用openssl库RSA加密解密

Posted 2020-10-05 窗户

 1 #include <stdio.h>
 2 #include <openssl/rsa.h>
 3 #include <openssl/pem.h>
 4 #include <openssl/err.h>
 5 
 6 //加密
 7 int my_encrypt(const char *input, int input_len,  char *output, int *output_len, const char *pri_key_fn)
 8 {
 9         RSA  *p_rsa = NULL;
10         FILE *file = NULL;
11         int ret = 0;
12 
13         if((file = fopen(pri_key_fn, "rb")) == NULL)
14         {
15                 ret = -1;
16                 goto End;
17         }
18 
19         if((p_rsa = PEM_read_RSAPrivateKey(file, NULL,NULL,NULL )) == NULL)
20         {
21                 ret = -2;
22                 goto End;
23         }
24 
25         if((*output_len = RSA_private_encrypt(input_len, (unsigned char*)input, (unsigned char*)output, p_rsa, RSA_PKCS1_PADDING)) < 0)
26         {
27                 ret = -4;
28                 goto End;
29         }
30 
31 End:
32         if(p_rsa != NULL)
33                 RSA_free(p_rsa);
34         if(file != NULL)
35                 fclose(file);
36 
37         return ret;
38 }
39 
40 //解密
41 int my_decrypt(const char *input, int input_len,  char *output, int *output_len, const char *pri_key_fn)
42 {
43         RSA  *p_rsa = NULL;
44         FILE *file = NULL;
45         int ret = 0;
46 
47         file = fopen(pri_key_fn, "rb");
48         if(!file)
49         {
50                 ret = -1;
51                 goto End;
52         }
53 
54         if((p_rsa = PEM_read_RSA_PUBKEY(file, NULL,NULL,NULL )) == NULL)
55         {
56                 ret = -2;
57                 goto End;
58         }
59 
60         if((*output_len=RSA_public_decrypt(input_len, (unsigned char*)input, (unsigned char*)output, p_rsa, RSA_PKCS1_PADDING)) < 0)
61         {
62                 ret = -3;
63                 goto End;
64         }
65 End:
66         if(p_rsa != NULL)
67                 RSA_free(p_rsa);
68         if(file != NULL)
69                 fclose(file);
70 
71         return ret;
72 }
73 
74 int main(int argc, char**argv)
75 {
76         char src[256];
77         char dst[256];
78         int src_len;
79         int dst_len;
80         int ret;
81         FILE *f;
82 
83         src_len = fread(src, 1, 256, stdin);
84 
85         if(argv[1][0] == ‘e‘) {
86                 ret = my_encrypt(src, src_len,  dst, &dst_len, argv[2]);
87         }else {
88                 ret = my_decrypt(src, src_len,  dst, &dst_len, argv[2]);
89         }
90 
91         if(ret) {
92                 fprintf(stderr, "Error\n");
93         }
94         fwrite(dst,1,dst_len,stdout);
95         return ret;
96 }

以上是一个示例，测试了私钥加密(签名)/公钥解密(验证)，main函数是一个测试

测试一下，先生成2048位公钥、私钥对

[email protected]:/tmp$ openssl genrsa -out pri2048.pem 2048
Generating RSA private key, 2048 bit long modulus
................................+++
.............+++
e is 65537 (0x10001)
[email protected]-VirtualBox:/tmp$ openssl rsa -in pri2048.pem -pubout -out pub2048.pem
writing RSA key

编译、文件测试

[email protected]:/tmp$ gcc t.c -lssl -lcrypto -lm
[email protected]-VirtualBox:/tmp$ ./a.out en pri2048.pem <data >data.en
[email protected]-VirtualBox:/tmp$ ./a.out enc pri2048.pem <data >data.en
[email protected]-VirtualBox:/tmp$ ./a.out dec pub2048.pem <data.en >data2
[email protected]-VirtualBox:/tmp$ openssl rsautl -verify -in data.en -inkey pub2048.pem -pubin -out data3

对比一下

[email protected]:/tmp$ cmp data data2
[email protected]-VirtualBox:/tmp$ cmp data data3
[email protected]-VirtualBox:/tmp$ md5sum data data2 data3
7a71146998ad521bab336a49f65c90c4  data
7a71146998ad521bab336a49f65c90c4  data2
7a71146998ad521bab336a49f65c90c4  data3

公钥加密、私钥解密就不写了，对着看就会很明白了。

int RSA_public_encrypt(int flen, const unsigned char *from,
unsigned char *to, RSA *rsa, int padding);
int RSA_private_encrypt(int flen, const unsigned char *from,
unsigned char *to, RSA *rsa, int padding);
int RSA_public_decrypt(int flen, const unsigned char *from,
unsigned char *to, RSA *rsa, int padding);
int RSA_private_decrypt(int flen, const unsigned char *from,
unsigned char *to, RSA *rsa, int padding);