使用 LuaJit 进行 FFI 加密/解密

Question

我正在尝试在 LuaJIT 中通过 FFI 使用 OpenSSL 进行加密和解密 - 我尝试了很多不同的变体，但运气不佳。我的代码似乎一直返回空字符串。

我正在尝试遵循 OpenSSL 文档中描述的模式：https://www.openssl.org/docs/manmaster/crypto/EVP_PKEY_decrypt.html

    local ffi = require "ffi"
    ffi.cdef[[
      EVP_PKEY_CTX *EVP_PKEY_CTX_new(EVP_PKEY *pkey, ENGINE *e);
      void *malloc(size_t size);
      void free(void *ptr);

      int EVP_PKEY_encrypt_init(EVP_PKEY_CTX *ctx);
      int EVP_PKEY_encrypt(EVP_PKEY_CTX *ctx, unsigned char *out, size_t *outlen, const unsigned char *in, size_t inlen);

      int EVP_PKEY_decrypt_init(EVP_PKEY_CTX *ctx);
      int EVP_PKEY_decrypt(EVP_PKEY_CTX *ctx, unsigned char *out, size_t *outlen, const unsigned char *in, size_t inlen);
    ]]

    local s = "hello world"
    local s_len = #s
    local out_len1 = ffi.new("size_t[1]")

    local ctx = ffi.C.EVP_PKEY_CTX_new(gen_key, nil)
    if not ctx then
      return nil
    end

    if ffi.C.EVP_PKEY_encrypt_init(ctx) == 0 then
      return nil
    end

    if ffi.C.EVP_PKEY_encrypt(ctx, nil, out_len1, s, s_len) == 0 then
      return nil
    end

    local buf = ffi.new("unsigned char[?]", out_len1[0])

    if ffi.C.EVP_PKEY_encrypt(ctx, buf, out_len1, s, s_len) == 0 then
      return nil
    end

    local s = ffi.string(buf, out_len1[0])
    local s_len = #s
    local out_len2 = ffi.new("size_t[1]")

    if ffi.C.EVP_PKEY_decrypt_init(ctx) == 0 then
      return nil
    end

    if ffi.C.EVP_PKEY_decrypt(ctx, nil, out_len2, s, s_len) == 0 then
      return nil
    end

    local buf = ffi.new("unsigned char[?]", out_len2[0])
    if ffi.C.EVP_PKEY_decrypt(ctx, buf, out_len2, s, s_len) == 0 then
      return nil
    end

    return ffi.string(buf, out_len2[0])

Answer 1

我认为您的代码缺少某些类型的声明，例如EVP_PKEY_CTX、EVP_PKEY 等。您还需要添加这些数据类型的定义。基本上，ffi.cdef 定义了将通过 FFI 使用的所有函数名称，因此 LuaJIT 可以解析它们。

另一方面，对这些函数的调用应该通过实际实现这些函数的库进行，例如 OpenSSL，而不是 ffi.C。 C 命名空间用于访问libc 以及其他C 库，例如libm 和libdl。示例：

local ffi = require("ffi")
local ssl = ffi.load("ssl")

ffi.cdef[[
struct evp_pkey_ctx_st {

};
typedef struct evp_pkey_ctx_st EVP_PKEY_CTX;

struct evp_pkey_st {

};
typedef struct evp_pkey_st EVP_PKEY;

EVP_PKEY_CTX *EVP_PKEY_CTX_new(EVP_PKEY *key, void *b);
]]

local ctx = ssl.EVP_PKEY_CTX_new(gen_key, nil)
if ctx then 
   print("ctx created") 
else
   return nil
end

Answer 2

回答我自己的问题。

我的原始代码没有严格遵循 OpenSSL 的 C 实现示例，因为它只获得了加密数据的长度。它也从未使用任何填充，它重用变量并且没有拆分为方法，并且故意缺少一些依赖项以隐藏一些实现细节。

以下代码现在可以工作（独立）并且结构更好，但它故意不进行错误检查，并且还会处理超过 (KeyLength - 42) 的内容。

为了提供一些上下文，此代码需要 PEM 格式的证书和密钥：

local ffi = require "ffi"
local ssl = ffi.load "ssl"

ffi.cdef[[
  typedef struct bio_st BIO;
  typedef struct bio_method_st BIO_METHOD;
  BIO *BIO_new(BIO_METHOD *type);
  BIO *BIO_new_mem_buf(void *buf, int len);
  typedef struct evp_pkey_ctx_st EVP_PKEY_CTX;
  typedef struct evp_pkey_st EVP_PKEY;
  typedef struct engine_st ENGINE;
  EVP_PKEY *EVP_PKEY_new(void);
  void EVP_PKEY_free(EVP_PKEY *key);
  typedef struct rsa_st RSA;
  typedef int pem_password_cb(char *buf, int size, int rwflag, void *userdata);
  RSA * PEM_read_bio_RSAPrivateKey(BIO *bp, RSA **rsa, pem_password_cb *cb, void *u);
  int EVP_PKEY_set1_RSA(EVP_PKEY *pkey,RSA *key);
  EVP_PKEY_CTX *EVP_PKEY_CTX_new(EVP_PKEY *pkey, ENGINE *e);
  int EVP_PKEY_CTX_ctrl(EVP_PKEY_CTX *ctx, int keytype, int optype, int cmd, int p1, void *p2);
  typedef struct x509_st X509;
  X509 *PEM_read_bio_X509(BIO *bp, X509 **x, pem_password_cb *cb, void *u);
  EVP_PKEY * X509_get_pubkey(X509 *x);
  void X509_free(X509 *a);
  int EVP_PKEY_encrypt_init(EVP_PKEY_CTX *ctx);
  int EVP_PKEY_encrypt(EVP_PKEY_CTX *ctx, unsigned char *out, size_t *outlen, const unsigned char *in, size_t inlen);
  int EVP_PKEY_decrypt_init(EVP_PKEY_CTX *ctx);
  int EVP_PKEY_decrypt(EVP_PKEY_CTX *ctx, unsigned char *out, size_t *outlen, const unsigned char *in, size_t inlen);
]]

