New base function `FT_Matrix_Check' (#54019).
* src/base/ftcalc.c (FT_Matrix_Check): New base function to properly reject degenerate font matrices. * include/freetype/internal/ftcalc.h: Updated. * src/cff/cffparse.c (cff_parse_font_matrix), src/cid/cidload.c (cid_parse_font_matrix), src/type1/t1load.c (t1_parse_font_matrix), src/type42/t42parse.c (t42_parse_font_matrix): Use `FT_Matrix_Check'.
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Werner Lemberg
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14
ChangeLog
14
ChangeLog
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@ -1,3 +1,17 @@
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2018-06-24 Werner Lemberg <wl@gnu.org>
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New base function `FT_Matrix_Check' (#54019).
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* src/base/ftcalc.c (FT_Matrix_Check): New base function to properly
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reject degenerate font matrices.
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* include/freetype/internal/ftcalc.h: Updated.
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* src/cff/cffparse.c (cff_parse_font_matrix), src/cid/cidload.c
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(cid_parse_font_matrix), src/type1/t1load.c (t1_parse_font_matrix),
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src/type42/t42parse.c (t42_parse_font_matrix): Use
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`FT_Matrix_Check'.
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2018-06-23 Werner Lemberg <wl@gnu.org>
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Fix typo.
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@ -292,6 +292,21 @@ FT_BEGIN_HEADER
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FT_Long scaling );
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/*
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* Check a matrix. If the transformation would lead to extreme shear or
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* extreme scaling, for example, return 0. If everything is OK, return 1.
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*
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* Based on geometric considerations we use the following inequality to
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* identify a degenerate matrix.
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*
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* 50 * abs(xx*yy - xy*yx) < xx^2 + xy^2 + yx^2 + yy^2
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*
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* Value 50 is heuristic.
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*/
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FT_BASE( FT_Bool )
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FT_Matrix_Check( const FT_Matrix* matrix );
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/*
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* A variant of FT_Vector_Transform. See comments for
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* FT_Matrix_Multiply_Scaled.
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@ -745,6 +745,72 @@
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}
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/* documentation is in ftcalc.h */
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FT_BASE_DEF( FT_Bool )
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FT_Matrix_Check( const FT_Matrix* matrix )
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{
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FT_Matrix m;
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FT_Fixed val[4];
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FT_Fixed nonzero_minval, maxval;
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FT_Fixed temp1, temp2;
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FT_UInt i;
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if ( !matrix )
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return 0;
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val[0] = FT_ABS( matrix->xx );
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val[1] = FT_ABS( matrix->xy );
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val[2] = FT_ABS( matrix->yx );
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val[3] = FT_ABS( matrix->yy );
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/*
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* To avoid overflow, we ensure that each value is not larger than
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*
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* int(sqrt(2^31 / 4)) = 23170 ;
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*
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* we also check that no value becomes zero if we have to scale.
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*/
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maxval = 0;
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nonzero_minval = FT_LONG_MAX;
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for ( i = 0; i < 4; i++ )
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{
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if ( val[i] > maxval )
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maxval = val[i];
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if ( val[i] && val[i] < nonzero_minval )
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nonzero_minval = val[i];
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}
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if ( maxval > 23170 )
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{
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FT_Fixed scale = FT_DivFix( maxval, 23170 );
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if ( !FT_DivFix( nonzero_minval, scale ) )
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return 0; /* value range too large */
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m.xx = FT_DivFix( matrix->xx, scale );
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m.xy = FT_DivFix( matrix->xy, scale );
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m.yx = FT_DivFix( matrix->yx, scale );
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m.yy = FT_DivFix( matrix->yy, scale );
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}
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else
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m = *matrix;
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temp1 = FT_ABS( m.xx * m.yy - m.xy * m.yx );
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temp2 = m.xx * m.xx + m.xy * m.xy + m.yx * m.yx + m.yy * m.yy;
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if ( temp1 == 0 ||
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temp2 / temp1 > 50 )
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return 0;
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return 1;
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}
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/* documentation is in ftcalc.h */
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FT_BASE_DEF( void )
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@ -604,7 +604,6 @@
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FT_Vector* offset = &dict->font_offset;
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FT_ULong* upm = &dict->units_per_em;
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FT_Byte** data = parser->stack;
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FT_Error error = FT_ERR( Stack_Underflow );
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if ( parser->top >= parser->stack + 6 )
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@ -616,8 +615,6 @@
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int i;
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error = FT_Err_Ok;
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dict->has_font_matrix = TRUE;
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/* We expect a well-formed font matrix, this is, the matrix elements */
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@ -646,22 +643,11 @@
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( max_scaling - min_scaling ) < 0 ||
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( max_scaling - min_scaling ) > 9 )
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{
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/* Return default matrix in case of unlikely values. */
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FT_TRACE1(( "cff_parse_font_matrix:"
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" strange scaling values (minimum %d, maximum %d),\n"
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" "
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" using default matrix\n", min_scaling, max_scaling ));
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matrix->xx = 0x10000L;
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matrix->yx = 0;
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matrix->xy = 0;
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matrix->yy = 0x10000L;
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offset->x = 0;
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offset->y = 0;
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*upm = 1;
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goto Exit;
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goto Unlikely;
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}
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for ( i = 0; i < 6; i++ )
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@ -708,10 +694,31 @@
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(double)matrix->yy / *upm / 65536,
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(double)offset->x / *upm / 65536,
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(double)offset->y / *upm / 65536 ));
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}
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Exit:
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return error;
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if ( !FT_Matrix_Check( matrix ) )
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{
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FT_TRACE1(( "cff_parse_font_matrix:"
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" degenerate values, using default matrix\n" ));
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goto Unlikely;
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}
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return FT_Err_Ok;
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}
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else
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return FT_THROW( Stack_Underflow );
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Unlikely:
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/* Return default matrix in case of unlikely values. */
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matrix->xx = 0x10000L;
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matrix->yx = 0;
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matrix->xy = 0;
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matrix->yy = 0x10000L;
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offset->x = 0;
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offset->y = 0;
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*upm = 1;
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return FT_Err_Ok;
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}
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@ -200,6 +200,13 @@
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matrix->xy = temp[2];
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matrix->yy = temp[3];
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if ( !FT_Matrix_Check( matrix ) )
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{
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FT_ERROR(( "t1_parse_font_matrix: invalid font matrix\n" ));
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parser->root.error = FT_THROW( Invalid_File_Format );
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return FT_THROW( Invalid_File_Format );
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}
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/* note that the font offsets are expressed in integer font units */
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offset->x = temp[4] >> 16;
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offset->y = temp[5] >> 16;
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@ -1286,6 +1286,13 @@
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matrix->xy = temp[2];
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matrix->yy = temp[3];
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if ( !FT_Matrix_Check( matrix ) )
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{
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FT_ERROR(( "t1_parse_font_matrix: invalid font matrix\n" ));
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parser->root.error = FT_THROW( Invalid_File_Format );
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return;
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}
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/* note that the offsets must be expressed in integer font units */
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offset->x = temp[4] >> 16;
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offset->y = temp[5] >> 16;
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@ -284,6 +284,13 @@
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matrix->xy = temp[2];
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matrix->yy = temp[3];
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if ( !FT_Matrix_Check( matrix ) )
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{
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FT_ERROR(( "t42_parse_font_matrix: invalid font matrix\n" ));
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parser->root.error = FT_THROW( Invalid_File_Format );
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return;
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}
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/* note that the offsets must be expressed in integer font units */
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offset->x = temp[4] >> 16;
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offset->y = temp[5] >> 16;
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