| // Copyright 2011 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| package x509 |
| |
| import ( |
| "bytes" |
| "errors" |
| "fmt" |
| "net" |
| "net/url" |
| "reflect" |
| "runtime" |
| "strings" |
| "time" |
| "unicode/utf8" |
| ) |
| |
| type InvalidReason int |
| |
| const ( |
| // NotAuthorizedToSign results when a certificate is signed by another |
| // which isn't marked as a CA certificate. |
| NotAuthorizedToSign InvalidReason = iota |
| // Expired results when a certificate has expired, based on the time |
| // given in the VerifyOptions. |
| Expired |
| // CANotAuthorizedForThisName results when an intermediate or root |
| // certificate has a name constraint which doesn't permit a DNS or |
| // other name (including IP address) in the leaf certificate. |
| CANotAuthorizedForThisName |
| // TooManyIntermediates results when a path length constraint is |
| // violated. |
| TooManyIntermediates |
| // IncompatibleUsage results when the certificate's key usage indicates |
| // that it may only be used for a different purpose. |
| IncompatibleUsage |
| // NameMismatch results when the subject name of a parent certificate |
| // does not match the issuer name in the child. |
| NameMismatch |
| // NameConstraintsWithoutSANs is a legacy error and is no longer returned. |
| NameConstraintsWithoutSANs |
| // UnconstrainedName results when a CA certificate contains permitted |
| // name constraints, but leaf certificate contains a name of an |
| // unsupported or unconstrained type. |
| UnconstrainedName |
| // TooManyConstraints results when the number of comparison operations |
| // needed to check a certificate exceeds the limit set by |
| // VerifyOptions.MaxConstraintComparisions. This limit exists to |
| // prevent pathological certificates can consuming excessive amounts of |
| // CPU time to verify. |
| TooManyConstraints |
| // CANotAuthorizedForExtKeyUsage results when an intermediate or root |
| // certificate does not permit a requested extended key usage. |
| CANotAuthorizedForExtKeyUsage |
| ) |
| |
| // CertificateInvalidError results when an odd error occurs. Users of this |
| // library probably want to handle all these errors uniformly. |
| type CertificateInvalidError struct { |
| Cert *Certificate |
| Reason InvalidReason |
| Detail string |
| } |
| |
| func (e CertificateInvalidError) Error() string { |
| switch e.Reason { |
| case NotAuthorizedToSign: |
| return "x509: certificate is not authorized to sign other certificates" |
| case Expired: |
| return "x509: certificate has expired or is not yet valid: " + e.Detail |
| case CANotAuthorizedForThisName: |
| return "x509: a root or intermediate certificate is not authorized to sign for this name: " + e.Detail |
| case CANotAuthorizedForExtKeyUsage: |
| return "x509: a root or intermediate certificate is not authorized for an extended key usage: " + e.Detail |
| case TooManyIntermediates: |
| return "x509: too many intermediates for path length constraint" |
| case IncompatibleUsage: |
| return "x509: certificate specifies an incompatible key usage" |
| case NameMismatch: |
| return "x509: issuer name does not match subject from issuing certificate" |
| case NameConstraintsWithoutSANs: |
| return "x509: issuer has name constraints but leaf doesn't have a SAN extension" |
| case UnconstrainedName: |
| return "x509: issuer has name constraints but leaf contains unknown or unconstrained name: " + e.Detail |
| } |
| return "x509: unknown error" |
| } |
| |
| // HostnameError results when the set of authorized names doesn't match the |
| // requested name. |
| type HostnameError struct { |
| Certificate *Certificate |
| Host string |
| } |
| |
| func (h HostnameError) Error() string { |
| c := h.Certificate |
| |
| if !c.hasSANExtension() && matchHostnames(c.Subject.CommonName, h.Host) { |
| return "x509: certificate relies on legacy Common Name field, use SANs instead" |
| } |
| |
| var valid string |
| if ip := net.ParseIP(h.Host); ip != nil { |
| // Trying to validate an IP |
| if len(c.IPAddresses) == 0 { |
| return "x509: cannot validate certificate for " + h.Host + " because it doesn't contain any IP SANs" |
| } |
| for _, san := range c.IPAddresses { |
| if len(valid) > 0 { |
| valid += ", " |
| } |
| valid += san.String() |
| } |
| } else { |
| valid = strings.Join(c.DNSNames, ", ") |
| } |
| |
| if len(valid) == 0 { |
| return "x509: certificate is not valid for any names, but wanted to match " + h.Host |
| } |
| return "x509: certificate is valid for " + valid + ", not " + h.Host |
