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authorVadim Yanitskiy <axilirator@gmail.com>2019-07-27 23:57:12 +0700
committerVadim Yanitskiy <axilirator@gmail.com>2019-07-30 17:17:15 +0000
commit757dea8d4abf611f40f39a128a970f8a6cb3c547 (patch)
parent74b6ff074b421c52e11fad0733ca9490eddc42dd (diff)
vty/vty.c: fix vty_read(): prevent further heap-buffer overrun
After reading data from the socket, assigned to a given VTY, we need to '\0'-terminate the received string. Otherwise, further access to that string, stored in a heap buffer vty->buf, would lead to a heap overrun. == How to reproduce? $ python -c "print 'A' * 512" | telnet $HOST $PORT ==21264==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6190000211e0 at pc 0x000000435d2f bp 0x7ffc06c7add0 sp 0x7ffc06c7a578 READ of size 1025 at 0x6190000211e0 thread T0 #0 0x435d2e in __interceptor_strlen (/usr/local/bin/osmo-msc+0x435d2e) #1 0x7fb95bfa5624 in talloc_strdup (/usr/lib/x86_64-linux-gnu/libtalloc.so.2+0x6624) #2 0x7fb95c1be2bc in vty_hist_add /opt/osmocom/libosmocore/src/vty/vty.c:578 #3 0x7fb95c1be2bc in vty_execute /opt/osmocom/libosmocore/src/vty/vty.c:703 #4 0x7fb95c1be2bc in vty_read /opt/osmocom/libosmocore/src/vty/vty.c:1425 #5 0x7fb95c1bfd78 in client_data /opt/osmocom/libosmocore/src/vty/telnet_interface.c:157 #6 0x7fb95b90bd33 in osmo_fd_disp_fds /opt/osmocom/libosmocore/src/select.c:223 #7 0x7fb95b90bd33 in osmo_select_main /opt/osmocom/libosmocore/src/select.c:263 #8 0x5006cc in main /opt/osmocom/osmo-msc/src/osmo-msc/msc_main.c:723:3 #9 0x7fb959935f44 in __libc_start_main /build/eglibc-xkFqqE/eglibc-2.19/csu/libc-start.c:287 #10 0x4226fb in _start (/usr/local/bin/osmo-msc+0x4226fb) == Why exactly 512? Because the initial size of the heap buffer is 512 (see VTY_BUFSIZ). Later on it can be realloc()ated, so X > 512 should also work. Found using AddressSanitizer and Radamsa [1] fuzzer. [1] https://gitlab.com/akihe/radamsa Change-Id: I82f774ad18d0e555eb8f3590a519946d9c583c78
1 files changed, 2 insertions, 0 deletions
diff --git a/src/vty/vty.c b/src/vty/vty.c
index 98b332d6..b1bb3f49 100644
--- a/src/vty/vty.c
+++ b/src/vty/vty.c
@@ -1416,6 +1416,8 @@ int vty_read(struct vty *vty)
case '\n':
case '\r':
vty_out(vty, "%s", VTY_NEWLINE);
+ /* '\0'-terminate the command buffer */
+ vty->buf[vty->length] = '\0';
case '\t':