ext_chk.c

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/****************************************************************************
*                                                                           *
*                   Certificate Attribute Checking Routines                 *
*                       Copyright Peter Gutmann 1996-2008                   *
*                                                                           *
****************************************************************************/

#if defined( INC_ALL )
  #include "cert.h"
  #include "certattr.h"
  #include "asn1.h"
  #include "asn1_ext.h"
#else
  #include "cert/cert.h"
  #include "cert/certattr.h"
  #include "enc_dec/asn1.h"
  #include "enc_dec/asn1_ext.h"
#endif /* Compiler-specific includes */

/* Define the following to print a trace of the certificate fields being 
   checked */

#if !defined( NDEBUG ) && 0
  #define TRACE_FIELDTYPE( attributeInfoPtr ) \
          { \
          if( ( attributeInfoPtr ) != NULL && \
              ( attributeInfoPtr )->description != NULL ) \
              DEBUG_PRINT(( ( attributeInfoPtr )->description )); \
          else \
              DEBUG_PRINT(( "<Unrecognised attribute>" )); \
          DEBUG_PRINT(( "\n" )); \
          }
  #define TRACE_DEBUG( message ) \
          DEBUG_PRINT( message )
#else
  #define TRACE_FIELDTYPE( attributeInfoPtr )
  #define TRACE_DEBUG( message )
#endif /* NDEBUG */

#ifdef USE_CERTIFICATES

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

/* Validate and preprocess a set of attributes and set up links to the 
   information in the attribute information table in preparation for 
   encoding the attribute.  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 that the list of fields is 
   consistent with the attribute information table.  In addition we set up 
   synchronisation points between the list and table that are used during 
   the encoding process.  For example assume that 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
    t2:     BOOLEAN     OPTIONAL
    t3:     SEQUENCE
    t4:     OID         END

   The first table entry t1 contains the OID, the SEQUENCE wrapper.  For the 
   purposes of comparison with the list this is a no-op 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.  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.  Finally, the 
   last table entry t4 contains the second attribute field, an OID, and the
   end-of-attribute flag.

   Assuming that the attribute list contains the following:

    BOOLEAN FALSE   -> t1
    OID     xxx     -> t3

   The attribute validation process sets the synchronisation 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) and then since the field IDs won't match we step on 
   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 synchronisation 
   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 that 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 */
    const 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 that 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 
   (isRelative = TRUE, 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 (isRelative = FALSE, in which case we undo 'count' stack 
   positions */

CHECK_RETVAL STDC_NONNULL_ARG( ( 1, 3 ) ) \
static int updateStackedInfo( INOUT_ARRAY_C( ATTRIBUTE_STACKSIZE ) \
                                ATTRIBUTE_STACK *stack, 
                              IN_RANGE( 0, ATTRIBUTE_STACKSIZE - 1 ) \
                                const int stackPos,
                              OUT_RANGE( 0, ATTRIBUTE_STACKSIZE - 1 ) \
                                int *newStackPosPtr,
                              IN_RANGE( 0, ATTRIBUTE_STACKSIZE - 1 ) int count, 
                              const BOOLEAN isRelative )
    {
    int currentStackPos = stackPos, iterationCount;

    assert( isWritePtr( stack, sizeof( ATTRIBUTE_STACK ) * \
                               ATTRIBUTE_STACKSIZE ) );
    assert( isWritePtr( newStackPosPtr, sizeof( int ) ) );

    static_assert( ENCODING_FIFO_SIZE >= ATTRIBUTE_STACKSIZE, \
                   "Stack size" );

    REQUIRES( stackPos >= 0 && stackPos < ATTRIBUTE_STACKSIZE );
    REQUIRES( count >= 0 && count <= stackPos );

    for( iterationCount = 0; \
         count > 0 && iterationCount < ATTRIBUTE_STACKSIZE; \
         count--, iterationCount++ )
        {
        ATTRIBUTE_LIST *attributeFifoPtr;
        const ATTRIBUTE_INFO *attributeInfoPtr;
        int size;

        ENSURES( count > 0 && count <= currentStackPos );

