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Description of the HTTP Signature Gravitee Policy
package org.tomitribe.auth.signatures;
import java.security.spec.AlgorithmParameterSpec;
import java.text.NumberFormat;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Signature {
/**
* REQUIRED. The `keyId` field is an opaque string that the server can
* use to look up the component they need to validate the signature. It
* could be an SSH key fingerprint, a URL to machine-readable key data,
* an LDAP DN, etc. Management of keys and assignment of `keyId` is out
* of scope for this document.
*/
private final String keyId;
/**
* RECOMMENDED. The `signingAlgorithm` parameter is used to specify the digital
* signature algorithm to use when generating the signature. Valid
* values for this parameter can be found in the Signature Algorithms
* registry located at http://www.iana.org/assignments/signature-
* algorithms and MUST NOT be marked "deprecated".
*
* Verifiers MUST determine the signature's Algorithm from the keyId parameter
* rather than from algorithm. If algorithm is provided and differs from or
* is incompatible with the algorithm or key material identified by keyId
* (for example, algorithm has a value of rsa-sha256 but keyId identifies
* an EdDSA key), then implementations MUST produce an error.
*
* https://datatracker.ietf.org/doc/draft-ietf-httpbis-message-signatures/
*/
private final SigningAlgorithm signingAlgorithm;
/**
* REQUIRED. The `algorithm` parameter is used to specify the digital
* signature algorithm to use when generating the signature. Valid
* values for this parameter can be found in the Signature Algorithms
* registry located at http://www.iana.org/assignments/signature-
* algorithms and MUST NOT be marked "deprecated".
*/
private final Algorithm algorithm;
/**
* REQUIRED. The `signature` parameter is a base 64 encoded digital
* signature, as described in RFC 4648 [RFC4648], Section 4 [4]. The
* client uses the `algorithm` and `headers` signature parameters to
* form a canonicalized `signing string`. This `signing string` is then
* signed with the key associated with `keyId` and the algorithm
* corresponding to `algorithm`. The `signature` parameter is then set
* to the base 64 encoding of the signature.
*
* Signing: this field is calculated from the input data.
* Verification: this field is parsed from the signature field in the
* Authorization header.
*/
private final String signature;
/**
* OPTIONAL. The `headers` parameter is used to specify the list of
* HTTP headers included when generating the signature for the message.
* If specified, it should be a lowercased, quoted list of HTTP header
* fields, separated by a single space character. If not specified,
* implementations MUST operate as if the field were specified with a
* single value, the `Date` header, in the list of HTTP headers. Note
* that the list order is important, and MUST be specified in the order
* the HTTP header field-value pairs are concatenated together during
* signing.
*/
private final List headers;
/**
* OPTIONAL. The `parameterSpec` is used to specify the cryptographic
* parameters. Some cryptographic algorithm such as RSASSA-PSS
* require parameters.
*/
private final AlgorithmParameterSpec parameterSpec;
/**
* OPTIONAL. The configurable signature's maximum validation duration, in milliseconds.
* This field is applicable when the signed headers include '(expires)'.
* In that case, the value of the '(expires)' field is calculated by adding
* maxSignatureValidityDuration to the timestamp of the signature creation time.
*
* This field is used to derive the signature expiration time when a cryptographic signature
* is generated.
*/
private final Long maxSignatureValidityDuration;
/**
* The signature's Creation Time, in milliseconds since the epoch.
*
* This field is set at the time the cryptographic signature is generated, or when
* the 'Authorization' header is parsed.
*/
private final Long signatureCreatedTime;
/**
* The signature's Expiration Time, in milliseconds since the epoch.
*
* This field is set at the time the cryptographic signature is generated, or when
* the 'Authorization' header is parsed.
*/
private final Long signatureExpiresTime;
/**
* Regular expression pattern for fields present in the Authorization field.
* Fields value may be double-quoted strings, e.g. algorithm="hs2019"
* Some fields may be numerical values without double-quotes, e.g. created=123456
* Fields that are numerical values with digits are formatted regarding the current Locale. The char used can be a "." (dot) or a "," coma.
*/
private static final Pattern RFC_2617_PARAM = Pattern.compile(
"(?\\w+)=((\"(?[^\"]*)\")|(?\\d+[.,]?\\d*))"
);
/**
* The maximum time skew between the client and the server.
* This is used to validate the (created) and (expires) fields in the HTTP signature.
*/
public static long maxTimeSkewInMilliseconds = 30 * 1000L;
/**
* Construct a signature configuration instance with the specified keyId, algorithm and HTTP headers.
*
* @param keyId An opaque string that the server can use to look up the component they need to validate the signature.
* @param signingAlgorithm An identifier for the HTTP Signature algorithm.
