关于openssl几个API的一点小收获

16820阅读 2评论2014-06-02 wjlkoorey258
分类:LINUX

    今天心血来潮突然想搞搞openssl了,趁着端午小假,刚好有空可以鼓捣孤岛自己喜欢的东西,出去东奔西跑的实在太造孽了,还是宅起来给自己充充电吧。下载openssl最新代码1.0.1g,修复了“心血漏洞”那个版本。编译安装那些小儿科的东西就不再浪费笔墨了,如果出现头文件或者库文件之类的错误,请在本人博客里寻找相关文章,应该主要集中在动态库那几篇博文。反正我在自己虚拟机里安装的时候是妥妥滴。

    因为我主要对非对称加密的RSA算法比较感兴趣,网上最多的就是这么用的:
   生成私钥文件(其中已经包含了公钥):
[root@localhost release]#openssl genrsa -out plainPrv.key 1024
   
   然后再从这个私钥文件里将公钥提取出来,保存到文件里:
[root@localhost release]#openssl rsa -in plainPrv.key -pubout -out plainPub.key

    RSA一般有两种应用场景:
   1、公钥加密、私钥解密:这是数据安全通信领域最常见情形;
   2、私钥加密、公钥解密:这主要用于数字签名。
   两种方式,一通百通,本文只看第一种场景。
  关于测试代码,网上到处都是,也都基本能用,我就先不摘抄了。大家问的最多的问题就是在读取公钥文件时,PEM_read_RSA_PUBKEY()函数和PEM_read_RSAPublicKEY()的疑惑。为什么读取私钥文件用的PEM_read_RSAPrivateKey(),针对上述openssl命令生成的公钥文件,在读取其内容时用对称的PEM_read_RSAPublicKEY()接口却会报错,必须要用PEM_read_RSA_PUBKEY()才可以。

   其实,我们要是看看一两个文件内容就明白了:
[root@localhost release]# cat plainPrv.key
-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----

[root@localhost release]# cat plainPub.key
-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDlGVxzTDVhnC16SW+D0WG8hvm1
wztmr0vBh2VK6CU7k90mdrCx4by1URcZ6iS6KxomxSqWmK9g2C0iRd8xx7OyykBH
KttjIx5Diq3wLXDP2qU4mjSIvHP3MwgrOR2Jwa4mNr1veM2c1pyXn5xIfZs2IFni
cMugj+0sXik1pLWwIwIDAQAB
-----END PUBLIC KEY-----

    当我们在用PEM_read_RSAPublicKEY()读取公钥文件plainPub.key时报的错误是酱紫滴:
3077879432:error:0906D06C:lib(9):func(109):reason(108):pem_lib.c:698:Expecting: RSA PUBLIC KEY

    所以我就天真地将公钥文件头和尾分别改成“-----BEGIN RSA PUBLIC KEY-----”和“-----BEGIN RSA PUBLIC KEY-----”,理想很丰满,显示很骨感。实践证明openssl是不能那么轻易就被忽悠过去的。没办法,查看openssl源码发现,提取公钥文件时除了-pubout参数可以设置外,还有有个参数叫做-RSAPublicKey_out,但是命令行提示和man手册里居然没有任何提及。幸好我还会读C代码,所以提取公钥时我改用下面的命令:
[root@localhost release]#openssl rsa -in plainPrv.key -RSAPublicKey_out -out plainPub.key

   这样做完的结果是,首先公钥文件的内容有点变化:
[root@localhost test_openssl]# cat plainPub2.key
-----BEGIN RSA PUBLIC KEY-----
MIGJAoGBAOUZXHNMNWGcLXpJb4PRYbyG+bXDO2avS8GHZUroJTuT3SZ2sLHhvLVR
FxnqJLorGibFKpaYr2DYLSJF3zHHs7LKQEcq22MjHkOKrfAtcM/apTiaNIi8c/cz
CCs5HYnBriY2vW94zZzWnJefnEh9mzYgWeJwy6CP7SxeKTWktbAjAgMBAAE=
-----END RSA PUBLIC KEY-----
[root@localhost release]# cat plainPub.key
-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDlGVxzTDVhnC16SW+D0WG8hvm1
wztmr0vBh2VK6CU7k90mdrCx4by1URcZ6iS6KxomxSqWmK9g2C0iRd8xx7OyykBH
KttjIx5Diq3wLXDP2qU4mjSIvHP3MwgrOR2Jwa4mNr1veM2c1pyXn5xIfZs2IFni
cMugj+0sXik1pLWwIwIDAQAB
-----END PUBLIC KEY-----

