UEFI Variable with Signature List: Java parsing library

Parse UEFI variables db and dbx that contain signatures, certificates and hashes. On a Linux system using UEFI, these variables are readable from /sys/firmware/efi/efivars/db-d719b2cb-3d3a-4596-a3bc-dad00e67656f, /sys/firmware/efi/efivars/dbDefault-8be4df61-93ca-11d2-aa0d-00e098032b8c, /sys/firmware/efi/efivars/dbx-d719b2cb-3d3a-4596-a3bc-dad00e67656f and /sys/firmware/efi/efivars/dbxDefault-8be4df61-93ca-11d2-aa0d-00e098032b8c. ("d719b2cb-3d3a-4596-a3bc-dad00e67656f" is defined as EFI_IMAGE_SECURITY_DATABASE_GUID and "8be4df61-93ca-11d2-aa0d-00e098032b8c" as EFI_GLOBAL_VARIABLE). Each file contains an EFI attribute (32-bit integer) followed by a list of EFI_SIGNATURE_LIST structures.

KS implementation details

License: CC0-1.0

References

This page hosts a formal specification of UEFI Variable with Signature List using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Usage

Runtime library

All parsing code for Java generated by Kaitai Struct depends on the Java runtime library. You have to install it before you can parse data.

The Java runtime library is published in the Maven Central Repository. Refer to the artifact page for instructions how to add it into your project with the build tool that you use.

Code

Parse a local file and get structure in memory:

EfivarSignatureList data = EfivarSignatureList.fromFile("path/to/local/file.UEFI Variable with Signature List");

Or parse structure from a byte array:

byte[] someArray = new byte[] { ... };
EfivarSignatureList data = new EfivarSignatureList(new ByteBufferKaitaiStream(someArray));

After that, one can get various attributes from the structure by invoking getter methods like:

data.varAttributes() // => Attributes of the UEFI variable

Java source code to parse UEFI Variable with Signature List

EfivarSignatureList.java

// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

import io.kaitai.struct.ByteBufferKaitaiStream;
import io.kaitai.struct.KaitaiStruct;
import io.kaitai.struct.KaitaiStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;


/**
 * Parse UEFI variables db and dbx that contain signatures, certificates and
 * hashes. On a Linux system using UEFI, these variables are readable from
 * /sys/firmware/efi/efivars/db-d719b2cb-3d3a-4596-a3bc-dad00e67656f,
 * /sys/firmware/efi/efivars/dbDefault-8be4df61-93ca-11d2-aa0d-00e098032b8c,
 * /sys/firmware/efi/efivars/dbx-d719b2cb-3d3a-4596-a3bc-dad00e67656f and
 * /sys/firmware/efi/efivars/dbxDefault-8be4df61-93ca-11d2-aa0d-00e098032b8c.
 * ("d719b2cb-3d3a-4596-a3bc-dad00e67656f" is defined as
 * EFI_IMAGE_SECURITY_DATABASE_GUID and "8be4df61-93ca-11d2-aa0d-00e098032b8c"
 * as EFI_GLOBAL_VARIABLE).
 * Each file contains an EFI attribute (32-bit integer) followed by a list of
 * EFI_SIGNATURE_LIST structures.
 * @see <a href="https://uefi.org/sites/default/files/resources/UEFI_Spec_2_8_final.pdf">Source</a>
 */
public class EfivarSignatureList extends KaitaiStruct {
    public static EfivarSignatureList fromFile(String fileName) throws IOException {
        return new EfivarSignatureList(new ByteBufferKaitaiStream(fileName));
    }

    public EfivarSignatureList(KaitaiStream _io) {
        this(_io, null, null);
    }

    public EfivarSignatureList(KaitaiStream _io, KaitaiStruct _parent) {
        this(_io, _parent, null);
    }

    public EfivarSignatureList(KaitaiStream _io, KaitaiStruct _parent, EfivarSignatureList _root) {
        super(_io);
        this._parent = _parent;
        this._root = _root == null ? this : _root;
        _read();
    }
    private void _read() {
        this.varAttributes = new EfiVarAttr(this._io, this, _root);
        this.signatures = new ArrayList<SignatureList>();
        {
            int i = 0;
            while (!this._io.isEof()) {
                this.signatures.add(new SignatureList(this._io, this, _root));
                i++;
            }
        }
    }

