PROV: Add the beginning of a DER writing library

[thirdparty/openssl.git] / crypto / der_writer.c

diff --git a/crypto/der_writer.c b/crypto/der_writer.c
new file mode 100644 (file)
index 0000000..26fd885
--- /dev/null
+++ b/crypto/der_writer.c
@@ -0,0 +1,142 @@
+/*
+ * Copyright 2020 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include "internal/cryptlib.h"
+#include "internal/der.h"
+#include "crypto/bn.h"
+
+static int int_start_context(WPACKET *pkt, int tag)
+{
+    if (tag < 0)
+        return 1;
+    if (!ossl_assert(tag <= 30))
+        return 0;
+    return WPACKET_start_sub_packet(pkt);
+}
+
+static int int_end_context(WPACKET *pkt, int tag)
+{
+    if (tag < 0)
+        return 1;
+    if (!ossl_assert(tag <= 30))
+        return 0;
+    return WPACKET_close(pkt)
+        && WPACKET_put_bytes_u8(pkt, DER_C_CONTEXT | tag);
+}
+
+int DER_w_precompiled(WPACKET *pkt, int tag,
+                      const unsigned char *precompiled, size_t precompiled_n)
+{
+    return int_start_context(pkt, tag)
+        && WPACKET_memcpy(pkt, precompiled, precompiled_n)
+        && int_end_context(pkt, tag);
+}
+
+int DER_w_boolean(WPACKET *pkt, int tag, int b)
+{
+    return int_start_context(pkt, tag)
+        && WPACKET_start_sub_packet(pkt)
+        && (!b || WPACKET_put_bytes_u8(pkt, 0xFF))
+        && !WPACKET_close(pkt)
+        && !WPACKET_put_bytes_u8(pkt, DER_P_BOOLEAN)
+        && int_end_context(pkt, tag);
+}
+
+static int int_der_w_integer(WPACKET *pkt, int tag,
+                             int (*put_bytes)(WPACKET *pkt, const void *v,
+                                              unsigned int *top_byte),
+                             const void *v)
+{
+    unsigned int top_byte = 0;
+
+    return int_start_context(pkt, tag)
+        && WPACKET_start_sub_packet(pkt)
+        && put_bytes(pkt, v, &top_byte)
+        && ((top_byte & 0x80) == 0 || WPACKET_put_bytes_u8(pkt, 0))
+        && WPACKET_close(pkt)
+        && WPACKET_put_bytes_u8(pkt, DER_P_INTEGER)
+        && int_end_context(pkt, tag);
+}
+
+static int int_put_bytes_ulong(WPACKET *pkt, const void *v,
+                               unsigned int *top_byte)
+{
+    const unsigned long *value = v;
+    unsigned long tmp = *value;
+    size_t n = 0;
+
+    while (tmp != 0) {
+        n++;
+        *top_byte = (tmp & 0xFF);
+        tmp >>= 8;
+    }
+    if (n == 0)
+        n = 1;
+
+    return WPACKET_put_bytes__(pkt, *value, n);
+}
+
+/* For integers, we only support unsigned values for now */
+int DER_w_ulong(WPACKET *pkt, int tag, unsigned long v)
+{
+    return int_der_w_integer(pkt, tag, int_put_bytes_ulong, &v);
+}
+
+static int int_put_bytes_bn(WPACKET *pkt, const void *v,
+                            unsigned int *top_byte)
+{
+    unsigned char *p = NULL;
+    size_t n = BN_num_bytes(v);
+
+    /* The BIGNUM limbs are in LE order */
+    *top_byte =
+        ((bn_get_words(v) [(n - 1) / BN_BYTES]) >> (8 * ((n - 1) % BN_BYTES)))
+        & 0xFF;
+
+    if (!WPACKET_allocate_bytes(pkt, n, &p))
+        return 0;
+    if (p != NULL)
+        BN_bn2bin(v, p);
+    return 1;
+}
+
+int DER_w_bn(WPACKET *pkt, int tag, const BIGNUM *v)
+{
+    if (v == NULL || BN_is_negative(v))
+        return 0;
+    if (BN_is_zero(v))
+        return DER_w_ulong(pkt, tag, 0);
+
+    return int_der_w_integer(pkt, tag, int_put_bytes_bn, v);
+}
+
+int DER_w_null(WPACKET *pkt, int tag)
+{
+    return int_start_context(pkt, tag)
+        && WPACKET_start_sub_packet(pkt)
+        && WPACKET_close(pkt)
+        && WPACKET_put_bytes_u8(pkt, DER_P_NULL)
+        && int_end_context(pkt, tag);
+}
+
+/* Constructed things need a start and an end */
+int DER_w_begin_sequence(WPACKET *pkt, int tag)
+{
+    return int_start_context(pkt, tag)
+        && WPACKET_start_sub_packet(pkt);
+}
+
+int DER_w_end_sequence(WPACKET *pkt, int tag)
+{
+    return WPACKET_close(pkt)
+        && WPACKET_put_bytes_u8(pkt, DER_F_CONSTRUCTED | DER_P_SEQUENCE)
+        && int_end_context(pkt, tag);
+}