gzip.NewReader()在给定类型为Reader的输入时返回nil。

huangapple
go评论97阅读模式
英文:

gzip.NewReader() returns nil when a type Reader is given as input

问题

我在解压缩之前遇到了一个问题，这些字节之前是被压缩过的。基本上，我试图使用函数bytes.NewReader()创建一个Reader，然后使用gzip.NewReader()函数解压缩流。最后，我想要以字符串或字节格式返回真实的值。

我知道gzip.NewReader需要io.Reader作为输入，然而，据我所知，类型Reader实现了接口io.Reader。我认为这不应该引起任何错误，但我想知道在这种情况下可能出现什么问题。如果你能帮我解决这个问题，我将非常感激！

如果你想知道这段文本是什么，

> "amZzRUR2NHVtcVpiZHNROHJiTTNYeGdUSndGTlVDZC9jaElSK1lXcFlJOD0="

这是从我的客户端Python脚本发送的示例输入。它按照gzip进行压缩，使用AES128进行加密，最后按照顺序进行base64编码。

客户端代码：

import time
import json
import requests
import random
import gzip
import base64

from Crypto.Cipher import AES

baseurl = 'http://0.0.0.0:80'
key = 'TfvY7I358yospfWKcoviZizOShpm5hyH'
iv = 'mb13KcoviZizvYhp'

MODE = AES.MODE_CFB
BLOCK_SIZE = 16
SEGMENT_SIZE = 128

def http_post(url, data):
    print('Going to make a request to {} with the following data: {}'.format(url, data))
    r = requests.post(url,
                  data=data,
                  headers={'Content-type': 'application/json; charset=utf-8',
                           'Connection': 'keep-alive'}, )
    if r.status_code != 200:
        print('Server returned unexpected response code {}, and content: {}'.format(r.status_code, r.content))
        return False
    else:
        data = r.json()
        return data


def post_sample_data(key, iv):
    fake_device_id = "MB88"
    Load_VA_Total_Mean = random.randint(1000, 100000)
    print('Data that should come back: {}'.format(Load_VA_Total_Mean))
    data = {'i': fake_device_id, 'p': [
    {'d': [54.3, 0, 99, 49.35, 3, 99, 51.533, 1, 98, 28964, 7348, 43590, Load_VA_Total_Mean, 10350, 55200, 49.7],
     't': time.time(), 'dt': 'p'}]}
    url = baseurl + '/realtimedata'
    encryption_key_reference = 1
    payload = '{}\n{}'.format(convert_pack(data, key, iv), encryption_key_reference)
    return http_post(url, payload)


def convert_pack(inputdict, key, iv):
    jsonpayload = json.dumps(inputdict)  # encode dict to json string
    gzippayload = gzip.compress(jsonpayload.encode('utf-8'))  # compress with gzip
    encryptedpayload = base64.b64encode(encrypt(key, iv, message))
    encoded = base64.b64encode(encryptedpayload)
    print('encoded: {}'.format(encoded))

    return str(encoded, encoding='utf-8')


def _pad_string(value):
    length = len(value)
    pad_size = BLOCK_SIZE - (length % BLOCK_SIZE)
    return value.ljust(length + pad_size, '\x00')


def encrypt(key, iv, plaintext):
    aes = AES.new(key, MODE, iv, segment_size=SEGMENT_SIZE)
    plaintext = _pad_string(plaintext)
    encrypted_text = aes.encrypt(plaintext)
    return encrypted_text


post_sample_data(key, iv)

