Add support for the draft dns-persist-01 challenge #536
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -34,7 +34,6 @@ linters: | |
| - nolintlint | ||
| - nonamedreturns | ||
| - nosprintfhostport | ||
| - predeclared | ||
| - reassign | ||
| - revive | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -9,6 +9,7 @@ import ( | |
| "encoding/asn1" | ||
| "encoding/base32" | ||
| "encoding/base64" | ||
| "errors" | ||
| "fmt" | ||
| "io" | ||
| "log" | ||
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@@ -18,6 +19,7 @@ import ( | |
| "net/url" | ||
| "os" | ||
| "runtime" | ||
| "slices" | ||
| "strconv" | ||
| "strings" | ||
| "time" | ||
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@@ -323,6 +325,8 @@ func (va VAImpl) performValidation(task *vaTask, results chan<- *core.Validation | |
| results <- va.validateDNS01(task) | ||
| case acme.ChallengeDNSAccount01: | ||
| results <- va.validateDNSAccount01(task) | ||
| case acme.ChallengeDNSPersist01: | ||
| results <- va.validateDNSPersist01(task) | ||
| default: | ||
| va.log.Printf("Error: performValidation(): Invalid challenge type: %q", task.Challenge.Type) | ||
| } | ||
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@@ -554,6 +558,185 @@ func (va VAImpl) validateHTTP01(task *vaTask) *core.ValidationRecord { | |
| return result | ||
| } | ||
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| type dnsPersistIssueValue struct { | ||
| issuerDomain string | ||
| accountURI string | ||
| policy string | ||
| persistUntil *time.Time | ||
| } | ||
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| // trimWSP trims RFC 8659 whitespace characters (space and tab) from the | ||
| // beginning and end of a string. | ||
| func trimWSP(s string) string { | ||
| return strings.TrimFunc(s, func(r rune) bool { | ||
| return r == ' ' || r == '\t' | ||
| }) | ||
| } | ||
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| // splitIssuerDomainName splits an RFC 8659 issue-value into issuer-domain-name | ||
| // and raw parameter segments. It returns zero values when issuer-domain-name is | ||
| // missing. | ||
| func splitIssuerDomainName(raw string) (string, []string) { | ||
| // Split into issuer-domain-name and parameters. | ||
| parts := strings.Split(raw, ";") | ||
| if len(parts) == 0 { | ||
| return "", nil | ||
| } | ||
| // Parse issuer-domain-name. | ||
| issuerDomainName := trimWSP(parts[0]) | ||
| if issuerDomainName == "" { | ||
| return "", nil | ||
| } | ||
| return issuerDomainName, parts[1:] | ||
| } | ||
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| // parseDNSPersistIssueValues parses RFC 8659 issue-value parameters for a | ||
| // dns-persist-01 TXT record and returns the extracted fields. It returns an | ||
| // error if any parameter is malformed. | ||
| func parseDNSPersistIssueValues(issuerDomainName string, paramsRaw []string) (*dnsPersistIssueValue, error) { | ||
| result := &dnsPersistIssueValue{issuerDomain: issuerDomainName} | ||
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| // Parse parameters (with optional surrounding WSP). | ||
| seenTags := make(map[string]bool) | ||
| for _, param := range paramsRaw { | ||
| param = trimWSP(param) | ||
| if param == "" { | ||
| return nil, errors.New("empty parameter or trailing semicolon provided") | ||
| } | ||
| // Capture each tag=value pair. | ||
| tagValue := strings.SplitN(param, "=", 2) | ||
| if len(tagValue) != 2 { | ||
| return nil, fmt.Errorf("malformed parameter %q should be tag=value pair", param) | ||
| } | ||
| tag := trimWSP(tagValue[0]) | ||
| value := trimWSP(tagValue[1]) | ||
| if tag == "" { | ||
| return nil, fmt.Errorf("malformed parameter %q, empty tag", param) | ||
| } | ||
| canonicalTag := strings.ToLower(tag) | ||
| if seenTags[canonicalTag] { | ||
| return nil, fmt.Errorf("duplicate parameter %q", tag) | ||
| } | ||
| seenTags[canonicalTag] = true | ||
| // Ensure values contain no whitespace/control/non-ASCII characters. | ||
| for _, r := range value { | ||
