文章目錄

• • [GXYCTF2019]SXMgdGhpcyBiYXNlPw==
  • [FlareOn1]Bob Doge

[GXYCTF2019]SXMgdGhpcyBiYXNlPw==

拿到一個(gè)題目，打開后顯示這樣

''' base64隱寫解密 '''base64chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'flag='' with open('flag.txt','r') as f:for line in f.readlines():line=line[:-1]num=line.count('=')if num == 0 :continuelastchar = line[-(num+1)]#print(line,num,lastchar)myindex = base64chars.index(lastchar)#print(myindex)bin_str = bin(myindex)[2:].zfill(6)#print(bin_str)flag+=bin_str[6-2*num:]#print(bin_str[6-2*num:]) print(''.join([chr(int(flag[i:i + 8], 2)) for i in range(0, len(flag), 8)]))

找到解密腳本，即可找出flag

[FlareOn1]Bob Doge

進(jìn)去之后發(fā)現(xiàn)這個(gè)：

private void btnDecode_Click(object sender, EventArgs e){this.pbRoge.Image = Resources.bob_roge;byte[] dat_secret = Resources.dat_secret;string text = "";foreach (byte b in dat_secret){text += (char)((b >> 4 | ((int)b << 4 & 240)) ^ 41);}text += "\0";string text2 = "";for (int j = 0; j < text.Length; j += 2){text2 += text[j + 1];text2 += text[j];}string text3 = "";for (int k = 0; k < text2.Length; k++){char c = text2[k];text3 += (char)((byte)text2[k] ^ 102);}this.lbl_title.Text = text3;}

動(dòng)態(tài)調(diào)試一下，發(fā)現(xiàn)一個(gè)以.com結(jié)尾的郵箱，而且含有@flare-on，進(jìn)去看看，再把它當(dāng)flag交了

3rmahg3rd.b0b.d0ge@flare-on.com

總結(jié)

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