dointisme/cve-2020-8597Démonstration de CVE-2020-8597 : un débordement de tampon dans le gestionnaire EAP de pppd, avec analyse d'exploit, discussion sur le contournement du canari de pile, et débogage de la carte mémoire pour la recherche en sécurité éducative.
eap.c dans pppd dans ppp 2.4.2 à 2.4.8 présente un débordement de tampon rhostname dans les fonctions eap_request et eap_response.
Si vous parvenez à obtenir "EAP: unauthenticated peer name" suffisamment long, il semble que mon client le limite à 255, vous pouvez provoquer un débordement de tampon.
Vous devez toujours contourner les canaris de pile, donc un crash est le plus probable.
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
Affecte ppp et pppoe (PPP over Ethernet)
Source (correctif) :
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]