| } |
| |
| // UnknownAuthorityError results when the certificate issuer is unknown |
| type UnknownAuthorityError struct { |
| Cert *Certificate |
| // hintErr contains an error that may be helpful in determining why an |
| // authority wasn't found. |
| hintErr error |
| // hintCert contains a possible authority certificate that was rejected |
| // because of the error in hintErr. |
| hintCert *Certificate |
| } |
| |
| func (e UnknownAuthorityError) Error() string { |
| s := "x509: certificate signed by unknown authority" |
| if e.hintErr != nil { |
| certName := e.hintCert.Subject.CommonName |
| if len(certName) == 0 { |
| if len(e.hintCert.Subject.Organization) > 0 { |
| certName = e.hintCert.Subject.Organization[0] |
| } else { |
| certName = "serial:" + e.hintCert.SerialNumber.String() |
| } |
| } |
| s += fmt.Sprintf(" (possibly because of %q while trying to verify candidate authority certificate %q)", e.hintErr, certName) |
| } |
| return s |
| } |
| |
| // SystemRootsError results when we fail to load the system root certificates. |
| type SystemRootsError struct { |
| Err error |
| } |
| |
| func (se SystemRootsError) Error() string { |
| msg := "x509: failed to load system roots and no roots provided" |
| if se.Err != nil { |
| return msg + "; " + se.Err.Error() |
| } |
| return msg |
| } |
| |
| func (se SystemRootsError) Unwrap() error { return se.Err } |
| |
| // errNotParsed is returned when a certificate without ASN.1 contents is |
| // verified. Platform-specific verification needs the ASN.1 contents. |
| var errNotParsed = errors.New("x509: missing ASN.1 contents; use ParseCertificate") |
| |
| // VerifyOptions contains parameters for Certificate.Verify. |
| type VerifyOptions struct { |
| // DNSName, if set, is checked against the leaf certificate with |
| // Certificate.VerifyHostname or the platform verifier. |
| DNSName string |
| |
| // Intermediates is an optional pool of certificates that are not trust |
| // anchors, but can be used to form a chain from the leaf certificate to a |
| // root certificate. |
| Intermediates *CertPool |
| // Roots is the set of trusted root certificates the leaf certificate needs |
| // to chain up to. If nil, the system roots or the platform verifier are used. |
| Roots *CertPool |
| |
| // CurrentTime is used to check the validity of all certificates in the |
| // chain. If zero, the current time is used. |
| CurrentTime time.Time |
| |
| // KeyUsages specifies which Extended Key Usage values are acceptable. A |
| // chain is accepted if it allows any of the listed values. An empty list |
| // means ExtKeyUsageServerAuth. To accept any key usage, include ExtKeyUsageAny. |
| KeyUsages []ExtKeyUsage |
| |
| // MaxConstraintComparisions is the maximum number of comparisons to |
| // perform when checking a given certificate's name constraints. If |
| // zero, a sensible default is used. This limit prevents pathological |
| // certificates from consuming excessive amounts of CPU time when |
| // validating. It does not apply to the platform verifier. |
| MaxConstraintComparisions int |
| } |
| |
| const ( |
| leafCertificate = iota |
| intermediateCertificate |
| rootCertificate |
| ) |
| |
| // rfc2821Mailbox represents a “mailbox” (which is an email address to most |
| // people) by breaking it into the “local” (i.e. before the '@') and “domain” |
| // parts. |
| type rfc2821Mailbox struct { |
| local, domain string |
| } |
| |
| // parseRFC2821Mailbox parses an email address into local and domain parts, |
| // based on the ABNF for a “Mailbox” from RFC 2821. According to RFC 5280, |
| // Section 4.2.1.6 that's correct for an rfc822Name from a certificate: “The |
| // format of an rfc822Name is a "Mailbox" as defined in RFC 2821, Section 4.1.2”. |
| func parseRFC2821Mailbox(in string) (mailbox rfc2821Mailbox, ok bool) { |
| if len(in) == 0 { |
| return mailbox, false |
| } |
| |
| localPartBytes := make([]byte, 0, len(in)/2) |
| |
| if in[0] == '"' { |
| // Quoted-string = DQUOTE *qcontent DQUOTE |
| // non-whitespace-control = %d1-8 / %d11 / %d12 / %d14-31 / %d127 |
| // qcontent = qtext / quoted-pair |
| // qtext = non-whitespace-control / |
| // %d33 / %d35-91 / %d93-126 |
| // quoted-pair = ("\" text) / obs-qp |
| // text = %d1-9 / %d11 / %d12 / %d14-127 / obs-text |
| // |
| // (Names beginning with “obs-” are the obsolete syntax from RFC 2822, |
| // Section 4. Since it has been 16 years, we no longer accept that.) |
| in = in[1:] |
| QuotedString: |
| for { |
| if len(in) == 0 { |