        /* Unstack the current entry */
        currentStackPos--;
        ENSURES( currentStackPos >= 0 && \
                 currentStackPos < ATTRIBUTE_STACKSIZE );
        attributeFifoPtr = stack[ currentStackPos ].attributeListPtr;
        attributeInfoPtr = stack[ currentStackPos ].attributeInfoPtr;
        size = stack[ currentStackPos ].size;
        ENSURES( size >= 0 && size < MAX_INTLENGTH );
        assert( isReadPtr( attributeInfoPtr, sizeof( ATTRIBUTE_INFO ) ) );

        /* 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) then 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( attributeFifoPtr == NULL )
            {
            ENSURES( size == 0 );
            continue;
            }
        if( size <= 0 && \
            !( ( attributeFifoPtr->flags & ATTR_FLAG_DEFAULTVALUE ) || \
               ( attributeInfoPtr->encodingFlags & FL_NONENCODING ) ) )
            continue;

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

        ENSURES( attributeFifoPtr->fifoEnd > 0 && \
                 attributeFifoPtr->fifoEnd < ENCODING_FIFO_SIZE );

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

        ENSURES( currentStackPos > 0 && \
                 currentStackPos < ATTRIBUTE_STACKSIZE );

        /* 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 )
            {
            int newLength;

            /* Calculate the size of the encoded field data.  A sequence of
               identifier fields has a final catch-all entry without an OID 
               which is only used for decoding, we should never see this 
               when encoding but we make the check explicit just in case */
            if( attributeInfoPtr->fieldType == FIELDTYPE_IDENTIFIER )
                {
                ENSURES( attributeInfoPtr->oid );
                newLength = sizeofOID( attributeInfoPtr->oid );
                }
            else
                newLength = ( 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[ currentStackPos - 1 ].size += size + newLength;
            if( isRelative )
                count++;
            }
        else
            {
            /* It's a constructed field, percolate the encapsulated content
               size up the stack */
            stack[ currentStackPos - 1 ].size += ( int ) sizeofObject( size );
            }
        }
    ENSURES( iterationCount < ATTRIBUTE_STACKSIZE );

    *newStackPosPtr = currentStackPos;

    return( CRYPT_OK );
    }

/* Some attributes contain a sequence of items of the attributeTypeAndValue 
   form (i.e. OID, ANY DEFINED BY OID).  To process these we check 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 */

CHECK_RETVAL STDC_NONNULL_ARG( ( 2 ) ) \
static int checkComponentPresent( IN_ATTRIBUTE const CRYPT_ATTRIBUTE_TYPE fieldID,
                                  INOUT ATTRIBUTE_INFO **attributeInfoPtrPtr )
    {
    const ATTRIBUTE_INFO *attributeInfoPtr = *attributeInfoPtrPtr;
    int nestLevel = 0, iterationCount;

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

    REQUIRES( ( fieldID > CRYPT_ATTRIBUTE_NONE && \
                fieldID < CRYPT_ATTRIBUTE_LAST ) || \
              ( fieldID == CRYPT_IATTRIBUTE_LAST ) );
              /* The latter is used when we've run out of values to match 
                 and just want to skip to the end of the 
                 attributeTypeAndValue */

    /* Check each field that we find until we find the end of the
       attributeTypeAndValue.  Unfortunately we don't know how many 
       attribute table entries are left so we have to use the generic
       FAILSAFE_ITERATIONS_LARGE for the bounds check */
    for( iterationCount = 0; iterationCount < FAILSAFE_ITERATIONS_LARGE; \
         iterationCount++ )
        {
        /* Sanity check to make sure that we don't fall off the end of the 
           table */
        ENSURES( attributeInfoPtr->fieldID != CRYPT_ERROR );

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

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

        /* 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->typeInfoFlags & FL_ATTR_ATTREND ) )
            break;

        attributeInfoPtr++;
        }
    ENSURES( iterationCount < FAILSAFE_ITERATIONS_LARGE );

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

/* 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 that 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 then 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 */
    const 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 */
    ARRAY( ATTRIBUTE_STACKSIZE, stackPos ) \
    ATTRIBUTE_STACK stack[ ATTRIBUTE_STACKSIZE + 8 ];
    int stackPos;                   /* Encoding stack position */
    int stackTop;

