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plugin/template: Add parseInt template function (#5609)

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* plugin/template: Add parseInt template function

Signed-off-by: Erik Johansson <ejohansson@spotify.com>
This commit is contained in:
Erik Johansson
2022-09-15 12:25:58 -07:00
committed by GitHub
parent 7beb76c045
commit e93e932ce8
5 changed files with 116 additions and 20 deletions
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21
plugin/template/README.md
View File

@@ -54,6 +54,10 @@ Each resource record is a full-featured [Go template](https://golang.org/pkg/tex
* `.Meta` a function that takes a metadata name and returns the value, if the
metadata plugin is enabled. For example, `.Meta "kubernetes/client-namespace"`
and the following predefined [template functions](https://golang.org/pkg/text/template#hdr-Functions)
* `parseInt` interprets a string in the given base and bit size. Equivalent to [strconv.ParseUint](https://golang.org/pkg/strconv#ParseUint).
The output of the template must be a [RFC 1035](https://tools.ietf.org/html/rfc1035) style resource record (commonly referred to as a "zone file").
**WARNING** there is a syntactical problem with Go templates and CoreDNS config files. Expressions
@@ -177,6 +181,23 @@ Having templates to map certain PTR/A pairs is a common pattern.
Fallthrough is needed for mixed domains where only some responses are templated.
### Resolve hexadecimal ip pattern using parseInt
~~~ corefile
. {
forward . 8.8.8.8
template IN A example {
match "^ip0a(?P<b>[a-f0-9]{2})(?P<c>[a-f0-9]{2})(?P<d>[a-f0-9]{2})[.]example[.]$"
answer "{{ .Name }} 60 IN A 10.{{ parseInt .Group.b 16 8 }}.{{ parseInt .Group.c 16 8 }}.{{ parseInt .Group.d 16 8 }}"
fallthrough
}
}
~~~
An IPv4 address can be expressed in a more compact form using its hexadecimal encoding.
For example `ip-10-123-123.example.` can instead be expressed as `ip0a7b7b7b.example.`
### Resolve multiple ip patterns
~~~ corefile

6
plugin/template/setup.go
View File

@@ -80,7 +80,7 @@ func templateParse(c *caddy.Controller) (handler Handler, err error) {
return handler, c.ArgErr()
}
for _, answer := range args {
tmpl, err := gotmpl.New("answer").Parse(answer)
tmpl, err := newTemplate("answer", answer)
if err != nil {
return handler, c.Errf("could not compile template: %s, %v", c.Val(), err)
}
@@ -93,7 +93,7 @@ func templateParse(c *caddy.Controller) (handler Handler, err error) {
return handler, c.ArgErr()
}
for _, additional := range args {
tmpl, err := gotmpl.New("additional").Parse(additional)
tmpl, err := newTemplate("additional", additional)
if err != nil {
return handler, c.Errf("could not compile template: %s, %v\n", c.Val(), err)
}
@@ -106,7 +106,7 @@ func templateParse(c *caddy.Controller) (handler Handler, err error) {
return handler, c.ArgErr()
}
for _, authority := range args {
tmpl, err := gotmpl.New("authority").Parse(authority)
tmpl, err := newTemplate("authority", authority)
if err != nil {
return handler, c.Errf("could not compile template: %s, %v\n", c.Val(), err)
}

21
plugin/template/setup_test.go
View File

@@ -83,6 +83,20 @@ func TestSetupParse(t *testing.T) {
}`,
true,
},
{
`template ANY ANY {
answer "{{ notAFunction }}"
}`,
