Fix OOB read in DNS resolver
The remote server specifies resplen, the length of the response it
intends to send. anssiz represents the size of the destination buffer.
If the reported resplen is larger than the anssiz, the code correctly
only reads up to anssiz bytes, but returns resplen. so later functions
will access far out of bounds.
The fix ensures that the length of send_vc return does not exceed the
buffer size.
Bug: 161362564
Test: build, flash, boot
Test: atest netd_integration_test
Merged-In: Id4b5df1be4652e4623847b0b0bad0af65b80fdd5
Change-Id: Id4b5df1be4652e4623847b0b0bad0af65b80fdd5
diff --git a/libc/dns/resolv/res_send.c b/libc/dns/resolv/res_send.c
index 18bb752..81b42a6 100644
--- a/libc/dns/resolv/res_send.c
+++ b/libc/dns/resolv/res_send.c
@@ -950,6 +950,8 @@
else
break;
}
+ // return size should never exceed container size
+ resplen = anssiz;
}
/*
* If the calling applicating has bailed out of
@@ -962,7 +964,7 @@
DprintQ((statp->options & RES_DEBUG) ||
(statp->pfcode & RES_PRF_REPLY),
(stdout, ";; old answer (unexpected):\n"),
- ans, (resplen > anssiz) ? anssiz: resplen);
+ ans, resplen);
goto read_len;
}
