Fix multiple bugs with shell detection:
1. We weren't correctly extracting the argument to be passed to
readlink. We needed to take the null terminator into account, as we
extract this string from memory.
2. readlink does **not** null terminate the output. Fix this.
3. `binary_name.compare(0, 2, "sh")` for detecting if the binary is "sh"
was too liberal, and included "shell_injection_poc_fuzzer" because the
prefix matched.
Also reduce some very noisy debug logging.
cc @oliverchang @Alan32Liu after #9100 and #8448
After compiling locally, I can see that
`./SystemSan ./target_dns -dict=vuln.dict`
crashes in a few seconds with
```
===BUG DETECTED: Arbitrary domain name resolution===
===Domain resolved: .f.z===
===DNS request type: 0, class: 256===
==315== ERROR: libFuzzer: deadly signal
#0 0x539131 in __sanitizer_print_stack_trace /src/llvm-project/compiler-rt/lib/asan/asan_stack.cpp:87:3
#1 0x457c48 in fuzzer::PrintStackTrace() /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerUtil.cpp:210:5
#2 0x43c923 in fuzzer::Fuzzer::CrashCallback() /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:233:3
#3 0x7fa57940041f (/lib/x86_64-linux-gnu/libpthread.so.0+0x1441f) (BuildId: 7b4536f41cdaa5888408e82d0836e33dcf436466)
#4 0x7fa5793ff7db in send (/lib/x86_64-linux-gnu/libpthread.so.0+0x137db) (BuildId: 7b4536f41cdaa5888408e82d0836e33dcf436466)
#5 0x503ba4 in __interceptor_send /src/llvm-project/compiler-rt/lib/asan/../sanitizer_common/sanitizer_common_interceptors.inc:6802:17
#6 0x7fa578abf462 (/lib/x86_64-linux-gnu/libresolv.so.2+0xb462) (BuildId: 4519041bde5b859c55798ac0745b0b6199cb7d94)
#7 0x7fa578abbc43 in __res_context_query (/lib/x86_64-linux-gnu/libresolv.so.2+0x7c43) (BuildId: 4519041bde5b859c55798ac0745b0b6199cb7d94)
#8 0x7fa578abc8ed in __res_context_search (/lib/x86_64-linux-gnu/libresolv.so.2+0x88ed) (BuildId: 4519041bde5b859c55798ac0745b0b6199cb7d94)
#9 0x7fa578ad2cc1 (/lib/x86_64-linux-gnu/libnss_dns.so.2+0x2cc1) (BuildId: 3fac4ec397ba8e8938fe298f103113f315465130)
#10 0x7fa578ad2e8b in _nss_dns_gethostbyname3_r (/lib/x86_64-linux-gnu/libnss_dns.so.2+0x2e8b) (BuildId: 3fac4ec397ba8e8938fe298f103113f315465130)
#11 0x7fa578ad2f41 in _nss_dns_gethostbyname2_r (/lib/x86_64-linux-gnu/libnss_dns.so.2+0x2f41) (BuildId: 3fac4ec397ba8e8938fe298f103113f315465130)
#12 0x7fa5792fdc9d in gethostbyname2_r (/lib/x86_64-linux-gnu/libc.so.6+0x130c9d) (BuildId: 1878e6b475720c7c51969e69ab2d276fae6d1dee)
#13 0x7fa5792d179e (/lib/x86_64-linux-gnu/libc.so.6+0x10479e) (BuildId: 1878e6b475720c7c51969e69ab2d276fae6d1dee)
#14 0x7fa5792d2f58 in getaddrinfo (/lib/x86_64-linux-gnu/libc.so.6+0x105f58) (BuildId: 1878e6b475720c7c51969e69ab2d276fae6d1dee)
#15 0x4d93ac in getaddrinfo /src/llvm-project/compiler-rt/lib/asan/../sanitizer_common/sanitizer_common_interceptors.inc:2667:13
#16 0x56c8d9 in LLVMFuzzerTestOneInput /out/SystemSan/target_dns.cpp:35:11
#17 0x43dec3 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:611:15
#18 0x43d6aa in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool, bool*) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:514:3
#19 0x43ed79 in fuzzer::Fuzzer::MutateAndTestOne() /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:757:19
#20 0x43fa45 in fuzzer::Fuzzer::Loop(std::__Fuzzer::vector<fuzzer::SizedFile, std::__Fuzzer::allocator<fuzzer::SizedFile> >&) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:895:5
#21 0x42edaf in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:912:6
#22 0x458402 in main /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerMain.cpp:20:10
#23 0x7fa5791f1082 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24082) (BuildId: 1878e6b475720c7c51969e69ab2d276fae6d1dee)
#24 0x41f7ed in _start (/out/SystemSan/target_dns+0x41f7ed)
NOTE: libFuzzer has rudimentary signal handlers.
Combine libFuzzer with AddressSanitizer or similar for better crash reports.
SUMMARY: libFuzzer: deadly signal
MS: 2 CrossOver-ManualDict- DE: "f.z"-; base unit: ac3478d69a3c81fa62e60f5c3696165a4e5e6ac4
0x66,0x2e,0x7a,
f.z
artifact_prefix='./'; Test unit written to ./crash-926813b2d6adde373f96a10594a5314951588384
Base64: Zi56
```
You can also try
```
echo -n f.z > toto
./SystemSan ./target_dns toto
```
Co-authored-by: Oliver Chang <oliverchang@users.noreply.github.com>
Co-authored-by: jonathanmetzman <31354670+jonathanmetzman@users.noreply.github.com>
cc @oliverchang
Log the file trying to be opened and the flags (read or write) for
opening the file
Co-authored-by: Oliver Chang <oliverchang@users.noreply.github.com>
* Rename execSan to SystemSan.
All of the bug detectors we've built (or plan to build) relate to system
state.
* fix documentation
* fix more documentation
jonathanmetzman