    /**
     * @see "EFI_SIGNATURE_LIST"
     */
    public static class SignatureList extends KaitaiStruct {
        public static SignatureList fromFile(String fileName) throws IOException {
            return new SignatureList(new ByteBufferKaitaiStream(fileName));
        }

        public SignatureList(KaitaiStream _io) {
            this(_io, null, null);
        }

        public SignatureList(KaitaiStream _io, EfivarSignatureList _parent) {
            this(_io, _parent, null);
        }

        public SignatureList(KaitaiStream _io, EfivarSignatureList _parent, EfivarSignatureList _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.signatureType = this._io.readBytes(16);
            this.lenSignatureList = this._io.readU4le();
            this.lenSignatureHeader = this._io.readU4le();
            this.lenSignature = this._io.readU4le();
            this.header = this._io.readBytes(lenSignatureHeader());
            if (lenSignature() > 0) {
                this._raw_signatures = new ArrayList<byte[]>(((Number) ((((lenSignatureList() - lenSignatureHeader()) - 28) / lenSignature()))).intValue());
                signatures = new ArrayList<SignatureData>(((Number) ((((lenSignatureList() - lenSignatureHeader()) - 28) / lenSignature()))).intValue());
                for (int i = 0; i < (((lenSignatureList() - lenSignatureHeader()) - 28) / lenSignature()); i++) {
                    this._raw_signatures.add(this._io.readBytes(lenSignature()));
                    KaitaiStream _io__raw_signatures = new ByteBufferKaitaiStream(_raw_signatures.get(_raw_signatures.size() - 1));
                    this.signatures.add(new SignatureData(_io__raw_signatures, this, _root));
                }
            }
        }
        private Boolean isCertSha512X509;

        /**
         * SHA512 hash of an X.509 certificate's To-Be-Signed contents, and a time of revocation
         * @see "EFI_CERT_X509_SHA512_GUID"
         */
        public Boolean isCertSha512X509() {
            if (this.isCertSha512X509 != null)
                return this.isCertSha512X509;
            boolean _tmp = (boolean) (Arrays.equals(signatureType(), new byte[] { 99, -65, 109, 68, 2, 37, -38, 76, -68, -6, 36, 101, -46, -80, -2, -99 }));
            this.isCertSha512X509 = _tmp;
            return this.isCertSha512X509;
        }
        private Boolean isCertSha224;

        /**
         * SHA-224 hash
         * @see "EFI_CERT_SHA224_GUID"
         */
        public Boolean isCertSha224() {
            if (this.isCertSha224 != null)
                return this.isCertSha224;
            boolean _tmp = (boolean) (Arrays.equals(signatureType(), new byte[] { 51, 82, 110, 11, 92, -90, -55, 68, -108, 7, -39, -85, -125, -65, -56, -67 }));
            this.isCertSha224 = _tmp;
            return this.isCertSha224;
        }
        private Boolean isCertX509;

        /**
         * X.509 certificate
         * @see "EFI_CERT_X509_GUID"
         */
        public Boolean isCertX509() {
            if (this.isCertX509 != null)
                return this.isCertX509;
            boolean _tmp = (boolean) (Arrays.equals(signatureType(), new byte[] { -95, 89, -64, -91, -28, -108, -89, 74, -121, -75, -85, 21, 92, 43, -16, 114 }));
            this.isCertX509 = _tmp;
            return this.isCertX509;
        }
        private Boolean isCertSha256X509;

        /**
         * SHA256 hash of an X.509 certificate's To-Be-Signed contents, and a time of revocation
         * @see "EFI_CERT_X509_SHA256_GUID"
         */
        public Boolean isCertSha256X509() {
            if (this.isCertSha256X509 != null)
                return this.isCertSha256X509;
            boolean _tmp = (boolean) (Arrays.equals(signatureType(), new byte[] { -110, -92, -46, 59, -64, -106, 121, 64, -76, 32, -4, -7, -114, -15, 3, -19 }));
            this.isCertSha256X509 = _tmp;
            return this.isCertSha256X509;
        }
        private Boolean isCertRsa2048Key;

        /**
         * RSA-2048 key (only the modulus since the public key exponent is known to be 0x10001)
         * @see "EFI_CERT_RSA2048_GUID"
         */
        public Boolean isCertRsa2048Key() {
            if (this.isCertRsa2048Key != null)
                return this.isCertRsa2048Key;
            boolean _tmp = (boolean) (Arrays.equals(signatureType(), new byte[] { -24, 102, 87, 60, -100, 38, 52, 78, -86, 20, -19, 119, 110, -123, -77, -74 }));
            this.isCertRsa2048Key = _tmp;
            return this.isCertRsa2048Key;
        }
        private Boolean isCertSha512;

        /**
         * SHA-512 hash
         * @see "EFI_CERT_SHA512_GUID"
         */
        public Boolean isCertSha512() {
            if (this.isCertSha512 != null)
                return this.isCertSha512;
            boolean _tmp = (boolean) (Arrays.equals(signatureType(), new byte[] { -82, 15, 62, 9, -60, -90, 80, 79, -97, 27, -44, 30, 43, -119, -63, -102 }));
            this.isCertSha512 = _tmp;
            return this.isCertSha512;
        }
        private Boolean isCertSha384;

