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+/*
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+ * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
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+ *
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+ * This program is free software; you can redistribute it and/or
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+ * modify it under the terms of the GNU General Public License as
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+ * published by the Free Software Foundation; either version 2 of the
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+ * License, or any later version.
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+ *
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+ * This program is distributed in the hope that it will be useful, but
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+ * WITHOUT ANY WARRANTY; without even the implied warranty of
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+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+ * General Public License for more details.
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+ *
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+ * You should have received a copy of the GNU General Public License
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+ * along with this program; if not, write to the Free Software
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+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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+ */
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+
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+#include <stdint.h>
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+#include <stddef.h>
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+#include <errno.h>
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+#include <gpxe/asn1.h>
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+
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+/** @file
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+ *
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+ * ASN.1 encoding
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+ *
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+ */
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+
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+/**
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+ * Start parsing ASN.1 object
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+ *
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+ * @v cursor ASN.1 object cursor
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+ * @v type Expected type
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+ * @ret len Length of object body, or -1 on error
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+ *
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+ * The object cursor will be updated to point to the start of the
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+ * object body (i.e. the first byte following the length byte(s)), and
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+ * the length of the object body (i.e. the number of bytes until the
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+ * following object tag, if any) is returned.
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+ *
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+ * If any error occurs (i.e. if the object is not of the expected
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+ * type, or if we overflow beyond the end of the ASN.1 object), then
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+ * the cursor will be invalidated and a negative value will be
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+ * returned.
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+ */
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+static int asn1_start_object ( struct asn1_cursor *cursor,
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+ unsigned int type ) {
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+ unsigned int len_len;
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+ unsigned int len;
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+
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+ /* Sanity check */
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+ if ( cursor->len < 2 /* Tag byte and first length byte */ ) {
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+ if ( cursor->len )
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+ DBGC ( cursor, "ASN1 %p too short\n", cursor );
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+ goto notfound;
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+ }
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+
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+ /* Check the tag byte */
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+ if ( cursor->data[0] != type ) {
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+ DBGC ( cursor, "ASN1 %p type mismatch (expected %d, got %d)\n",
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+ cursor, type, cursor->data[0] );
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+ goto notfound;
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+ }
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+ cursor->data++;
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+ cursor->len--;
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+
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+ /* Extract length of the length field and sanity check */
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+ len_len = cursor->data[0];
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+ if ( len_len & 0x80 ) {
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+ len_len = ( len_len & 0x7f );
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+ cursor->data++;
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+ cursor->len--;
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+ } else {
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+ len_len = 1;
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+ }
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+ if ( cursor->len < len_len ) {
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+ DBGC ( cursor, "ASN1 %p bad length field length %d (max %d)\n",
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+ cursor, len_len, cursor->len );
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+ goto notfound;
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+ }
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+
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+ /* Extract the length and sanity check */
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+ for ( len = 0 ; len_len ; len_len-- ) {
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+ len <<= 8;
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+ len |= cursor->data[0];
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+ cursor->data++;
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+ cursor->len--;
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+ }
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+ if ( cursor->len < len ) {
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+ DBGC ( cursor, "ASN1 %p bad length %d (max %d)\n",
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+ cursor, len, cursor->len );
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+ goto notfound;
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+ }
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+
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+ return len;
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+
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+ notfound:
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+ cursor->data = NULL;
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+ cursor->len = 0;
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+ return -1;
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+}
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+
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+/**
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+ * Enter ASN.1 object
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+ *
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+ * @v cursor ASN.1 object cursor
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+ * @v type Expected type
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+ * @ret rc Return status code
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+ *
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+ * The object cursor will be updated to point to the body of the
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+ * current ASN.1 object. If any error occurs, the object cursor will
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+ * be invalidated.
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+ */
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+int asn1_enter_object ( struct asn1_cursor *cursor, unsigned int type ) {
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+ int len;
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+
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+ len = asn1_start_object ( cursor, type );
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+ if ( len < 0 )
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+ return -ENOENT;
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+
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+ cursor->len = len;
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+ DBGC ( cursor, "ASN1 %p entered object type %02x (len %x)\n",
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+ cursor, type, len );
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+
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+ return 0;
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+}
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+
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+/**
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+ * Skip ASN.1 object
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+ *
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+ * @v cursor ASN.1 object cursor
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+ * @v type Expected type
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+ * @ret rc Return status code
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+ *
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+ * The object cursor will be updated to point to the next ASN.1
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+ * object. If any error occurs, the object cursor will be
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+ * invalidated.
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+ */
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+int asn1_skip_object ( struct asn1_cursor *cursor, unsigned int type ) {
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+ int len;
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+
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+ len = asn1_start_object ( cursor, type );
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+ if ( len < 0 )
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+ return -ENOENT;
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+
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+ cursor->data += len;
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+ cursor->len -= len;
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+ DBGC ( cursor, "ASN1 %p skipped object type %02x (len %x)\n",
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+ cursor, type, len );
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+
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+ if ( ! cursor->len ) {
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+ DBGC ( cursor, "ASN1 %p reached end of object\n", cursor );
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+ cursor->data = NULL;
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+ return -ENOENT;
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+ }
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+
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+ return 0;
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+}
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