fix bNetStr2Bstr: prevent OOB read on crafted netstring length#149
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The declared length field is parsed into `x` with an overflow guard against INT_MAX, but there was no check that `i + 1 + x` falls within the actual buffer before accessing `buff[i + 1 + x]` to verify the terminating comma. A crafted input such as "99999999:.<data>" causes the parser to set x = 99999999 and then read `buff[100000008]`, triggering a SEGV. Found by libFuzzer + ASan. Fix: compute `blen = strlen(buff)` on entry and return NULL if `(size_t)i + 1 + (size_t)x >= blen` before the terminator check. The bug was detected by libFuzzer fuzz testing.
Replace strlen with memchr(buff, '\0', i + 2 + x), limiting the scan to exactly the bytes a valid netstring of the claimed length requires. If a null byte appears before the expected comma position the buffer is truncated and NULL is returned. memchr is C89 standard, replacing the non-portable strnlen.
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The declared length field is parsed into
xwith an overflow guard against INT_MAX, but there was no check thati + 1 + xfalls within the actual buffer before accessingbuff[i + 1 + x]to verify the terminating comma.A crafted input such as "99999999:." causes the parser to set x = 99999999 and then read
buff[100000008], triggering a SEGV. Found by libFuzzer + ASan.Fix: compute
blen = strlen(buff)on entry and return NULL if(size_t)i + 1 + (size_t)x >= blenbefore the terminator check.The bug was detected by libFuzzer fuzz testing.