Validate hostnames in DNS responses and discard from malicious servers #406
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…ormed DNS replies, validate hostnames returned in responses and return EBADRESP if they are not valid. It is not clear what legitimate issues this may cause at this point.
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@bagder any reservations about doing this? |
AdamMajer
reviewed
Sep 8, 2021
| return 1; | ||
| if (ch >= '0' && ch <= '9') | ||
| return 1; | ||
| if (ch == '-' || ch == '.') |
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. is not a valid character for hostnames
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function name is misleading, its validating a full domain name response which can include .
kylebevans
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Nov 11, 2021
Update the new cares parse ns, ptr, and soa to have the is_hostname parameter passed to ares__expand_name_for_response. This is to make sure the fix for issue c-ares#406 is applied.
sergepetrenko
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Jul 29, 2022
c-ares#406) To prevent possible users having XSS issues due to intentionally malformed DNS replies, validate hostnames returned in responses and return EBADRESP if they are not valid. It is not clear what legitimate issues this may cause at this point. Bug Reported By: philipp.jeitner@sit.fraunhofer.de Fix By: Brad House (@bradh352)
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DNS servers could intentionally return malformed DNS responses that could cause client-side issues (like XSS). Attempt to identify such responses and throw them away and return EBADRESP.
It is not clear if there are any legitimate use cases where a DNS response might return a non-validly formatted hostname.