dointisme/cve-2020-8597Demonstração de CVE-2020-8597: um buffer overflow no manipulador EAP do pppd, com análise de exploit, discussão de bypass de canário de pilha e depuração de mapa de memória para pesquisa educacional de segurança.
eap.c em pppd em ppp 2.4.2 até 2.4.8 tem um estouro de buffer de rhostname nas funções eap_request e eap_response.
Se você conseguir fazer com que "EAP: unauthenticated peer name" fique longo o suficiente, parece que meu cliente o limita a 255, você pode fazer um estouro de buffer.
Você ainda precisa superar os canários de pilha, então o crash é o mais provável.
RELRO STACK CANARY NX PIE RPATH RUNPATH Symbols FORTIFY Fortified Fortifiable FILE
Full RELRO Canary found NX enabled PIE enabled No RPATH No RUNPATH No Symbols Yes 12 22 /usr/sbin/pppd
Afeta ppp e pppoe (PPP sobre Ethernet)
Fonte (patch):
https://github.com/paulusmack/ppp/commit/8d7970b8f3db727fe798b65f3377fe6787575426
*** buffer overflow detected ***: pppd terminated
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x777e5)[0x7fea131337e5]
/lib/x86_64-linux-gnu/libc.so.6(__fortify_fail+0x5c)[0x7fea131d515c]
/lib/x86_64-linux-gnu/libc.so.6(+0x117160)[0x7fea131d3160]
pppd[0x42a858]
pppd(main+0x95f)[0x40981f]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0)[0x7fea130dc830]
pppd(_start+0x29)[0x409db9]
======= Memory map: ========
00400000-00448000 r-xp 00000000 fd:01 11540966 /usr/sbin/pppd
00648000-00649000 r--p 00048000 fd:01 11540966 /usr/sbin/pppd
00649000-0064f000 rw-p 00049000 fd:01 11540966 /usr/sbin/pppd
0064f000-0069b000 rw-p 00000000 00:00 0
01c7b000-01c9c000 rw-p 00000000 00:00 0 [heap]
7fea12666000-7fea1267c000 r-xp 00000000 fd:01 13898255 /lib/x86_64-linux-gnu/libgcc_s.so.1
7fea1267c000-7fea1287b000 ---p 00016000 fd:01 13898255 /lib/x86_64-linux-gnu/libgcc_s.so.1
7fea1287b000-7fea1287c000 rw-p 00015000 fd:01 13898255 /lib/x86_64-linux-gnu/libgcc_s.so.1
7fea1287c000-7fea12887000 r-xp 00000000 fd:01 13908799 /lib/x86_64-linux-gnu/libnss_files-2.23.so
7fea12887000-7fea12a86000 ---p 0000b000 fd:01 13908799 /lib/x86_64-linux-gnu/libnss_files-2.23.so
7fea12a86000-7fea12a87000 r--p 0000a000 fd:01 13908799 /lib/x86_64-linux-gnu/libnss_files-2.23.so
7fea12a87000-7fea12a88000 rw-p 0000b000 fd:01 13908799 /lib/x86_64-linux-gnu/libnss_files-2.23.so
7fea12a88000-7fea12a8e000 rw-p 00000000 00:00 0
7fea12a8e000-7fea12a99000 r-xp 00000000 fd:01 13908792 /lib/x86_64-linux-gnu/libnss_nis-2.23.so
7fea12a99000-7fea12c98000 ---p 0000b000 fd:01 13908792 /lib/x86_64-linux-gnu/libnss_nis-2.23.so
7fea12c98000-7fea12c99000 r--p 0000a000 fd:01 13908792 /lib/x86_64-linux-gnu/libnss_nis-2.23.so
7fea12c99000-7fea12c9a000 rw-p 0000b000 fd:01 13908792 /lib/x86_64-linux-gnu/libnss_nis-2.23.so
7fea12c9a000-7fea12cb0000 r-xp 00000000 fd:01 13908797 /lib/x86_64-linux-gnu/libnsl-2.23.so
7fea12cb0000-7fea12eaf000 ---p 00016000 fd:01 13908797 /lib/x86_64-linux-gnu/libnsl-2.23.so
