从字符缓冲区x509（PKCS7）EVP_PKEY

Question

我有一个DER证书，我从中检索公钥在无符号字符缓冲区如下，它是正确的方式获取？

pStoredPublicKey = X509_get_pubkey(x509); 
if(pStoredPublicKey == NULL) 
{ 
     printf(": publicKey is NULL\n"); 
} 
if(pStoredPublicKey->type == EVP_PKEY_RSA) { 
     RSA *x = pStoredPublicKey->pkey.rsa; 
     bn = x->n; 
} 
else if(pStoredPublicKey->type == EVP_PKEY_DSA) { 

} 
else if(pStoredPublicKey->type == EVP_PKEY_EC) { 
} 
else { 
     printf(" : Unkown publicKey\n"); 
} 
//extracts the bytes from public key & convert into unsigned char buffer 
buf_len = (size_t) BN_num_bytes (bn); 
key = (unsigned char *)malloc (buf_len); 
n = BN_bn2bin (bn, (unsigned char *) key); 
for (i = 0; i < n; i++) 
{ 
     printf("%02x\n", (unsigned char) key[i]); 
} 
keyLen = EVP_PKEY_size(pStoredPublicKey); 
EVP_PKEY_free(pStoredPublicKey); 

，与此无符号的字符缓冲区，如何获得回来RSA的EVP_PKEY？ OR我可以透过以下???，

EVP_PKEY *d2i_PublicKey(int type, EVP_PKEY **a, unsigned char **pp, long length); 
int i2d_PublicKey(EVP_PKEY *a, unsigned char **pp); 

Answer 1

以下OpenSSL的API适用于无符号字符缓冲区EVP_PKEY，

EVP_PKEY *d2i_PublicKey(int type, EVP_PKEY **a, unsigned char **pp, long length); 
int i2d_PublicKey(EVP_PKEY *a, unsigned char **pp); 

而且，下面的作品转换EVP_PKEY为unsigned char缓冲区。

int pkeyLen; 
unsigned char *ucBuf, *uctempBuf; 
pkeyLen = i2d_PublicKey(pkey, NULL); 
ucBuf = (unsigned char *)malloc(pkeyLen+1); 
uctempBuf = ucBuf; 
i2d_PublicKey(pkey, &uctempBuf); 
int ii; 
for (ii = 0; ii < pkeyLen; ii++) 
{ 
     printf("%02x\n", (unsigned char) ucBuf[ii]); 
} 

感谢-opensid