英文:
Overwrite private key in Go
问题
在服务器端的Go代码中，我获取私钥并使用它们来签名断言，但我不想让它们留在内存中。以下代码是否合理？
var private ed25519.PrivateKey
// 获取并使用私钥
// 现在我想要覆盖它，以便它不再留在内存中
privKeyBytes := []byte(private)
_, _ = rand.Read(privKeyBytes)
以下是翻译好的内容：
在服务器端的Go代码中，我获取私钥并使用它们来签名断言，但我不想让它们留在内存中。以下代码是否合理？
var private ed25519.PrivateKey
// 获取并使用私钥
// 现在我想要覆盖它，以便它不再留在内存中
privKeyBytes := []byte(private)
_, _ = rand.Read(privKeyBytes)
英文:
In server-side Go code I acquire private keys and use them to sign assertions, but I don't want to leave them lying around in memory. Is the following sane?
var private ed25519.PrivateKey
// acquire and use the private key
// now I want to overwrite it so it's not lurking in memory
privKeyBytes := []byte(private)
_, _ = rand.Read(privKeyBytes)
答案1
得分: 2
是的，在大多数情况下，覆盖密钥字节应该可以解决问题。
请注意，目前 Go CMS 垃圾收集器是一种非移动的分代 GC，这意味着如果您不复制对象，GC 也不会复制。这是实现细节，可能会在将来发生变化。
另外，根据// acquire and use the private key部分的具体操作，可能会将密钥泄漏到堆上。例如，以 PEM 格式读取文件可能会泄漏 PEM 编码的字符串。
要确切知道，请在覆盖密钥后立即在gdb中断点，并将整个堆转储到文件中。然后在文件中搜索密钥字节。
$ go build -gcflags "-N -l"
$ gdb ./test
(gdb) source /usr/go/src/runtime/runtime-gdb.py
加载 Go 运行时支持。
(gdb) b test.go:16
(gdb) r
线程 1“test”命中断点 1，位于 test/test.go:16
(gdb) info i
Num Description Executable
* 1 process 14176 test/test
(gdb) (Ctrl-Z)
[1]+ Stopped gdb ./test
$ cat /proc/14176/maps|grep '[heap]'|(read a; x=(${a//-/ }); dd if=/proc/14176/mem bs=4096 iflag=skip_bytes,count_bytes skip=$((0x${x[0]})) count=$((0x${x[1]}-0x${x[0]})) of=heap.bin)
$ grep -obUaP "\x01\x02\x03..." heap.bin
$ fg
(gdb) q
英文:
Yes, overwriting the key bytes should do it in most cases.
Note that currently the Go CMS garbage collector is a non-moving generational GC, meaning that if you don't make a copy of an object, then GC won't make copies either. This is implementation detail and may change in the future though.
Also, the // acquire and use the private key part, depending on what it does, may also leak the key onto the heap. For example, reading a file in PEM format would probably leak the PEM-encoded string.
To really know for sure, break in gdb immediately after overwriting the key and dump the entire heap to a file. Then search in it for the key bytes.
$ go build -gcflags "-N -l"
$ gdb ./test
(gdb) source /usr/go/src/runtime/runtime-gdb.py
Loading Go Runtime support.
(gdb) b test.go:16
(gdb) r
Thread 1 "test" hit Breakpoint 1, main.main () at test/test.go:16
(gdb) info i
Num Description Executable
* 1 process 14176 test/test
(gdb) (Ctrl-Z)
[1]+ Stopped gdb ./test
$ cat /proc/14176/maps|grep '\[heap\]'|(read a; x=(${a//-/ }); dd if=/proc/14176/mem bs=4096 iflag=skip_bytes,count_bytes skip=$((0x${x[0]})) count=$((0x${x[1]}-0x${x[0]})) of=heap.bin)
$ grep -obUaP "\x01\x02\x03..." heap.bin
$ fg
(gdb) q
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