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fix: reject hostnames exceeding 253 characters #445

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fix: reject hostnames exceeding 253 characters #445

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14 changes: 14 additions & 0 deletions src/validators/hostname.py
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Original file line number Diff line number Diff line change
Expand Up @@ -113,6 +113,20 @@ def hostname(
if not value:
return False

# Determine the host part (strip port if present) for length validation
host_part = value
if may_have_port:
if (seg := _port_validator(value)):
host_part = seg

# Strip IPv6 brackets for length check
host_part = host_part.lstrip("[").rstrip("]")

# RFC 1123: total hostname length must not exceed 253 characters
# (excluding optional trailing dot)
if len(host_part.rstrip(".")) > 253:
return False

if may_have_port and (host_seg := _port_validator(value)):
return (
(_simple_hostname_regex().match(host_seg) if maybe_simple else False)
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