* This should be "hs2019" except for legacy applications that use an older version of the draft HTTP signature specification.
* @param algorithm The detailed algorithm used to sign the message.
* @param parameterSpec optional cryptographic parameters for the signature.
* @param headers The list of HTTP headers that will be used in the signature.
*/
public Signature(
final String keyId,
final String signingAlgorithm,
final String algorithm,
final AlgorithmParameterSpec parameterSpec,
final List headers
) {
this(keyId, getSigningAlgorithm(signingAlgorithm), getAlgorithm(algorithm), parameterSpec, null, headers);
}
private static Algorithm getAlgorithm(final String algorithm) {
if (algorithm == null) throw new IllegalArgumentException("Algorithm cannot be null");
return Algorithm.get(algorithm);
}
private static SigningAlgorithm getSigningAlgorithm(final String scheme) {
if (scheme == null) throw new IllegalArgumentException("Signing scheme cannot be null");
return SigningAlgorithm.get(scheme);
}
@Deprecated
public Signature(final String keyId, final String algorithm, final String signature, final String... headers) {
this(keyId, getAlgorithm(algorithm), signature, headers);
}
@Deprecated
public Signature(final String keyId, final Algorithm algorithm, final String signature, final String... headers) {
this(keyId, algorithm, signature, Arrays.asList(headers));
}
@Deprecated
public Signature(final String keyId, final String algorithm, final String signature, final List headers) {
this(keyId, getAlgorithm(algorithm), signature, headers);
}
@Deprecated
public Signature(final String keyId, final Algorithm algorithm, final String signature, final List headers) {
this(keyId, null, algorithm, null, signature, headers, null, null, null);
}
public Signature(
final String keyId,
final String signingAlgorithm,
final String algorithm,
final AlgorithmParameterSpec parameterSpec,
final String signature,
final List headers
) {
this(keyId, getSigningAlgorithm(signingAlgorithm), getAlgorithm(algorithm), parameterSpec, signature, headers);
}
public Signature(
final String keyId,
final SigningAlgorithm signingAlgorithm,
final Algorithm algorithm,
final AlgorithmParameterSpec parameterSpec,
final String signature,
final List headers
) {
this(keyId, signingAlgorithm, algorithm, parameterSpec, signature, headers, null);
}
public Signature(
final String keyId,
final SigningAlgorithm signingAlgorithm,
final Algorithm algorithm,
final AlgorithmParameterSpec parameterSpec,
final String signature,
final List headers,
final Long maxSignatureValidityDuration
) {
this(keyId, signingAlgorithm, algorithm, parameterSpec, signature, headers, maxSignatureValidityDuration, null, null);
}
public Signature(
final String keyId,
final SigningAlgorithm signingAlgorithm,
final Algorithm algorithm,
final AlgorithmParameterSpec parameterSpec,
final String signature,
final List headers,
final Long maxSignatureValidityDuration,
final Long signatureCreatedTime,
final Long signatureExpiresTime
) {
if (keyId == null || keyId.trim().isEmpty()) {
throw new IllegalArgumentException("keyId is required.");
}
if (algorithm == null) {
throw new IllegalArgumentException("algorithm is required.");
}
if (
signingAlgorithm != null &&
signingAlgorithm.getSupportedAlgorithms() != null &&
!signingAlgorithm.getSupportedAlgorithms().contains(algorithm)
) {
throw new IllegalArgumentException(
"Signing algorithm " + signingAlgorithm.getAlgorithmName() + " is not compatible with " + algorithm.getPortableName()
);
}
this.keyId = keyId;
this.signingAlgorithm = signingAlgorithm;
this.algorithm = algorithm;
if (maxSignatureValidityDuration != null && maxSignatureValidityDuration <= 0) {
throw new IllegalArgumentException("Signature max validity must be a positive number");
}
this.maxSignatureValidityDuration = maxSignatureValidityDuration;
this.signatureCreatedTime = signatureCreatedTime;
this.signatureExpiresTime = signatureExpiresTime;
// this is the only one that can be null cause the object
// can be used as a template/specification
this.signature = signature;
this.parameterSpec = parameterSpec;
if (headers == null || headers.size() == 0) {
final List list = Arrays.asList("date");
this.headers = Collections.unmodifiableList(list);
} else {
this.headers = Collections.unmodifiableList(lowercase(headers));
}
}
/**
* Returns the signature creation time.
*
* @return the signature creation time.
*/
public Date getSignatureCreation() {
if (signatureCreatedTime == null) return null;
return new Date(signatureCreatedTime);
}
/**
* Returns the signature creation time in milliseconds since the epoch.
*
* @return the signature creation time in milliseconds since the epoch.