服务器代码：

package main

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base64"
	"fmt"
	"io"
	"compress/gzip"
	"io/ioutil"
	"bytes"
)

func main() {
    receivedText := "amZzRUR2NHVtcVpiZHNROHJiTTNYeGdUSndGTlVDZC9jaElSK1lXcFlJOD0="
    fmt.Println("encrypted + encoded + gzipped: ", originalText)
    key := []byte("TfvY7I358yospfWKcoviZizOShpm5hyH")

    text := decrypt(key, originalText)
    fmt.Println("decrypted: ", string(text))
    reader := bytes.NewReader(text)
    gzReader, err1 := gzip.NewReader(reader)
    fmt.Println(gzReader)

    if err1 != nil {
        fmt.Println("error1")
    }

    content, err2 := ioutil.ReadAll(gzReader)

    if err2 != nil {
        fmt.Println("error2")
    }

    fmt.Println(string(content))
}

func decrypt(key []byte, cryptoText string) []byte {
    ciphertext, _ := base64.StdEncoding.DecodeString(cryptoText)
    fmt.Println("decoded: ", string(ciphertext))
    block, err := aes.NewCipher(key)
    if err != nil {
        panic(err)
    }

    iv := []byte("mb13KcoviZizvYhp")
    stream := cipher.NewCFBDecrypter(block, iv)
    stream.XORKeyStream(ciphertext, ciphertext)

    return ciphertext
}

输出：

<nil>
error1
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x288 pc=0x10a9167]
goroutine 1 [running]:
io/ioutil.readAll.func1(0xc420037dd0)
/usr/local/go/src/io/ioutil/ioutil.go:30 +0x119
panic(0x10c4580, 0x1154d00)
/usr/local/go/src/runtime/panic.go:489 +0x2cf
compress/gzip.(*Reader).Read(0x0, 0xc420092000, 0x200, 0x200, 0x1024ade, 0xc400000008, 0xc4200120c0)
/usr/local/go/src/compress/gzip/gunzip.go:247 +0x37
bytes.(*Buffer).ReadFrom(0xc420037d28, 0x11451a0, 0x0, 0xc420092000, 0x0, 0x200)
/usr/local/go/src/bytes/buffer.go:179 +0x160
io/ioutil.readAll(0x11451a0, 0x0, 0x200, 0x0, 0x0, 0x0, 0x0, 0x0)
/usr/local/go/src/io/ioutil/ioutil.go:33 +0x150
io/ioutil.ReadAll(0x11451a0, 0x0, 0x1, 0x7, 0x0, 0x0, 0x20)
/usr/local/go/src/io/ioutil/ioutil.go:42 +0x3e
main.main()
/Users/bkaankuguoglu/Desktop/Go-dev/tool-backend/tester.go:43 
+0x404
exit status 2
英文:

I've come across a problem while uncompressing a stream of bytes that are previously compressed. Basically, I'm trying to create a Reader using the function bytes.NewReader() and then to unzip the stream by using gzip.NewReader() function. At last, I'd like to return the real values in either string or byte format.

I know gzip.NewReader requires io.Reader as an input, however, as far as I know, type Reader implements the interface io.Reader. I assume this should not cause any errors but I wonder what might be the problem in this case. I'd really appreciate if you help me out with this!

In case you wonder what this piece of text is,

> "amZzRUR2NHVtcVpiZHNROHJiTTNYeGdUSndGTlVDZC9jaElSK1lXcFlJOD0="

it's a sample input sent from my client python script. It compresses by using gzip, does encryption by using AES128 and finally encodes in base64, in this order.

The client code:

import time
import json
import requests
import random
import gzip
import base64
from Crypto.Cipher import AES
baseurl = &#39;http://0.0.0.0:80&#39;
key = &#39;TfvY7I358yospfWKcoviZizOShpm5hyH&#39;
iv = &#39;mb13KcoviZizvYhp&#39;
MODE = AES.MODE_CFB
BLOCK_SIZE = 16
SEGMENT_SIZE = 128
def http_post(url, data):
print(&#39;Going to make a request to {} with the following data: {}&#39;.format(url, data))
r = requests.post(url,
data=data,
headers={&#39;Content-type&#39;: &#39;application/json; charset=utf-8&#39;,
&#39;Connection&#39;: &#39;keep-alive&#39;}, )
if r.status_code != 200:
print(&#39;Server returned unexpected response code {}, and content: {}&#39;.format(r.status_code, r.content))
return False
else:
data = r.json()
return data
def post_sample_data(key, iv):
fake_device_id = &quot;MB88&quot;
Load_VA_Total_Mean = random.randint(1000, 100000)
print(&#39;Data that should come back: {}&#39;.format(Load_VA_Total_Mean))
data = {&#39;i&#39;: fake_device_id, &#39;p&#39;: [
{&#39;d&#39;: [54.3, 0, 99, 49.35, 3, 99, 51.533, 1, 98, 28964, 7348, 43590, Load_VA_Total_Mean, 10350, 55200, 49.7],
&#39;t&#39;: time.time(), &#39;dt&#39;: &#39;p&#39;}]}
url = baseurl + &#39;/realtimedata&#39;
encryption_key_reference = 1
payload = &#39;{}\n{}&#39;.format(convert_pack(data, key, iv), encryption_key_reference)
return http_post(url, payload)
def convert_pack(inputdict, key, iv):
jsonpayload = json.dumps(inputdict)  # encode dict to json string
gzippayload = gzip.compress(jsonpayload.encode(&#39;utf-8&#39;))  # compress with gzip
encryptedpayload = base64.b64encode(encrypt(key, iv, message))
encoded = base64.b64encode(encryptedpayload)
print(&#39;encoded: {}&#39;.format(encoded))
return str(encoded, encoding=&#39;utf-8&#39;)
def _pad_string(value):
length = len(value)
pad_size = BLOCK_SIZE - (length % BLOCK_SIZE)
return value.ljust(length + pad_size, &#39;\x00&#39;)
def encrypt(key, iv, plaintext):
aes = AES.new(key, MODE, iv, segment_size=SEGMENT_SIZE)
plaintext = _pad_string(plaintext)
encrypted_text = aes.encrypt(plaintext)
return encrypted_text
post_sample_data(key, iv)

The server code:

package main
import (
&quot;crypto/aes&quot;
&quot;crypto/cipher&quot;
&quot;crypto/rand&quot;
&quot;encoding/base64&quot;
&quot;fmt&quot;
&quot;io&quot;
&quot;compress/gzip&quot;
&quot;io/ioutil&quot;
&quot;bytes&quot;
)
func main() {
receivedText := &quot;amZzRUR2NHVtcVpiZHNROHJiTTNYeGdUSndGTlVDZC9jaElSK1lXcFlJOD0=&quot;
fmt.Println(&quot;encrypted + encoded + gzipped: &quot;, originalText)
key := []byte(&quot;TfvY7I358yospfWKcoviZizOShpm5hyH&quot;)
text := decrypt(key, originalText)
fmt.Println(&quot;decrypted: &quot;, string(text))
reader := bytes.NewReader(text)
gzReader, err1 := gzip.NewReader(reader)
fmt.Println(gzReader)
if err1 != nil {
fmt.Println(&quot;error1&quot;)
}
content, err2 := ioutil.ReadAll(gzReader)
if err2 != nil {
fmt.Println(&quot;error2&quot;)
}
fmt.Println(string(content))
}
func decrypt(key []byte, cryptoText string) []byte {
ciphertext, _ := base64.StdEncoding.DecodeString(cryptoText)
fmt.Println(&quot;decoded: &quot;, string(ciphertext))
block, err := aes.NewCipher(key)
if err != nil {
panic(err)
}
iv := []byte(&quot;mb13KcoviZizvYhp&quot;)
stream := cipher.NewCFBDecrypter(block, iv)
stream.XORKeyStream(ciphertext, ciphertext)
return ciphertext
}

The output:

