diff --git a/internal/x509util/verify.go b/internal/x509util/verify.go index 1ccad19..620e84b 100644 --- a/internal/x509util/verify.go +++ b/internal/x509util/verify.go @@ -11,8 +11,6 @@ import ( "crypto/x509/pkix" "errors" "fmt" - "net" - "net/url" "strings" ) @@ -68,295 +66,6 @@ const ( 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 i == 0 { // domain == "" - // domain is prefixed with an empty label, append an empty - // string to reverseLabels to indicate this. - reverseLabels = append(reverseLabels, "") - } - } - } - - 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 -} - // isValid performs validity checks on c given that it is a candidate to append // to the chain in currentChain. func isValid(c *x509.Certificate, certType int, currentChain []*x509.Certificate, opts *VerifyOptions) error {