| return mailbox, false |
| } |
| c := in[0] |
| in = in[1:] |
| |
| switch { |
| case c == '"': |
| break QuotedString |
| |
| case c == '\\': |
| // quoted-pair |
| if len(in) == 0 { |
| return mailbox, false |
| } |
| if in[0] == 11 || |
| in[0] == 12 || |
| (1 <= in[0] && in[0] <= 9) || |
| (14 <= in[0] && in[0] <= 127) { |
| localPartBytes = append(localPartBytes, in[0]) |
| in = in[1:] |
| } else { |
| return mailbox, false |
| } |
| |
| case c == 11 || |
| c == 12 || |
| // Space (char 32) is not allowed based on the |
| // BNF, but RFC 3696 gives an example that |
| // assumes that it is. Several “verified” |
| // errata continue to argue about this point. |
| // We choose to accept it. |
| c == 32 || |
| c == 33 || |
| c == 127 || |
| (1 <= c && c <= 8) || |
| (14 <= c && c <= 31) || |
| (35 <= c && c <= 91) || |
| (93 <= c && c <= 126): |
| // qtext |
| localPartBytes = append(localPartBytes, c) |
| |
| default: |
| return mailbox, false |
| } |
| } |
| } else { |
| // Atom ("." Atom)* |
| NextChar: |
| for len(in) > 0 { |
| // atext from RFC 2822, Section 3.2.4 |
| c := in[0] |
| |
| switch { |
| case c == '\\': |
| // Examples given in RFC 3696 suggest that |
| // escaped characters can appear outside of a |
| // quoted string. Several “verified” errata |
| // continue to argue the point. We choose to |
| // accept it. |
| in = in[1:] |
| if len(in) == 0 { |
| return mailbox, false |
| } |
| fallthrough |
| |
| case ('0' <= c && c <= '9') || |
| ('a' <= c && c <= 'z') || |
| ('A' <= c && c <= 'Z') || |
| c == '!' || c == '#' || c == '$' || c == '%' || |
| c == '&' || c == '\'' || c == '*' || c == '+' || |
| c == '-' || c == '/' || c == '=' || c == '?' || |
| c == '^' || c == '_' || c == '`' || c == '{' || |
| c == '|' || c == '}' || c == '~' || c == '.': |
| localPartBytes = append(localPartBytes, in[0]) |
| in = in[1:] |
| |
| default: |
| break NextChar |
| } |
| } |
| |
| if len(localPartBytes) == 0 { |
| return mailbox, false |
| } |
| |
| // From RFC 3696, Section 3: |
| // “period (".") may also appear, but may not be used to start |
| // or end the local part, nor may two or more consecutive |
| // periods appear.” |
| twoDots := []byte{'.', '.'} |
| if localPartBytes[0] == '.' || |
| localPartBytes[len(localPartBytes)-1] == '.' || |
| bytes.Contains(localPartBytes, twoDots) { |
| return mailbox, false |
| } |
| } |
| |
| if len(in) == 0 || in[0] != '@' { |
| return mailbox, false |
| } |
| in = in[1:] |
| |
| // The RFC species a format for domains, but that's known to be |
| // violated in practice so we accept that anything after an '@' is the |
| // domain part. |
| if _, ok := domainToReverseLabels(in); !ok { |
| return mailbox, false |
| } |
| |
| mailbox.local = string(localPartBytes) |
| mailbox.domain = in |
| return mailbox, true |
| } |
| |
| // domainToReverseLabels converts a textual domain name like foo.example.com to |
| // the list of labels in reverse order, e.g. ["com", "example", "foo"]. |
| func domainToReverseLabels(domain string) (reverseLabels []string, ok bool) { |
| for len(domain) > 0 { |
| if i := strings.LastIndexByte(domain, '.'); i == -1 { |
| reverseLabels = append(reverseLabels, domain) |
| domain = "" |
| } else { |
| reverseLabels = append(reverseLabels, domain[i+1:]) |
| domain = domain[:i] |
| } |
| } |
| |
| if len(reverseLabels) > 0 && len(reverseLabels[0]) == 0 { |
| // An empty label at the end indicates an absolute value. |
| return nil, false |
| } |
| |
| for _, label := range reverseLabels { |
| if len(label) == 0 { |
| // Empty labels are otherwise invalid. |
| return nil, false |
| } |
| |
| for _, c := range label { |
| if c < 33 || c > 126 { |
| // Invalid character. |
| return nil, false |
| } |
| } |
| } |
| |
| return reverseLabels, true |
| } |
| |
| func matchEmailConstraint(mailbox rfc2821Mailbox, constraint string) (bool, error) { |
| // If the constraint contains an @, then it specifies an exact mailbox |
| // name. |
| if strings.Contains(constraint, "@") { |
| constraintMailbox, ok := parseRFC2821Mailbox(constraint) |
| if !ok { |
| return false, fmt.Errorf("x509: internal error: cannot parse constraint %q", constraint) |
| } |
| return mailbox.local == constraintMailbox.local && strings.EqualFold(mailbox.domain, constraintMailbox.domain), nil |
| } |
| |
| // Otherwise the constraint is like a DNS constraint of the domain part |
| // of the mailbox. |
| return matchDomainConstraint(mailbox.domain, constraint) |
| } |
| |
| func matchURIConstraint(uri *url.URL, constraint string) (bool, error) { |
