blobmsg: blobmsg_parse and blobmsg_parse_array oob read fixes

Fix out of bounds read in blobmsg_parse and blobmsg_check_name. The
out of bounds read happens because blob_attr and blobmsg_hdr have
flexible array members, whose size is 0 in the corresponding sizeofs.
For example the __blob_for_each_attr macro checks whether rem >=
sizeof(struct blob_attr). However, what LibFuzzer discovered was,
if the input data was only 4 bytes, the data would be casted to blob_attr,
and later on blob_data(attr) would be called even though attr->data was empty.
The same issue could appear with data larger than 4 bytes, where data
wasn't empty, but contained only the start of the blobmsg_hdr struct,
and blobmsg_hdr name was empty. The bugs were discovered by fuzzing
blobmsg_parse and blobmsg_array_parse with LibFuzzer.

CC: Luka Perkov <luka.perkov@sartura.hr>
Reviewed-by: Jo-Philipp Wich <jo@mein.io>
Signed-off-by: Juraj Vijtiuk <juraj.vijtiuk@sartura.hr>
[refactored some checks, added fuzz inputs, adjusted unit test results]
Signed-off-by: Petr Štetiar <ynezz@true.cz>

4 files changed, 24 insertions, 12 deletions

diff --git a/tests/cram/test_blob_parse.t b/tests/cram/test_blob_parse.t
index 1fd60bc..b6cbbaa 100644
--- a/tests/cram/test_blob_parse.t
+++ b/tests/cram/test_blob_parse.t
@@ -68,6 +68,10 @@ check that blob_parse is producing expected results:
   cannot parse cert crash-813f3e68661da09c26d4a87dbb9d5099e92be50f
   cannot parse cert crash-98595faa58ba01d85ba4fd0b109cd3d490b45795
   cannot parse cert crash-98595faa58ba01d85ba4fd0b109cd3d490b45795
+  cannot parse cert crash-a3585b70f1c7ffbdec10f6dadc964336118485c4
+  cannot parse cert crash-a3585b70f1c7ffbdec10f6dadc964336118485c4
+  cannot parse cert crash-b3585b70f1c7ffbdec10f6dadc964336118485c4
+  cannot parse cert crash-b3585b70f1c7ffbdec10f6dadc964336118485c4
   cannot parse cert crash-d0f3aa7d60a094b021f635d4edb7807c055a4ea1
   cannot parse cert crash-d0f3aa7d60a094b021f635d4edb7807c055a4ea1
   cannot parse cert crash-df9d1243057b27bbad6211e5a23d1cb699028aa2
diff --git a/tests/cram/test_blobmsg_parse.t b/tests/cram/test_blobmsg_parse.t
index 37e09ce..afed22c 100644
--- a/tests/cram/test_blobmsg_parse.t
+++ b/tests/cram/test_blobmsg_parse.t
@@ -27,37 +27,45 @@ check that blobmsg_parse is producing expected results:
   crash-333757b203a44751d3535f24b05f467183a96d09: blobmsg_parse_array: ... (0)
   crash-333757b203a44751d3535f24b05f467183a96d09: blobmsg_parse: ... (0)
   crash-333757b203a44751d3535f24b05f467183a96d09: blobmsg_parse_array: ... (0)
-  crash-4c4d2c3c9ade5da9347534e290305c3b9760f627: blobmsg_parse: ... (0)
+  crash-4c4d2c3c9ade5da9347534e290305c3b9760f627: blobmsg_parse: ... (-1)
   crash-4c4d2c3c9ade5da9347534e290305c3b9760f627: blobmsg_parse_array: ... (-1)
-  crash-4c4d2c3c9ade5da9347534e290305c3b9760f627: blobmsg_parse: ... (0)
+  crash-4c4d2c3c9ade5da9347534e290305c3b9760f627: blobmsg_parse: ... (-1)
   crash-4c4d2c3c9ade5da9347534e290305c3b9760f627: blobmsg_parse_array: ... (-1)
-  crash-5e9937b197c88bf4e7b7ee2612456cad4cb83f5b: blobmsg_parse: ... (0)
+  crash-5e9937b197c88bf4e7b7ee2612456cad4cb83f5b: blobmsg_parse: ... (-1)
   crash-5e9937b197c88bf4e7b7ee2612456cad4cb83f5b: blobmsg_parse_array: ... (-1)
-  crash-5e9937b197c88bf4e7b7ee2612456cad4cb83f5b: blobmsg_parse: ... (0)
+  crash-5e9937b197c88bf4e7b7ee2612456cad4cb83f5b: blobmsg_parse: ... (-1)
   crash-5e9937b197c88bf4e7b7ee2612456cad4cb83f5b: blobmsg_parse_array: ... (-1)
-  crash-75b146c4e6fac64d3e62236b27c64b50657bab2a: blobmsg_parse: ... (0)
+  crash-75b146c4e6fac64d3e62236b27c64b50657bab2a: blobmsg_parse: ... (-1)