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

CHECK_RETVAL STDC_NONNULL_ARG( ( 1, 3 ) ) \
static int stackInfo( INOUT ATTRIBUTE_CHECK_INFO *attributeCheckInfo,
                      IN_OPT ATTRIBUTE_LIST *attributeListPtr,
                      const ATTRIBUTE_INFO *attributeInfoPtr )
    {
    ATTRIBUTE_STACK *stack = attributeCheckInfo->stack;

    assert( isWritePtr( attributeCheckInfo, \
                        sizeof( ATTRIBUTE_CHECK_INFO ) ) );
    assert( attributeListPtr == NULL || \
            isReadPtr( attributeListPtr, sizeof( ATTRIBUTE_LIST ) ) );
    assert( isReadPtr( attributeInfoPtr, sizeof( ATTRIBUTE_INFO ) ) );

    REQUIRES( attributeCheckInfo->stackPos >= 0 && \
              attributeCheckInfo->stackPos < ATTRIBUTE_STACKSIZE - 1 );

    stack[ attributeCheckInfo->stackPos ].size = 0;
    stack[ attributeCheckInfo->stackPos ].attributeListPtr = attributeListPtr;
    stack[ attributeCheckInfo->stackPos++ ].attributeInfoPtr = attributeInfoPtr;

    return( CRYPT_OK );
    }

CHECK_RETVAL STDC_NONNULL_ARG( ( 1 ) ) \
static int checkAttribute( INOUT ATTRIBUTE_CHECK_INFO *attributeCheckInfo );
                           /* Forward declaration for function */

CHECK_RETVAL STDC_NONNULL_ARG( ( 1 ) ) \
static int checkAttributeEntry( INOUT ATTRIBUTE_CHECK_INFO *attributeCheckInfo )
    {
    ATTRIBUTE_LIST *attributeListPtr = attributeCheckInfo->attributeListPtr;
    const ATTRIBUTE_INFO *attributeInfoPtr = attributeCheckInfo->attributeInfoPtr;
    ATTRIBUTE_STACK *stack = attributeCheckInfo->stack;
    CRYPT_ATTRIBUTE_TYPE fieldID;

    assert( isWritePtr( attributeCheckInfo, \
                        sizeof( ATTRIBUTE_CHECK_INFO ) ) );
    assert( attributeListPtr == NULL || \
            isWritePtr( attributeListPtr, sizeof( ATTRIBUTE_LIST ) ) );
    assert( isReadPtr( attributeInfoPtr, sizeof( ATTRIBUTE_INFO ) ) );
    assert( isWritePtr( stack, \
                        sizeof( ATTRIBUTE_STACK ) * ATTRIBUTE_STACKSIZE ) );

    /* Determine the fieldID for the current attribute field.  Once we get 
       to the end of an attribute list entry we may still run through this 
       function multiple times with attributeListPtr set to NULL but 
       attributeInfoPtr advancing on each step, see the comment in 
       updateStackedInfo() for details */
    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_IATTRIBUTE_LAST;
        }
    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 )
        {
        /* If it's a subtyped or CHOICE field, check the components using
           their own encoding table */
        if( attributeInfoPtr->fieldType == FIELDTYPE_SUBTYPED || \
            attributeInfoPtr->fieldType == FIELDTYPE_CHOICE )
            {
            int status;

            /* Switch to the new encoding table, record the fact that
               we've done this, and set the new stack top to the level at
               which we start encoding the subtype */
            if( attributeInfoPtr->fieldType == FIELDTYPE_CHOICE )
                {
                /* Stack the value start position in the attribute list and
                   record the fact that we're processing a CHOICE */
                status = stackInfo( attributeCheckInfo, attributeListPtr,
                                    attributeInfoPtr );
                if( cryptStatusError( status ) )
                    return( status );
                attributeCheckInfo->choiceState = CHOICE_START;
                }
            attributeCheckInfo->attributeInfoPtr = \
                    ( const ATTRIBUTE_INFO * ) attributeInfoPtr->extraData;
            attributeCheckInfo->subtypeParent = attributeListPtr->fieldID;
            attributeCheckInfo->stackTop = attributeCheckInfo->stackPos;
            status = checkAttribute( attributeCheckInfo );
            attributeCheckInfo->attributeInfoPtr = attributeInfoPtr;
            attributeCheckInfo->subtypeParent = CRYPT_ATTRIBUTE_NONE;
            attributeCheckInfo->stackTop = 0;
            if( !( attributeInfoPtr->encodingFlags & FL_OPTIONAL ) && \
                attributeCheckInfo->attributeListPtr == attributeListPtr )
                {
                /* The subtyped field was non-optional but we failed to 
                   match anything in it against the current attribute list 
                   entry (meaning that the atributeListPtr in the check info
                   hasn't been advanced), there's a problem with the 
                   encoding table.  This check is used to catch situations 
                   where a subtyped field is used to encode a CHOICE for 
                   which each CHOICE field is optional but at least one 
                   component of the CHOICE must be present */
                retIntError();
                }
            return( status );
            }

