certechk.c

老外写的加密库cryptlib(版本3.1)

/****************************************************************************
*																			*
*					Certificate Attribute Checking Routines					*
*						Copyright Peter Gutmann 1996-2003					*
*																			*
****************************************************************************/

#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#if defined( INC_ALL ) ||  defined( INC_CHILD )
  #include "cert.h"
  #include "certattr.h"
  #include "../misc/asn1_rw.h"
  #include "../misc/asn1s_rw.h"
#else
  #include "cert/cert.h"
  #include "cert/certattr.h"
  #include "misc/asn1_rw.h"
  #include "misc/asn1s_rw.h"
#endif /* Compiler-specific includes */

/****************************************************************************
*																			*
*							Attribute Field Type Checking					*
*																			*
****************************************************************************/

/* Validate and preprocess a set of attributes in preparation for writing
   them to a certificate or CRL and set up links to the information in the
   attribute information table prior to encoding the attributes.  This is a
   rather complex process that relies on stepping through the list of
   attribute fields and the attribute information table in sync and making
   sure the list of fields is consistent with the attribute information
   table.  In addition we set up sync points between the list and table that
   are used during the encoding process.  For example assume we have the
   following attribute:

	attribute ::= SEQUENCE {
		foo		BOOLEAN DEFAULT TRUE,
		bar		SEQUENCE OF OBJECT IDENTIFIER
		}

   The attribute information table would encode this attribute as:

	t1:	OID	SEQUENCE	MORE
	t2:		BOOLEAN		MORE	OPTIONAL
	t3:		SEQUENCE	MORE
	t4:		OID

   The first table entry t1 contains the OID, the SEQUENCE wrapper, and a
   continuation flag.  For the purposes of comparison with the list, this is
   a nop and can be skipped since it's only used for encoding purposes.  The
   next table entry t2 contains the first attribute field, an optional
   boolean and a continuation flag.  The next table entry t3 contains another
   SEQUENCE wrapper that again is only used for encoding and can be skipped
   for comparing with the list, and a continuation flag.  Finally, the last
   table entry t4 contains the second attribute field, an OID.

   Assuming the attribute list contains the following:

	BOOLEAN	FALSE	-> t1
	OID		xxx		-> t3

   The attribute validation process sets the sync point for the first
   attribute list entry to point to t1, and the second one to point to t3.
   When we encode the attribute, we encode t1 (the OID, critical flag, and
   SEQUENCE wrapper), since the field IDs won't match we step to t2 and use
   that to encode the boolean.  We then do the same for t3 with the SEQUENCE
   and OID.

   If the attribute list instead contained only:

	OID		xxx		-> t1

   then this time the attribute validation process sets the sync point to t1.
   When encoding we encode t1 as before, step to t2, the field IDs won't
   match but t2 is optional so we skip it, then encode t3 as for t1 and
   finally encode the OID using t4.

   At this point we also evaluate the encoded size of each attribute.  For
   invidual fields, we just store their encoded size.  For constructed
   objects, we stack the attribute list entry where the constructed object
   starts and, until we reach the end of the constructed object, accumulate
   the total size of the fields that make up the object.  When we reach the
   end of the object, we unstack the pointer to the attribute list and store
   the total size in it.

   To handle nested constructed objects, we only update the size of the
   topmost item on the stack.  When this is unstacked, we add the size of
   that entry, plus the size of its tag and length information, to the next
   entry on the stack.

   In addition to updating the size, we also record the sequence of table
   entries that are required to encode the constructed item.  A worst-case
   sequence of entries would be:

	SEQUENCE {
		SEQUENCE OPTIONAL { ... }		| Not encoded
		SEQUENCE {
			SEQUENCE OPTIONAL { ... }	| Not encoded
			SEQUENCE {
				value
				}
			}
		}

   which contains an alternating sequence of encoded and non-encoded fields.
   Because of this, the validation check performs the complex task of
   recording which table entries are used for the encoding by stacking and
   unstacking them and discarding the ones that evaluate to a zero size
   during the unstacking process.

   Each entry in the stack contains the list item it applies to, the table
   entry which is used to encode the stacked item, and the size of the item */

#define ATTRIBUTE_STACKSIZE		10

typedef struct {
	ATTRIBUTE_LIST *attributeListPtr;	/* List entry that this applies to */
	ATTRIBUTE_INFO *attributeInfoPtr;	/* Encoding point for sequence */
	int size;							/* Size of sequence */
	} ATTRIBUTE_STACK;

/* Once we reach the end of the constructed item, we need to unwind the stack
   and update everything we've gone past.  If it's an optional item (so that
   nothing gets encoded), we don't do anything.  The count argument specifies
   the level of unwinding to perform, this can be relative (in which case we
   undo 'count' levels of nesting, which may be more than count stack
   positions if non-nested data was stacked) or absolute (in which case we
   undo 'count' stack positions */

static void updateStackedInfo( ATTRIBUTE_STACK *stack, int *stackPosPtr,
							   int count, const BOOLEAN isRelative )
	{
	int stackPos = *stackPosPtr;

	assert( isWritePtr( stack, ATTRIBUTE_STACK ) );
	assert( isWritePtr( stackPosPtr, int ) );
	assert( count <= stackPos );

	while( count-- )
		{
		ATTRIBUTE_LIST *attributeFifoPtr = stack[ --stackPos ].attributeListPtr;
		const ATTRIBUTE_INFO *attributeInfoPtr = stack[ stackPos ].attributeInfoPtr;
		const int size = stack[ stackPos ].size;

		assert( isReadPtr( attributeInfoPtr, ATTRIBUTE_INFO ) );
		assert( size >= 0 );
		assert( count >= 0 );
		assert( stackPos >= 0 );

