DER证书读取保存和转换

 1 /**读取文本中的内容，返回值需要自己手动释放，utf8，unicode格式的文本读取后需要自己转换*/
 2 char* ReadFileContent(char *filePath, int &contentLen)
 3 {
 4   FILE *fp = NULL;
 5   fopen_s(&fp, filePath, "rb");
 6   assert(fp!=NULL);
 7   if (fp == NULL) return NULL;
 8 
 9   fseek(fp, 0, SEEK_END);
10   int isize = ftell(fp);
11   fseek(fp, 0, SEEK_SET);
12   char *buf = (char*)malloc(sizeof(char)*(isize+1));
13   assert(fp!=NULL);
14   memset(buf, 0, isize+1);
15 
16   contentLen = fread(buf, 1, isize, fp);
17   fclose(fp);
18   return buf;
19 }
20 
21 /*写文件*/
22 int WriteContentToFile(char *filePath, char *pContent, int iLen)
23 {
24   assert(filePath!=NULL);
25   assert(pContent!=NULL);
26   assert(iLen>0);
27 
28   FILE *fp = NULL;
29   fopen_s(&fp, filePath, "wb");//二进制方式打开
30   assert(fp!=NULL);
31   if (fp == NULL) return NULL;
32   fwrite(pContent, sizeof(char), iLen, fp);
33   fclose(fp);
34   return 1;
35 }
36 
37 /**根据X509获取DER编码，返回值需要自己手动释放*/
38 char* ConvertX509ToDer(X509* pCertx509, int& contentLen)
39 {
40   char *pCertBuf = NULL;
41   char *pTemp = NULL;
42 
43   int len = i2d_X509(pCertx509, NULL);
44   pTemp = (char*)malloc(len);
45   memset(pTemp, 0, sizeof(char)*len);
46 
47   pCertBuf = pTemp;
48   contentLen = i2d_X509(pCertx509, (unsigned char**)&pTemp); ///<pTemp发生了变化已经是pCertBuf+contentLen
49   return pCertBuf;
50 }
51 
52 
53 /**读取DER格式文件，并转化为X509格式*/
54 X509* GetX509FromDer(char *filePath)
55 {
56   int content_length = 0;
57   char* pContent = ReadFileContent(filePath, content_length);
58   char* pTemp = pContent;
59   X509* pCert = d2i_X509(NULL, (const unsigned char**)&pTemp, content_length);
60   if (pContent!=NULL){
61     free(pContent);
62     pContent = NULL;
63   }
64   return pCert;
65 }
66 
67 /**保存为DER格式文件*/
68 int SaveFileDer(X509* pCert, char *filePath)
69 {
70   int iLen = 0;
71   char *pDerStr = ConvertX509ToDer(pCert, iLen);
72   int iRes = WriteContentToFile(filePath, pDerStr, iLen);
73 
74   free(pDerStr);
75   pDerStr = NULL;
76 
77   return iRes;
78 }
79 
80 
81 int    main()
82 {
83   X509 *pCert = GetX509FromDer("D:\\derTest.cer");
84   SaveFileDer(pCert, "D:\\saveTest.cer");
85 
86   X509_free(pCert);
87   return 0;
88 }
文章出处：http://www.cnblogs.com/zhfuliang/archive/2013/05/10/3071139.html