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Increase the maximum number of allowed compression pointers

This commit is contained in:
Tom Thorogood 2018-11-28 19:52:41 +10:30
parent 7ae05cdcf8
commit c567cfc2bb
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GPG Key ID: 86C63CDA416C6D2F
1 changed files with 13 additions and 1 deletions
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14
msg.go
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@ -24,6 +24,18 @@ import (
const (
maxCompressionOffset = 2 << 13 // We have 14 bits for the compression pointer
maxDomainNameWireOctets = 255 // See RFC 1035 section 2.3.4
// This is the maximum number of compression pointers that should occur in a
// semantically valid message. Each label in a domain name must be at least one
// octet and is separated by a period. The root label won't be represented by a
// compression pointer to a compression pointer, hence the -2 to exclude the
// smallest valid root label.
//
// It is possible to construct a valid message that has more compression pointers
// than this, and still doesn't loop, by pointing to a previous pointer. This is
// not something a well written implementation should ever do, so we ignore that
// possibility.
maxCompressionPointers = (maxDomainNameWireOctets+1)/2 - 2
)
// Errors defined in this package.
@ -399,7 +411,7 @@ Loop:
if ptr == 0 {
off1 = off
}
if ptr++; ptr > 10 {
if ptr++; ptr > maxCompressionPointers {
return "", lenmsg, &Error{err: "too many compression pointers"}
}
// pointer should guarantee that it advances and points forwards at least