        /**
         * SHA-384 hash
         * @see "EFI_CERT_SHA384_GUID"
         */
        public Boolean isCertSha384() {
            if (this.isCertSha384 != null)
                return this.isCertSha384;
            boolean _tmp = (boolean) (Arrays.equals(signatureType(), new byte[] { 7, 83, 62, -1, -48, -97, -55, 72, -123, -15, -118, -43, 108, 112, 30, 1 }));
            this.isCertSha384 = _tmp;
            return this.isCertSha384;
        }
        private Boolean isCertSha1;

        /**
         * SHA-1 hash
         * @see "EFI_CERT_SHA1_GUID"
         */
        public Boolean isCertSha1() {
            if (this.isCertSha1 != null)
                return this.isCertSha1;
            boolean _tmp = (boolean) (Arrays.equals(signatureType(), new byte[] { 18, -91, 108, -126, 16, -49, -55, 74, -79, -121, -66, 1, 73, 102, 49, -67 }));
            this.isCertSha1 = _tmp;
            return this.isCertSha1;
        }
        private Boolean isCertRsa2048Sha1;

        /**
         * RSA-2048 signature of a SHA-1 hash
         * @see "EFI_CERT_RSA2048_SHA1_GUID"
         */
        public Boolean isCertRsa2048Sha1() {
            if (this.isCertRsa2048Sha1 != null)
                return this.isCertRsa2048Sha1;
            boolean _tmp = (boolean) (Arrays.equals(signatureType(), new byte[] { 79, 68, -8, 103, 67, -121, -15, 72, -93, 40, 30, -86, -72, 115, 96, -128 }));
            this.isCertRsa2048Sha1 = _tmp;
            return this.isCertRsa2048Sha1;
        }
        private Boolean isCertSha256;

        /**
         * SHA-256 hash
         * @see "EFI_CERT_SHA256_GUID"
         */
        public Boolean isCertSha256() {
            if (this.isCertSha256 != null)
                return this.isCertSha256;
            boolean _tmp = (boolean) (Arrays.equals(signatureType(), new byte[] { 38, 22, -60, -63, 76, 80, -110, 64, -84, -87, 65, -7, 54, -109, 67, 40 }));
            this.isCertSha256 = _tmp;
            return this.isCertSha256;
        }
        private Boolean isCertSha384X509;

        /**
         * SHA384 hash of an X.509 certificate's To-Be-Signed contents, and a time of revocation
         * @see "EFI_CERT_X509_SHA384_GUID"
         */
        public Boolean isCertSha384X509() {
            if (this.isCertSha384X509 != null)
                return this.isCertSha384X509;
            boolean _tmp = (boolean) (Arrays.equals(signatureType(), new byte[] { 110, -121, 118, 112, -62, -128, -26, 78, -86, -46, 40, -77, 73, -90, -122, 91 }));
            this.isCertSha384X509 = _tmp;
            return this.isCertSha384X509;
        }
        private Boolean isCertRsa2048Sha256;

        /**
         * RSA-2048 signature of a SHA-256 hash
         * @see "EFI_CERT_RSA2048_SHA256_GUID"
         */
        public Boolean isCertRsa2048Sha256() {
            if (this.isCertRsa2048Sha256 != null)
                return this.isCertRsa2048Sha256;
            boolean _tmp = (boolean) (Arrays.equals(signatureType(), new byte[] { -112, 97, -77, -30, -101, -121, 61, 74, -83, -115, -14, -25, -69, -93, 39, -124 }));
            this.isCertRsa2048Sha256 = _tmp;
            return this.isCertRsa2048Sha256;
        }
        private Boolean isCertDerPkcs7;

        /**
         * DER-encoded PKCS #7 version 1.5 [RFC2315]
         * @see "EFI_CERT_TYPE_PKCS7_GUID"
         */
        public Boolean isCertDerPkcs7() {
            if (this.isCertDerPkcs7 != null)
                return this.isCertDerPkcs7;
            boolean _tmp = (boolean) (Arrays.equals(signatureType(), new byte[] { -99, -46, -81, 74, -33, 104, -18, 73, -118, -87, 52, 125, 55, 86, 101, -89 }));
            this.isCertDerPkcs7 = _tmp;
            return this.isCertDerPkcs7;
        }
        private byte[] signatureType;
        private long lenSignatureList;
        private long lenSignatureHeader;
        private long lenSignature;
        private byte[] header;
        private ArrayList<SignatureData> signatures;
        private EfivarSignatureList _root;
        private EfivarSignatureList _parent;
        private ArrayList<byte[]> _raw_signatures;

        /**
         * Type of the signature as a GUID
         */
        public byte[] signatureType() { return signatureType; }

        /**
         * Total size of the signature list, including this header
         */
        public long lenSignatureList() { return lenSignatureList; }

        /**
         * Size of the signature header which precedes the array of signatures
         */
        public long lenSignatureHeader() { return lenSignatureHeader; }