function encrypt(publicPEM, body)
  local bioIn = ffi.new("unsigned char[?]", #publicPEM)
  ffi.copy(bioIn, publicPEM, #publicPEM)
  local bio = ffi.C.BIO_new_mem_buf(bioIn, -1)
  local x509 = ffi.C.PEM_read_bio_X509(bio, nil, nil, nil)
  ffi.gc(x509, ffi.C.X509_free)
  local pKey = ffi.C.X509_get_pubkey(x509)
  local ctx = ffi.C.EVP_PKEY_CTX_new(pKey, nil)
  ffi.C.EVP_PKEY_encrypt_init(ctx)

  -- Adds OEAP padding
  ffi.C.EVP_PKEY_CTX_ctrl(ctx, 6, -1, 4097, 4, null)

  -- Get the length
  local outputLength = ffi.new("size_t[1]")
  ffi.C.EVP_PKEY_encrypt(ctx, nil, outputLength, body, #body)

  -- Encrypt into outputBuffer
  local outputBuffer = ffi.new("unsigned char[?]", outputLength[0])
  ffi.C.EVP_PKEY_encrypt(ctx, outputBuffer, outputLength, body, #body)

  -- Turn it into a string
  return ffi.string(outputBuffer, outputLength[0])
end

function decrypt(privatePEM, body)
  local bioIn = ffi.new("unsigned char[?]", #privatePEM)
  ffi.copy(bioIn, privatePEM, #privatePEM)
  local bio = ffi.C.BIO_new_mem_buf(bioIn, -1)
  if not bio then
    return nil
  end
  local rsa = ffi.C.PEM_read_bio_RSAPrivateKey(bio, nil, nil, nil)
  local pKey = ffi.C.EVP_PKEY_new()

  ffi.C.EVP_PKEY_set1_RSA(pKey, rsa)
  ctx = ffi.C.EVP_PKEY_CTX_new(pKey, nil)
  ffi.C.EVP_PKEY_decrypt_init(ctx)

  -- Adds OEAP padding
  ffi.C.EVP_PKEY_CTX_ctrl(ctx, 6, -1, 4097, 4, null)

  -- Get the length
  local outputLength = ffi.new("size_t[1]")
  ffi.C.EVP_PKEY_decrypt(ctx, nil, outputLength, body, #body)

  -- Decrypt into outputBuffer
  local outputBuffer = ffi.new("unsigned char[?]", outputLength[0])
  ffi.C.EVP_PKEY_decrypt(ctx, outputBuffer, outputLength, body, #body)

  -- Turn it into a string
  return ffi.string(outputBuffer, outputLength[0])
end

io.write("Result: "..tostring(decrypt([[-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----
]], encrypt([[-----BEGIN CERTIFICATE-----
MIICYTCCAcoCCQCT+Ubn23B63TANBgkqhkiG9w0BAQUFADB1MQswCQYDVQQGEwJV
UzETMBEGA1UECBMKQ2FsaWZvcm5pYTEWMBQGA1UEBxMNU2FuIEZyYW5jaXNjbzEN
MAsGA1UEChMES29uZzEWMBQGA1UECxMNSVQgRGVwYXJ0bWVudDESMBAGA1UEAxMJ
bG9jYWxob3N0MB4XDTE2MDExODEwNDUyOVoXDTE3MDExNzEwNDUyOVowdTELMAkG
A1UEBhMCVVMxEzARBgNVBAgTCkNhbGlmb3JuaWExFjAUBgNVBAcTDVNhbiBGcmFu
Y2lzY28xDTALBgNVBAoTBEtvbmcxFjAUBgNVBAsTDUlUIERlcGFydG1lbnQxEjAQ
BgNVBAMTCWxvY2FsaG9zdDCBnzANBgkqhkiG9w0BAQEFAAOBjQAwgYkCgYEAqDnh
X5XSt23LLp9ZJRW/nd3oEipH6t6BQH+p+oUNkd0682NwW/uIWEq+S4az/x2Dr3O2
8ZPk9xkHugvAf+2jmCUPgzsHiqDSvdLlREEbRTvBGeGe6yX2ktq4T7l+9QJ38Lrz
Rv02eVBa7r8FKr7Noc8Oe4JfiMxYALRvK7VV/88CAwEAATANBgkqhkiG9w0BAQUF
AAOBgQAEC5ugqY6rOd3BbIam172OVQQwxcVx8BVfuiqX0zsFdBwTm/AvvdyJXRwo
64AqEIanvJF8Htq3Q9As6PNgHJ4eWEAZYTKlsf0PRM+d1T/uce3HY2SePuwr1Kqx
gFQjYTabjv361j8X3zB3HwrGsuED2UXxerXczszyiQNv/6BQlg==
-----END CERTIFICATE-----
]], "hello world"))).."\n")