生成公私钥

void generateKeys(){
    EVP_PKEY* pkey = EVP_RSA_gen(1024);
    if(pkey == NULL){
        fprintf(stderr,"error: rsa gen\n");
        ERR_print_errors_fp(stderr);
        return;
    }
    FILE* fp = fopen("public.pem","wt");
    if(fp! = NULL){
        PEM_write_PUBKEY(fp,pkey);
        fclose(fp);
    }else{
        perror("file error");
    }
    fp = fopen("private.pem","wt");
    if(fp != NULL){
        PEM_write_PrivateKey(fp,pkey,NULL,NULL,0,NULL,NULL);
        fclose(fp);
    }else{
        perror("file error");
    }
    EVP_PKEY_free(pkey);
}
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公钥加密

uchar *encrypt_public(uchar *src, uint len, int *length)
{
    FILE *fp;
    fopen_s(&fp, "public.pem", "r");
    if (fp == NULL)
    {
        perror("file error");
        return NULL;
    }
    EVP_PKEY *pkey;
    pkey = PEM_read_PUBKEY(fp, NULL, NULL, NULL);
    fclose(fp);
    if (pkey == NULL)
    {
        fprintf(stderr, "error: read publics key\n");
        return NULL;
    }
    EVP_PKEY_CTX *ctx = EVP_PKEY_CTX_new(pkey, NULL);
    EVP_PKEY_encrypt_init(ctx);
    uchar *dst = (uchar *)malloc(2048);
    size_t outl = 2048;
    if (!EVP_PKEY_encrypt(ctx, dst, &outl, src, (size_t)len))
    {
        fprintf(stderr, "error: encrypt\n");
        EVP_PKEY_free(pkey);
        free(dst);
        return NULL;
    }
    int len2 = outl;
    EVP_PKEY_free(pkey);
    EVP_PKEY_CTX_free(ctx);
    BIO_dump_fp(stdout, dst, len2);
    printf("len: %d, len2: %d\n", len, len2);
    if (length != NULL)
    {
        *length = len2;
    }
    return dst;
}
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私钥解密

uchar *decrypt_private(uchar *src, int len)
{
    FILE *fp;
    fopen_s(&fp, "private.pem", "r");
    if (fp == NULL)
    {
        perror("file error");
        return NULL;
    }
    EVP_PKEY *pkey = PEM_read_PrivateKey(fp, NULL, NULL, NULL);
    fclose(fp);
    if (pkey == NULL)
    {
        fprintf(stderr, "error: read private key\n");
        return NULL;
    }
    EVP_PKEY_CTX *ctx = EVP_PKEY_CTX_new(pkey, NULL);
    EVP_PKEY_decrypt_init(ctx);
    uchar *dst = (uchar *)malloc(2048);
    size_t outl;
    size_t inl = len;
    if (!EVP_PKEY_decrypt(ctx, dst, &outl, src, inl))
    {
        fprintf(stderr, "error: decrypt\n");
        free(dst);
        dst = NULL;
    }
    else
    {
        BIO_dump_fp(stdout, dst, (int)outl);
        printf("len: %d, outl: %lld\n", len, outl);
    }
    EVP_PKEY_free(pkey);
    EVP_PKEY_CTX_free(ctx);
    return dst;
}
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cmake 静态链接openssl

...
...
...
IF(CMAKE_CL_64)
    include_directories("C:\\Program Files\\OpenSSL-Win64\\include")
    link_directories("C:\\Program Files\\OpenSSL-Win64\\lib")
ELSE(CMAKE_CL_64)
    include_directories("C:\\Program Files (x86)\\OpenSSL-Win32\\include")
    link_directories("C:\\Program Files (x86)\\OpenSSL-Win32\\lib")
ENDIF(CMAKE_CL_64)
# STATIC编译 取消openssl依赖
set(OPENSSL_USE_STATIC_LIBS TRUE)   
find_package(OpenSSL REQUIRED)
add_library(RSA SHARED library.c)
target_link_libraries(RSA OpenSSL::Crypto)
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OPENSSL_Uplink(100F2010,05): no OPENSSL_Applink

在非动态链接库当中可以通过添加头问题的方式添加文件applink.c:

#include <openssl/applink.c>
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如果是在动态链接库当中的话, 主要检查IO方式的影响(读取文件和输出等地方), 比如可以将读取公钥私钥的方式换成BIO的形式:

BIO* in=NULL;
in = BIO_new(BIO_s_file());
BIO_read_filename(in,"private.pem");
if (in == NULL){
    perror("private.pem");
    return NULL;
}
EVP_PKEY *pkey = PEM_read_bio_PrivateKey(in, NULL, NULL, NULL);
BIO_free(in);
EVP_PKEY_CTX *ctx = EVP_PKEY_CTX_new(pkey, NULL);
EVP_PKEY_decrypt_init(ctx);
uchar *dst = (uchar *) malloc(2048);
size_t outl;
size_t inl = len;
if (!EVP_PKEY_decrypt(ctx, dst, &outl, src, inl)) {
    fprintf(stderr, "error: decrypt\n");
    free(dst);
    dst = NULL;
} else {
    printf("len: %d, outl: %lld\n", len, outl);
}
EVP_PKEY_free(pkey);
EVP_PKEY_CTX_free(ctx);
return dst;
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