true,
},
{
`template ANY ANY {
answer "{{ parseInt }}"
additional "{{ parseInt }}"
authority "{{ parseInt }}"
}`,
false,
},
// examples
{`template ANY ANY (?P<x>`, false},
{
@@ -128,6 +142,13 @@ func TestSetupParse(t *testing.T) {
}`,
false,
},
{
`template IN A example {
match ^ip0a(?P<b>[a-f0-9]{2})(?P<c>[a-f0-9]{2})(?P<d>[a-f0-9]{2})[.]example[.]$
answer "{{ .Name }} 3600 IN A 10.{{ parseInt .Group.b 16 8 }}.{{ parseInt .Group.c 16 8 }}.{{ parseInt .Group.d 16 8 }}"
}`,
false,
},
{
`template IN MX example {
match ^ip-10-(?P<b>[0-9]*)-(?P<c>[0-9]*)-(?P<d>[0-9]*)[.]example[.]$

7
plugin/template/template.go
View File

@@ -150,6 +150,13 @@ func executeRRTemplate(server, view, section string, template *gotmpl.Template,
return rr, nil
}
func newTemplate(name, text string) (*gotmpl.Template, error) {
funcMap := gotmpl.FuncMap{
"parseInt": strconv.ParseUint,
}
return gotmpl.New(name).Funcs(funcMap).Parse(text)
}
func (t template) match(ctx context.Context, state request.Request) (*templateData, bool, bool) {
q := state.Req.Question[0]
data := &templateData{md: metadata.ValueFuncs(ctx), Remote: state.IP()}

81
plugin/template/template_test.go
View File

@@ -19,7 +19,15 @@ import (
func TestHandler(t *testing.T) {
exampleDomainATemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile("(^|[.])ip-10-(?P<b>[0-9]*)-(?P<c>[0-9]*)-(?P<d>[0-9]*)[.]example[.]$")},
answer: []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse("{{ .Name }} 60 IN A 10.{{ .Group.b }}.{{ .Group.c }}.{{ .Group.d }}"))},
answer: []*gotmpl.Template{gotmpl.Must(newTemplate("answer", "{{ .Name }} 60 IN A 10.{{ .Group.b }}.{{ .Group.c }}.{{ .Group.d }}"))},
qclass: dns.ClassANY,
qtype: dns.TypeANY,
fall: fall.Root,
zones: []string{"."},
}
exampleDomainAParseIntTemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile("^ip0a(?P<b>[a-f0-9]{2})(?P<c>[a-f0-9]{2})(?P<d>[a-f0-9]{2})[.]example[.]$")},
answer: []*gotmpl.Template{gotmpl.Must(newTemplate("answer", "{{ .Name }} 60 IN A 10.{{ parseInt .Group.b 16 8 }}.{{ parseInt .Group.c 16 8 }}.{{ parseInt .Group.d 16 8 }}"))},
qclass: dns.ClassANY,
qtype: dns.TypeANY,
fall: fall.Root,
@@ -27,7 +35,7 @@ func TestHandler(t *testing.T) {
}
exampleDomainIPATemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile(".*")},
answer: []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse("{{ .Name }} 60 IN A {{ .Remote }}"))},
answer: []*gotmpl.Template{gotmpl.Must(newTemplate("answer", "{{ .Name }} 60 IN A {{ .Remote }}"))},
qclass: dns.ClassINET,
qtype: dns.TypeA,
fall: fall.Root,
@@ -35,9 +43,9 @@ func TestHandler(t *testing.T) {
}
exampleDomainANSTemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile("(^|[.])ip-10-(?P<b>[0-9]*)-(?P<c>[0-9]*)-(?P<d>[0-9]*)[.]example[.]$")},
answer: []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse("{{ .Name }} 60 IN A 10.{{ .Group.b }}.{{ .Group.c }}.{{ .Group.d }}"))},
additional: []*gotmpl.Template{gotmpl.Must(gotmpl.New("additional").Parse("ns0.example. IN A 203.0.113.8"))},
authority: []*gotmpl.Template{gotmpl.Must(gotmpl.New("authority").Parse("example. IN NS ns0.example.com."))},
answer: []*gotmpl.Template{gotmpl.Must(newTemplate("answer", "{{ .Name }} 60 IN A 10.{{ .Group.b }}.{{ .Group.c }}.{{ .Group.d }}"))},