7fea12eaf000-7fea12eb0000 r--p 00015000 fd:01 13908797 /lib/x86_64-linux-gnu/libnsl-2.23.so
7fea12eb0000-7fea12eb1000 rw-p 00016000 fd:01 13908797 /lib/x86_64-linux-gnu/libnsl-2.23.so
7fea12eb1000-7fea12eb3000 rw-p 00000000 00:00 0
7fea12eb3000-7fea12ebb000 r-xp 00000000 fd:01 13908803 /lib/x86_64-linux-gnu/libnss_compat-2.23.so
7fea12ebb000-7fea130ba000 ---p 00008000 fd:01 13908803 /lib/x86_64-linux-gnu/libnss_compat-2.23.so
7fea130ba000-7fea130bb000 r--p 00007000 fd:01 13908803 /lib/x86_64-linux-gnu/libnss_compat-2.23.so
7fea130bb000-7fea130bc000 rw-p 00008000 fd:01 13908803 /lib/x86_64-linux-gnu/libnss_compat-2.23.so
7fea130bc000-7fea1327c000 r-xp 00000000 fd:01 13908802 /lib/x86_64-linux-gnu/libc-2.23.so
7fea1327c000-7fea1347c000 ---p 001c0000 fd:01 13908802 /lib/x86_64-linux-gnu/libc-2.23.so
7fea1347c000-7fea13480000 r--p 001c0000 fd:01 13908802 /lib/x86_64-linux-gnu/libc-2.23.so
7fea13480000-7fea13482000 rw-p 001c4000 fd:01 13908802 /lib/x86_64-linux-gnu/libc-2.23.so
7fea13482000-7fea13486000 rw-p 00000000 00:00 0
7fea13486000-7fea13489000 r-xp 00000000 fd:01 13908787 /lib/x86_64-linux-gnu/libdl-2.23.so
7fea13489000-7fea13688000 ---p 00003000 fd:01 13908787 /lib/x86_64-linux-gnu/libdl-2.23.so
7fea13688000-7fea13689000 r--p 00002000 fd:01 13908787 /lib/x86_64-linux-gnu/libdl-2.23.so
7fea13689000-7fea1368a000 rw-p 00003000 fd:01 13908787 /lib/x86_64-linux-gnu/libdl-2.23.so
7fea1368a000-7fea1368c000 r-xp 00000000 fd:01 13908804 /lib/x86_64-linux-gnu/libutil-2.23.so
7fea1368c000-7fea1388b000 ---p 00002000 fd:01 13908804 /lib/x86_64-linux-gnu/libutil-2.23.so
7fea1388b000-7fea1388c000 r--p 00001000 fd:01 13908804 /lib/x86_64-linux-gnu/libutil-2.23.so
7fea1388c000-7fea1388d000 rw-p 00002000 fd:01 13908804 /lib/x86_64-linux-gnu/libutil-2.23.so
7fea1388d000-7fea13896000 r-xp 00000000 fd:01 13908796 /lib/x86_64-linux-gnu/libcrypt-2.23.so
7fea13896000-7fea13a95000 ---p 00009000 fd:01 13908796 /lib/x86_64-linux-gnu/libcrypt-2.23.so
7fea13a95000-7fea13a96000 r--p 00008000 fd:01 13908796 /lib/x86_64-linux-gnu/libcrypt-2.23.so
7fea13a96000-7fea13a97000 rw-p 00009000 fd:01 13908796 /lib/x86_64-linux-gnu/libcrypt-2.23.so
7fea13a97000-7fea13ac5000 rw-p 00000000 00:00 0
7fea13ac5000-7fea13aeb000 r-xp 00000000 fd:01 13908788 /lib/x86_64-linux-gnu/ld-2.23.so
7fea13cb5000-7fea13cba000 rw-p 00000000 00:00 0
7fea13ce5000-7fea13ce6000 rw-p 00000000 00:00 0
7fea13ce6000-7fea13cea000 rw-s 00000000 00:17 983 /run/pppd2.tdb
7fea13cea000-7fea13ceb000 r--p 00025000 fd:01 13908788 /lib/x86_64-linux-gnu/ld-2.23.so
7fea13ceb000-7fea13cec000 rw-p 00026000 fd:01 13908788 /lib/x86_64-linux-gnu/ld-2.23.so
7fea13cec000-7fea13ced000 rw-p 00000000 00:00 0
7ffc7c941000-7ffc7c962000 rw-p 00000000 00:00 0 [stack]
7ffc7c9b3000-7ffc7c9b6000 r--p 00000000 00:00 0 [vvar]
7ffc7c9b6000-7ffc7c9b8000 r-xp 00000000 00:00 0 [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]