| if (r >= 0x21 && r <= 0x3A) || (r >= 0x3C && r <= 0x7E) { | ||
| continue | ||
| } | ||
| return nil, fmt.Errorf("malformed value %q for tag %q", value, tag) | ||
| } | ||
| // Finally, capture expected tag values. | ||
| // | ||
| // Note: according to RFC 8659 matching of tags is case insensitive. | ||
| switch canonicalTag { | ||
| case "accounturi": | ||
| if value == "" { | ||
| return nil, fmt.Errorf("empty value provided for mandatory accounturi") | ||
| } | ||
| result.accountURI = value | ||
| case "policy": | ||
| // Per the dns-persist-01 specification, if the policy tag is | ||
| // present parameter's tag and defined values MUST be treated as | ||
| // case-insensitive. | ||
| if value != "" && strings.ToLower(value) != "wildcard" { | ||
| // If the policy parameter's value is anything other than | ||
| // "wildcard", the CA MUST proceed as if the policy parameter | ||
| // were not present. | ||
| value = "" | ||
| } | ||
| result.policy = value | ||
| case "persistuntil": | ||
| persistUntilVal, err := strconv.ParseInt(value, 10, 64) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("malformed persistUntil timestamp %q", value) | ||
| } | ||
| persistUntil := time.Unix(persistUntilVal, 0).UTC() | ||
| result.persistUntil = &persistUntil | ||
| } | ||
| } | ||
| return result, nil | ||
| } | ||
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| func (va VAImpl) validateDNSPersist01(task *vaTask) *core.ValidationRecord { | ||
| challengeSubdomain := fmt.Sprintf("%s.%s", "_validation-persist", task.Identifier.Value) | ||
| result := &core.ValidationRecord{ | ||
| URL: challengeSubdomain, | ||
| ValidatedAt: time.Now(), | ||
| } | ||
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| txtRecords, err := va.getTXTEntry(challengeSubdomain) | ||
| if err != nil { | ||
| result.Error = acme.UnauthorizedProblem( | ||
| fmt.Sprintf("Error retrieving TXT records for DNS-PERSIST-01 challenge: %s", err)) | ||
| return result | ||
| } | ||
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| if len(txtRecords) == 0 { | ||
| result.Error = acme.UnauthorizedProblem("No TXT records found for DNS-PERSIST-01 challenge") | ||
| return result | ||
| } | ||
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| task.Challenge.RLock() | ||
| issuerNames := append([]string(nil), task.Challenge.IssuerDomainNames...) | ||
|
beautifulentropy marked this conversation as resolved.
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| task.Challenge.RUnlock() | ||
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| var syntaxErrs []string | ||
| var authorizationErrs []string | ||
| for _, record := range txtRecords { | ||
| issuerDomainName, paramsRaw := splitIssuerDomainName(record) | ||
| if !slices.Contains(issuerNames, issuerDomainName) { | ||
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beautifulentropy marked this conversation as resolved.
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| continue | ||
| } | ||
| issueValue, err := parseDNSPersistIssueValues(issuerDomainName, paramsRaw) | ||
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beautifulentropy marked this conversation as resolved.
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| if err != nil { | ||
| // We know if this record was intended for us but it is malformed, | ||
| // we can continue checking other records but we should report the | ||
| // syntax error if no other record authorizes the challenge. | ||
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Comment on lines
+692
to
+694
Contributor
There was a problem hiding this comment. Checking the spec, it seems not fully specified whether a CA should ignore malformed records that are intended for it. Closest seems to be: 4.1.1. Coexistence of Records But honestly I think it would be better to just error on any malformed record that has your issuer; or maybe any malformed record at all. I'll file an issue on the spec. Let's keep the behavior here as-is, pending any spec changes.