&lt;nil&gt;
error1
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x288 pc=0x10a9167]
goroutine 1 [running]:
io/ioutil.readAll.func1(0xc420037dd0)
/usr/local/go/src/io/ioutil/ioutil.go:30 +0x119
panic(0x10c4580, 0x1154d00)
/usr/local/go/src/runtime/panic.go:489 +0x2cf
compress/gzip.(*Reader).Read(0x0, 0xc420092000, 0x200, 0x200, 0x1024ade, 0xc400000008, 0xc4200120c0)
/usr/local/go/src/compress/gzip/gunzip.go:247 +0x37
bytes.(*Buffer).ReadFrom(0xc420037d28, 0x11451a0, 0x0, 0xc420092000, 0x0, 0x200)
/usr/local/go/src/bytes/buffer.go:179 +0x160
io/ioutil.readAll(0x11451a0, 0x0, 0x200, 0x0, 0x0, 0x0, 0x0, 0x0)
/usr/local/go/src/io/ioutil/ioutil.go:33 +0x150
io/ioutil.ReadAll(0x11451a0, 0x0, 0x1, 0x7, 0x0, 0x0, 0x20)
/usr/local/go/src/io/ioutil/ioutil.go:42 +0x3e
main.main()
/Users/bkaankuguoglu/Desktop/Go-dev/tool-backend/tester.go:43 
+0x404
exit status 2

答案1

得分: 1

问题在于你传递给gz.NewReader()的读取器生成的“内容”不是有效的gzip流（数据）。如果gzip.NewReader()返回一个非nil的错误（在你的情况下是这样），返回的gzReader可能是nil（通常是这样）。

如果你传递一个有效的gzip流给gzip.NewReader()，返回的gzReader将不会是nil，解码将会成功。

例如，文本“hello”的gzip编码形式是：

[31 139 8 0 0 0 0 0 0 255 203 72 205 201 201 7 0 134 166 16 54 5 0 0 0]

使用这个作为输入：

data := []byte{31, 139, 8, 0, 0, 0, 0, 0, 0,
255, 203, 72, 205, 201, 201, 7, 0, 134, 166, 16, 54, 5, 0, 0, 0}
reader := bytes.NewReader(data)
// 其余部分不变

它可以工作，并且输出结果是（在Go Playground上尝试一下）：

&{[31 139 8 0 0 0 0 0 0 255 203 72 205 201 201 7 0 134 166 16 54 5 0 0 0] 0 -1}
&{{ [] 0001-01-01 00:00:00 +0000 UTC  255} 0x10440260 0x10462000 0 0 [31 139 8 0 0 0 0 0 0 255 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
英文:

The problem is that the "content" produced by the reader you pass to gz.NewReader() is not a valid gzip stream (data). If gzip.NewReader() returns a non-nil error (as it does in your case), the returned gzReader may be nil (and it usually is).

If you pass a valid gzip stream to gzip.NewReader(), the returned gzReader will not be nil, and decoding will succeed.

For example the gzip encoded form of the text &quot;hello&quot; is:

[31 139 8 0 0 0 0 0 0 255 203 72 205 201 201 7 0 134 166 16 54 5 0 0 0]

Using this as the input:

data := []byte{31, 139, 8, 0, 0, 0, 0, 0, 0,
255, 203, 72, 205, 201, 201, 7, 0, 134, 166, 16, 54, 5, 0, 0, 0}
reader := bytes.NewReader(data)
// The rest is unchanged

It works, and the output is (try it on the Go Playground):

&amp;{[31 139 8 0 0 0 0 0 0 255 203 72 205 201 201 7 0 134 166 16 54 5 0 0 0] 0 -1}
&amp;{{ [] 0001-01-01 00:00:00 +0000 UTC  255} 0x10440260 0x10462000 0 0 [31 139 8 0 0 0 0 0 0 255 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0] &lt;nil&gt; true}
hello

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  • 本文由 发表于 2017年7月3日 19:47:20
  • 转载请务必保留本文链接：https://go.coder-hub.com/44884766.html
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  • python
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:?: :razz: :sad: :evil: :!: :smile: :oops: :grin: :eek: :shock: :???: :cool: :lol: :mad: :twisted: :roll: :wink: :idea: :arrow: :neutral: :cry: :mrgreen:

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