        /**
         * Size of each signature
         */
        public long lenSignature() { return lenSignature; }

        /**
         * Header before the array of signatures
         */
        public byte[] header() { return header; }

        /**
         * An array of signatures
         */
        public ArrayList<SignatureData> signatures() { return signatures; }
        public EfivarSignatureList _root() { return _root; }
        public EfivarSignatureList _parent() { return _parent; }
        public ArrayList<byte[]> _raw_signatures() { return _raw_signatures; }
    }

    /**
     * @see "EFI_SIGNATURE_DATA"
     */
    public static class SignatureData extends KaitaiStruct {
        public static SignatureData fromFile(String fileName) throws IOException {
            return new SignatureData(new ByteBufferKaitaiStream(fileName));
        }

        public SignatureData(KaitaiStream _io) {
            this(_io, null, null);
        }

        public SignatureData(KaitaiStream _io, EfivarSignatureList.SignatureList _parent) {
            this(_io, _parent, null);
        }

        public SignatureData(KaitaiStream _io, EfivarSignatureList.SignatureList _parent, EfivarSignatureList _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.owner = this._io.readBytes(16);
            this.data = this._io.readBytesFull();
        }
        private byte[] owner;
        private byte[] data;
        private EfivarSignatureList _root;
        private EfivarSignatureList.SignatureList _parent;

        /**
         * An identifier which identifies the agent which added the signature to the list
         */
        public byte[] owner() { return owner; }

        /**
         * The format of the signature is defined by the SignatureType.
         */
        public byte[] data() { return data; }
        public EfivarSignatureList _root() { return _root; }
        public EfivarSignatureList.SignatureList _parent() { return _parent; }
    }

    /**
     * Attributes of a UEFI variable
     */
    public static class EfiVarAttr extends KaitaiStruct {
        public static EfiVarAttr fromFile(String fileName) throws IOException {
            return new EfiVarAttr(new ByteBufferKaitaiStream(fileName));
        }

        public EfiVarAttr(KaitaiStream _io) {
            this(_io, null, null);
        }

        public EfiVarAttr(KaitaiStream _io, EfivarSignatureList _parent) {
            this(_io, _parent, null);
        }

        public EfiVarAttr(KaitaiStream _io, EfivarSignatureList _parent, EfivarSignatureList _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.enhancedAuthenticatedAccess = this._io.readBitsIntBe(1) != 0;
            this.appendWrite = this._io.readBitsIntBe(1) != 0;
            this.timeBasedAuthenticatedWriteAccess = this._io.readBitsIntBe(1) != 0;
            this.authenticatedWriteAccess = this._io.readBitsIntBe(1) != 0;
            this.hardwareErrorRecord = this._io.readBitsIntBe(1) != 0;
            this.runtimeAccess = this._io.readBitsIntBe(1) != 0;
            this.bootserviceAccess = this._io.readBitsIntBe(1) != 0;
            this.nonVolatile = this._io.readBitsIntBe(1) != 0;
            this.reserved1 = this._io.readBitsIntBe(24);
        }
        private boolean enhancedAuthenticatedAccess;
        private boolean appendWrite;
        private boolean timeBasedAuthenticatedWriteAccess;
        private boolean authenticatedWriteAccess;
        private boolean hardwareErrorRecord;
        private boolean runtimeAccess;
        private boolean bootserviceAccess;
        private boolean nonVolatile;
        private long reserved1;
        private EfivarSignatureList _root;
        private EfivarSignatureList _parent;
        public boolean enhancedAuthenticatedAccess() { return enhancedAuthenticatedAccess; }
        public boolean appendWrite() { return appendWrite; }
        public boolean timeBasedAuthenticatedWriteAccess() { return timeBasedAuthenticatedWriteAccess; }
        public boolean authenticatedWriteAccess() { return authenticatedWriteAccess; }
        public boolean hardwareErrorRecord() { return hardwareErrorRecord; }
        public boolean runtimeAccess() { return runtimeAccess; }
        public boolean bootserviceAccess() { return bootserviceAccess; }
        public boolean nonVolatile() { return nonVolatile; }

        /**
         * Reserved (unused) bits
         */
        public long reserved1() { return reserved1; }
        public EfivarSignatureList _root() { return _root; }
        public EfivarSignatureList _parent() { return _parent; }
    }
    private EfiVarAttr varAttributes;
    private ArrayList<SignatureList> signatures;
    private EfivarSignatureList _root;
    private KaitaiStruct _parent;

    /**
     * Attributes of the UEFI variable
     */
    public EfiVarAttr varAttributes() { return varAttributes; }
    public ArrayList<SignatureList> signatures() { return signatures; }
    public EfivarSignatureList _root() { return _root; }
    public KaitaiStruct _parent() { return _parent; }
}