*/
public Long getSignatureCreationTimeMilliseconds() {
return signatureCreatedTime;
}
/**
* Returns the signature max validity duration, in milliseconds.
*
* @return the signature max validity duration, in milliseconds.
*/
public Long getSignatureMaxValidityMilliseconds() {
return maxSignatureValidityDuration;
}
/**
* Returns the signature expiration time.
*
* @return the signature expiration time.
*/
public Date getSignatureExpiration() {
if (signatureExpiresTime == null) return null;
return new Date(signatureExpiresTime);
}
/**
* Returns the signature expiration time in milliseconds since the epoch.
*
* @return the signature expiration time in milliseconds since the epoch.
*/
public Long getSignatureExpirationTimeMilliseconds() {
return signatureExpiresTime;
}
private List lowercase(final List headers) {
final List list = new ArrayList(headers.size());
for (final String header : headers) {
list.add(header.toLowerCase());
}
return list;
}
public String getKeyId() {
return keyId;
}
/**
* Returns the detailed implementation algorithm for HTTP signatures.
*
* @return the cryptographic algorithm.
*/
public Algorithm getAlgorithm() {
return algorithm;
}
/**
* Returns the identifier for the HTTP Signature Algorithm, as registered
* in the HTTP Signature Algorithms Registry.
*
* @return the identifier for the HTTP Signature Algorithm.
*/
public SigningAlgorithm getSigningAlgorithm() {
return signingAlgorithm;
}
/**
* Returns the base-64 encoded value of the signature.
*
* @return the base-64 encoded value of the signature.
*/
public String getSignature() {
return signature;
}
/**
* Returns the specification of cryptographic parameters.
*
* @return specification of cryptographic parameters.
*/
public AlgorithmParameterSpec getParameterSpec() {
return parameterSpec;
}
public List getHeaders() {
return headers;
}
/**
* Verify the signature is valid with regards to the (created) and (expires) fields.
*
* When the '(created)' field is present in the HTTP signature, the '(created)' field
* represents the date when the signature has been created.
* When the '(expires)' field is present in the HTTP signature, the '(expires)' field
* represents the date when the signature expires.
*/
public void verifySignatureValidityDates() {
if (signatureCreatedTime != null && signatureCreatedTime > System.currentTimeMillis() + maxTimeSkewInMilliseconds) {
throw new InvalidCreatedFieldException("Signature is not valid yet");
}
if (signatureExpiresTime != null && signatureExpiresTime < System.currentTimeMillis()) {
throw new InvalidExpiresFieldException("Signature has expired");
}
}
/**
* Constructs a Signature object by parsing the 'Authorization' header.
*
* As stated in the HTTP signature specification, the value of the algorithm parameter in
* the 'Authorization' header should be set to generic identifier. The detailed algorithm
* should be derived from the keyId. Hence it is not possible to determine the detailed
* algorithm by inspecting the signature data.
*
* @param authorization The value of the HTTP 'Authorization' header containing the signature data.
* @param algorithm The detailed cryptographic algorithm for the HTTP signature.
*
* @return The Signature object.
*/
public static Signature fromString(String authorization, final Algorithm algorithm) {
/**
* A HTTP signature field value in the authorization header.
*/
class FieldValue {
/**
* The field value. It may be a string or number.
*/
private Object value;
/**
* A flag indicating whether the field is a string or number.
*/
private boolean isNumber;
FieldValue(final String value, final boolean isNumber) throws ParseException {
this.isNumber = isNumber;
if (isNumber) {
this.value = NumberFormat.getInstance().parse(value);
} else {
this.value = value;
}
}
/** Returns true if the field is a string */
boolean isString() {
return !isNumber;
}
/** Returns true if the field is a number */
boolean isNumber() {
return isNumber;
}
/** Returns true if the field is an integer value */
boolean isInteger() {
return value instanceof Long;
}
/** Returns the field as a string, or null if the field is not a string. */
String getValueAsString() {
if (!isString()) return null;
return (String) value;
}
/** Returns the field as a long value, or null if the field is not a integer number. */
Long getValueAsLong() {
if (!isInteger()) return null;
return ((Number) value).longValue();
}
/** Returns the field as a double value, or null if the field is not a number. */
Double getValueAsDouble() {
if (!isNumber()) return null;
return ((Number) value).doubleValue();
}
}
try {
authorization = normalize(authorization);
final Map map = new HashMap();
final Matcher matcher = RFC_2617_PARAM.matcher(authorization);
while (matcher.find()) {
final String key = matcher.group("key").toLowerCase();
// The field value may be a double-quoted string or a number.
