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Fix stack over-read in mnet_jsonf() integer conversions - #15
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Covers duplicate Content-Length (400), Content-Length with Transfer-Encoding (501), bare LF line endings, obs-fold continuations, Expect: 100-continue, negative/overflowing/non-numeric Content-Length (400/413/400), a version-less request line, a space before a header colon, and pipelined requests. No source changes were needed: every case already behaves correctly. The tests document the behavior and guard it, including the two deliberately lenient choices (obs-fold and a version-less request line are served rather than rejected, per the existing lenient policy). Wired into Make, CMake, Meson and the CI jobs.
The integer conversion path of mnet_jsonfv() formats into a fixed 64-byte
stack buffer without sizing it first, unlike the float path which grows
its buffer to the needed length. snprintf() returns the length the
output *would* have had, so a wide conversion like %4096d truncates into
the 64-byte buffer while the returned length still reports 4096; the
following memcpy (src/mnet_response.c:739) then over-reads ~4 KB of stack
and copies adjacent stack memory into the HTTP response.
Confirmed under AddressSanitizer:
ERROR: AddressSanitizer: stack-buffer-overflow
READ of size 4096 at ... in mnet_jsonfv
src/mnet_response.c:739
Both integer branches now size their buffer with snprintf(NULL, 0, ...)
and grow it, the same way the float path does.
Test: wide-integer case in test/test_security.c — ASan failure before the
fix, passes after (62 passed, 0 failed, asan_issues=0).
The test block names its response variable 'wide' rather than 'r': the
old name shadowed an outer local, which MSVC reports as C4456 and the
project treats as an error under /WX.
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Fixes #8.
The integer path of
mnet_jsonfv()formats into a fixed 64-byte stack buffer without sizing it first (unlike the float path, which grows its buffer).snprintf()returns the length the output would have had, so a wide conversion like%4096dtruncates into the 64-byte buffer while the returned length still reports 4096; the followingmemcpythen over-reads ~4 KB of stack and copies adjacent stack memory into the HTTP response.ASan on the unfixed code:
Fix: the integer path now sizes its buffer like the float path (grow to the needed length).
Tests: wide-integer case added to
test/test_security.c— ASan failure before, passes after (62 passed, 0 failed, asan_issues=0).Stacked on the previous PR in the series; merge in order.