additional: []*gotmpl.Template{gotmpl.Must(newTemplate("additional", "ns0.example. IN A 203.0.113.8"))},
authority: []*gotmpl.Template{gotmpl.Must(newTemplate("authority", "example. IN NS ns0.example.com."))},
qclass: dns.ClassANY,
qtype: dns.TypeANY,
fall: fall.Root,
@@ -45,8 +53,8 @@ func TestHandler(t *testing.T) {
}
exampleDomainMXTemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile("(^|[.])ip-10-(?P<b>[0-9]*)-(?P<c>[0-9]*)-(?P<d>[0-9]*)[.]example[.]$")},
answer: []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse("{{ .Name }} 60 MX 10 {{ .Name }}"))},
additional: []*gotmpl.Template{gotmpl.Must(gotmpl.New("additional").Parse("{{ .Name }} 60 IN A 10.{{ .Group.b }}.{{ .Group.c }}.{{ .Group.d }}"))},
answer: []*gotmpl.Template{gotmpl.Must(newTemplate("answer", "{{ .Name }} 60 MX 10 {{ .Name }}"))},
additional: []*gotmpl.Template{gotmpl.Must(newTemplate("additional", "{{ .Name }} 60 IN A 10.{{ .Group.b }}.{{ .Group.c }}.{{ .Group.d }}"))},
qclass: dns.ClassANY,
qtype: dns.TypeANY,
fall: fall.Root,
@@ -55,7 +63,7 @@ func TestHandler(t *testing.T) {
invalidDomainTemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile("[.]invalid[.]$")},
rcode: dns.RcodeNameError,
answer: []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse("invalid. 60 {{ .Class }} SOA a.invalid. b.invalid. (1 60 60 60 60)"))},
answer: []*gotmpl.Template{gotmpl.Must(newTemplate("answer", "invalid. 60 {{ .Class }} SOA a.invalid. b.invalid. (1 60 60 60 60)"))},
qclass: dns.ClassANY,
qtype: dns.TypeANY,
fall: fall.Root,
@@ -71,7 +79,15 @@ func TestHandler(t *testing.T) {
}
brokenTemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile("[.]example[.]$")},
answer: []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse("{{ .Name }} 60 IN TXT \"{{ index .Match 2 }}\""))},
answer: []*gotmpl.Template{gotmpl.Must(newTemplate("answer", "{{ .Name }} 60 IN TXT \"{{ index .Match 2 }}\""))},
qclass: dns.ClassANY,
qtype: dns.TypeANY,
fall: fall.Root,
zones: []string{"."},
}
brokenParseIntTemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile("[.]example[.]$")},
answer: []*gotmpl.Template{gotmpl.Must(newTemplate("answer", "{{ .Name }} 60 IN TXT \"{{ parseInt \"gg\" 16 8 }}\""))},
qclass: dns.ClassANY,
qtype: dns.TypeANY,
fall: fall.Root,
@@ -79,7 +95,7 @@ func TestHandler(t *testing.T) {
}
nonRRTemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile("[.]example[.]$")},
answer: []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse("{{ .Name }}"))},
answer: []*gotmpl.Template{gotmpl.Must(newTemplate("answer", "{{ .Name }}"))},
qclass: dns.ClassANY,
qtype: dns.TypeANY,
fall: fall.Root,
@@ -87,7 +103,7 @@ func TestHandler(t *testing.T) {
}
nonRRAdditionalTemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile("[.]example[.]$")},
additional: []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse("{{ .Name }}"))},
additional: []*gotmpl.Template{gotmpl.Must(newTemplate("answer", "{{ .Name }}"))},
qclass: dns.ClassANY,
qtype: dns.TypeANY,
fall: fall.Root,
@@ -95,7 +111,7 @@ func TestHandler(t *testing.T) {
}
nonRRAuthoritativeTemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile("[.]example[.]$")},
authority: []*gotmpl.Template{gotmpl.Must(gotmpl.New("authority").Parse("{{ .Name }}"))},
