c - EVP 读取 PEM 私钥无法正常工作

Question

当我运行以下代码时，它生成一个 key ，将其写入一个字符串，打印它，将其读入 key ，然后再次打印，针对 OpenSSL_1_0_2e:

#include <openssl/evp.h>
#include <openssl/pem.h>
#include <openssl/aes.h>
#include <openssl/err.h>
#include <openssl/rand.h>

#define RSA_KEYLEN 2048
int main()
{
  // Key generation
  EVP_PKEY_CTX *ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_RSA, NULL);
  EVP_PKEY* key = NULL;
  EVP_PKEY_keygen_init(ctx);
  EVP_PKEY_CTX_set_rsa_keygen_bits(ctx, RSA_KEYLEN);
  EVP_PKEY_keygen(ctx, &key);
  EVP_PKEY_CTX_free(ctx);

  // Serialize to string
  unsigned char* keyStr;
  BIO *bio = BIO_new(BIO_s_mem());
  PEM_write_bio_PrivateKey(bio, key, NULL, NULL, 0, 0, NULL);
  int priKeyLen = BIO_pending(bio);
  keyStr = (unsigned char*)malloc(priKeyLen + 1);
  BIO_read(bio, keyStr, priKeyLen);
  keyStr[priKeyLen] = '\0';
  BIO_free_all(bio);

  // Print the string
  printf("%s", keyStr);

  // Reset the key
  EVP_PKEY_free(key);
  key = NULL;

  // Read from string
  bio = BIO_new(BIO_s_mem());
  BIO_write(bio, keyStr, priKeyLen);
  PEM_read_bio_PrivateKey(bio, &key, NULL, NULL);
  BIO_free_all(bio);

  // Free the string
  free(keyStr);

  // Serialize to string (again)
  bio = BIO_new(BIO_s_mem());
  PEM_write_bio_PrivateKey(bio, key, NULL, NULL, 0, 0, NULL);
  priKeyLen = BIO_pending(bio);
  keyStr = (unsigned char*)malloc(priKeyLen + 1);
  BIO_read(bio, keyStr, priKeyLen); 
  keyStr[priKeyLen] = '\0';
  BIO_free_all(bio);

  // Print string
  printf("%s", keyStr);
}

第二个输出中的私钥显然太短了。我做错了什么？

Answer 1

我的特定问题的解决方案是我试图在 EVP_PKEY 上设置公钥和私钥，认为我需要加载这两个 key 才能将其用作 key 对。实际上，您只加载两者之一。有了私钥，就可以推导出公钥。