crypto: add ASN.1 DER decoder

Add an ANS.1 DER decoder which is used to parse asymmetric
cipher keys

Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
Signed-off-by: lei he <helei.sig11@bytedance.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

3 files changed, 271 insertions, 0 deletions

diff --git a/crypto/der.c b/crypto/der.c
new file mode 100644
index 0000000..f877390
--- /dev/null
+++ b/crypto/der.c
@@ -0,0 +1,189 @@
+/*
+ * QEMU Crypto ASN.1 DER decoder
+ *
+ * Copyright (c) 2022 Bytedance
+ * Author: lei he <helei.sig11@bytedance.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "crypto/der.h"
+
+enum QCryptoDERTypeTag {
+    QCRYPTO_DER_TYPE_TAG_BOOL = 0x1,
+    QCRYPTO_DER_TYPE_TAG_INT = 0x2,
+    QCRYPTO_DER_TYPE_TAG_BIT_STR = 0x3,
+    QCRYPTO_DER_TYPE_TAG_OCT_STR = 0x4,
+    QCRYPTO_DER_TYPE_TAG_OCT_NULL = 0x5,
+    QCRYPTO_DER_TYPE_TAG_OCT_OID = 0x6,
+    QCRYPTO_DER_TYPE_TAG_SEQ = 0x10,
+    QCRYPTO_DER_TYPE_TAG_SET = 0x11,
+};
+
+#define QCRYPTO_DER_CONSTRUCTED_MASK 0x20
+#define QCRYPTO_DER_SHORT_LEN_MASK 0x80
+
+static uint8_t qcrypto_der_peek_byte(const uint8_t **data, size_t *dlen)
+{
+    return **data;
+}
+
+static void qcrypto_der_cut_nbytes(const uint8_t **data,
+                                   size_t *dlen,
+                                   size_t nbytes)
+{
+    *data += nbytes;
+    *dlen -= nbytes;
+}
+
+static uint8_t qcrypto_der_cut_byte(const uint8_t **data, size_t *dlen)
+{
+    uint8_t val = qcrypto_der_peek_byte(data, dlen);
+
+    qcrypto_der_cut_nbytes(data, dlen, 1);
+
+    return val;
+}
+
+static int qcrypto_der_invoke_callback(QCryptoDERDecodeCb cb, void *ctx,
+                                       const uint8_t *value, size_t vlen,
+                                       Error **errp)
+{
+    if (!cb) {
+        return 0;
+    }
+
+    return cb(ctx, value, vlen, errp);
+}
+
+static int qcrypto_der_extract_definite_data(const uint8_t **data, size_t *dlen,
+                                             QCryptoDERDecodeCb cb, void *ctx,
+                                             Error **errp)
+{
+    const uint8_t *value;
+    size_t vlen = 0;
+    uint8_t byte_count = qcrypto_der_cut_byte(data, dlen);
+
+    /* short format of definite-length */
+    if (!(byte_count & QCRYPTO_DER_SHORT_LEN_MASK)) {
+        if (byte_count > *dlen) {
+            error_setg(errp, "Invalid content length: %u", byte_count);
+            return -1;
+        }
+
+        value = *data;
+        vlen = byte_count;
+        qcrypto_der_cut_nbytes(data, dlen, vlen);
+
+        if (qcrypto_der_invoke_callback(cb, ctx, value, vlen, errp) != 0) {
+            return -1;
+        }
+        return vlen;
+    }
+
+    /* Ignore highest bit */
+    byte_count &= ~QCRYPTO_DER_SHORT_LEN_MASK;
+
+    /*
+     * size_t is enough to store the value of length, although the DER
+     * encoding standard supports larger length.
+     */
+    if (byte_count > sizeof(size_t)) {
+        error_setg(errp, "Invalid byte count of content length: %u",
+                   byte_count);
+        return -1;
+    }
+
+    if (byte_count > *dlen) {
+        error_setg(errp, "Invalid content length: %u", byte_count);
+        return -1;
+    }
+    while (byte_count--) {
+        vlen <<= 8;
+        vlen += qcrypto_der_cut_byte(data, dlen);
+    }
+
+    if (vlen > *dlen) {
+        error_setg(errp, "Invalid content length: %zu", vlen);
+        return -1;
+    }
+
+    value = *data;
+    qcrypto_der_cut_nbytes(data, dlen, vlen);
+
+    if (qcrypto_der_invoke_callback(cb, ctx, value, vlen, errp) != 0) {
+        return -1;
+    }
+    return vlen;
+}
+
+static int qcrypto_der_extract_data(const uint8_t **data, size_t *dlen,
+                                    QCryptoDERDecodeCb cb, void *ctx,
+                                    Error **errp)
+{
+    uint8_t val;
+    if (*dlen < 1) {
+        error_setg(errp, "Need more data");
+        return -1;
+    }
+    val = qcrypto_der_peek_byte(data, dlen);
+
+    /* must use definite length format */
+    if (val == QCRYPTO_DER_SHORT_LEN_MASK) {
