openssl 非对称加密 RSA 加密解密以及签名验证签名

1. 简介

openssl  rsa.h 提供了密码学中公钥加密体系的一些接口，

本文主要讨论利用rsa.h接口开发以下功能

• 公钥私钥的生成
• 公钥加密，私钥解密
• 私钥加密，公钥解密
• 签名：私钥签名
• 验证签名：公钥验签

2. 生成公钥私钥对

主要接口，

/* Deprecated version */
DEPRECATEDIN_0_9_8(RSA *RSA_generate_key(int bits, unsigned long e, void
                                         (*callback) (int, int, void *),
                                         void *cb_arg))

/* New version */
int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e, BN_GENCB *cb);

接口调用需要先生成一个大数，如下生成密钥对示例

    //生成密钥对
    RSA *r = RSA_new();
    int bits = ;
    BIGNUM *e = BN_new();
    BN_set_word(e, );
    RSA_generate_key_ex(r, bits, e, NULL);
    //打印密钥
    RSA_print_fp(stdout, r, );

打印的密钥对结果:

Private-Key: ( bit)
modulus:
    :c0::6c:::ed:4e::bb::ec:be:d6::
    :bf:9b:be:4f:8b:fb::ae:f2::9c:e7:b8::
    a2::9c::cc:4a:a2::1d:::c8:f6:e0::
    3a:::c8:1a:d4:b7::::4c:3b:2a::0b:
    :::4f:f9
publicExponent:  (0x10001)
privateExponent:
    :8f::9e:ca:8f:9f::3a:ed:eb:ec:5a::a0:
    c1:2f:::::4c::6a:6e:b8:4a:ab:2c::
    :e2:3e:c8:aa::bb::9e:e5:::b4:8f::
    ::dc:::::::ac::f8:fe:4d::
    e1:e2:bf:fd:
prime1:
    :fd::4d:f0::a0::5e:d1:c9:0e:b8::f9:
    ce:0a:ef::e7:a4:::d8:fd:dd:e6:c4:::
    dd:e6:
prime2:
    :c2::a9:7b:c8:::::f0::9a::a2:
    0b::3b::c0::6d:c6:c7:d1:a1::1d:d3:7d:
    :cd:
exponent1:
    6c::d8:2a:6b:4f::dd:::::f7:b5:c7:
    ad:f2::5b:f7:7b:ca:::0c:eb:d3::f9:ac:
    :f5
exponent2:
    ::e2:5a:::db:1e::2a::3c:6a:e7::
    ac:e2:d7:a5::5f::c3:4d:cf::d8::7f::
    :9d
coefficient:
    :d7:0d:9b:e8:2f:3c::::a0:b2:8b::1d:
    e2:b9:0f:9f:ca:b2:::ea:c8:9d:5e::e5:e3:
    ::aa

3. 公钥加密，私钥解密

主要接口

int RSA_public_encrypt(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);

由于较长数据需要分组加密，如下封装了一层

//公钥加密
int kkrsa_public_encrypt(char *inStr,char *outData,RSA *r)
{
    int encRet = ;
    unsigned long inLen = strlen(inStr);
    int pdBlock = RSA_size(r)-;
    unsigned int eCount = (inLen / pdBlock) +;
    //分组加密,可以看出outData最大不超过malloc[eCount*pdBlock]
    for (int i=; i < eCount; i++) {
        RSA_public_encrypt(inLen > pdBlock?pdBlock:inLen, inStr, outData, r, RSA_PKCS1_PADDING);
        inStr += pdBlock;
        outData+=RSA_size(r);
        encRet+=RSA_size(r);
        inLen -= pdBlock;
    }
    return encRet;
}
//私钥解密
int kkrsa_private_decrypt(char *inStr,char *outData,RSA *r)
{
    int decRet = ;
    unsigned long inLen = strlen(inStr);
    int pdBlock = RSA_size(r);
    unsigned int dCount = inLen / pdBlock;
    //分组解密
    for (int i=; i < dCount; i++) {
        int ret = RSA_private_decrypt(pdBlock, inStr, outData, r, RSA_PKCS1_PADDING);
        inStr += pdBlock;
        outData+=ret;
        decRet+=ret;
    }
    return decRet;
}

测试例子，例子中的r，就是上面生成的RSA密钥对，

    //测试一
    printf("block:%d \n",RSA_size(r));
    char *src = "this is test encrypt data use RSA_PKCS1_PADDING";
    printf("src:%s  len=%d\n",src,strlen(src));
    char *encDat = malloc();
    //公钥加密
    int encRet = kkrsa_public_encrypt(src, encDat, r);
    printf("enc:%d\n",encRet);

    char *decDat = malloc();
    //私钥解密
    int decRet = kkrsa_private_decrypt(encDat, decDat, r);
    printf("dec:%s  len=%d\n",decDat,decRet);

    free(encDat);
    free(decDat);
    