        /* If there's an extended validation function attached to this field,
           call it */
        if( attributeInfoPtr->extraData != NULL )
            {
            VALIDATION_FUNCTION validationFunction = \
                    ( VALIDATION_FUNCTION ) attributeInfoPtr->extraData;

            attributeCheckInfo->errorType = \
                                    validationFunction( attributeListPtr );
            if( attributeCheckInfo->errorType != CRYPT_ERRTYPE_NONE )
                return( CRYPT_ERROR_INVALID );
            }

        /* If this is an optional field and the value is the same as the
           default value remember that it doesn't get encoded */
        if( ( attributeInfoPtr->encodingFlags & FL_DEFAULT ) && \
            ( attributeInfoPtr->defaultValue == attributeListPtr->intValue ) )
            {
            attributeListPtr->flags |= ATTR_FLAG_DEFAULTVALUE;
            attributeCheckInfo->attributeListPtr = attributeListPtr->next;

            return( CRYPT_OK );
            }

        /* Remember the encoded size of this field.  writeAttributeField()
           takes a compliance-level parameter that controls stricter 
           encoding of some string types at higher compliance levels but 
           this doesn't affect the encoded size so we always use 
           CRYPT_COMPLIANCELEVEL_STANDARD for the size calculation */
        attributeListPtr->attributeInfoPtr = attributeInfoPtr;
        attributeListPtr->encodedSize = \
                    writeAttributeField( NULL, attributeListPtr, 
                                         CRYPT_COMPLIANCELEVEL_STANDARD );
        if( attributeCheckInfo->stackPos > 0 )
            {
            stack[ attributeCheckInfo->stackPos - 1 ].size += \
                                        attributeListPtr->encodedSize;
            }

        /* If this is a CHOICE field update the choice state */
        if( attributeCheckInfo->choiceState != CHOICE_NONE )
            {
            if( attributeCheckInfo->choiceState == CHOICE_DONE )
                {
                /* If we've already processed one of the CHOICE options 
                   there can't be another one present */
                attributeCheckInfo->errorType = CRYPT_ERRTYPE_ATTR_PRESENT;
                return( CRYPT_ERROR_INVALID );
                }
            if( attributeCheckInfo->choiceState == CHOICE_START )
                {
                /* Remember that we've seen a CHOICE option */
                attributeCheckInfo->choiceState = CHOICE_DONE;
                }
            }

        /* Move on to the next attribute field */
        attributeCheckInfo->attributeListPtr = attributeListPtr->next;
        return( CRYPT_OK );
        }

    /* If it's an attributeTypeAndValue sequence check whether it contains
       the field that we want:

            t0: BER_SEQUENCE    IDENTIFIER
            t1: OID
          [ t2: params          NONENCODING ]

       The initialisation sanity-check has already confirmed the validity of 
       the above format in the encoding table on startup */
    if( attributeInfoPtr->encodingFlags & FL_IDENTIFIER )
        {
        BOOLEAN endOfAttributeField = FALSE;
        int status;

        status = checkComponentPresent( fieldID, 
                                        ( ATTRIBUTE_INFO ** ) &attributeInfoPtr );
        if( status == CRYPT_ERROR_NOTFOUND )
            {
            /* Since we've jumped over several items we may be pointing at an
               end-of-sequence flag for which no sequence start was stacked 
               so we skip the stack update step */
            attributeCheckInfo->attributeInfoPtr = attributeInfoPtr;
            return( OK_SPECIAL );
            }
        if( cryptStatusError( status ) )
            return( status );

        /* Stack the position of the sequence start and the following OID */
        status = stackInfo( attributeCheckInfo, attributeListPtr, 
                            attributeInfoPtr++ );
        if( cryptStatusOK( status ) )
            status = stackInfo( attributeCheckInfo, attributeListPtr, 
                                attributeInfoPtr );
        if( cryptStatusError( status ) )
            return( status );

