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fix: reject invalid dotted-decimal in hostname_rfc1123 validation #1607

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fix: reject invalid dotted-decimal in hostname_rfc1123 validation #1607

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29 changes: 28 additions & 1 deletion baked_in.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2911,7 +2911,34 @@ func isHostnameRFC952(fl FieldLevel) bool {
}

func isHostnameRFC1123(fl FieldLevel) bool {
return hostnameRegexRFC1123().MatchString(fl.Field().String())
val := fl.Field().String()
if !hostnameRegexRFC1123().MatchString(val) {
return false
}
// RFC 1123 §2.1: "a valid host name can never have the dotted-decimal
// form #.#.#.#, since at least the highest-level component label will
// be alphabetic." If the value has exactly four dot-separated all-numeric
// parts (i.e. it looks like an IPv4 address), accept it only when
// net.ParseIP confirms it is a valid IPv4 address.
if looksLikeIPv4(val) {
return net.ParseIP(val) != nil
}
return true
}

// looksLikeIPv4 reports whether s has exactly four dot-separated parts that
// are each composed entirely of ASCII digits (e.g. "192.168.0.1", "277.168.0.1").
func looksLikeIPv4(s string) bool {
parts := 1
for i := 0; i < len(s); i++ {
c := s[i]
if c == '.' {
parts++
} else if c < '0' || c > '9' {
return false
}
}
return parts == 4
}

func isFQDN(fl FieldLevel) bool {
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12 changes: 12 additions & 0 deletions validator_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -11078,6 +11078,18 @@ func TestHostnameRFC1123Validation(t *testing.T) {
{"example.", false},
{"test_example", false},
{"192.168.0.1", true},
{"277.168.0.1", false},
{"999.999.999.999", false},
{"0.0.0.0", true},
{"255.255.255.255", true},
{"1.2.3.256", false},
{"3com.com", true},
{"1and1.com", true},
{"7-eleven.com", true},
{"1234", true},
{"12345", true},
{"1.2.3", true},
{"1.2.3.4.5", true},
{"email@example.com", false},
{"2001:cdba:0000:0000:0000:0000:3257:9652", false},
{"2001:cdba:0:0:0:0:3257:9652", false},
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