diff options
author | Tor Brede Vekterli <vekterli@yahooinc.com> | 2023-06-06 13:18:47 +0200 |
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committer | Tor Brede Vekterli <vekterli@yahooinc.com> | 2023-06-06 13:43:46 +0200 |
commit | 071d65629215994094b580861e06edb760958af2 (patch) | |
tree | 7b69400674b1abb5ee70f6570a56a8b0485ead72 /security-utils/src/main/java | |
parent | 212a1934ff38662183609827ac91a67a34179eb0 (diff) |
Add a simple token primitive to security utils
A token is an arbitrary, opaque (secret) string from which a
fingerprint and audience-specific access-check hashes can be
derived. A CSPRNG-backed token generator that returns random
Base62-encoded tokens (with an optional prefix) is included.
Diffstat (limited to 'security-utils/src/main/java')
5 files changed, 273 insertions, 0 deletions
diff --git a/security-utils/src/main/java/com/yahoo/security/token/Token.java b/security-utils/src/main/java/com/yahoo/security/token/Token.java new file mode 100644 index 00000000000..e830bdfd63d --- /dev/null +++ b/security-utils/src/main/java/com/yahoo/security/token/Token.java @@ -0,0 +1,85 @@ +// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root. +package com.yahoo.security.token; + +import com.yahoo.security.HKDF; + +import java.util.Objects; + +import static com.yahoo.security.ArrayUtils.toUtf8Bytes; + +/** + * <p>A token represents an arbitrary, opaque sequence of secret bytes (preferably from a secure + * random source) whose possession gives the holder the right to some resource(s) or action(s). + * For a token to be recognized it must be presented in its entirety, i.e. bitwise exact. This + * includes any (optional) text prefixes. + * </p><p> + * Only the party <em>presenting</em> the token should store the token secret itself; any + * parties that need to identify and/or verify the token should store <em>derivations</em> + * of the token instead (TokenFingerprint and TokenCheckHash, respectively). + * </p><p> + * A Token <em>object</em> is bound to a particular TokenDomain, but any given secret token + * string may be used to create many Token objects for any number of domains; it is opaque and + * not in and by itself tied to any specific domain. + * </p> + */ +public class Token { + + private final TokenDomain domain; + private final String secretTokenString; + private final byte[] secretTokenBytes; + private final TokenFingerprint fingerprint; + + Token(TokenDomain domain, String secretTokenString) { + this.domain = domain; + this.secretTokenString = secretTokenString; + this.secretTokenBytes = toUtf8Bytes(secretTokenString); + this.fingerprint = TokenFingerprint.of(this); + } + + public static Token of(TokenDomain domain, String secretTokenString) { + return new Token(domain, secretTokenString); + } + + public TokenDomain domain() { return domain; } + public String secretTokenString() { return secretTokenString; } + public TokenFingerprint fingerprint() { return fingerprint; } + + @Override + public boolean equals(Object o) { + if (this == o) return true; + if (o == null || getClass() != o.getClass()) return false; + Token token = (Token) o; + // We assume that domain+fingerprint suffices for equality check. + // If underlying secret bytes checking is added it MUST use SideChannelSafe.arraysEqual() + // to avoid leaking secret data via timing side-channels. + return Objects.equals(domain, token.domain) && + Objects.equals(fingerprint, token.fingerprint); + } + + // Important: actual secret bytes must NOT be part of hashCode calculation, as that risks + // leaking parts of the secret to an attacker that can influence and observe side effects + // of the hash code. + @Override + public int hashCode() { + return Objects.hash(domain, fingerprint); + } + + @Override + public String toString() { + // Avoid leaking raw token secret as part of toString() output + return "Token(fingerprint: %s)".formatted(fingerprint.toHexString()); + } + + /** + * Token derivations are created by invoking a HKDF (using HMAC-SHA256) that