		/* Safety check in case of an invalid encoding table */
		if( count < 0 || stackPos < 0 )
			{
			assert( NOTREACHED );
			return;
			}

		/* If there's nothing to encode, continue.  There are a few special
		   cases here where even if the sequence is of zero length, we may
		   have to encode something.  Firstly, if there's a member with a
		   default value present (resulting in nothing being encoded) we still
		   have to encode a zero-length sequence.  In addition if all of the
		   members have non-encoding values (e.g. OIDs and fixed attributes,
		   none of which are specified by the user) we have to encode these
		   even though there's no actual value associated with them since
		   their mere presence conveys the necessary information.

		   In addition sometimes we can reach the end of the attribute list
		   but there are further actions defined in the encoding table (for
		   example cleanup actions in nested sequences).  In this case the
		   stacked attributeFifoPtr is NULL and the size is zero, so we
		   perform an additional check to make sure that the pointer is non-
		   null */
		if( !( size || ( attributeFifoPtr != NULL && \
						 ( ( attributeFifoPtr->flags & ATTR_FLAG_DEFAULTVALUE ) || \
						   ( attributeInfoPtr->flags & FL_NONENCODING ) ) ) ) )
			continue;

		assert( isWritePtr( attributeFifoPtr, ATTRIBUTE_LIST ) );

		/* Remember the size and table entry used to encode this stack entry */
		attributeFifoPtr->sizeFifo[ attributeFifoPtr->fifoEnd ] = size;
		attributeFifoPtr->encodingFifo[ attributeFifoPtr->fifoEnd++ ] = \
										stack[ stackPos ].attributeInfoPtr;

		/* If there are no further items on the stack, continue */
		if( stackPos <= 0 )
			continue;

		/* If it's a non-constructed field, add the length of the existing and
		   new fields */
		if( attributeInfoPtr->fieldType != BER_SEQUENCE && \
			attributeInfoPtr->fieldType != BER_SET )
			{
			const int newLength = \
					( attributeInfoPtr->fieldType == FIELDTYPE_IDENTIFIER ) ? \
					sizeofOID( attributeInfoPtr->oid ) : \
					( int ) attributeInfoPtr->defaultValue;

			/* Add the new length to the existing data size.  Since this is a
			   non-constructed field, it doesn't count as a reduction in the
			   nesting level, so if we're unnesting by a relative amount we
			   adjust the nesting count to give a net change of zero for this
			   item */
			stack[ stackPos - 1 ].size += size + newLength;
			if( isRelative )
				count++;
			}
		else
			/* It's a constructed field, percolate the encapsulated content
			   size up the stack */
			stack[ stackPos - 1 ].size += ( int ) sizeofObject( size );
		}

	*stackPosPtr = stackPos;
	}

/* Some attributes contain a sequence of items of the attributeTypeAndValue
   form (i.e. OID, ANY DEFINED BY OID).  To process these, a check is made to
   determine whether the named value component in the attribute list is
   present in the current attributeTypeAndValue definition.  If it isn't, the
   item is given a zero length, which means that it's never encoded since the 
   field is marked as optional.  The following function checks whether a 
   named value component is present in the item */

static BOOLEAN checkComponentPresent( const CRYPT_ATTRIBUTE_TYPE fieldID,
									  ATTRIBUTE_INFO **attributeInfoPtrPtr )
	{
	const ATTRIBUTE_INFO *attributeInfoPtr = *attributeInfoPtrPtr;
	int nestLevel = 0;

	assert( isWritePtr( attributeInfoPtrPtr, ATTRIBUTE_INFO * ) );
	assert( isReadPtr( *attributeInfoPtrPtr, ATTRIBUTE_INFO ) );

	/* Check each field we find until we find the end of the
	   attributeTypeAndValue */
	while( TRUE )
		{
		/* Sanity check to make sure we don't fall off the end of the 
		   table */
		if( attributeInfoPtr->fieldID == CRYPT_ERROR )
			{
			assert( NOTREACHED );
			return( FALSE );
			}

		/* Adjust the nesting level depending on whether we're entering or
		   leaving a sequence */
		if( attributeInfoPtr->fieldType == BER_SEQUENCE )
			nestLevel++;
		nestLevel -= decodeNestingLevel( attributeInfoPtr->flags );

		/* If the field is present in this attributeTypeAndValue, return */
		if( attributeInfoPtr->fieldID == fieldID )
			return( TRUE );