authority: []*gotmpl.Template{gotmpl.Must(newTemplate("answer", "{{ .Name }}"))},
qclass: dns.ClassANY,
qtype: dns.TypeANY,
fall: fall.Root,
@@ -103,7 +119,7 @@ func TestHandler(t *testing.T) {
}
cnameTemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile("example[.]net[.]")},
answer: []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse("example.net 60 IN CNAME target.example.com"))},
answer: []*gotmpl.Template{gotmpl.Must(newTemplate("answer", "example.net 60 IN CNAME target.example.com"))},
qclass: dns.ClassANY,
qtype: dns.TypeANY,
fall: fall.Root,
@@ -111,9 +127,9 @@ func TestHandler(t *testing.T) {
}
mdTemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile("(^|[.])ip-10-(?P<b>[0-9]*)-(?P<c>[0-9]*)-(?P<d>[0-9]*)[.]example[.]$")},
answer: []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse(`{{ .Meta "foo" }}-{{ .Name }} 60 IN A 10.{{ .Group.b }}.{{ .Group.c }}.{{ .Group.d }}`))},
additional: []*gotmpl.Template{gotmpl.Must(gotmpl.New("additional").Parse(`{{ .Meta "bar" }}.example. IN A 203.0.113.8`))},
authority: []*gotmpl.Template{gotmpl.Must(gotmpl.New("authority").Parse(`example. IN NS {{ .Meta "bar" }}.example.com.`))},
answer: []*gotmpl.Template{gotmpl.Must(newTemplate("answer", `{{ .Meta "foo" }}-{{ .Name }} 60 IN A 10.{{ .Group.b }}.{{ .Group.c }}.{{ .Group.d }}`))},
additional: []*gotmpl.Template{gotmpl.Must(newTemplate("additional", `{{ .Meta "bar" }}.example. IN A 203.0.113.8`))},
authority: []*gotmpl.Template{gotmpl.Must(newTemplate("authority", `example. IN NS {{ .Meta "bar" }}.example.com.`))},
qclass: dns.ClassANY,
qtype: dns.TypeANY,
fall: fall.Root,
@@ -121,7 +137,7 @@ func TestHandler(t *testing.T) {
}
mdMissingTemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile("(^|[.])ip-10-(?P<b>[0-9]*)-(?P<c>[0-9]*)-(?P<d>[0-9]*)[.]example[.]$")},
answer: []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse(`{{ .Meta "foofoo" }}{{ .Name }} 60 IN A 10.{{ .Group.b }}.{{ .Group.c }}.{{ .Group.d }}`))},
answer: []*gotmpl.Template{gotmpl.Must(newTemplate("answer", `{{ .Meta "foofoo" }}{{ .Name }} 60 IN A 10.{{ .Group.b }}.{{ .Group.c }}.{{ .Group.d }}`))},
qclass: dns.ClassANY,
qtype: dns.TypeANY,
fall: fall.Root,
@@ -242,6 +258,37 @@ func TestHandler(t *testing.T) {
return nil
},
},
{
name: "ExampleDomainMatchHexIp",
tmpl: exampleDomainAParseIntTemplate,
qclass: dns.ClassINET,
qtype: dns.TypeA,
qname: "ip0a5f0c09.example.",
verifyResponse: func(r *dns.Msg) error {
if len(r.Answer) != 1 {
return fmt.Errorf("expected 1 answer, got %v", len(r.Answer))
}
if r.Answer[0].Header().Rrtype != dns.TypeA {
return fmt.Errorf("expected an A record answer, got %v", dns.TypeToString[r.Answer[0].Header().Rrtype])
}
if r.Answer[0].(*dns.A).A.String() != "10.95.12.9" {
return fmt.Errorf("expected an A record for 10.95.12.9, got %v", r.Answer[0].String())
}
return nil
},
},
{
name: "BrokenParseIntTemplate",
tmpl: brokenParseIntTemplate,
qclass: dns.ClassINET,
qtype: dns.TypeANY,
qname: "test.example.",
expectedCode: dns.RcodeServerFailure,
expectedErr: "template: answer:1:26: executing \"answer\" at <parseInt \"gg\" 16 8>: error calling parseInt: strconv.ParseUint: parsing \"gg\": invalid syntax",
verifyResponse: func(r *dns.Msg) error {
return nil
},
},
{
name: "ExampleDomainMXMatch",
tmpl: exampleDomainMXTemplate,