* The name constraints extension provides permitted and excluded * subtrees that place restrictions on names that may be included within * a certificate issued by a given CA. Restrictions may apply to the * subject distinguished name or subject alternative names. Any name * matching a restriction in the excluded subtrees field is invalid * regardless of information appearing in the permitted subtrees. *
* The ASN.1 syntax for this is: *
* NameConstraints ::= SEQUENCE {
* permittedSubtrees [0] GeneralSubtrees OPTIONAL,
* excludedSubtrees [1] GeneralSubtrees OPTIONAL
* }
* GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
*
*
* @author Amit Kapoor
* @author Hemma Prafullchandra
* @see Extension
*/
public class NameConstraintsExtension extends Extension
implements Cloneable {
public static final String NAME = "NameConstraints";
// Private data members
private static final byte TAG_PERMITTED = 0;
private static final byte TAG_EXCLUDED = 1;
private GeneralSubtrees permitted = null;
private GeneralSubtrees excluded = null;
private boolean hasMin;
private boolean hasMax;
private boolean minMaxValid = false;
// Recalculate hasMin and hasMax flags.
private void calcMinMax() {
hasMin = false;
hasMax = false;
if (excluded != null) {
for (int i = 0; i < excluded.size(); i++) {
GeneralSubtree subtree = excluded.get(i);
if (subtree.getMinimum() != 0)
hasMin = true;
if (subtree.getMaximum() != -1)
hasMax = true;
}
}
if (permitted != null) {
for (int i = 0; i < permitted.size(); i++) {
GeneralSubtree subtree = permitted.get(i);
if (subtree.getMinimum() != 0)
hasMin = true;
if (subtree.getMaximum() != -1)
hasMax = true;
}
}
minMaxValid = true;
}
// Encode this extension value.
private void encodeThis() {
minMaxValid = false;
if (permitted == null && excluded == null) {
this.extensionValue = null;
return;
}
DerOutputStream seq = new DerOutputStream();
DerOutputStream tagged = new DerOutputStream();
if (permitted != null) {
DerOutputStream tmp = new DerOutputStream();
permitted.encode(tmp);
tagged.writeImplicit(DerValue.createTag(DerValue.TAG_CONTEXT,
true, TAG_PERMITTED), tmp);
}
if (excluded != null) {
DerOutputStream tmp = new DerOutputStream();
excluded.encode(tmp);
tagged.writeImplicit(DerValue.createTag(DerValue.TAG_CONTEXT,
true, TAG_EXCLUDED), tmp);
}
seq.write(DerValue.tag_Sequence, tagged);
this.extensionValue = seq.toByteArray();
}
/**
* The default constructor for this class. Both parameters are optional
* but at least one should be non null. The extension criticality
* is set to true.
*
* @param permitted the permitted GeneralSubtrees (null for optional).
* @param excluded the excluded GeneralSubtrees (null for optional).
*/
public NameConstraintsExtension(GeneralSubtrees permitted,
GeneralSubtrees excluded) {
if (permitted == null && excluded == null) {
throw new IllegalArgumentException(
"permitted and excluded cannot both be null");
}
this.permitted = permitted;
this.excluded = excluded;
this.extensionId = PKIXExtensions.NameConstraints_Id;
this.critical = true;
encodeThis();
}
/**
* Create the extension from the passed DER encoded value.
*
* @param critical true if the extension is to be treated as critical.
* @param value an array of DER encoded bytes of the actual value.
* @exception ClassCastException if value is not an array of bytes
* @exception IOException on error.
*/
public NameConstraintsExtension(Boolean critical, Object value)
throws IOException {
this.extensionId = PKIXExtensions.NameConstraints_Id;
this.critical = critical.booleanValue();
this.extensionValue = (byte[]) value;
DerValue val = new DerValue(this.extensionValue);
if (val.tag != DerValue.tag_Sequence) {
throw new IOException("Invalid encoding for" +
" NameConstraintsExtension.");
}
// NB. this is always encoded with the IMPLICIT tag
// The checks only make sense if we assume implicit tagging,
// with explicit tagging the form is always constructed.
// Note that all the fields in NameConstraints are defined as
// being OPTIONAL, i.e., there could be an empty SEQUENCE, resulting
// in val.data being null.
if (val.data == null)
return;
while (val.data.available() != 0) {
DerValue opt = val.data.getDerValue();
if (opt.isContextSpecific(TAG_PERMITTED) && opt.isConstructed()) {
if (permitted != null) {
throw new IOException("Duplicate permitted " +
"GeneralSubtrees in NameConstraintsExtension.");
}
opt.resetTag(DerValue.tag_Sequence);
permitted = new GeneralSubtrees(opt);
} else if (opt.isContextSpecific(TAG_EXCLUDED) &&
opt.isConstructed()) {
if (excluded != null) {
throw new IOException("Duplicate excluded " +
"GeneralSubtrees in NameConstraintsExtension.");
}
opt.resetTag(DerValue.tag_Sequence);
excluded = new GeneralSubtrees(opt);
} else
throw new IOException("Invalid encoding of " +
"NameConstraintsExtension.");
}
minMaxValid = false;
}
/**
* Return the printable string.