| // From RFC 5280, Section 4.2.1.10: |
| // “a uniformResourceIdentifier that does not include an authority |
| // component with a host name specified as a fully qualified domain |
| // name (e.g., if the URI either does not include an authority |
| // component or includes an authority component in which the host name |
| // is specified as an IP address), then the application MUST reject the |
| // certificate.” |
| |
| host := uri.Host |
| if len(host) == 0 { |
| return false, fmt.Errorf("URI with empty host (%q) cannot be matched against constraints", uri.String()) |
| } |
| |
| if strings.Contains(host, ":") && !strings.HasSuffix(host, "]") { |
| var err error |
| host, _, err = net.SplitHostPort(uri.Host) |
| if err != nil { |
| return false, err |
| } |
| } |
| |
| if strings.HasPrefix(host, "[") && strings.HasSuffix(host, "]") || |
| net.ParseIP(host) != nil { |
| return false, fmt.Errorf("URI with IP (%q) cannot be matched against constraints", uri.String()) |
| } |
| |
| return matchDomainConstraint(host, constraint) |
| } |
| |
| func matchIPConstraint(ip net.IP, constraint *net.IPNet) (bool, error) { |
| if len(ip) != len(constraint.IP) { |
| return false, nil |
| } |
| |
| for i := range ip { |
| if mask := constraint.Mask[i]; ip[i]&mask != constraint.IP[i]&mask { |
| return false, nil |
| } |
| } |
| |
| return true, nil |
| } |
| |
| func matchDomainConstraint(domain, constraint string) (bool, error) { |
| // The meaning of zero length constraints is not specified, but this |
| // code follows NSS and accepts them as matching everything. |
| if len(constraint) == 0 { |
| return true, nil |
| } |
| |
| domainLabels, ok := domainToReverseLabels(domain) |
| if !ok { |
| return false, fmt.Errorf("x509: internal error: cannot parse domain %q", domain) |
| } |
| |
| // RFC 5280 says that a leading period in a domain name means that at |
| // least one label must be prepended, but only for URI and email |
| // constraints, not DNS constraints. The code also supports that |
| // behaviour for DNS constraints. |
| |
| mustHaveSubdomains := false |
| if constraint[0] == '.' { |
| mustHaveSubdomains = true |
| constraint = constraint[1:] |
| } |
| |
| constraintLabels, ok := domainToReverseLabels(constraint) |
| if !ok { |
| return false, fmt.Errorf("x509: internal error: cannot parse domain %q", constraint) |
| } |
| |
| if len(domainLabels) < len(constraintLabels) || |
| (mustHaveSubdomains && len(domainLabels) == len(constraintLabels)) { |
| return false, nil |
| } |
| |
| for i, constraintLabel := range constraintLabels { |
| if !strings.EqualFold(constraintLabel, domainLabels[i]) { |
| return false, nil |
| } |
| } |
| |
| return true, nil |
| } |
| |
| // checkNameConstraints checks that c permits a child certificate to claim the |
| // given name, of type nameType. The argument parsedName contains the parsed |
| // form of name, suitable for passing to the match function. The total number |
| // of comparisons is tracked in the given count and should not exceed the given |
| // limit. |
| func (c *Certificate) checkNameConstraints(count *int, |
| maxConstraintComparisons int, |
| nameType string, |
| name string, |
| parsedName any, |
| match func(parsedName, constraint any) (match bool, err error), |
| permitted, excluded any) error { |
| |
| excludedValue := reflect.ValueOf(excluded) |
| |
| *count += excludedValue.Len() |
| if *count > maxConstraintComparisons { |
| return CertificateInvalidError{c, TooManyConstraints, ""} |
| } |
| |
| for i := 0; i < excludedValue.Len(); i++ { |
| constraint := excludedValue.Index(i).Interface() |
| match, err := match(parsedName, constraint) |
| if err != nil { |
| return CertificateInvalidError{c, CANotAuthorizedForThisName, err.Error()} |
| } |
| |
| if match { |
| return CertificateInvalidError{c, CANotAuthorizedForThisName, fmt.Sprintf("%s %q is excluded by constraint %q", nameType, name, constraint)} |
| } |
| } |
| |
| permittedValue := reflect.ValueOf(permitted) |
| |
| *count += permittedValue.Len() |
| if *count > maxConstraintComparisons { |
| return CertificateInvalidError{c, TooManyConstraints, ""} |
| } |
| |
| ok := true |
| for i := 0; i < permittedValue.Len(); i++ { |
| constraint := permittedValue.Index(i).Interface() |
| |
| var err error |
| if ok, err = match(parsedName, constraint); err != nil { |
| return CertificateInvalidError{c, CANotAuthorizedForThisName, err.Error()} |
| } |
| |
| if ok { |
| break |
| } |
| } |
| |
| if !ok { |
