From db4e0e4ac7edf3d06f6f371c4a30e20f31c7b8e0 Mon Sep 17 00:00:00 2001 From: Jonas Gunz Date: Fri, 26 Apr 2019 01:16:15 +0200 Subject: Rewrote JFIF stripper to use whitelist --- src/main.c | 106 ++++++++++++++++++++++++++++++++++++++++--------------------- 1 file changed, 70 insertions(+), 36 deletions(-) diff --git a/src/main.c b/src/main.c index 1e97ad7..06e7f41 100644 --- a/src/main.c +++ b/src/main.c @@ -32,12 +32,19 @@ #define _MAGIC_TFF 0x2A00 //TIFF Magic Value //JPG -#define _JPG_EXIF 0xE1 //EXIF -#define _JPG_COM 0xFE //Comments -#define _JPG_COPY 0xEE //Copyright notice +#define _JPG_SOI 0xFFD8 +#define _JPG_APP0 0xFFE0 +#define _JPG_CX 0xFFC0 +#define _JPG_DQT 0xFFDB +#define _JPG_DRI 0xFFDD +#define _JPG_SOS 0xFFDA //Start of image data +#define _JPG_EOI 0xFFD9 //End of image + +//Stuff to ignore +#define _JPG_EXIF 0xFFE1 //EXIF +#define _JPG_COM 0xFFFE //Comments +#define _JPG_COPY 0xFFEE //Copyright notice -#define _JPG_SOS 0xDA //Start of image data -#define _JPG_EOI 0xD9 //End of image //PNG //Essential chunks @@ -133,45 +140,72 @@ int strip_jpg(char *_filename) return 1; } + uint16_t magic_num = 0xD8FF; + fwrite(&magic_num, 1, 2, out); + + uint16_t segment = 0xFFD8; + while(1) { unsigned char c = fgetc(in); - if(c == 0xFF) + segment = (segment << 8) + (c & 0x00FF); + if(segment == _JPG_APP0 || + segment == _JPG_DQT || + segment == _JPG_DRI || + (segment & 0xFFF0) == (_JPG_CX & 0xFFF0)) { - unsigned char c2 = fgetc(in); - if( c2 == _JPG_EXIF || c2 == _JPG_COM || c2 == _JPG_COPY ) //Add tags here - { - unsigned char c3 = fgetc(in); - unsigned char c4 = fgetc(in); - uint16_t seg_len = (( c3 << 8 ) & 0xff00) + c4; - - DEBUG_PRINTF("SEG %X SEGLEN %uB START @%li", c2, seg_len, ftell(in) ); - - seg_len -= 2; //2B are already read! - - uint16_t i; - for (i = 0; i < seg_len; i++) { - fgetc(in); - } - DEBUG_PRINTF(" FINISHED. Read %uB, UNTIL %li\n", i, ftell(in) ); - } - else if ( c2 == _JPG_EOI ) - { - DEBUG_PRINTF("ENDSEG @%li\n", ftell(in)); + unsigned char l1 = fgetc(in); + unsigned char l2 = fgetc(in); + uint16_t seg_len = (( l1 << 8 ) & 0xff00) + l2; - fputc(c, out); - fputc(c2, out); - break; - } - else + DEBUG_PRINTF("Segment %X, size %uB @%liB\n", segment, seg_len, ftell(in)); + + char *f__buffer = malloc(seg_len - 2); + + fread(f__buffer, 1, seg_len - 2, in); + fputc(segment >> 8, out); + fputc(segment, out); + fputc(seg_len >> 8, out); + fputc(seg_len, out); + fwrite(f__buffer, 1, seg_len - 2, out); + + free(f__buffer); + } + else if(segment == _JPG_EXIF || + segment == _JPG_COM || + segment == _JPG_COPY ) + { + unsigned char l1 = fgetc(in); + unsigned char l2 = fgetc(in); + uint16_t seg_len = (( l1 << 8 ) & 0xff00) + l2; + + DEBUG_PRINTF("Ignoring segment %X, size %uB @%liB\n", segment, seg_len, ftell(in)); + + char *f__buffer = malloc(seg_len - 2); + + fread(f__buffer, 1, seg_len - 2, in); + free(f__buffer); + + } + else if(segment == _JPG_SOS) + { + DEBUG_PRINTF("SOS @%li\n", ftell(in)); + uint16_t endseg = _JPG_SOS; + fputc(segment >> 8, out); + fputc(segment, out); + while(1) { - fputc(c, out); - fputc(c2, out); + unsigned char cc = fgetc(in); + endseg = (endseg << 8) + (cc & 0x00FF); + if(endseg == _JPG_EOI) + break; + else + fputc(cc, out); } + DEBUG_PRINTF("ENDSEG @%li\n", ftell(in)); + fwrite(&endseg, 1, 2, out); + break; } - else - fputc(c, out); - if(feof(in)) { DEBUG_PRINTF("Reached EOF before ENDSEG @%li\n", ftell(in)); -- cgit v1.2.3