		/* If we're at the end of the attribute or the attributeTypeAndValue,
		   exit the loop before adjusting the attributeInfoPtr so that we're
		   still pointing at the end-of-attribute field */
		if( nestLevel <= 0 || !( attributeInfoPtr->flags & FL_MORE ) )
			break;

		attributeInfoPtr++;
		}

	/* The field isn't present, update the pointer to the next
	   attributeTypeAndValue or the end of the attribute */
	*attributeInfoPtrPtr = ( ATTRIBUTE_INFO * ) attributeInfoPtr;
	return( FALSE );
	}

/* State machine for checking a CHOICE.  When we get to the start of a
   CHOICE, we move from CHOICE_NONE to CHOICE_START.  Once we've checked one
   of the CHOICE options, we move to CHOICE_DONE.  If a further option is
   found in the CHOICE_DONE state, we record an error.  This is a somewhat
   crude mechanism which works because the only CHOICE fields that can't be
   handled by rewriting them as alternative representations are complete
   attributes so that the CHOICE applies over the entire attribute.  If a
   CHOICE is ever present as an attribute subfield, the checking would be
   handled by recursively checking it as a subtyped field */

typedef enum { CHOICE_NONE, CHOICE_START, CHOICE_DONE } CHOICE_STATE;

/* Check an entry in the attribute table.  While we're performing the check
   we need to pass a lot of state information around, this is contained in
   the following structure */

typedef struct {
	/* State information.  When we're encoding a subtyped field (using an
	   alternative encoding table), we need to remember the field ID of the
	   parent to both tell the encoding routines that we're using an
	   alternative encoding table, and to remember the overall field ID so we
	   don't treat two adjacent field subfields as though they were part of
	   the same parent field.  If we're not currently encoding a subtyped
	   field, this field is set to CRYPT_ATTRIBUTE_NONE */
	ATTRIBUTE_LIST *attributeListPtr;	/* Position in attribute list */
	ATTRIBUTE_INFO *attributeInfoPtr;	/* Position in attribute table */
	CRYPT_ATTRIBUTE_TYPE subtypeParent;	/* Parent of subtype being processed */
	CHOICE_STATE choiceState;			/* State of CHOICE processing */

	/* Encoding stack.  When we're encoding subfields, the stack contains
	   items from both the subfield and the encapsulating field, so we also
	   record the current stack top to make sure that we don't go past this 
	   level when popping items after we've finished encoding a subfield */
	ATTRIBUTE_STACK stack[ ATTRIBUTE_STACKSIZE ];
	int stackPos;					/* Encoding stack position */
	int stackTop;

	/* Error information */
	CRYPT_ATTRIBUTE_TYPE errorLocus;/* Error locus */
	int errorType;					/* Error type */
	} ATTRIBUTE_CHECK_INFO;

static int stackInfo( ATTRIBUTE_CHECK_INFO *attributeCheckInfo,
					  ATTRIBUTE_LIST *attributeListPtr,
					  ATTRIBUTE_INFO *attributeInfoPtr )
	{
	ATTRIBUTE_STACK *stack = attributeCheckInfo->stack;

	if( attributeCheckInfo->stackPos >= ATTRIBUTE_STACKSIZE - 1 )
		{
		assert( NOTREACHED );
		return( CRYPT_ERROR_OVERFLOW );
		}
	stack[ attributeCheckInfo->stackPos ].size = 0;
	stack[ attributeCheckInfo->stackPos ].attributeListPtr = attributeListPtr;
	stack[ attributeCheckInfo->stackPos++ ].attributeInfoPtr = attributeInfoPtr;

	return( CRYPT_OK );
	}

static int checkAttributeEntry( ATTRIBUTE_CHECK_INFO *attributeCheckInfo )
	{
	STATIC_FN int checkAttribute( ATTRIBUTE_CHECK_INFO *attributeCheckInfo );
	ATTRIBUTE_LIST *attributeListPtr = attributeCheckInfo->attributeListPtr;
	ATTRIBUTE_INFO *attributeInfoPtr = attributeCheckInfo->attributeInfoPtr;
	ATTRIBUTE_STACK *stack = attributeCheckInfo->stack;
	CRYPT_ATTRIBUTE_TYPE fieldID;

	assert( isWritePtr( attributeCheckInfo, ATTRIBUTE_CHECK_INFO ) );

	/* Determine the fieldID for the current attribute field */
	if( attributeListPtr == NULL || attributeListPtr->fieldID == CRYPT_ATTRIBUTE_NONE )
		/* If we've reached the end of the list of recognised attributes, 
		   use a non-ID that doesn't match any table entry */
		fieldID = CRYPT_UNUSED;
	else
		/* If we're encoding a subtyped field, the fieldID is the field ID
		   within the parent field, or the subFieldID */
		if( attributeCheckInfo->subtypeParent == attributeListPtr->fieldID )
			fieldID = attributeListPtr->subFieldID;
		else
			/* It's a standard attribute field */
			fieldID = attributeListPtr->fieldID;

	/* If the field in the attribute list matches the one in the table,
	   process it and move on to the next one */
	if( attributeListPtr != NULL && attributeInfoPtr->fieldID == fieldID )