        /* If the OID entry is marked as the end-of-sequence there are no
           parameters attached so we move on to the next entry */
        if( attributeInfoPtr->encodingFlags & FL_SEQEND_MASK )
            endOfAttributeField = TRUE;

        /* Sometimes the OID is followed by a fixed-value blob field that
           constitutes parameters for the OID, if this is present we stack it
           as well */
        if( attributeInfoPtr[ 1 ].encodingFlags & FL_NONENCODING )
            {
            attributeInfoPtr++;
            status = stackInfo( attributeCheckInfo, attributeListPtr, 
                                attributeInfoPtr );
            if( cryptStatusError( status ) )
                return( status );

            /* If the fields are fixed-value we always move on to the next
               entry since there are no user-supplied parameters present */
            endOfAttributeField = TRUE;
            }

        attributeCheckInfo->attributeInfoPtr = attributeInfoPtr;
        if( endOfAttributeField )
            {
            /* If this is all that needs to be encoded move on to the next
               attribute field */
            if( attributeListPtr == NULL )
                attributeCheckInfo->attributeListPtr = NULL;
            else
                attributeCheckInfo->attributeListPtr = attributeListPtr->next;
            }
        return( CRYPT_OK );
        }

    /* If it's a SEQUENCE/SET or a non-encoding value then it's a no-op entry
       used only for encoding purposes and can be skipped, however we need to
       remember it for later encoding */
    if( attributeInfoPtr->fieldType == BER_SEQUENCE || \
        attributeInfoPtr->fieldType == BER_SET || \
        attributeInfoPtr->encodingFlags & FL_NONENCODING )
        {
        /* Stack the sequence or value start position in the attribute list */
        return( stackInfo( attributeCheckInfo, attributeListPtr, 
                           attributeInfoPtr ) );
        }

    /* If it's a non-optional field and the attribute field doesn't match,
       it's an error - attribute attributeID is missing field
       attributeInfoPtr->fieldID (optional subfield
       attributeInfoPtr->subFieldID) (set by the error handler in the calling
       code) */
    if( !( attributeInfoPtr->encodingFlags & FL_OPTIONAL ) )
        {
        attributeCheckInfo->errorType = CRYPT_ERRTYPE_ATTR_ABSENT;
        return( CRYPT_ERROR_NOTINITED );
        }

    return( CRYPT_OK );
    }

/* Check an individual attribute */

CHECK_RETVAL STDC_NONNULL_ARG( ( 1 ) ) \
static int checkAttribute( INOUT ATTRIBUTE_CHECK_INFO *attributeCheckInfo )
    {
    ATTRIBUTE_LIST *restartEntry = NULL;
    const ATTRIBUTE_INFO *restartPoint = NULL;
    int restartStackPos = 0, iterationCount;

    assert( isWritePtr( attributeCheckInfo, \
                        sizeof( ATTRIBUTE_CHECK_INFO ) ) );
    assert( isReadPtr( attributeCheckInfo->attributeInfoPtr,
                       sizeof( ATTRIBUTE_INFO ) ) );

    TRACE_DEBUG(( "Checking attribute " ));
    TRACE_FIELDTYPE( attributeCheckInfo->attributeInfoPtr );

    /* Step through the attribute comparing the fields that are present in
       the attribute list with the fields that should be present according
       to the table and set encoding synchronisation points as required */
    for( iterationCount = 0; iterationCount < FAILSAFE_ITERATIONS_LARGE; 
         iterationCount++ )
        {
        int typeInfoFlags, status;

        /* Sanity check to make sure that we don't fall off the end of the 
           encoding table */
        ENSURES( attributeCheckInfo->attributeInfoPtr->fieldID != CRYPT_ERROR );

        /* Check whether this is a repeated instance of the same attribute
           and if it is remember the encoding restart point.  We have to do
           this before we check the attribute information because it usually
           updates the information after the check */
        if( restartEntry == NULL && \
            attributeCheckInfo->attributeListPtr != NULL && \
            attributeCheckInfo->attributeListPtr->next != NULL && \
            ( attributeCheckInfo->attributeListPtr->fieldID == \
              attributeCheckInfo->attributeListPtr->next->fieldID ) && \
            ( attributeCheckInfo->attributeListPtr->subFieldID == \
              attributeCheckInfo->attributeListPtr->next->subFieldID ) )
            {
            restartEntry = attributeCheckInfo->attributeListPtr;
            restartPoint = attributeCheckInfo->attributeInfoPtr + 1;
            restartStackPos = attributeCheckInfo->stackPos + 1;
            }

