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/*
* Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or any later version.
*
* This program 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
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <stdint.h>
#include <stddef.h>
#include <errno.h>
#include <gpxe/asn1.h>
/** @file
*
* ASN.1 encoding
*
*/
/**
* Start parsing ASN.1 object
*
* @v cursor ASN.1 object cursor
* @v type Expected type
* @ret len Length of object body, or negative error
*
* The object cursor will be updated to point to the start of the
* object body (i.e. the first byte following the length byte(s)), and
* the length of the object body (i.e. the number of bytes until the
* following object tag, if any) is returned.
*
* If any error occurs (i.e. if the object is not of the expected
* type, or if we overflow beyond the end of the ASN.1 object), then
* the cursor will be invalidated and a negative value will be
* returned.
*/
static int asn1_start ( struct asn1_cursor *cursor,
unsigned int type ) {
unsigned int len_len;
unsigned int len;
int rc;
/* Sanity check */
if ( cursor->len < 2 /* Tag byte and first length byte */ ) {
if ( cursor->len )
DBGC ( cursor, "ASN1 %p too short\n", cursor );
rc = -EINVAL;
goto notfound;
}
/* Check the tag byte */
if ( *( ( uint8_t * ) cursor->data ) != type ) {
DBGC ( cursor, "ASN1 %p type mismatch (expected %d, got %d)\n",
cursor, type, *( ( uint8_t * ) cursor->data ) );
rc = -ENXIO;
goto notfound;
}
cursor->data++;
cursor->len--;
/* Extract length of the length field and sanity check */
len_len = *( ( uint8_t * ) cursor->data );
if ( len_len & 0x80 ) {
len_len = ( len_len & 0x7f );
cursor->data++;
cursor->len--;
} else {
len_len = 1;
}
if ( cursor->len < len_len ) {
DBGC ( cursor, "ASN1 %p bad length field length %d (max "
"%zd)\n", cursor, len_len, cursor->len );
rc = -EINVAL;
goto notfound;
}
/* Extract the length and sanity check */
for ( len = 0 ; len_len ; len_len-- ) {
len <<= 8;
len |= *( ( uint8_t * ) cursor->data );
cursor->data++;
cursor->len--;
}
if ( cursor->len < len ) {
DBGC ( cursor, "ASN1 %p bad length %d (max %zd)\n",
cursor, len, cursor->len );
rc = -EINVAL;
goto notfound;
}
return len;
notfound:
cursor->data = NULL;
cursor->len = 0;
return rc;
}
/**
* Enter ASN.1 object
*
* @v cursor ASN.1 object cursor
* @v type Expected type
* @ret rc Return status code
*
* The object cursor will be updated to point to the body of the
* current ASN.1 object. If any error occurs, the object cursor will
* be invalidated.
*/
int asn1_enter ( struct asn1_cursor *cursor, unsigned int type ) {
int len;
len = asn1_start ( cursor, type );
if ( len < 0 )
return len;
cursor->len = len;
DBGC ( cursor, "ASN1 %p entered object type %02x (len %x)\n",
cursor, type, len );
return 0;
}
/**
* Skip ASN.1 object
*
* @v cursor ASN.1 object cursor
* @v type Expected type
* @ret rc Return status code
*
* The object cursor will be updated to point to the next ASN.1
* object. If any error occurs, the object cursor will be
* invalidated.
*/
int asn1_skip ( struct asn1_cursor *cursor, unsigned int type ) {
int len;
len = asn1_start ( cursor, type );
if ( len < 0 )
return len;
cursor->data += len;
cursor->len -= len;
DBGC ( cursor, "ASN1 %p skipped object type %02x (len %x)\n",
cursor, type, len );
if ( ! cursor->len ) {
DBGC ( cursor, "ASN1 %p reached end of object\n", cursor );
cursor->data = NULL;
return -ENOENT;
}
return 0;
}
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