| return CertificateInvalidError{c, CANotAuthorizedForThisName, fmt.Sprintf("%s %q is not permitted by any constraint", nameType, name)} |
| } |
| |
| return nil |
| } |
| |
| // isValid performs validity checks on c given that it is a candidate to append |
| // to the chain in currentChain. |
| func (c *Certificate) isValid(certType int, currentChain []*Certificate, opts *VerifyOptions) error { |
| if len(c.UnhandledCriticalExtensions) > 0 { |
| return UnhandledCriticalExtension{} |
| } |
| |
| if len(currentChain) > 0 { |
| child := currentChain[len(currentChain)-1] |
| if !bytes.Equal(child.RawIssuer, c.RawSubject) { |
| return CertificateInvalidError{c, NameMismatch, ""} |
| } |
| } |
| |
| now := opts.CurrentTime |
| if now.IsZero() { |
| now = time.Now() |
| } |
| if now.Before(c.NotBefore) { |
| return CertificateInvalidError{ |
| Cert: c, |
| Reason: Expired, |
| Detail: fmt.Sprintf("current time %s is before %s", now.Format(time.RFC3339), c.NotBefore.Format(time.RFC3339)), |
| } |
| } else if now.After(c.NotAfter) { |
| return CertificateInvalidError{ |
| Cert: c, |
| Reason: Expired, |
| Detail: fmt.Sprintf("current time %s is after %s", now.Format(time.RFC3339), c.NotAfter.Format(time.RFC3339)), |
| } |
| } |
| |
| maxConstraintComparisons := opts.MaxConstraintComparisions |
| if maxConstraintComparisons == 0 { |
| maxConstraintComparisons = 250000 |
| } |
| comparisonCount := 0 |
| |
| var leaf *Certificate |
| if certType == intermediateCertificate || certType == rootCertificate { |
| if len(currentChain) == 0 { |
| return errors.New("x509: internal error: empty chain when appending CA cert") |
| } |
| leaf = currentChain[0] |
| } |
| |
| if (certType == intermediateCertificate || certType == rootCertificate) && |
| c.hasNameConstraints() && leaf.hasSANExtension() { |
| err := forEachSAN(leaf.getSANExtension(), func(tag int, data []byte) error { |
| switch tag { |
| case nameTypeEmail: |
| name := string(data) |
| mailbox, ok := parseRFC2821Mailbox(name) |
| if !ok { |
| return fmt.Errorf("x509: cannot parse rfc822Name %q", mailbox) |
| } |
| |
| if err := c.checkNameConstraints(&comparisonCount, maxConstraintComparisons, "email address", name, mailbox, |
| func(parsedName, constraint any) (bool, error) { |
| return matchEmailConstraint(parsedName.(rfc2821Mailbox), constraint.(string)) |
| }, c.PermittedEmailAddresses, c.ExcludedEmailAddresses); err != nil { |
| return err |
| } |
| |
| case nameTypeDNS: |
| name := string(data) |
| if _, ok := domainToReverseLabels(name); !ok { |
| return fmt.Errorf("x509: cannot parse dnsName %q", name) |
| } |
| |
| if err := c.checkNameConstraints(&comparisonCount, maxConstraintComparisons, "DNS name", name, name, |
| func(parsedName, constraint any) (bool, error) { |
| return matchDomainConstraint(parsedName.(string), constraint.(string)) |
| }, c.PermittedDNSDomains, c.ExcludedDNSDomains); err != nil { |
| return err |
| } |
| |
| case nameTypeURI: |
| name := string(data) |
| uri, err := url.Parse(name) |
| if err != nil { |
| return fmt.Errorf("x509: internal error: URI SAN %q failed to parse", name) |
| } |
| |
| if err := c.checkNameConstraints(&comparisonCount, maxConstraintComparisons, "URI", name, uri, |
| func(parsedName, constraint any) (bool, error) { |
| return matchURIConstraint(parsedName.(*url.URL), constraint.(string)) |
| }, c.PermittedURIDomains, c.ExcludedURIDomains); err != nil { |
| return err |
| } |
| |
| case nameTypeIP: |
| ip := net.IP(data) |
| if l := len(ip); l != net.IPv4len && l != net.IPv6len { |
| return fmt.Errorf("x509: internal error: IP SAN %x failed to parse", data) |
| } |
| |
| if err := c.checkNameConstraints(&comparisonCount, maxConstraintComparisons, "IP address", ip.String(), ip, |
| func(parsedName, constraint any) (bool, error) { |
| return matchIPConstraint(parsedName.(net.IP), constraint.(*net.IPNet)) |
| }, c.PermittedIPRanges, c.ExcludedIPRanges); err != nil { |
| return err |
| } |
| |
| default: |
| // Unknown SAN types are ignored. |
| } |
| |
| return nil |
| }) |
| |
| if err != nil { |
| return err |
| } |
| } |
| |
| // KeyUsage status flags are ignored. From Engineering Security, Peter |
| // Gutmann: A European government CA marked its signing certificates as |
| // being valid for encryption only, but no-one noticed. Another |
| // European CA marked its signature keys as not being valid for |
| // signatures. A different CA marked its own trusted root certificate |
| // as being invalid for certificate signing. Another national CA |
| // distributed a certificate to be used to encrypt data for the |
