openssl pem 生成公钥和私钥及文件

openssl pem.h 中提供了关于pem格式密钥对的操作接口

通常使用.pem的格式文件来保存openssl 生成的密钥对；

在终端下 cat xxx.pem 可以看到

-----BEGIN RSA PRIVATE KEY-----

XXXX

-----END RSA PRIVATE KEY-----

密钥数据进行了BASE64编码

1. 示例：将生成的密钥对保存成pem文件

void testWriteRSA2PEM()
{
    //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);

    RSA_print_fp(stdout, r, );

    BIO *out;
    out = BIO_new_file("/Users/cocoajin/Desktop/opriv.pem","w");
    //这里生成的私钥没有加密，可选加密
    int ret = PEM_write_bio_RSAPrivateKey(out, r, NULL, NULL, , NULL, NULL);
    printf("writepri:%d\n",ret);
    BIO_flush(out);
    BIO_free(out);

    out = BIO_new_file("/Users/cocoajin/Desktop/opub.pem","w");
    ret = PEM_write_bio_RSAPublicKey(out, r);
    printf("writepub:%d\n",ret);
    BIO_flush(out);
    BIO_free(out);

    BN_free(e);
    RSA_free(r);

}

在目标路径保存了生成的公钥opub.pem和私钥oprov.pem

输出日志

Private-Key: ( bit)
modulus:
    :e6::f5:6f:4d:5e:c2:ad:0d:f5:::::
    ca:6f::4f:3a:::e2:ee:a2:cc::::e2:
    3d:0d:e3:0d:c0:6a:::b6:c7:de:e2:d6:::
    9e::::dd:2d::c5:a8:f2:c1::8b::f9:
    :0a:7a::
publicExponent:  (0x10001)
privateExponent:
    :ca:1b::6f:c5:de:c2:bf:2f:b6::f7:ad:d8:
    ::fc::fd:0a:e0::6b::::ea::8c:
    b0:7a:d3:d8::b7:fb::f1:4e::9d:bf::3a:
    e0:f3:fa::d3::fd:b0:f5:cd:5c::d1::8c:
    :e3:fb:c7:
prime1:
    :f6:d7::c4:1a:2f:eb:0b:c4:::3b:fe:f6:
    0d:c1:::ca:6c::fc:de:d7::ac::9d::
    :fe:9b
prime2:
    :ef:::::4d:ac::aa:ed:e9:a7:1d:5d:
    b1:7d:1c:1a:ef::8f:2d:bc:8a:e7::f5:f8::
    ::
exponent1:
    :f4:d2:c0:6f:b8:ed::fa:::2f::::
    b3::9f:c0:6c:b8:::b1:df:b4::fd:2a::
    :ec:2b
exponent2:
    :b5::c1::bc:3d::f8:::db:f9:5c:c4:
    :d8::fe:::7e:a6:b4:6a:::db::d0:
    ::
coefficient:
    0a:::2f:e9:ca:b6::::3b:5a::ea:5e:
    8d:::b9:7a:::c4::cb::0e::6b:1b:
    e5:c4
writepri:
writepub:
Program ended with exit code: 

2. 示例：从pem文件中获取公钥私钥方式一（利用了BIO）

void testReadRSAFromPEM()
{
    RSA *pubkey = RSA_new();
    RSA *prikey = RSA_new();

    BIO *pubio;
    BIO *priio;

    priio = BIO_new_file("/Users/cocoajin/Desktop/opriv.pem", "rb");
    prikey = PEM_read_bio_RSAPrivateKey(priio, &prikey, NULL, NULL);

    pubio = BIO_new_file("/Users/cocoajin/Desktop/opub.pem", "rb");
    pubkey = PEM_read_bio_RSAPublicKey(pubio, &pubkey, NULL, NULL);

    RSA_print_fp(stdout, pubkey, );
    RSA_print_fp(stdout, prikey, );

    RSA_free(pubkey);
    BIO_free(pubio);
    RSA_free(prikey);
    BIO_free(priio);