打印结果：

block:
src:this is test encrypt data use RSA_PKCS1_PADDING  len=
enc:
dec:this is test encrypt data use RSA_PKCS1_PADDING  len=

test2
src:this is test private encrypt data use RSA_PKCS1_PADDING  len=
enc:
dec:this is test private encrypt data use RSA_PKCS1_PADDI  len=

4. 私钥加密，公钥解密

主要接口

int RSA_private_encrypt(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);

同样如果数据较长需要进行分组加密，如下简单封装的接口

//私钥加密
int kkrsa_private_encrypt(char *inStr,char *outData,RSA *r)
{
    int encRet = ;
    unsigned long inLen = strlen(inStr);
    int pdBlock = RSA_size(r)-;
    unsigned int eCount = (inLen / pdBlock) +;
    //分组加密,可以看出outData最大不超过malloc[eCount*pdBlock]
    for (int i=; i < eCount; i++) {
        RSA_private_encrypt(inLen > pdBlock?pdBlock:inLen, inStr, outData, r, RSA_PKCS1_PADDING);
        inStr += pdBlock;
        outData+=RSA_size(r);
        encRet+=RSA_size(r);
        inLen -= pdBlock;
    }
    return encRet;
}
//公钥解密
int kkrsa_public_decrypt(char *inStr,char *outData,RSA *r)
{
    int decRet = ;
    unsigned long inLen = strlen(inStr);
    int pdBlock = RSA_size(r);
    unsigned int dCount = inLen / pdBlock;
    //分组解密
    for (int i=; i < dCount; i++) {
        int ret = RSA_public_decrypt(pdBlock, inStr, outData, r, RSA_PKCS1_PADDING);
        inStr += pdBlock;
        outData+=ret;
        decRet+=ret;
    }
    return decRet;
}

调用示例：需要上面生成的密钥对RSA r

  //测试二
    printf("\ntest2\n");
    char *src2 = "this is test private encrypt data use RSA_PKCS1_PADDING";
    printf("src:%s  len=%d\n",src2,strlen(src2));
    char *encDat2 = malloc();
    //私钥加密
    int encRet2 = kkrsa_private_encrypt(src2, encDat2, r);
    printf("enc:%d\n",encRet2);

    char *decDat2 = malloc();
    //公钥解密
    int decRet2 = kkrsa_public_decrypt(encDat2, decDat2, r);
    printf("dec:%s  len=%d\n",decDat2,decRet2);

    free(encDat2);
    free(decDat2);

测试结果：

test2
src:this is test private encrypt data use RSA_PKCS1_PADDING  len=
enc:
dec:this is test private encrypt data use RSA_PKCS1_PADDING\\\375۷GO\  len=

5. 签名与验证签名

主要接口

int RSA_sign(int type, const unsigned char *m, unsigned int m_length,
             unsigned char *sigret, unsigned int *siglen, RSA *rsa);
int RSA_verify(int type, const unsigned char *m, unsigned int m_length,
               const unsigned char *sigbuf, unsigned int siglen, RSA *rsa);

测试示例，同样需要上面生成的RSA密钥对

    //签名
    printf("\ntest sign and verify\n");
    char *msg = "";
    char *sinDat = malloc(RSA_size(r));
    int sinLen = ;
    RSA_sign(NID_sha1, msg,strlen(msg),sinDat,&sinLen, r);

    int vret = RSA_verify(NID_sha1, msg, strlen(msg), sinDat, sinLen, r);
    printf("sign_verify=%d\n",vret);

打印结果

test sign and verify
sign_verify=

6. 总结

上述RSA分组加密中使用了RSA_PKCS1_PADDING 的补位方式；当然还有如下

不同的补位方式，在进行分组加密时，需要注意分组块的处理

# define RSA_PKCS1_PADDING
# define RSA_SSLV23_PADDING
# define RSA_NO_PADDING
# define RSA_PKCS1_OAEP_PADDING
# define RSA_X931_PADDING
/* EVP_PKEY_ only */
# define RSA_PKCS1_PSS_PADDING   

# define RSA_PKCS1_PADDING_SIZE  

测试使用 openssl 1.1.0c

参考：https://www.openssl.org/docs/man1.0.2/crypto/RSA_public_encrypt.html

https://www.openssl.org/docs/manmaster/man3/RSA_verify.html