| // country’s tax authority that was marked as only being usable for |
| // digital signatures but not for encryption. Yet another CA reversed |
| // the order of the bit flags in the keyUsage due to confusion over |
| // encoding endianness, essentially setting a random keyUsage in |
| // certificates that it issued. Another CA created a self-invalidating |
| // certificate by adding a certificate policy statement stipulating |
| // that the certificate had to be used strictly as specified in the |
| // keyUsage, and a keyUsage containing a flag indicating that the RSA |
| // encryption key could only be used for Diffie-Hellman key agreement. |
| |
| if certType == intermediateCertificate && (!c.BasicConstraintsValid || !c.IsCA) { |
| return CertificateInvalidError{c, NotAuthorizedToSign, ""} |
| } |
| |
| if c.BasicConstraintsValid && c.MaxPathLen >= 0 { |
| numIntermediates := len(currentChain) - 1 |
| if numIntermediates > c.MaxPathLen { |
| return CertificateInvalidError{c, TooManyIntermediates, ""} |
| } |
| } |
| |
| return nil |
| } |
| |
| // Verify attempts to verify c by building one or more chains from c to a |
| // certificate in opts.Roots, using certificates in opts.Intermediates if |
| // needed. If successful, it returns one or more chains where the first |
| // element of the chain is c and the last element is from opts.Roots. |
| // |
| // If opts.Roots is nil, the platform verifier might be used, and |
| // verification details might differ from what is described below. If system |
| // roots are unavailable the returned error will be of type SystemRootsError. |
| // |
| // Name constraints in the intermediates will be applied to all names claimed |
| // in the chain, not just opts.DNSName. Thus it is invalid for a leaf to claim |
| // example.com if an intermediate doesn't permit it, even if example.com is not |
| // the name being validated. Note that DirectoryName constraints are not |
| // supported. |
| // |
| // Name constraint validation follows the rules from RFC 5280, with the |
| // addition that DNS name constraints may use the leading period format |
| // defined for emails and URIs. When a constraint has a leading period |
| // it indicates that at least one additional label must be prepended to |
| // the constrained name to be considered valid. |
| // |
| // Extended Key Usage values are enforced nested down a chain, so an intermediate |
| // or root that enumerates EKUs prevents a leaf from asserting an EKU not in that |
| // list. (While this is not specified, it is common practice in order to limit |
| // the types of certificates a CA can issue.) |
| // |
| // WARNING: this function doesn't do any revocation checking. |
| func (c *Certificate) Verify(opts VerifyOptions) (chains [][]*Certificate, err error) { |
| // Platform-specific verification needs the ASN.1 contents so |
| // this makes the behavior consistent across platforms. |
| if len(c.Raw) == 0 { |
| return nil, errNotParsed |
| } |
| for i := 0; i < opts.Intermediates.len(); i++ { |
| c, err := opts.Intermediates.cert(i) |
| if err != nil { |
| return nil, fmt.Errorf("crypto/x509: error fetching intermediate: %w", err) |
| } |
| if len(c.Raw) == 0 { |
| return nil, errNotParsed |
| } |
| } |
| |
| // Use platform verifiers, where available, if Roots is from SystemCertPool. |
| if runtime.GOOS == "windows" || runtime.GOOS == "darwin" || runtime.GOOS == "ios" { |
| if opts.Roots == nil { |
| return c.systemVerify(&opts) |
| } |
| if opts.Roots != nil && opts.Roots.systemPool { |
| platformChains, err := c.systemVerify(&opts) |
| // If the platform verifier succeeded, or there are no additional |
| // roots, return the platform verifier result. Otherwise, continue |
| // with the Go verifier. |
| if err == nil || opts.Roots.len() == 0 { |
| return platformChains, err |
| } |
| } |
| } |
| |
| if opts.Roots == nil { |
| opts.Roots = systemRootsPool() |
| if opts.Roots == nil { |
| return nil, SystemRootsError{systemRootsErr} |
| } |
| } |
| |
| err = c.isValid(leafCertificate, nil, &opts) |
| if err != nil { |
| return |
| } |
| |
| if len(opts.DNSName) > 0 { |
| err = c.VerifyHostname(opts.DNSName) |
| if err != nil { |
| return |
| } |
| } |
| |
| var candidateChains [][]*Certificate |
| if opts.Roots.contains(c) { |
| candidateChains = append(candidateChains, []*Certificate{c}) |
| } else { |
| if candidateChains, err = c.buildChains(nil, []*Certificate{c}, nil, &opts); err != nil { |
| return nil, err |
| } |
| } |
| |
