AddressSanitizer: heap-buffer-overflow

[E4ck]

A heap-buffer-overflow in prelexer.hpp:69:14 in char const* Sass::Prelexer::skip_over_scopes<&(char const* Sass::Prelexer::exactly<(char)40>(char const*)), &(char const* Sass::Prelexer::exactly<(char)41>(char const*))>(char const*, char const*)

Compile and reproduce:
CC=afl-clang-fast CXX=afl-clang-fast++ AFL_USE_ASAN=1 make -C sassc -j4

ldd:

$ ldd sassc
	linux-vdso.so.1 =>  (0x00007fffc6365000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f731150d000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f7311204000)
	libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f7310e82000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f7310c65000)
	librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f7310a5d000)
	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f7310847000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f731047d000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f7311711000)

System information:
Linux ubuntu64 4.15.0-29-generic #31~16.04.1-Ubuntu SMP Wed Jul 18 08:54:04 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

Version: libsass-3.5.5、sassc-3.4.8

Poc: crash46.zip

Run: cat crash46 | ./sassc

ASAN:

=================================================================
==3349==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6040000048ba at pc 0x000000812255 bp 0x7fffe43bc350 sp 0x7fffe43bc348
READ of size 1 at 0x6040000048ba thread T0
    #0 0x812254 in char const* Sass::Prelexer::skip_over_scopes<&(char const* Sass::Prelexer::exactly<(char)40>(char const*)), &(char const* Sass::Prelexer::exactly<(char)41>(char const*))>(char const*, char const*) /home/eack/libsass/src/prelexer.hpp:69:14
    #1 0x812254 in char const* Sass::Prelexer::skip_over_scopes<&(char const* Sass::Prelexer::exactly<(char)40>(char const*)), &(char const* Sass::Prelexer::exactly<(char)41>(char const*))>(char const*) /home/eack/libsass/src/prelexer.hpp:122
    #2 0x812254 in char const* Sass::Parser::peek<&(char const* Sass::Prelexer::skip_over_scopes<&(char const* Sass::Prelexer::exactly<(char)40>(char const*)), &(char const* Sass::Prelexer::exactly<(char)41>(char const*))>(char const*))>(char const*) /home/eack/libsass/src/parser.hpp:136
    #3 0x812254 in Sass::Parser::parse_import() /home/eack/libsass/src/parser.cpp:349
    #4 0x7f6922 in Sass::Parser::parse_block_node(bool) /home/eack/libsass/src/parser.cpp:249:24
    #5 0x7eee86 in Sass::Parser::parse_block_nodes(bool) /home/eack/libsass/src/parser.cpp:197:11
    #6 0x7ea18f in Sass::Parser::parse() /home/eack/libsass/src/parser.cpp:123:5
    #7 0x611d5b in Sass::Context::register_resource(Sass::Include const&, Sass::Resource const&) /home/eack/libsass/src/context.cpp:324:24
    #8 0x62e930 in Sass::Data_Context::parse() /home/eack/libsass/src/context.cpp:636:5
    #9 0x5b9926 in Sass::sass_parse_block(Sass_Compiler*) /home/eack/libsass/src/sass_context.cpp:234:31
    #10 0x5b9926 in sass_compiler_parse /home/eack/libsass/src/sass_context.cpp:483
    #11 0x5b85c2 in sass_compile_context(Sass_Context*, Sass::Context*) /home/eack/libsass/src/sass_context.cpp:371:7
    #12 0x5b81ac in sass_compile_data_context /home/eack/libsass/src/sass_context.cpp:456:12
    #13 0x5a7069 in compile_stdin /home/eack/sassc/sassc.c:138:5
    #14 0x5a81ed in main /home/eack/sassc/sassc.c:375:18
    #15 0x7f84ef93182f in __libc_start_main /build/glibc-Cl5G7W/glibc-2.23/csu/../csu/libc-start.c:291
    #16 0x4aad88 in _start (/home/eack/sassc/bin/sassc+0x4aad88)

0x6040000048ba is located 0 bytes to the right of 42-byte region [0x604000004890,0x6040000048ba)
allocated by thread T0 here:
    #0 0x56f420 in realloc /home/eack/llvm-install/llvm-6.0.1.src/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:107
    #1 0x5a6f22 in compile_stdin /home/eack/sassc/sassc.c:112:25
    #2 0x5a81ed in main /home/eack/sassc/sassc.c:375:18
    #3 0x7f84ef93182f in __libc_start_main /build/glibc-Cl5G7W/glibc-2.23/csu/../csu/libc-start.c:291

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/eack/libsass/src/prelexer.hpp:69:14 in char const* Sass::Prelexer::skip_over_scopes<&(char const* Sass::Prelexer::exactly<(char)40>(char const*)), &(char const* Sass::Prelexer::exactly<(char)41>(char const*))>(char const*, char const*)
Shadow bytes around the buggy address:
  0x0c087fff88c0: fa fa 00 00 00 00 00 00 fa fa 00 00 00 00 00 00
  0x0c087fff88d0: fa fa 00 00 00 00 00 00 fa fa 00 00 00 00 00 00
  0x0c087fff88e0: fa fa 00 00 00 00 00 00 fa fa 00 00 00 00 00 00
  0x0c087fff88f0: fa fa 00 00 00 00 00 00 fa fa 00 00 00 00 00 00
  0x0c087fff8900: fa fa 00 00 00 00 00 00 fa fa 00 00 00 00 00 00
=>0x0c087fff8910: fa fa 00 00 00 00 00[02]fa fa 00 00 00 00 00 01
  0x0c087fff8920: fa fa fd fd fd fd fd fd fa fa fd fd fd fd fd fd
  0x0c087fff8930: fa fa fd fd fd fd fd fd fa fa fd fd fd fd fd fd
  0x0c087fff8940: fa fa fd fd fd fd fd fd fa fa fd fd fd fd fd fd
  0x0c087fff8950: fa fa fd fd fd fd fd fd fa fa 00 00 00 00 00 fa
  0x0c087fff8960: fa fa fd fd fd fd fd fd fa fa fd fd fd fd fd fd
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
==3349==ABORTING

[fgeek]

CVE-2019-6286 has been assigned for this vulnerability