expands the + * original token secret to the provided number of bytes and the provided domain separation + * context. The same source token secret will result in different derivations when + * different contexts are used, but will always generate a deterministic result for the + * same token+#bytes+context combination. + */ + byte[] toDerivedBytes(int nHashBytes, byte[] domainSeparationContext) { + var hkdf = HKDF.unsaltedExtractedFrom(secretTokenBytes); + return hkdf.expand(nHashBytes, domainSeparationContext); + } + +} diff --git a/security-utils/src/main/java/com/yahoo/security/token/TokenCheckHash.java b/security-utils/src/main/java/com/yahoo/security/token/TokenCheckHash.java new file mode 100644 index 00000000000..e4d9825842e --- /dev/null +++ b/security-utils/src/main/java/com/yahoo/security/token/TokenCheckHash.java @@ -0,0 +1,46 @@ +// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root. +package com.yahoo.security.token; + +import java.util.Arrays; + +import static com.yahoo.security.ArrayUtils.hex; + +/** + * A token check hash represents a hash derived from a token in such a way that + * distinct "audiences" for the token compute entirely different hashes even for + * identical token values. + */ +public record TokenCheckHash(byte[] hashBytes) { + + @Override + public boolean equals(Object o) { + if (this == o) return true; + if (o == null || getClass() != o.getClass()) return false; + TokenCheckHash tokenCheckHash = (TokenCheckHash) o; + // We don't consider token hashes secret data, so no harm in data-dependent equals() + return Arrays.equals(hashBytes, tokenCheckHash.hashBytes); + } + + @Override + public int hashCode() { + return Arrays.hashCode(hashBytes); + } + + public String toHexString() { + return hex(hashBytes); + } + + @Override + public String toString() { + return toHexString(); + } + + public static TokenCheckHash of(Token token, int nHashBytes) { + return new TokenCheckHash(token.toDerivedBytes(nHashBytes, token.domain().checkHashContext())); + } + + public static TokenCheckHash ofRawBytes(byte[] hashBytes) { + return new TokenCheckHash(Arrays.copyOf(hashBytes, hashBytes.length)); + } + +} diff --git a/security-utils/src/main/java/com/yahoo/security/token/TokenDomain.java b/security-utils/src/main/java/com/yahoo/security/token/TokenDomain.java new file mode 100644 index 00000000000..b29815f3a56 --- /dev/null +++ b/security-utils/src/main/java/com/yahoo/security/token/TokenDomain.java @@ -0,0 +1,51 @@ +// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root. +package com.yahoo.security.token; + +import java.util.Arrays; + +import static com.yahoo.security.ArrayUtils.toUtf8Bytes; + +/** + * <p>A token domain controls how token fingerprints and check-hashes are derived from + * a particular token. Even with identical token contents, different domain contexts + * are expected to produce entirely different derivations (with an extremely high + * probability). + * </p><p> + * Since tokens are just opaque sequences of high entropy bytes (with an arbitrary + * prefix), they do not by themselves provide any kind of inherent domain separation. + * Token domains exist to allow for <em>explicit</em> domain separation between + * different usages of tokens. + * </p><p> + * Fingerprint contexts will usually be the same across an entire deployment of a token + * evaluation infrastructure, in order to allow for identifying tokens "globally" + * across that deployment. + * </p><p> + * Access check hash contexts should be unique for each logical token evaluation audience, + * ensuring that access hashes from an unrelated audience (with a different context) can + * never be made to match, be it accidentally or deliberately. + * </p> + */ +public record TokenDomain(byte[] fingerprintContext, byte[] checkHashContext) { + + @Override + public boolean equals(Object o) { + if (this == o) return true; + if (o == null || getClass() != o.getClass()) return false; + TokenDomain that = (TokenDomain) o; + return