Fix DNS name encode/decode buffer overflows (#851)#854
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dns_name_decode and dns_name_encode did not enforce DNS_NAME_MAXLEN or label length limits, allowing OOB writes into dns_rr_t.name and the encode stack buffer. Compression-pointer RRs also left name[] uninitialized. Add bounds checks, reject overlong labels, NUL-terminate name on compression pointers, and fail encode/pack on overflow (see ithewei#851).
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Pull request overview
This PR addresses the memory-safety issues reported in #851 by adding stricter bounds/validation to DNS name encoding/decoding and by ensuring dns_rr_unpack does not leave rr->name uninitialized when encountering compression pointers.
Changes:
- Add DNS label length validation (<= 63) and cap encode/decode operations to
DNS_NAME_MAXLEN. - Make
dns_rr_packfail fast when name encoding fails, and size the encoded-name buffer usingDNS_NAME_MAXLEN. - Ensure
dns_rr_unpackNUL-terminatesrr->namefor compression-pointer names and adds additional length checks.
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| *plen = (char)len; | ||
| if (buf >= end) return -1; | ||
| *buf++ = '\0'; | ||
| return (int)(buf - start); |
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| else { | ||
| namelen = dns_name_decode(buf, rr->name); | ||
| } | ||
| if (namelen < 0) return -1; | ||
| if (namelen > len) return -1; |
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Summary
Fixes #851.
Bound DNS name encode/decode to DNS_NAME_MAXLEN, reject overlong labels, NUL-terminate name on compression pointers, fail pack on encode error.
Test plan