Add README.md

Signed-off-by: Alan Jowett <[email protected]>

libfuzzer/README.md

@@ -0,0 +1,94 @@
+# ubpf_fuzzer
+
+This is a libfuzzer based fuzzer.
+
+To build, run:
+```
+cmake \
+    -G Ninja \
+    -S . \
+    -B build \
+    -DCMAKE_BUILD_TYPE=Debug \
+    -DCMAKE_C_COMPILER=clang \
+    -DCMAKE_CXX_COMPILER=clang++ \
+    -DUBPF_ENABLE_LIBFUZZER=1 \
+    -DCMAKE_BUILD_TYPE=Debug
+
+cmake --build build
+```
+
+To run:
+Create folder for the corpus and any crashes found, then run the fuzzer.
+
+```
+mkdir corpus
+mkdir artifacts
+build/bin/ubpf_fuzzer corpus -artifact_prefix=artifacts/
+```
+
+Optionally, add the "-jobs=100" to gather 100 crashes at a time.
+
+This will produce a lot of output that looks like:
+```
+#529745 REDUCE cov: 516 ft: 932 corp: 442/22Kb lim: 2875 exec/s: 264872 rss: 429Mb L: 50/188 MS: 3 CrossOver-ChangeBit-EraseBytes-
+#529814 REDUCE cov: 516 ft: 932 corp: 442/22Kb lim: 2875 exec/s: 264907 rss: 429Mb L: 45/188 MS: 4 ChangeBit-ShuffleBytes-PersAutoDict-EraseBytes- DE: "\005\000\000\000\000\000\000\000"-
+#530202 REDUCE cov: 516 ft: 932 corp: 442/22Kb lim: 2875 exec/s: 265101 rss: 429Mb L: 52/188 MS: 3 ChangeByte-ChangeASCIIInt-EraseBytes-
+#531224 REDUCE cov: 518 ft: 934 corp: 443/22Kb lim: 2875 exec/s: 265612 rss: 429Mb L: 73/188 MS: 2 CopyPart-PersAutoDict- DE: "\001\000\000\000"-
+#531750 REDUCE cov: 518 ft: 934 corp: 443/22Kb lim: 2875 exec/s: 265875 rss: 429Mb L: 45/188 MS: 1 EraseBytes-
+#532127 REDUCE cov: 519 ft: 935 corp: 444/22Kb lim: 2875 exec/s: 266063 rss: 429Mb L: 46/188 MS: 2 ChangeBinInt-ChangeByte-
+#532246 REDUCE cov: 519 ft: 935 corp: 444/22Kb lim: 2875 exec/s: 266123 rss: 429Mb L: 66/188 MS: 4 ChangeBit-CrossOver-ShuffleBytes-EraseBytes-
+#532357 NEW    cov: 520 ft: 936 corp: 445/22Kb lim: 2875 exec/s: 266178 rss: 429Mb L: 55/188 MS: 1 ChangeBinInt-
+#532404 REDUCE cov: 520 ft: 936 corp: 445/22Kb lim: 2875 exec/s: 266202 rss: 429Mb L: 57/188 MS: 2 ChangeBit-EraseBytes-
+#532486 REDUCE cov: 520 ft: 936 corp: 445/22Kb lim: 2875 exec/s: 266243 rss: 429Mb L: 44/188 MS: 2 EraseByte
+```
+
+Eventually it will probably crash and produce a message like:
+```
+=================================================================
+==376403==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x000000000000 bp 0x7ffca9d3cda0 sp 0x7ffca9d3cb98 T0)
+==376403==Hint: pc points to the zero page.
+==376403==The signal is caused by a READ memory access.
+==376403==Hint: address points to the zero page.
+    #0 0x0  (<unknown module>)
+    #1 0x50400001a48f  (<unknown module>)
+
+AddressSanitizer can not provide additional info.
+SUMMARY: AddressSanitizer: SEGV (<unknown module>)
+==376403==ABORTING
+MS: 1 ChangeByte-; base unit: cea14e5e2ecdc723b9beb640471a18b4ea529f75
+0x28,0x0,0x0,0x0,0xb4,0x50,0x10,0x6a,0x6a,0x4a,0x6a,0x2d,0x2e,0x1,0x0,0x0,0x0,0x0,0x0,0x0,0x4,0x21,0x0,0x0,0x0,0x0,0x95,0x95,0x26,0x21,0xfc,0xff,0xff,0xff,0x95,0x95,0x95,0x95,0x97,0xb7,0x97,0x97,0x0,0x8e,0x0,0x24,
+(\000\000\000\264P\020jjJj-.\001\000\000\000\000\000\000\004!\000\000\000\000\225\225&!\374\377\377\377\225\225\225\225\227\267\227\227\000\216\000$
+artifact_prefix='artifacts/'; Test unit written to artifacts/crash-7036cbef2b568fa0b6e458a9c8062571a65144e1
+Base64: KAAAALRQEGpqSmotLgEAAAAAAAAEIQAAAACVlSYh/P///5WVlZWXt5eXAI4AJA==
+```
+
+To triage the crash, the crash can be post processed using:
+```
+libfuzzer/split.sh artifacts/crash-7036cbef2b568fa0b6e458a9c8062571a65144e1
+
+
+Extracting program-7036cbef2b568fa0b6e458a9c8062571a65144e1...
+Extracting memory-7036cbef2b568fa0b6e458a9c8062571a65144e1...
+Disassembling program-7036cbef2b568fa0b6e458a9c8062571a65144e1...
+Program size: 40
+Memory size: 2
+Disassembled program:
+mov32 %r0, 0x2d6a4a6a
+jgt32 %r1, %r0, +0
+add32 %r1, 0x95950000
+jgt32 %r1, 0x9595ffff, -4
+exit
+Memory contents:
+00000000: 0024                                     .$
+```
+
+To repro the crash, you can run:
+```
+build/bin/ubpf_fuzzer artifacts/crash-7036cbef2b568fa0b6e458a9c8062571a65144e1
+```
+
+Or you can repro it using ubpf_test:
+```
+build/bin/ubpf-test --mem artifacts/memory-7036cbef2b568fa0b6e458a9c8062571a65144e1 artifacts/program-7036cbef2b568fa0b6e458a9c8062571a65144e1 --jit
+```
+

libfuzzer/split.sh

@@ -5,7 +5,7 @@ path=$(dirname $1)
 base=$(basename $1)
 
 # Get the first 4 bytes from the file (which is the length of the program)
-input="$(xxd -p -l 4 $base)"
+input="$(xxd -p -l 4 $1)"
 # Convert from little endian
 input="${input:6:2}${input:4:2}${input:2:2}${input:0:2}"