Contributor
There was a problem hiding this comment. Considering those statements:
I would read that as "all intended records are validated", but you are right that it isn't clear what to do then. It is a bigger question with regards to how multiple records that are intended for the same CA are handled,
In particular this is an important use case to allow in my opinion. |
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| syntaxErrs = append(syntaxErrs, fmt.Sprintf( | ||
| "Error parsing DNS-PERSIST-01 challenge TXT record with issuer-domain-name %q: %s", issuerDomainName, err)) | ||
| continue | ||
| } | ||
| if issueValue.accountURI == "" { | ||
| syntaxErrs = append(syntaxErrs, fmt.Sprintf( | ||
| "Error parsing DNS-PERSIST-01 challenge TXT record with issuer-domain-name %q: missing mandatory accountURI parameter", issuerDomainName)) | ||
| continue | ||
| } | ||
| if issueValue.accountURI != task.AccountURL { | ||
| authorizationErrs = append(authorizationErrs, fmt.Sprintf( | ||
| "Error parsing DNS-PERSIST-01 challenge TXT record with issuer-domain-name %q: accounturi mismatch: expected %q, got %q", | ||
| issuerDomainName, task.AccountURL, issueValue.accountURI)) | ||
| continue | ||
| } | ||
| // Per the dns-persist-01 specification, if the policy tag is present | ||
| // parameter's defined values MUST be treated as case-insensitive. | ||
| if task.Wildcard && strings.ToLower(issueValue.policy) != "wildcard" { | ||
| authorizationErrs = append(authorizationErrs, fmt.Sprintf( | ||
| "Error parsing DNS-PERSIST-01 challenge TXT record with issuer-domain-name %q: policy mismatch: expected \"wildcard\", got %q", | ||
| issuerDomainName, issueValue.policy)) | ||
| continue | ||
| } | ||
| if issueValue.persistUntil != nil && result.ValidatedAt.After(*issueValue.persistUntil) { | ||
| authorizationErrs = append(authorizationErrs, fmt.Sprintf( | ||
| "Error parsing DNS-PERSIST-01 challenge TXT record with issuer-domain-name %q, validation time %s is after persistUntil %s", | ||
| issuerDomainName, result.ValidatedAt.Format(time.RFC3339), issueValue.persistUntil.Format(time.RFC3339))) | ||
| continue | ||
| } | ||
| return result | ||
| } | ||
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| if len(syntaxErrs) > 0 { | ||
| result.Error = acme.MalformedProblem(strings.Join(syntaxErrs, "; ")) | ||
| return result | ||
| } | ||
| if len(authorizationErrs) > 0 { | ||
| result.Error = acme.UnauthorizedProblem(strings.Join(authorizationErrs, "; ")) | ||
| return result | ||
| } | ||
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| result.Error = acme.UnauthorizedProblem("No valid TXT record found for DNS-PERSIST-01 challenge") | ||
| return result | ||
| } | ||
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| // NOTE(@cpu): fetchHTTP only fetches the ACME HTTP-01 challenge path for | ||
| // a given challenge & identifier domain. It is not a challenge agnostic general | ||
| // purpose HTTP function | ||
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@@ -662,8 +845,12 @@ func (va VAImpl) getTXTEntry(name string) ([]string, error) { | |
| } | ||
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| for _, record := range in.Answer { | ||
| t, ok := record.(*dns.TXT) | ||
| if ok { | ||
| // One TXT RR may contain multiple RFC 1035 <character-string> | ||
| // elements (each up to 255 data octets). Concatenate them to | ||
| // recover the full value. | ||
| txts = append(txts, strings.Join(t.Txt, "")) | ||
| } | ||
| } | ||
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I don't love splitting these two functions like this, but I'm not seeing a better way to peek at the issuer-domain-name, without performing a second split. So, it feels like if we're going to split we might as well return the issuer-domain-name string and the remainder []string. That way we don't have to do that work again. Let me know if you have other alternatives.