   crash-75b146c4e6fac64d3e62236b27c64b50657bab2a: blobmsg_parse_array: ... (-1)
-  crash-75b146c4e6fac64d3e62236b27c64b50657bab2a: blobmsg_parse: ... (0)
+  crash-75b146c4e6fac64d3e62236b27c64b50657bab2a: blobmsg_parse: ... (-1)
   crash-75b146c4e6fac64d3e62236b27c64b50657bab2a: blobmsg_parse_array: ... (-1)
-  crash-813f3e68661da09c26d4a87dbb9d5099e92be50f: blobmsg_parse: ... (0)
+  crash-813f3e68661da09c26d4a87dbb9d5099e92be50f: blobmsg_parse: ... (-1)
   crash-813f3e68661da09c26d4a87dbb9d5099e92be50f: blobmsg_parse_array: ... (-1)
-  crash-813f3e68661da09c26d4a87dbb9d5099e92be50f: blobmsg_parse: ... (0)
+  crash-813f3e68661da09c26d4a87dbb9d5099e92be50f: blobmsg_parse: ... (-1)
   crash-813f3e68661da09c26d4a87dbb9d5099e92be50f: blobmsg_parse_array: ... (-1)
   crash-98595faa58ba01d85ba4fd0b109cd3d490b45795: blobmsg_parse: ... (0)
   crash-98595faa58ba01d85ba4fd0b109cd3d490b45795: blobmsg_parse_array: ... (0)
   crash-98595faa58ba01d85ba4fd0b109cd3d490b45795: blobmsg_parse: ... (0)
   crash-98595faa58ba01d85ba4fd0b109cd3d490b45795: blobmsg_parse_array: ... (0)
+  crash-a3585b70f1c7ffbdec10f6dadc964336118485c4: blobmsg_parse: ... (-1)
+  crash-a3585b70f1c7ffbdec10f6dadc964336118485c4: blobmsg_parse_array: ... (-1)
+  crash-a3585b70f1c7ffbdec10f6dadc964336118485c4: blobmsg_parse: ... (-1)
+  crash-a3585b70f1c7ffbdec10f6dadc964336118485c4: blobmsg_parse_array: ... (-1)
+  crash-b3585b70f1c7ffbdec10f6dadc964336118485c4: blobmsg_parse: ... (-1)
+  crash-b3585b70f1c7ffbdec10f6dadc964336118485c4: blobmsg_parse_array: ... (-1)
+  crash-b3585b70f1c7ffbdec10f6dadc964336118485c4: blobmsg_parse: ... (-1)
+  crash-b3585b70f1c7ffbdec10f6dadc964336118485c4: blobmsg_parse_array: ... (-1)
   crash-d0f3aa7d60a094b021f635d4edb7807c055a4ea1: blobmsg_parse: ... (0)
   crash-d0f3aa7d60a094b021f635d4edb7807c055a4ea1: blobmsg_parse_array: ... (0)
   crash-d0f3aa7d60a094b021f635d4edb7807c055a4ea1: blobmsg_parse: ... (0)
   crash-d0f3aa7d60a094b021f635d4edb7807c055a4ea1: blobmsg_parse_array: ... (0)
-  crash-df9d1243057b27bbad6211e5a23d1cb699028aa2: blobmsg_parse: ... (0)
+  crash-df9d1243057b27bbad6211e5a23d1cb699028aa2: blobmsg_parse: ... (-1)
   crash-df9d1243057b27bbad6211e5a23d1cb699028aa2: blobmsg_parse_array: ... (0)
-  crash-df9d1243057b27bbad6211e5a23d1cb699028aa2: blobmsg_parse: ... (0)
+  crash-df9d1243057b27bbad6211e5a23d1cb699028aa2: blobmsg_parse: ... (-1)
   crash-df9d1243057b27bbad6211e5a23d1cb699028aa2: blobmsg_parse_array: ... (0)
-  crash-e2fd5ecb3b37926743256f1083f47a07c39e10c2: blobmsg_parse: ... (0)
+  crash-e2fd5ecb3b37926743256f1083f47a07c39e10c2: blobmsg_parse: ... (-1)
   crash-e2fd5ecb3b37926743256f1083f47a07c39e10c2: blobmsg_parse_array: ... (-1)
-  crash-e2fd5ecb3b37926743256f1083f47a07c39e10c2: blobmsg_parse: ... (0)
+  crash-e2fd5ecb3b37926743256f1083f47a07c39e10c2: blobmsg_parse: ... (-1)
   crash-e2fd5ecb3b37926743256f1083f47a07c39e10c2: blobmsg_parse_array: ... (-1)
   valid-blobmsg.bin: blobmsg_parse: MLT (0)
   valid-blobmsg.bin: blobmsg_parse_array: MLT (0)
diff --git a/tests/fuzz/corpus/crash-a3585b70f1c7ffbdec10f6dadc964336118485c4 b/tests/fuzz/corpus/crash-a3585b70f1c7ffbdec10f6dadc964336118485c4
new file mode 100644
index 0000000..879ba4d
--- /dev/null
+++ b/tests/fuzz/corpus/crash-a3585b70f1c7ffbdec10f6dadc964336118485c4
diff --git a/tests/fuzz/corpus/crash-b3585b70f1c7ffbdec10f6dadc964336118485c4 b/tests/fuzz/corpus/crash-b3585b70f1c7ffbdec10f6dadc964336118485c4
new file mode 100644
index 0000000..12b832b
--- /dev/null
+++ b/tests/fuzz/corpus/crash-b3585b70f1c7ffbdec10f6dadc964336118485c4