        /* Check the current encoding table entry */
        status = checkAttributeEntry( attributeCheckInfo );
        if( status != OK_SPECIAL )
            {
            if( cryptStatusError( status ) )
                {
                attributeCheckInfo->errorLocus = \
                            attributeCheckInfo->attributeInfoPtr->fieldID;
                return( status );
                }

            /* If this is the end of a constructed item unstack it and
               update the attribute list entry with the length information.
               If it's a sequence with all fields optional (so that nothing
               gets encoded) we don't do anything */
            status = updateStackedInfo( attributeCheckInfo->stack,
                                        attributeCheckInfo->stackPos,
                                        &attributeCheckInfo->stackPos,
                decodeNestingLevel( attributeCheckInfo->attributeInfoPtr->encodingFlags ),
                                        TRUE );
            if( cryptStatusError( status ) )
                return( status );
            }

        /* If there's another instance of the same item, don't move on to
           the next table entry */
        if( restartEntry != NULL && \
            restartEntry != attributeCheckInfo->attributeListPtr )
            {
            /* Restart at the table entry for the previous instance of the 
               item and adjust the stack to match */
            attributeCheckInfo->attributeInfoPtr = restartPoint;
            if( attributeCheckInfo->stackPos > restartStackPos )
                {
                status = updateStackedInfo( attributeCheckInfo->stack,
                                            attributeCheckInfo->stackPos,
                                            &attributeCheckInfo->stackPos,
                                            attributeCheckInfo->stackPos - \
                                                restartStackPos, TRUE );
                if( cryptStatusError( status ) )
                    return( status );
                }
            restartEntry = NULL;
            restartPoint = NULL;
            restartStackPos = 0;

            continue;
            }

        /* Move on to the next table entry.  We have to check the
           continuation flag before we move to the next table entry in order
           to include processing of the last field in an attribute */
        typeInfoFlags = attributeCheckInfo->attributeInfoPtr->typeInfoFlags;
        attributeCheckInfo->attributeInfoPtr++;
        if( typeInfoFlags & FL_ATTR_ATTREND )
            break;
        }
    ENSURES( iterationCount < FAILSAFE_ITERATIONS_LARGE );
    attributeCheckInfo->choiceState = CHOICE_NONE;
    
    /* We've reached the end of the attribute, if there are still constructed
       objects stacked, unstack them and update their length information.  If
       it's a sequence with all fields optional (so that nothing gets
       encoded) this won't do anything */
    return( updateStackedInfo( attributeCheckInfo->stack, 
                               attributeCheckInfo->stackPos,
                               &attributeCheckInfo->stackPos,
                               attributeCheckInfo->stackPos - \
                                    attributeCheckInfo->stackTop, FALSE ) );
    }

/* Check the entire list of attributes */

CHECK_RETVAL STDC_NONNULL_ARG( ( 2, 3, 4 ) ) \
int checkAttributes( IN_ENUM( ATTRIBUTE ) const ATTRIBUTE_TYPE attributeType,
                     const ATTRIBUTE_PTR *listHeadPtr,
                     OUT_ENUM_OPT( CRYPT_ATTRIBUTE ) \
                        CRYPT_ATTRIBUTE_TYPE *errorLocus,
                     OUT_ENUM_OPT( CRYPT_ERRTYPE ) \
                        CRYPT_ERRTYPE_TYPE *errorType )
    {
    ATTRIBUTE_CHECK_INFO attributeCheckInfo;
    const ATTRIBUTE_INFO *attributeInfoStartPtr;
    ATTRIBUTE_LIST *attributeListPtr;
    int dummy, iterationCount, status;

    assert( isReadPtr( listHeadPtr, sizeof( ATTRIBUTE_LIST ) ) );
    assert( isWritePtr( errorLocus, sizeof( CRYPT_ATTRIBUTE_TYPE ) ) );
    assert( isWritePtr( errorType, sizeof( CRYPT_ERRTYPE_TYPE ) ) );