   其次,当我再用PEM_read_RSAPublicKEY()接口来读取公钥文件plainPub2.key时,居然成功了。说明RSA PUBLIC KEY和PUBLIC KEY的两种公钥文件其存储方式是不一样的,PEM_read_RSAPublicKEY()只能读取RSA PUBLIC KEY形式的公钥文件;而PEM_read_RSA_PUBKEY()只能读取PUBLIC KEY格式的公钥文件。由于本人密码学基础较薄弱,现在还不能说出两者的区别,请各位见谅,还望密码方面的大牛们予以点拨。演示代码如下:

点击(此处)折叠或打开

  1. /* filename: tmp.c
  2. */
  3. #include<stdio.h>
  4. #include<stdlib.h>
  5. #include<string.h>
  6. #include<openssl/rsa.h>
  7. #include<openssl/pem.h>
  8. #include<openssl/err.h>

  9. void hexprint(char *str,int len)
  10. {
  11.     int i=0;
  12.     for(i=0;i<len;i++){
  13.         printf("%s%02x%s",((i%16==0?"|":"")),*((unsigned char*)str+i),(((i+1)%16==0)?"|\n":" "));
  14.     }
  15.     if(i%16!=0)
  16.         printf("|\n");
  17. }

  18. static int do_operation(RSA* rsa_ctx,char *instr,char* path_key,int inlen,char** outstr,int type)
  19. {
  20.     if(rsa_ctx == NULL || instr == NULL || path_key == NULL)
  21.     {
  22.         perror("input elems error,please check them!");
  23.         return -1;
  24.     }
  25.     int rsa_len,num;
  26.     rsa_len=RSA_size(rsa_ctx);
  27.     *outstr=(unsigned char *)malloc(rsa_len+1);
  28.     memset(*outstr,0,rsa_len+1);
  29.     switch(type){
  30.         case 1: //pub enc
  31.         if(inlen == 0){
  32.             perror("input str len is zero!");
  33.             goto err;
  34.         }
  35.         num = RSA_public_encrypt(inlen,(unsigned char *)instr,(unsigned char*)*outstr,rsa_ctx,RSA_PKCS1_OAEP_PADDING);
  36.         break;
  37.         case 2: //prv dec
  38.         num = RSA_private_decrypt(inlen,(unsigned char *)instr,(unsigned char*)*outstr,rsa_ctx,RSA_PKCS1_OAEP_PADDING);        
  39.         default:
  40.         break;
  41.     }

  42.     if(num == -1)
  43.     {
  44.         printf("Got error on enc/dec!\n");
  45. err:
  46.         free(*outstr);
  47.         *outstr = NULL;
  48.         num = -1;
  49.     }
  50.     return num;
  51. }

  52. int rsa_pub_encrypt(char *str,char *path_key,char** outstr){
  53.     RSA *p_rsa;
  54.     FILE *file;
  55.     int flen,rsa_len,num;
  56.     if((file=fopen(path_key,"r"))==NULL){
  57.         perror("open key file error");
  58.         return -1;
  59.     }
  60. #ifdef RSAPUBKEY
  61.     if((p_rsa=PEM_read_RSA_PUBKEY(file,NULL,NULL,NULL))==NULL){
  62. #else
  63.     if((p_rsa=PEM_read_RSAPublicKey(file,NULL,NULL,NULL))==NULL){
  64. #endif
  65.         ERR_print_errors_fp(stdout);
  66.         return -1;
  67.     }

