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va: Match CAA parameter tags case insensitively #8975

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va: Match CAA parameter tags case insensitively #8975

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10 changes: 8 additions & 2 deletions va/caa.go
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Original file line number Diff line number Diff line change
Expand Up @@ -494,7 +494,12 @@ func caaAccountURIMatches(caaParams []caaParameter, accountURIPrefixes []string,
var found bool
var accountURI string
for _, c := range caaParams {
if c.tag == "accounturi" {
// RFC 8659 Section 4.1 makes matching of Property Tags case insensitive but
// specifies no comparison rule for parameter tags. We lowercase the parameter
// tag as a safety choice: treating a differently-cased "accounturi" as an
// unrecognized parameter would drop the restriction the subscriber intended
// and make this Property match any account, a false-positive validation.
if strings.ToLower(c.tag) == "accounturi" {
if found {
// A Property with multiple "accounturi" parameters is
// unsatisfiable.
Expand Down Expand Up @@ -536,7 +541,8 @@ func caaValidationMethodMatches(caaParams []caaParameter, method core.AcmeChalle
var validationMethods string
var found bool
for _, param := range caaParams {
if param.tag == "validationmethods" {
// Match the parameter tag case insensitively, as in caaAccountURIMatches.
if strings.ToLower(param.tag) == "validationmethods" {
if found {
// RFC 8657 does not define what behavior to take when multiple
// "validationmethods" parameters exist, but we make the
Expand Down
30 changes: 30 additions & 0 deletions va/caa_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1421,6 +1421,24 @@ func TestAccountURIMatches(t *testing.T) {
id: 654321,
want: false,
},
{
name: "mixed-case tag matches the expected account",
params: []caaParameter{{tag: "AccountURI", val: "https://acme-v02.api.letsencrypt.org/acme/acct/123456"}},
prefixes: []string{
"https://acme-v02.api.letsencrypt.org/acme/acct/",
},
id: 123456,
want: true,
},
{
name: "mixed-case tag still restricts a non-matching account",
params: []caaParameter{{tag: "AccountURI", val: "https://acme-v02.api.letsencrypt.org/acme/acct/123456"}},
prefixes: []string{
"https://acme-v02.api.letsencrypt.org/acme/acct/",
},
id: 654321,
want: false,
},
}

for _, tc := range tests {
Expand Down Expand Up @@ -1536,6 +1554,18 @@ func TestValidationMethodMatches(t *testing.T) {
method: core.ChallengeTypeTLSALPN01,
want: false,
},
{
name: "mixed-case tag matches the method in use",
params: []caaParameter{{tag: "ValidationMethods", val: "dns-01"}},
method: core.ChallengeTypeDNS01,
want: true,
},
{
name: "mixed-case tag still restricts a non-matching method",
params: []caaParameter{{tag: "ValidationMethods", val: "dns-01"}},
method: core.ChallengeTypeHTTP01,
want: false,
},
}

for _, tc := range tests {
Expand Down