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Refactor is_subzone to use Name::zone_of with additional checks for partially/fully qualified domains.

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This commit is contained in:
Marcus Butler 2024-01-04 06:50:56 -06:00 committed by Benjamin Fry
parent 4809a0d10b
commit 356bb541a4
1 changed files with 9 additions and 40 deletions
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49
crates/recursor/src/recursor.rs
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@ -495,7 +495,8 @@ fn recursor_opts() -> ResolverOpts {
///
/// # Overview
///
/// This function checks that two host names have a parent/child relationship.
/// This function checks that two host names have a parent/child relationship, but does so more strictly than elsewhere in the libraries
/// (see implementation notes.)
///
/// A resolver should not return answers outside of its delegated authority -- if we receive a delegation from the root servers for
/// "example.com", that server should only return answers related to example.com or a sub-domain thereof. Note that record data may point
@ -516,10 +517,10 @@ fn recursor_opts() -> ResolverOpts {
///
/// # Implementation Notes
///
/// * This function is nominally a wrapper around Name::zone_of, with two additional checks:
/// * If the caller doesn't provide a parent at all, we'll return false.
/// * ".".split('.') will evaluate to ["", ""], which for our purposes doesn't work -- that's the reason for the ends_with tests and
/// manually pushing the root entry onto the parent/child vectors, as well as skipping the first list element if the name was already
/// fully qualified.
/// * If the domains have mixed qualification -- that is, if one is fully-qualified and the other partially-qualified, we'll return
/// false.
///
/// # References
///
@ -527,46 +528,15 @@ fn recursor_opts() -> ResolverOpts {
/// * [The Hitchiker's Guide to DNS Cache Poisoning](https://www.cs.utexas.edu/%7Eshmat/shmat_securecomm10.pdf) -- for a more in-depth
/// discussion of DNS cache poisoning attacks, see section 4, specifically, for a discussion of the Bailiwick rule.
fn is_subzone(parent: Name, child: Name) -> bool {
let parent_str = parent.to_string();
let child_str = child.to_string();
if parent_str.is_empty() {
if parent.is_empty() {
return false;
}
let mut rev_parent: Vec<&str> = vec![];
let mut rev_child: Vec<&str> = vec![];
let mut parent_offset = 0;
let mut child_offset = 0;
if child_str.ends_with('.') {
rev_child.push(".");
child_offset = 1;
if (parent.is_fqdn() && !child.is_fqdn()) || (!parent.is_fqdn() && child.is_fqdn()) {
return false;
}
child_str
.rsplit('.')
.skip(child_offset)
.collect::<Vec<_>>()
.iter()
.filter(|x| !x.is_empty())
.for_each(|x| rev_child.push(x));
if parent_str.ends_with('.') {
rev_parent.push(".");
parent_offset = 1;
}
parent_str
.rsplit('.')
.skip(parent_offset)
.collect::<Vec<_>>()
.iter()
.filter(|x| !x.is_empty())
.for_each(|x| rev_parent.push(x));
rev_parent
.into_iter()
.enumerate()
.all(|(i, elem)| rev_child[i] == elem)
parent.zone_of(&child)
}
#[test]
@ -587,7 +557,6 @@ fn is_subzone_test() {
Name::from_str("example.com.").unwrap(),
Name::from_str("host.multilevel.example.com.").unwrap()
));
assert!(!is_subzone(
Name::from_str("").unwrap(),
Name::from_str("example.com.").unwrap()