+        error_setg(errp, "Only definite length format is allowed");
+        return -1;
+    }
+
+    return qcrypto_der_extract_definite_data(data, dlen, cb, ctx, errp);
+}
+
+int qcrypto_der_decode_int(const uint8_t **data, size_t *dlen,
+                           QCryptoDERDecodeCb cb, void *ctx, Error **errp)
+{
+    uint8_t tag;
+    if (*dlen < 1) {
+        error_setg(errp, "Need more data");
+        return -1;
+    }
+    tag = qcrypto_der_cut_byte(data, dlen);
+
+    /* INTEGER must encoded in primitive-form */
+    if (tag != QCRYPTO_DER_TYPE_TAG_INT) {
+        error_setg(errp, "Invalid integer type tag: %u", tag);
+        return -1;
+    }
+
+    return qcrypto_der_extract_data(data, dlen, cb, ctx, errp);
+}
+
+int qcrypto_der_decode_seq(const uint8_t **data, size_t *dlen,
+                           QCryptoDERDecodeCb cb, void *ctx, Error **errp)
+{
+    uint8_t tag;
+    if (*dlen < 1) {
+        error_setg(errp, "Need more data");
+        return -1;
+    }
+    tag = qcrypto_der_cut_byte(data, dlen);
+
+    /* SEQUENCE must use constructed form */
+    if (tag != (QCRYPTO_DER_TYPE_TAG_SEQ | QCRYPTO_DER_CONSTRUCTED_MASK)) {
+        error_setg(errp, "Invalid type sequence tag: %u", tag);
+        return -1;
+    }
+
+    return qcrypto_der_extract_data(data, dlen, cb, ctx, errp);
+}
diff --git a/crypto/der.h b/crypto/der.h
new file mode 100644
index 0000000..e3d3aea
--- /dev/null
+++ b/crypto/der.h
@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) 2022 Bytedance
+ * Author: lei he <helei.sig11@bytedance.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef QCRYPTO_ASN1_DECODER_H
+#define QCRYPTO_ASN1_DECODER_H
+
+#include "qapi/error.h"
+
+/* Simple decoder used to parse DER encoded rsa keys. */
+
+/**
+ *  @opaque: user context.
+ *  @value: the starting address of |value| part of 'Tag-Length-Value' pattern.
+ *  @vlen: length of the |value|.
+ *  Returns: 0 for success, any other value is considered an error.
+ */
+typedef int (*QCryptoDERDecodeCb) (void *opaque, const uint8_t *value,
+                                   size_t vlen, Error **errp);
+
+/**
+ * qcrypto_der_decode_int:
+ * @data: pointer to address of input data
+ * @dlen: pointer to length of input data
+ * @cb: callback invoked when decode succeed, if cb equals NULL, no
+ * callback will be invoked
+ * @opaque: parameter passed to cb
+ *
+ * Decode integer from DER-encoded data.
+ *
+ * Returns: On success, *data points to rest data, and *dlen
+ * will be set to the rest length of data, if cb is not NULL, must
+ * return 0 to make decode success, at last, the length of the data
+ * part of the decoded INTEGER will be returned. Otherwise, -1 is
+ * returned.
+ */
+int qcrypto_der_decode_int(const uint8_t **data,
+                           size_t *dlen,
+                           QCryptoDERDecodeCb cb,
+                           void *opaque,
+                           Error **errp);
+
+/**
+ * qcrypto_der_decode_seq:
+ *
+ * Decode sequence from DER-encoded data, similar with der_decode_int.
+ *
+ * @data: pointer to address of input data
+ * @dlen: pointer to length of input data
+ * @cb: callback invoked when decode succeed, if cb equals NULL, no
+ * callback will be invoked
+ * @opaque: parameter passed to cb
+ *
+ * Returns: On success, *data points to rest data, and *dlen
+ * will be set to the rest length of data, if cb is not NULL, must
+ * return 0 to make decode success, at last, the length of the data
+ * part of the decoded SEQUENCE will be returned. Otherwise, -1 is
+ * returned.
+ */
+int qcrypto_der_decode_seq(const uint8_t **data,
+                           size_t *dlen,
+                           QCryptoDERDecodeCb cb,
+                           void *opaque,
+                           Error **errp);
+
+#endif  /* QCRYPTO_ASN1_DECODER_H */
diff --git a/crypto/meson.build b/crypto/meson.build
index 313f935..b8152ae 100644
--- a/crypto/meson.build
+++ b/crypto/meson.build
@@ -6,6 +6,7 @@ crypto_ss.add(files(
   'block-qcow.c',
   'block.c',
   'cipher.c',
+  'der.c',
   'hash.c',
   'hmac.c',
   'ivgen-essiv.c',