tableChanged(TestTableModel.java:63) at javax.swing.table.AbstractTableModel.fireTableChanged(AbstractTableModel.java:280) at javax.swing.table.AbstractTableModel.fireTableCellUpdated(AbstractTableModel.java:259) at javax.swing.table.DefaultTableModel.setValueAt(DefaultTableModel.java:650) at javax.swing.JTable.setValueAt(JTable.java:2719) Any help appreciated.

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  • NHibernate ManyToMany Relationship Cascading AllDeleteOrphan StackOverflowException

    - by Chris
    I have two objects that have a ManyToMany relationship with one another through a mapping table. Though, when I try to save it, I get a stack overflow exception. The following is the code for the mappings: //EventMapping.cs HasManyToMany(x => x.Performers).Table("EventPerformer").Inverse().Cascade.AllDeleteOrphan().LazyLoad().ParentKeyColumn("EventId").ChildKeyColumn("PerformerId"); //PerformerMapping.cs HasManyToMany<Event>(x => x.Events).Table("EventPerformer").Inverse().Cascade.AllDeleteOrphan().LazyLoad().ParentKeyColumn("PerformerId").ChildKeyColumn("EventId"); When I change the performermapping.cs to Cascade.None() I get rid of the exception but then my Event Object doesn't have the performer I associate with it. //In a unit test, paraphrased event.Performers.Add(performer); //Event eventRepository.Save<Event>(event); eventResult = eventRepository.GetById<Event>(event.id); //Event eventResult.Performers[0]; //is null, should have performer in it How should I be writing this properly? Thanks

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  • Webservice creates Stack Overflow

    - by mouthpiec
    I have an application that when executed as a windows application works fine, but when converted to a webservice, in some instances (which were tested successfully) by the windows app) creates a stack overflow. Do you have an idea of what can cause this? (Note that it works fine when the web service is placed on the localhost). Could it be that the stack size of a Web Service is smaller than that of a Window Application? UPDATE The below is the code in which I am getting a stack overflow error private bool CheckifPixelsNeighbour(Pixel c1, Pixel c2, int DistanceAllowed) { bool Neighbour = false; if ((Math.Abs(c1.X - c2.X) <= DistanceAllowed) && Math.Abs(c1.Y - c2.Y) <= DistanceAllowed) { Neighbour = true; } return Neighbour; }

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