    REQUIRES( attributeType == ATTRIBUTE_CERTIFICATE || \
              attributeType == ATTRIBUTE_CMS );

    /* Get the attribute encoding information.  We can't use the size value
       returned from this because of the nested-loop structure below which 
       only ever iterates through a subset of the encoding information so we
       leave it as a dummy value */
    status = getAttributeInfo( attributeType, &attributeInfoStartPtr, 
                               &dummy );
    ENSURES( cryptStatusOK( status ) );

    /* If we've already done a validation pass some of the fields will
       contain values that were previously set so before we begin we walk
       down the list resetting the fields that are updated by this
       function */
    for( attributeListPtr = ( ATTRIBUTE_LIST * ) listHeadPtr, \
            iterationCount = 0;
         attributeListPtr != NULL && \
            isValidAttributeField( attributeListPtr ) && \
            iterationCount < FAILSAFE_ITERATIONS_LARGE; 
         attributeListPtr = attributeListPtr->next, iterationCount++ )
        {
        if( attributeListPtr->next != NULL && \
            isValidAttributeField( attributeListPtr->next ) && \
            attributeListPtr->attributeID > \
                        attributeListPtr->next->attributeID )
            {
            /* Safety check in case of an invalid attribute list */
            retIntError();
            }
        attributeListPtr->attributeInfoPtr = NULL;
        attributeListPtr->encodedSize = attributeListPtr->fifoPos = \
            attributeListPtr->fifoEnd = 0;
        attributeListPtr->flags &= ~ATTR_FLAG_DEFAULTVALUE;
        }
    ENSURES( iterationCount < FAILSAFE_ITERATIONS_LARGE );

    /* Set up the attribute-checking state information */
    memset( &attributeCheckInfo, 0, sizeof( ATTRIBUTE_CHECK_INFO ) );
    attributeCheckInfo.attributeListPtr = ( ATTRIBUTE_LIST * ) listHeadPtr;
    attributeCheckInfo.attributeInfoPtr = attributeInfoStartPtr;

    /* Walk down the list of known attributes checking each one for
       consistency */
    for( iterationCount = 0;
         attributeCheckInfo.attributeListPtr != NULL && \
            attributeCheckInfo.attributeListPtr->fieldID != CRYPT_ATTRIBUTE_NONE && \
            iterationCount < FAILSAFE_ITERATIONS_LARGE;
         iterationCount++ )
        {
        int innerIterationCount;

        /* Find the start of this attribute in the attribute information 
           table and remember it as an encoding synchronisation point.  
           Comparing the field ID with the attribute ID is usually valid 
           because the attribute information table always begins the series 
           of entries for an attribute with the attribute ID.  The one 
           exception is where the attribute ID is the same as the field ID 
           but they're separate entries in the table, in which case the 
           first entries will contain a FIELDID_FOLLOWS code to indicate 
           that the following field contains the attribute/fieldID */
        for( innerIterationCount = 0;
             attributeCheckInfo.attributeInfoPtr->fieldID != CRYPT_ERROR && \
                innerIterationCount < FAILSAFE_ITERATIONS_LARGE;
             attributeCheckInfo.attributeInfoPtr++, innerIterationCount++ )
            {
            if( attributeCheckInfo.attributeInfoPtr->fieldID == FIELDID_FOLLOWS )
                {
                if( attributeCheckInfo.attributeInfoPtr[ 1 ].fieldID == \
                        attributeCheckInfo.attributeListPtr->attributeID )
                    break;
                }
            else
                {
                if( attributeCheckInfo.attributeInfoPtr->fieldID == \
                        attributeCheckInfo.attributeListPtr->attributeID )
                    break;
                }
            }
        ENSURES( innerIterationCount < FAILSAFE_ITERATIONS_LARGE );
        ENSURES( attributeCheckInfo.attributeInfoPtr->fieldID != CRYPT_ERROR );

        /* Check this attribute */
        status = checkAttribute( &attributeCheckInfo );
        if( cryptStatusError( status ) )
            {
            *errorLocus = attributeCheckInfo.errorLocus;
            *errorType = attributeCheckInfo.errorType;
            return( status );
            }
        }
    ENSURES( iterationCount < FAILSAFE_ITERATIONS_LARGE );

    return( CRYPT_OK );
    }
#endif /* USE_CERTIFICATES */