While fuzzing opensips I discovered a heap buffer overflow under strlen function during a READ operation, indicating an attempt to read beyond the allocated buffer leading to code execution or denial of service under opnesips tested against commit "64c0042".
==263085==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60c0000000b8 at pc 0x0000004454f9 bp 0x7fffffffc6d0 sp 0x7fffffffbe90
READ of size 121 at 0x60c0000000b8 thread T0
#0 0x4454f8 in strlen (/opensips/opensips+0x4454f8)
#1 0x657d51 in __flatten_opensips_cfg /opensips/cfg_pp.c:371:15
#2 0x64df02 in flatten_opensips_cfg /opensips/cfg_pp.c:476:6
#3 0x64c986 in parse_opensips_cfg /opensips/cfg_pp.c:88:6
#4 0x802312 in main /opensips/main.c:707:13
#5 0x7ffff7c2e082 in __libc_start_main /build/glibc-e2p3jK/glibc-2.31/csu/../csu/libc-start.c:308:16
#6 0x4328cd in _start (/opensips/opensips+0x4328cd)
0x60c0000000b8 is located 0 bytes to the right of 120-byte region [0x60c000000040,0x60c0000000b8)
allocated by thread T0 here:
#0 0x4ab00d in malloc (/opensips/opensips+0x4ab00d)
#1 0x7ffff7c8d543 in getdelim /build/glibc-e2p3jK/glibc-2.31/libio/iogetdelim.c:62:27
SUMMARY: AddressSanitizer: heap-buffer-overflow (/opensips/opensips+0x4454f8) in strlen
Shadow bytes around the buggy address:
0x0c187fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c187fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c187fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c187fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c187fff8000: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
=>0x0c187fff8010: 00 00 00 00 00 00 00[fa]fa fa fa fa fa fa fa fa
0x0c187fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c187fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c187fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c187fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c187fff8060: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
Shadow gap: cc
==263085==ABORTING
Configuration file
#
# OpenSIPS residential configuration script
# by OpenSIPS Solutions <[email protected]>
#
# This script was generated via "make menuconfig", from
# the "Residential" scenario.
# You can enable / disable more features / functional#
# OpenSIPS residential configuration script
# by OpenSIPS Solutions <[email protected]>
#
# This script was generated via "make menuconfig", from
# the "Residential" scenarioelf("$rd")) {
append_hf("P-hine features / functionalities by
# re-generating the scenario with d‡fferent options.#
#
# Please refer to the Core CookBook at:
# https://opensips.org/Resources/DocsCookbooks
# for a exxxxxxxxxxxxxxxxxxxxplanation of possible statements, functions and parameters.
#<0x1a>
Commit refernece: 50b651c
File reference: (cfg_pp.c)
@@ -368,7 +368,7 @@ static int __flatten_opensips_cfg(FILE *cfg, const char *cfg_path,
goto out_err;
}
line_len = strlen(line);
line_len = 0;
break;
} else if (line_len == 0) {The above commit checks when getline() returns -1, the @lineptr argument is never safe to read, nor is this recommended. So when both rc == -1 and EOF conditions
occur, it is safe to assume we read 0 bytes, without doing the strlen().