  68.     num = do_operation(p_rsa,str,path_key,strlen(str),outstr,1);
  69.     RSA_free(p_rsa);
  70.     fclose(file);
  71.     return num;
  72. }

  73. int rsa_prv_decrypt(char *str,char *path_key,int inlen,char** outstr){    
  74.     RSA *p_rsa;
  75.     FILE *file;
  76.     int rsa_len,num;
  77.         
  78.     if((file=fopen(path_key,"r"))==NULL){
  79.         perror("open key file error");
  80.         return -1;
  81.     }
  82.     if((p_rsa=PEM_read_RSAPrivateKey(file,NULL,NULL,NULL))==NULL){
  83.         ERR_print_errors_fp(stdout);
  84.         return -1;
  85.     }    
  86.     num = do_operation(p_rsa,str,path_key,inlen,outstr,2);
  87.     RSA_free(p_rsa);
  88.     fclose(file);
  89.     return num;
  90. }

  91. int main(int argc,char** argv){
  92.     char *ptr_en,*ptr_de;
  93.     int len;
  94.    
  95.     printf("source is :%s\n",argv[1]);
  96.     len=rsa_pub_encrypt(argv[1],argv[2],&ptr_en);
  97.     printf("pubkey encrypt:\n");
  98.     hexprint(ptr_en,len);
  99.     
  100.     rsa_prv_decrypt(ptr_en,argv[3],len,&ptr_de);
  101.     printf("prvkey decrypt:%s\n",ptr_de==NULL?"NULL":ptr_de);
  102.     
  103.     if(ptr_en!=NULL){
  104.         free(ptr_en);
  105.     }
  106.     if(ptr_de!=NULL){
  107.         free(ptr_de);
  108.     }
  109.     
  110.     return 0;
  111. }

    如果开启RSAPUBKEY宏,则用PEM_read_RSA_PUBKEY()来读取公钥文件;否则用PEM_read_RSAPublicKey()读取:
[root@localhost release]#gcc -o pub rsatest.c -lcrypto -g -DRSAPUBKEY
[root@localhost release]#gcc -o nopub rsatest.c -lcrypto -g 

   测试结果如下:

   实际应用中,出于安全考虑我们一般会对私钥文件加密。我们可以用如下的方式来重新生成经3DES加密后私钥文件:
[root@localhost release]#openssl genrsa -des3 -out cipherPrv.key 1024

   这样生成的私钥文件使用3DES加过密的,看看内容就晓得和之前的有什么不同了。头部多了一些信息:Proc-Type和DEK-Info,猜想这肯定是某种加密信息(这TM不废话么),但是我看不懂,现阶段“会用”是首要问题:

   上述加密私钥文件的口令是123456,分别提取RSA PUBLIC KEY和PUBLIC KEY格式的公钥文件:
[root@localhost release]# openssl rsa -in cipherPrv.key -pubout -out cipherPub.key
[root@localhost release]# openssl rsa -in cipherPrv.key -RSAPublicKey_out -out cipherPub2.key

   在代码中我们需要通过下面的方式来读取经3DES加密处理后的私钥文件:

点击(此处)折叠或打开

  1. RSA* getPRV(char *path_key_fullname,char* pwd)
  2. {
  3.     RSA *rsaK=RSA_new();
  4.     OpenSSL_add_all_algorithms();
  5.     BIO *BP = BIO_new_file(path_key_fullname,"rb");
  6.     if(NULL == BP)
  7.         return NULL;

  8.     rsaK=PEM_read_bio_RSAPrivateKey(BP,NULL,NULL,pwd);
  9.     return rsaK;
  10. }
    然后将tmp.c中第85行从:
   if((p_rsa=PEM_read_RSAPrivateKey(file,NULL,NULL,NULL))==NULL){
   替换成:
   if((p_rsa=getPRV(path_key,"123456"))==NULL){
   重新编译,运行后结果如下:

   关于openssl有很多值得学习的地方,空了再慢慢研究。
上一篇:经典排序算法归纳笔记(4)
下一篇:Linux 内核通知链随笔【上】

文章评论