*/
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append(super.toString())
.append("NameConstraints: [");
if (permitted != null) {
sb.append("\n Permitted:")
.append(permitted);
}
if (excluded != null) {
sb.append("\n Excluded:")
.append(excluded);
}
sb.append(" ]\n");
return sb.toString();
}
/**
* Write the extension to the OutputStream.
*
* @param out the DerOutputStream to write the extension to.
*/
@Override
public void encode(DerOutputStream out) {
if (this.extensionValue == null) {
this.extensionId = PKIXExtensions.NameConstraints_Id;
this.critical = true;
encodeThis();
}
super.encode(out);
}
public GeneralSubtrees getPermittedSubtrees() {
return permitted;
}
public GeneralSubtrees getExcludedSubtrees() {
return excluded;
}
/**
* Return the name of this extension.
*/
@Override
public String getName() {
return NAME;
}
/**
* Merge additional name constraints with existing ones.
* This function is used in certification path processing
* to accumulate name constraints from successive certificates
* in the path. Note that NameConstraints can never be
* expanded by a merge, just remain constant or become more
* limiting.
* * IETF RFC 5280 specifies the processing of Name Constraints as * follows: *
* (j) If permittedSubtrees is present in the certificate, set the * constrained subtrees state variable to the intersection of its * previous value and the value indicated in the extension field. *
* (k) If excludedSubtrees is present in the certificate, set the * excluded subtrees state variable to the union of its previous * value and the value indicated in the extension field. * * @param newConstraints additional NameConstraints to be applied * @throws IOException on error */ public void merge(NameConstraintsExtension newConstraints) throws IOException { if (newConstraints == null) { // absence of any explicit constraints implies unconstrained return; } boolean updated = false; /* * If excludedSubtrees is present in the certificate, set the * excluded subtrees state variable to the union of its previous * value and the value indicated in the extension field. */ GeneralSubtrees newExcluded = newConstraints.getExcludedSubtrees(); if (excluded == null) { if (newExcluded != null) { excluded = (GeneralSubtrees) newExcluded.clone(); updated = true; } } else { if (newExcluded != null) { // Merge new excluded with current excluded (union) excluded.union(newExcluded); updated = true; } } /* * If permittedSubtrees is present in the certificate, set the * constrained subtrees state variable to the intersection of its * previous value and the value indicated in the extension field. */ GeneralSubtrees newPermitted = newConstraints.getPermittedSubtrees(); if (permitted == null) { if (newPermitted != null) { permitted = (GeneralSubtrees) newPermitted.clone(); updated = true; } } else { if (newPermitted != null) { // Merge new permitted with current permitted (intersection) newExcluded = permitted.intersect(newPermitted); // Merge new excluded subtrees to current excluded (union) if (newExcluded != null) { if (excluded != null) { excluded.union(newExcluded); } else { excluded = (GeneralSubtrees)newExcluded.clone(); } updated = true; } } } // Optional optimization: remove permitted subtrees that are excluded. // This is not necessary for algorithm correctness, but it makes // subsequent operations on the NameConstraints faster and require // less space. if (permitted != null) { permitted.reduce(excluded); updated = true; } // The NameConstraints have been changed, so re-encode them. Methods in // this class assume that the encodings have already been done. if (updated) { encodeThis(); } } /** * check whether a certificate conforms to these NameConstraints. * This involves verifying that the subject name and subjectAltName * extension (critical or noncritical) is consistent with the permitted * subtrees state variables. Also verify that the subject name and * subjectAltName extension (critical or noncritical) is consistent with * the excluded subtrees state variables. * * @param cert X509Certificate to be verified * @return true if certificate verifies successfully * @throws IOException on error */ public boolean verify(X509Certificate cert) throws IOException { if (cert == null) { throw new IOException("Certificate is null"); } // Calculate hasMin and hasMax booleans (if necessary) if (!minMaxValid) { calcMinMax(); } if (hasMin) { throw new IOException("Non-zero minimum BaseDistance in" + " name constraints not supported"); } if (hasMax) { throw new IOException("Maximum BaseDistance in" + " name constraints not supported"); } X500Principal subjectPrincipal = cert.getSubjectX500Principal(); X500Name subject = X500Name.asX500Name(subjectPrincipal); // Check subject as an X500Name if (!subject.isEmpty()) { if (!verify(subject)) { return false; } } GeneralNames altNames = null; // extract altNames try { // extract extensions, if any, from certInfo // following returns null if certificate contains no extensions X509CertImpl certImpl = X509CertImpl.toImpl(cert); SubjectAlternativeNameExtension altNameExt = certImpl.getSubjectAlternativeNameExtension(); if (altNameExt != null) { // extract altNames from extension; this call does not // return an IOException on null altnames altNames = altNameExt.getNames(); } } catch (CertificateException ce) { throw new IOException("Unable to extract extensions from " + "certificate: " + ce.getMessage()); } if (altNames == null) { altNames = new GeneralNames(); // RFC 5280 4.2.1.10: // When constraints are imposed on the rfc822Name name form, // but the certificate does not include a subject alternative name, // the rfc822Name constraint MUST be applied to the attribute of // type emailAddress in the subject distinguished name. for (AVA ava : subject.allAvas()) { ObjectIdentifier attrOID = ava.getObjectIdentifier(); if (attrOID.equals(PKCS9Attribute.EMAIL_ADDRESS_OID)) { String attrValue = ava.getValueString(); if (attrValue != null) { try { altNames.add(new GeneralName( new RFC822Name(attrValue))); } catch (IOException ioe) { continue; } } } } } // If there is no IPAddressName or DNSName in subjectAlternativeNames, // see if the last CN inside subjectName can be used instead. DerValue derValue = subject.findMostSpecificAttribute (X500Name.commonName_oid); String cn = derValue == null ? null : derValue.getAsString(); if (cn != null) { try { if (IPAddressUtil.isIPv4LiteralAddress(cn) || IPAddressUtil.isIPv6LiteralAddress(cn)) { if (!hasNameType(altNames, GeneralNameInterface.NAME_IP)) { altNames.add(new GeneralName(new IPAddressName(cn))); } } else { if (!hasNameType(altNames, GeneralNameInterface.NAME_DNS)) { altNames.add(new GeneralName(new DNSName(cn))); } } } catch (IOException ioe) { // OK, cn is neither IP nor DNS } } // verify each subjectAltName for (int i = 0; i < altNames.size(); i++) { GeneralNameInterface altGNI = altNames.get(i).getName(); if (!verify(altGNI)) { return false; } } // All tests passed. return true; } private static boolean hasNameType(GeneralNames names, int type) { for (GeneralName name : names.names()) { if (name.getType() == type) { return true; } } return false; } /** * check whether a name conforms to these NameConstraints. * This involves verifying that the name is consistent with the * permitted and excluded subtrees variables. * * @param name GeneralNameInterface name to be verified * @return true if certificate verifies successfully * @throws IOException on error */ public boolean verify(GeneralNameInterface name) throws IOException { if (name == null) { throw new IOException("name is null"); } // Verify that the name is consistent with the excluded subtrees if (excluded != null && excluded.size() > 0) { for (int i = 0; i < excluded.size(); i++) { GeneralSubtree gs = excluded.get(i); if (gs == null) continue; GeneralName gn = gs.getName(); if (gn == null) continue; GeneralNameInterface exName = gn.getName(); if (exName == null) continue; // Match a wildcard in DNSName only against the excluded subtree int matchResult = exName.getType() == GeneralNameInterface.NAME_DNS ? ((DNSName) exName).constrains(name, true) : exName.constrains(name); // if name matches or narrows any excluded subtree, // return false switch (matchResult) { case GeneralNameInterface.NAME_DIFF_TYPE: case GeneralNameInterface.NAME_WIDENS: // name widens excluded case GeneralNameInterface.NAME_SAME_TYPE: break; case GeneralNameInterface.NAME_MATCH: case GeneralNameInterface.NAME_NARROWS: // subject name excluded return false; } } } // Verify that the name is consistent with the permitted subtrees if (permitted != null && permitted.size() > 0) { boolean sameType = false; for (int i = 0; i < permitted.size(); i++) { GeneralSubtree gs = permitted.get(i); if (gs == null) continue; GeneralName gn = gs.getName(); if (gn == null) continue; GeneralNameInterface perName = gn.getName(); if (perName == null) continue; // if Name matches any type in permitted, // and Name does not match or narrow some permitted subtree, // return false switch (perName.constrains(name)) { case GeneralNameInterface.NAME_DIFF_TYPE: continue; // continue checking other permitted names case GeneralNameInterface.NAME_WIDENS: // name widens permitted case GeneralNameInterface.NAME_SAME_TYPE: sameType = true; continue; // continue to look for a match or narrow case GeneralNameInterface.NAME_MATCH: case GeneralNameInterface.NAME_NARROWS: // name narrows permitted return true; // name is definitely OK, so break out of loop } } return !sameType; } return true; } /** * Clone all objects that may be modified during certificate validation. */ public Object clone() { try { NameConstraintsExtension newNCE = (NameConstraintsExtension) super.clone(); if (permitted != null) { newNCE.permitted = (GeneralSubtrees) permitted.clone(); } if (excluded != null) { newNCE.excluded = (GeneralSubtrees) excluded.clone(); } return newNCE; } catch (CloneNotSupportedException cnsee) { throw new RuntimeException("CloneNotSupportedException while " + "cloning NameConstraintsException. This should never happen."); } } }