boolean isNumber = false;
String value = matcher.group("stringValue");
if (value == null) {
value = matcher.group("numberValue");
isNumber = true;
}
map.put(key, new FieldValue(value, isNumber));
}
final List headers = new ArrayList();
FieldValue fieldValue = map.get("headers");
if (fieldValue != null) {
if (!fieldValue.isString()) {
throw new IllegalArgumentException("headers field must be a double-quoted string");
}
Collections.addAll(headers, fieldValue.getValueAsString().toLowerCase().split(" +"));
}
String keyid = null;
fieldValue = map.get("keyid");
if (fieldValue != null && fieldValue.isString()) {
keyid = fieldValue.getValueAsString();
}
if (keyid == null) throw new MissingKeyIdException();
String algorithmField = null;
fieldValue = map.get("algorithm");
if (fieldValue != null && fieldValue.isString()) {
algorithmField = fieldValue.getValueAsString();
}
if (algorithmField == null) throw new MissingAlgorithmException();
String signature = null;
fieldValue = map.get("signature");
if (fieldValue != null && fieldValue.isString()) {
signature = fieldValue.getValueAsString();
}
if (signature == null) throw new MissingSignatureException();
Long created = null; // The signature creation time, in milliseconds since the epoch.
fieldValue = map.get("created");
if (fieldValue != null) {
if (!fieldValue.isInteger()) {
throw new InvalidCreatedFieldException("Field must be an integer value");
}
created = fieldValue.getValueAsLong() * 1000L;
}
Long expires = null; // The signature expiration time, in milliseconds since the epoch.
fieldValue = map.get("expires");
if (fieldValue != null) {
if (!fieldValue.isNumber()) {
throw new InvalidExpiresFieldException("Field must be a number");
}
expires = (long) (fieldValue.getValueAsDouble() * 1000L);
}
SigningAlgorithm parsedSigningAlgorithm = null;
try {
parsedSigningAlgorithm = SigningAlgorithm.get(algorithmField);
} catch (final UnsupportedAlgorithmException ex) {
// This may happen for older implementations that pass the serialize the detailed
// algorithm instead of using 'hs2019'. In that case, the value of 'algorithm'
// should be one of the supported values in the Algorithm enum. If not, an
// exception is raised.
}
Algorithm parsedAlgorithm = null;
try {
parsedAlgorithm = Algorithm.get(algorithmField);
if (algorithm != null && parsedAlgorithm.getPortableName() != algorithm.getPortableName()) {
throw new IllegalArgumentException("The algorithm does not match the value of the 'Authorization' header.");
}
} catch (final UnsupportedAlgorithmException ex) {
// This is expected for new conformant implementations that set the algorithm
// field in the 'Authorization' header to 'hs2019'. The algorithm must be
// derived from the keyId. The client is responsible for maintaining the
// mapping between the keyId and the detailed cryptographic algorithm.
if (algorithm == null) {
throw new IllegalArgumentException("The algorithm is required.");
}
parsedAlgorithm = algorithm;
}
final Signature s = new Signature(
keyid,
parsedSigningAlgorithm,
parsedAlgorithm,
null,
signature,
headers,
null,
created,
expires
);
s.verifySignatureValidityDates();
return s;
} catch (final AuthenticationException e) {
throw e;
} catch (final Throwable e) {
throw new UnparsableSignatureException(authorization, e);
}
}
public static Signature fromString(String authorization) {
return fromString(authorization, null);
}
private static String normalize(String authorization) {
final String start = "signature ";
final String prefix = authorization.substring(0, start.length()).toLowerCase();
if (prefix.equals(start)) {
authorization = authorization.substring(start.length());
}
return authorization.trim();
}
@Override
public String toString() {
return toString("Signature");
}
/**
* Returns the formatted signature parameters without any "Signature " prefix
*/
public String toParamString() {
return toString(null);
}
public String toString(final String prefix) {
final Object alg;
if (SigningAlgorithm.HS2019.equals(signingAlgorithm)) {
// When the signing algorithm is set to 'hs2019', the value of the algorithm
// field must be set to 'hs2019'. The specific crypto algorithm is not
// serialized in the 'Authorization' header, the server must derive the value
// from the keyId.
alg = signingAlgorithm;
} else {
alg = algorithm;
}
return (
(prefix != null ? prefix + " " : "") +
"keyId=\"" +
keyId +
'\"' +
(
signatureCreatedTime != null && headers.contains("(created)")
? String.format(",created=%d", signatureCreatedTime / 1000L)
: ""
) +
(
signatureExpiresTime != null && headers.contains("(expires)")
? String.format(",expires=%.3f", signatureExpiresTime / 1000.0)
: ""
) +
",algorithm=\"" +
alg +
'\"' +
",headers=\"" +
Join.join(" ", headers) +
'\"' +
",signature=\"" +
signature +
'\"'
);
}
}
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