| keyUsages := opts.KeyUsages |
| if len(keyUsages) == 0 { |
| keyUsages = []ExtKeyUsage{ExtKeyUsageServerAuth} |
| } |
| |
| // If any key usage is acceptable then we're done. |
| for _, usage := range keyUsages { |
| if usage == ExtKeyUsageAny { |
| return candidateChains, nil |
| } |
| } |
| |
| for _, candidate := range candidateChains { |
| if checkChainForKeyUsage(candidate, keyUsages) { |
| chains = append(chains, candidate) |
| } |
| } |
| |
| if len(chains) == 0 { |
| return nil, CertificateInvalidError{c, IncompatibleUsage, ""} |
| } |
| |
| return chains, nil |
| } |
| |
| func appendToFreshChain(chain []*Certificate, cert *Certificate) []*Certificate { |
| n := make([]*Certificate, len(chain)+1) |
| copy(n, chain) |
| n[len(chain)] = cert |
| return n |
| } |
| |
| // maxChainSignatureChecks is the maximum number of CheckSignatureFrom calls |
| // that an invocation of buildChains will (transitively) make. Most chains are |
| // less than 15 certificates long, so this leaves space for multiple chains and |
| // for failed checks due to different intermediates having the same Subject. |
| const maxChainSignatureChecks = 100 |
| |
| func (c *Certificate) buildChains(cache map[*Certificate][][]*Certificate, currentChain []*Certificate, sigChecks *int, opts *VerifyOptions) (chains [][]*Certificate, err error) { |
| var ( |
| hintErr error |
| hintCert *Certificate |
| ) |
| |
| considerCandidate := func(certType int, candidate *Certificate) { |
| for _, cert := range currentChain { |
| if cert.Equal(candidate) { |
| return |
| } |
| } |
| |
| if sigChecks == nil { |
| sigChecks = new(int) |
| } |
| *sigChecks++ |
| if *sigChecks > maxChainSignatureChecks { |
| err = errors.New("x509: signature check attempts limit reached while verifying certificate chain") |
| return |
| } |
| |
| if err := c.CheckSignatureFrom(candidate); err != nil { |
| if hintErr == nil { |
| hintErr = err |
| hintCert = candidate |
| } |
| return |
| } |
| |
| err = candidate.isValid(certType, currentChain, opts) |
| if err != nil { |
| return |
| } |
| |
| switch certType { |
| case rootCertificate: |
| chains = append(chains, appendToFreshChain(currentChain, candidate)) |
| case intermediateCertificate: |
| if cache == nil { |
| cache = make(map[*Certificate][][]*Certificate) |
| } |
| childChains, ok := cache[candidate] |
| if !ok { |
| childChains, err = candidate.buildChains(cache, appendToFreshChain(currentChain, candidate), sigChecks, opts) |
| cache[candidate] = childChains |
| } |
| chains = append(chains, childChains...) |
| } |
| } |
| |
| for _, root := range opts.Roots.findPotentialParents(c) { |
| considerCandidate(rootCertificate, root) |
| } |
| for _, intermediate := range opts.Intermediates.findPotentialParents(c) { |
| considerCandidate(intermediateCertificate, intermediate) |
| } |
| |
| if len(chains) > 0 { |
| err = nil |
| } |
| if len(chains) == 0 && err == nil { |
| err = UnknownAuthorityError{c, hintErr, hintCert} |
| } |
| |
| return |
| } |
| |
| func validHostnamePattern(host string) bool { return validHostname(host, true) } |
| func validHostnameInput(host string) bool { return validHostname(host, false) } |
| |
| // validHostname reports whether host is a valid hostname that can be matched or |
| // matched against according to RFC 6125 2.2, with some leniency to accommodate |
| // legacy values. |
| func validHostname(host string, isPattern bool) bool { |
| if !isPattern { |
| host = strings.TrimSuffix(host, ".") |
| } |
| if len(host) == 0 { |
| return false |
| } |
| |
| for i, part := range strings.Split(host, ".") { |
| if part == "" { |
| // Empty label. |
| return false |
| } |
| if isPattern && i == 0 && part == "*" { |
| // Only allow full left-most wildcards, as those are the only ones |
| // we match, and matching literal '*' characters is probably never |
| // the expected behavior. |
| continue |
| } |
| for j, c := range part { |
| if 'a' <= c && c <= 'z' { |
| continue |
| } |
| if '0' <= c && c <= '9' { |
| continue |
| } |
| if 'A' <= c && c <= 'Z' { |
| continue |
| } |
| if c == '-' && j != 0 { |
| continue |
| } |
| if c == '_' { |
| // Not a valid character in hostnames, but commonly |
| // found in deployments outside the WebPKI. |
| continue |
| } |
| return false |
| } |
| } |
| |
| return true |
| } |
| |
| func matchExactly(hostA, hostB string) bool { |
| if hostA == "" || hostA == "." || hostB == "" || hostB == "." { |
| return false |
| } |
| return toLowerCaseASCII(hostA) == toLowerCaseASCII(hostB) |
| } |
| |