Arrays.equals(fingerprintContext, that.fingerprintContext) && + Arrays.equals(checkHashContext, that.checkHashContext); + } + + @Override + public int hashCode() { + int result = Arrays.hashCode(fingerprintContext); + result = 31 * result + Arrays.hashCode(checkHashContext); + return result; + } + + public static TokenDomain of(String fingerprintContext, String checkHashContext) { + return new TokenDomain(toUtf8Bytes(fingerprintContext), + toUtf8Bytes(checkHashContext)); + } + +} diff --git a/security-utils/src/main/java/com/yahoo/security/token/TokenFingerprint.java b/security-utils/src/main/java/com/yahoo/security/token/TokenFingerprint.java new file mode 100644 index 00000000000..acbf7c085fd --- /dev/null +++ b/security-utils/src/main/java/com/yahoo/security/token/TokenFingerprint.java @@ -0,0 +1,52 @@ +// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root. +package com.yahoo.security.token; + +import java.util.Arrays; + +import static com.yahoo.security.ArrayUtils.hex; + +/** + * <p>A token fingerprint represents an opaque sequence of bytes that is expected + * to globally identify any particular token within a particular token domain. + * </p><p> + * Token fingerprints should not be used directly for access checks; use derived + * {@link TokenCheckHash} instances for this purpose. + * </p> + */ +public record TokenFingerprint(byte[] hashBytes) { + + public static final int FINGERPRINT_BITS = 128; + public static final int FINGERPRINT_BYTES = FINGERPRINT_BITS / 8; + + @Override + public boolean equals(Object o) { + if (this == o) return true; + if (o == null || getClass() != o.getClass()) return false; + TokenFingerprint that = (TokenFingerprint) o; + // We don't consider token fingerprints secret data, so no harm in data-dependent equals() + return Arrays.equals(hashBytes, that.hashBytes); + } + + @Override + public int hashCode() { + return Arrays.hashCode(hashBytes); + } + + public String toHexString() { + return hex(hashBytes); + } + + @Override + public String toString() { + return toHexString(); + } + + public static TokenFingerprint of(Token token) { + return new TokenFingerprint(token.toDerivedBytes(FINGERPRINT_BYTES, token.domain().fingerprintContext())); + } + + public static TokenFingerprint ofRawBytes(byte[] hashBytes) { + return new TokenFingerprint(Arrays.copyOf(hashBytes, hashBytes.length)); + } + +} diff --git a/security-utils/src/main/java/com/yahoo/security/token/TokenGenerator.java b/security-utils/src/main/java/com/yahoo/security/token/TokenGenerator.java new file mode 100644 index 00000000000..4dabca4b4ba --- /dev/null +++ b/security-utils/src/main/java/com/yahoo/security/token/TokenGenerator.java @@ -0,0 +1,39 @@ +// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root. +package com.yahoo.security.token; + +import com.yahoo.security.Base62; + +import java.security.SecureRandom; + +/** + * <p> + * Generates new {@link Token} instances that encapsulate a given number of cryptographically + * secure random bytes and, with a sufficiently high number of bytes (>= 16), can be expected + * to be globally unique and computationally infeasible to guess or brute force. + * </p><p> + * Tokens are returned in a printable and copy/paste-friendly form (Base62) with an optional + * prefix string. + * </p><p> + * Example of token string generated with the prefix "itsa_me_mario_" and 32 random bytes: + * </p> + * <pre> + * itsa_me_mario_nALfICMyrC4NFagwAkiOdGh80DPS1vSUPprGUKVPLya + * </pre> + * <p> + * Tokens are considered secret information, and must be treated as such. + * </p> + */ +public class TokenGenerator { + + private static final SecureRandom CSPRNG = new SecureRandom(); + + public static Token generateToken(TokenDomain domain, String prefix, int nRandomBytes) { + if (nRandomBytes <= 0) { + throw new IllegalArgumentException("Token bytes must be a positive integer"); + } + byte[] tokenRand = new byte[nRandomBytes]; + CSPRNG.nextBytes(tokenRand); + return new Token(domain, "%s%s".formatted(prefix, Base62.codec().encode(tokenRand))); + } + +} |