getjavacert

#include <stdio.h>

#define BUFLEN (1<<16)
unsigned char buf[BUFLEN];
#define cbuf ((char*)buf)

int main(const int argc, const char **argv){
    if(isatty(fileno(stdin))){fprintf(stderr,"unzip -p FILE.apk|jar \"META-INF/*.RSA\" | getjavacert\n");return -1;}
    fread(buf,1,0x38,stdin);//fseek(stdin,0x38,SEEK_SET);
    fread(buf+(BUFLEN/2),1,2,stdin);
    if(buf[(BUFLEN/2)]!=0x30||buf[(BUFLEN/2)+1]>0x84){fprintf(stderr,"cannot parse header\n");return 1;}
    u32 len=0;
    if(buf[(BUFLEN/2)+1]<0x80)len=buf[(BUFLEN/2)+1];
    u32 i=0,j=0;
    for(;i<buf[(BUFLEN/2)+1]-0x80;i++){
        buf[(BUFLEN/2)+2+i]=fgetc(stdin);len=(len<<8)+buf[(BUFLEN/2)+2+i];
    }
    if(len>BUFLEN/4){fprintf(stderr,"length too large (%d)\n",len);return 1;}
    fread(buf+(BUFLEN/2)+2+i,1,len,stdin); //total=2+i+len
    for(;j<2+i+len;j++){
        int x=buf[(BUFLEN/2)+j]>>4,y=buf[(BUFLEN/2)+j]&0xf;
        buf[2*j+0]=x>9?(x-10+'a'):(x+'0');
        buf[2*j+1]=y>9?(y-10+'a'):(y+'0');
    }
    buf[2*j+0]=0;
    puts(cbuf);

    return 0;
}