}

从目标路径读取公钥opub.pem和私钥opriv.pem

输出日志

Public-Key: ( bit)
Modulus:
    :e6::f5:6f:4d:5e:c2:ad:0d:f5:::::
    ca:6f::4f:3a:::e2:ee:a2:cc::::e2:
    3d:0d:e3:0d:c0:6a:::b6:c7:de:e2:d6:::
    9e::::dd:2d::c5:a8:f2:c1::8b::f9:
    :0a:7a::
Exponent:  (0x10001)
Private-Key: ( bit)
modulus:
    :e6::f5:6f:4d:5e:c2:ad:0d:f5:::::
    ca:6f::4f:3a:::e2:ee:a2:cc::::e2:
    3d:0d:e3:0d:c0:6a:::b6:c7:de:e2:d6:::
    9e::::dd:2d::c5:a8:f2:c1::8b::f9:
    :0a:7a::
publicExponent:  (0x10001)
privateExponent:
    :ca:1b::6f:c5:de:c2:bf:2f:b6::f7:ad:d8:
    ::fc::fd:0a:e0::6b::::ea::8c:
    b0:7a:d3:d8::b7:fb::f1:4e::9d:bf::3a:
    e0:f3:fa::d3::fd:b0:f5:cd:5c::d1::8c:
    :e3:fb:c7:
prime1:
    :f6:d7::c4:1a:2f:eb:0b:c4:::3b:fe:f6:
    0d:c1:::ca:6c::fc:de:d7::ac::9d::
    :fe:9b
prime2:
    :ef:::::4d:ac::aa:ed:e9:a7:1d:5d:
    b1:7d:1c:1a:ef::8f:2d:bc:8a:e7::f5:f8::
    ::
exponent1:
    :f4:d2:c0:6f:b8:ed::fa:::2f::::
    b3::9f:c0:6c:b8:::b1:df:b4::fd:2a::
    :ec:2b
exponent2:
    :b5::c1::bc:3d::f8:::db:f9:5c:c4:
    :d8::fe:::7e:a6:b4:6a:::db::d0:
    ::
coefficient:
    0a:::2f:e9:ca:b6::::3b:5a::ea:5e:
    8d:::b9:7a:::c4::cb::0e::6b:1b:
    e5:c4
Program ended with exit code: 

3. 示例：从pem文件中读取公钥私钥方式二(利用FILE)

void testPEMReadRSA()
{
    RSA *pubkey = RSA_new();
    RSA *prikey = RSA_new();

    FILE *pubf = fopen("/Users/cocoajin/Desktop/opub.pem", "rb");
    pubkey = PEM_read_RSAPublicKey(pubf, &pubkey, NULL, NULL);

    FILE *prif = fopen("/Users/cocoajin/Desktop/opriv.pem", "rb");
    prikey = PEM_read_RSAPrivateKey(prif, &prikey, NULL, NULL);

    RSA_print_fp(stdout, pubkey, );
    RSA_print_fp(stdout, prikey, );

    fclose(pubf);
    fclose(prif);
    RSA_free(pubkey);
    RSA_free(prikey);

}

输出日志

Public-Key: ( bit)
Modulus:
    :e6::f5:6f:4d:5e:c2:ad:0d:f5:::::
    ca:6f::4f:3a:::e2:ee:a2:cc::::e2:
    3d:0d:e3:0d:c0:6a:::b6:c7:de:e2:d6:::
    9e::::dd:2d::c5:a8:f2:c1::8b::f9:
    :0a:7a::
Exponent:  (0x10001)
Private-Key: ( bit)
modulus:
    :e6::f5:6f:4d:5e:c2:ad:0d:f5:::::
    ca:6f::4f:3a:::e2:ee:a2:cc::::e2:
    3d:0d:e3:0d:c0:6a:::b6:c7:de:e2:d6:::
    9e::::dd:2d::c5:a8:f2:c1::8b::f9:
    :0a:7a::
publicExponent:  (0x10001)
privateExponent:
    :ca:1b::6f:c5:de:c2:bf:2f:b6::f7:ad:d8:
    ::fc::fd:0a:e0::6b::::ea::8c:
    b0:7a:d3:d8::b7:fb::f1:4e::9d:bf::3a:
    e0:f3:fa::d3::fd:b0:f5:cd:5c::d1::8c:
    :e3:fb:c7:
prime1:
    :f6:d7::c4:1a:2f:eb:0b:c4:::3b:fe:f6:
    0d:c1:::ca:6c::fc:de:d7::ac::9d::
    :fe:9b
prime2:
    :ef:::::4d:ac::aa:ed:e9:a7:1d:5d:
    b1:7d:1c:1a:ef::8f:2d:bc:8a:e7::f5:f8::
    ::
exponent1:
    :f4:d2:c0:6f:b8:ed::fa:::2f::::
    b3::9f:c0:6c:b8:::b1:df:b4::fd:2a::
    :ec:2b
exponent2:
    :b5::c1::bc:3d::f8:::db:f9:5c:c4:
    :d8::fe:::7e:a6:b4:6a:::db::d0:
    ::
coefficient:
    0a:::2f:e9:ca:b6::::3b:5a::ea:5e:
    8d:::b9:7a:::c4::cb::0e::6b:1b:
    e5:c4
Program ended with exit code: 

4. 在终端下使用openssl命令生成公钥私钥

//生成1024位的RSA私钥
openssl genrsa -out private.pem 

//再由私钥生成公钥
openssl rsa -in private.pem -pubout -out public.pem

//私钥文件private.pem
//公钥文件public.pem
//上面私钥是没加密的，可选加密，指定一个加密算法生成时输入密码

以上测试使用openssl 1.1.0c

参考：https://www.openssl.org/docs/man1.1.0/crypto/PEM_read_bio_RSAPublicKey.html