| func matchHostnames(pattern, host string) bool { |
| pattern = toLowerCaseASCII(pattern) |
| host = toLowerCaseASCII(strings.TrimSuffix(host, ".")) |
| |
| if len(pattern) == 0 || len(host) == 0 { |
| return false |
| } |
| |
| patternParts := strings.Split(pattern, ".") |
| hostParts := strings.Split(host, ".") |
| |
| if len(patternParts) != len(hostParts) { |
| return false |
| } |
| |
| for i, patternPart := range patternParts { |
| if i == 0 && patternPart == "*" { |
| continue |
| } |
| if patternPart != hostParts[i] { |
| return false |
| } |
| } |
| |
| return true |
| } |
| |
| // toLowerCaseASCII returns a lower-case version of in. See RFC 6125 6.4.1. We use |
| // an explicitly ASCII function to avoid any sharp corners resulting from |
| // performing Unicode operations on DNS labels. |
| func toLowerCaseASCII(in string) string { |
| // If the string is already lower-case then there's nothing to do. |
| isAlreadyLowerCase := true |
| for _, c := range in { |
| if c == utf8.RuneError { |
| // If we get a UTF-8 error then there might be |
| // upper-case ASCII bytes in the invalid sequence. |
| isAlreadyLowerCase = false |
| break |
| } |
| if 'A' <= c && c <= 'Z' { |
| isAlreadyLowerCase = false |
| break |
| } |
| } |
| |
| if isAlreadyLowerCase { |
| return in |
| } |
| |
| out := []byte(in) |
| for i, c := range out { |
| if 'A' <= c && c <= 'Z' { |
| out[i] += 'a' - 'A' |
| } |
| } |
| return string(out) |
| } |
| |
| // VerifyHostname returns nil if c is a valid certificate for the named host. |
| // Otherwise it returns an error describing the mismatch. |
| // |
| // IP addresses can be optionally enclosed in square brackets and are checked |
| // against the IPAddresses field. Other names are checked case insensitively |
| // against the DNSNames field. If the names are valid hostnames, the certificate |
| // fields can have a wildcard as the left-most label. |
| // |
| // Note that the legacy Common Name field is ignored. |
| func (c *Certificate) VerifyHostname(h string) error { |
| // IP addresses may be written in [ ]. |
| candidateIP := h |
| if len(h) >= 3 && h[0] == '[' && h[len(h)-1] == ']' { |
| candidateIP = h[1 : len(h)-1] |
| } |
| if ip := net.ParseIP(candidateIP); ip != nil { |
| // We only match IP addresses against IP SANs. |
| // See RFC 6125, Appendix B.2. |
| for _, candidate := range c.IPAddresses { |
| if ip.Equal(candidate) { |
| return nil |
| } |
| } |
| return HostnameError{c, candidateIP} |
| } |
| |
| candidateName := toLowerCaseASCII(h) // Save allocations inside the loop. |
| validCandidateName := validHostnameInput(candidateName) |
| |
| for _, match := range c.DNSNames { |
| // Ideally, we'd only match valid hostnames according to RFC 6125 like |
| // browsers (more or less) do, but in practice Go is used in a wider |
| // array of contexts and can't even assume DNS resolution. Instead, |
| // always allow perfect matches, and only apply wildcard and trailing |
| // dot processing to valid hostnames. |
| if validCandidateName && validHostnamePattern(match) { |
| if matchHostnames(match, candidateName) { |
| return nil |
| } |
| } else { |
| if matchExactly(match, candidateName) { |
| return nil |
| } |
| } |
| } |
| |
| return HostnameError{c, h} |
| } |
| |
| func checkChainForKeyUsage(chain []*Certificate, keyUsages []ExtKeyUsage) bool { |
| usages := make([]ExtKeyUsage, len(keyUsages)) |
| copy(usages, keyUsages) |
| |
| if len(chain) == 0 { |
| return false |
| } |
| |
| usagesRemaining := len(usages) |
| |
| // We walk down the list and cross out any usages that aren't supported |
| // by each certificate. If we cross out all the usages, then the chain |
| // is unacceptable. |
| |
| NextCert: |
| for i := len(chain) - 1; i >= 0; i-- { |
| cert := chain[i] |
| if len(cert.ExtKeyUsage) == 0 && len(cert.UnknownExtKeyUsage) == 0 { |
| // The certificate doesn't have any extended key usage specified. |
| continue |
| } |
| |
| for _, usage := range cert.ExtKeyUsage { |
| if usage == ExtKeyUsageAny { |
| // The certificate is explicitly good for any usage. |
| continue NextCert |
| } |
| } |
| |
| const invalidUsage ExtKeyUsage = -1 |
| |
| NextRequestedUsage: |
| for i, requestedUsage := range usages { |
| if requestedUsage == invalidUsage { |
| continue |
| } |
| |
| for _, usage := range cert.ExtKeyUsage { |
| if requestedUsage == usage { |
| continue NextRequestedUsage |
| } |
| } |
| |
| usages[i] = invalidUsage |
| usagesRemaining-- |
| if usagesRemaining == 0 { |
| return false |
| } |
| } |
| } |
| |
| return true |
| } |