scusi ревизій цього gist 6 months ago. До ревизії
1 file changed, 2 insertions
gifExeExtract.go
| @@ -1,3 +1,5 @@ | |||
| 1 | + | ## see also https://0x41414141.de/blog/2017-03-30-trojan-ransom.win32.foreign-hides-payload-exe-in-gif-file/ | |
| 2 | + | # | |
| 1 | 3 | package main | |
| 2 | 4 | ||
| 3 | 5 | import ( | |
scusi ревизій цього gist 6 months ago. До ревизії
Без змін
Florian Walther ревизій цього gist 8 years ago. До ревизії
1 file changed, 105 insertions
gifExeExtract.go(файл створено)
| @@ -0,0 +1,105 @@ | |||
| 1 | + | package main | |
| 2 | + | ||
| 3 | + | import ( | |
| 4 | + | "bufio" | |
| 5 | + | "bytes" | |
| 6 | + | "container/ring" | |
| 7 | + | "encoding/hex" | |
| 8 | + | "flag" | |
| 9 | + | "fmt" | |
| 10 | + | "io/ioutil" | |
| 11 | + | "log" | |
| 12 | + | "os" | |
| 13 | + | ) | |
| 14 | + | ||
| 15 | + | var inFile string | |
| 16 | + | ||
| 17 | + | func init() { | |
| 18 | + | flag.StringVar(&inFile, "in", "", "path to input file") | |
| 19 | + | } | |
| 20 | + | ||
| 21 | + | func check(err error) { | |
| 22 | + | if err != nil { | |
| 23 | + | log.Fatal(err) | |
| 24 | + | } | |
| 25 | + | } | |
| 26 | + | ||
| 27 | + | func main() { | |
| 28 | + | // parse flags | |
| 29 | + | flag.Parse() | |
| 30 | + | // check if inputFile is given | |
| 31 | + | if inFile == "" { | |
| 32 | + | err := fmt.Errorf("no input file given") | |
| 33 | + | check(err) | |
| 34 | + | } | |
| 35 | + | // determine fileSize of inputFile | |
| 36 | + | var fileSize int64 | |
| 37 | + | file, err := os.Open(inFile) | |
| 38 | + | check(err) | |
| 39 | + | fi, err := file.Stat() | |
| 40 | + | check(err) | |
| 41 | + | fileSize = fi.Size() | |
| 42 | + | ||
| 43 | + | var offset int64 | |
| 44 | + | var bytesRead int | |
| 45 | + | ||
| 46 | + | // extract XOR key | |
| 47 | + | keyBuf := make([]byte, 256) | |
| 48 | + | offset, err = file.Seek(10, 0) | |
| 49 | + | check(err) | |
| 50 | + | bytesRead, err = file.Read(keyBuf) | |
| 51 | + | check(err) | |
| 52 | + | log.Printf("read %d at offset %d into keyBuf\n", bytesRead, offset) | |
| 53 | + | log.Println("Key extracted is:") | |
| 54 | + | d := hex.Dumper(os.Stdout) | |
| 55 | + | defer d.Close() | |
| 56 | + | d.Write(keyBuf) | |
| 57 | + | err = ioutil.WriteFile("key", keyBuf, 0755) | |
| 58 | + | check(err) | |
| 59 | + | log.Printf("key was written to the file 'key'\n") | |
| 60 | + | ||
| 61 | + | // extract encrypted EXE from inFile | |
| 62 | + | encBlockSize := fileSize - 10 - 256 - 266 | |
| 63 | + | encBlockBuf := make([]byte, encBlockSize) | |
| 64 | + | offset, err = file.Seek(266, 0) | |
| 65 | + | check(err) | |
| 66 | + | bytesRead, err = file.Read(encBlockBuf) | |
| 67 | + | check(err) | |
| 68 | + | log.Printf("read %d at offset %d into encBlockBuf\n", bytesRead, offset) | |
| 69 | + | ||
| 70 | + | // extract last block from inFile | |
| 71 | + | lastBlockBuf := make([]byte, 266) | |
| 72 | + | offset, err = file.Seek(-532, 2) | |
| 73 | + | check(err) | |
| 74 | + | bytesRead, err = file.Read(lastBlockBuf) | |
| 75 | + | check(err) | |
| 76 | + | log.Printf("read %d at offset %d into lastBlock\n", bytesRead, offset) | |
| 77 | + | // xor encBlockBuf with XOR key | |
| 78 | + | decBlock := XOR(encBlockBuf, keyBuf) | |
| 79 | + | // decBlock = append(decBlock, lastBlockBuf) | |
| 80 | + | var exeBuf bytes.Buffer | |
| 81 | + | w := bufio.NewWriter(&exeBuf) | |
| 82 | + | w.Write(decBlock) | |
| 83 | + | w.Write(lastBlockBuf) | |
| 84 | + | w.Flush() | |
| 85 | + | // write exe file out | |
| 86 | + | err = ioutil.WriteFile("exe", exeBuf.Bytes(), 0755) | |
| 87 | + | check(err) | |
| 88 | + | log.Printf("wrote output to file 'exe'\n") | |
| 89 | + | } | |
| 90 | + | ||
| 91 | + | // XOR implements a rolling xor where the key size is allowed not to be the same size as the data | |
| 92 | + | func XOR(data, key []byte) []byte { | |
| 93 | + | // setup ring buffer with key data | |
| 94 | + | r := ring.New(len(key)) | |
| 95 | + | for i := 0; i < r.Len(); i++ { | |
| 96 | + | r.Value = key[i] | |
| 97 | + | r = r.Next() | |
| 98 | + | } | |
| 99 | + | // do the actual xor operation | |
| 100 | + | for i := 0; i < len(data); i++ { // foreach byte of data | |
| 101 | + | data[i] = r.Value.(byte) ^ data[i] // xor data byte with current ring element | |
| 102 | + | r = r.Next() // move ring forward | |
| 103 | + | } | |
| 104 | + | return data | |
| 105 | + | } | |
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