OpenSSL入门-常用编码

Base64

BIO_new将参数type中各个变量赋值给BIO街头中的method成员：

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BIO* BIO_new(
    BIO_METHOD* type
);

参数type可由BIO_f_base64返回，写的时候编码，读的时候解码：

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BIO_METHOD* BIO_f_base64();

其中BIO_METHOD结构为：

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typedef struct bio_method_st{
    int type; //类型
    const char* name; //名字
    int (*bwrite)(BIO*,const char*,int); //二进制写回调函数
    int (*bread)(BIO*,char*,int); //二进制读回调函数
    int (*bputs)(BIO*,const char*); //文本写回调函数
    int (*bgets)(BIO*,char*,int); //文本读回调函数
    long (*ctrl)(BIO*,int,long,void*); //控制回调函数
    int (*create)(BIO*); //生成回调函数
    int (*destroy)(BIO*); //销毁回调函数
    long (*callback_ctrl)(BIO*,int,bio_info_cb*); //控制回调函数 由调用者实现 用BIO_set_callback设置
}BIO_METHOD;

OpenSSL实现：

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#include <iostream>
#include <stdio.h>
#include <string.h>
#include <openssl/pem.h>
#include <openssl/bio.h>
#include <openssl/evp.h>
int base64_encode(char* in_str, int in_len, char* out_str) { //编码
    BIO* b64, * bio;
    BUF_MEM* bptr = NULL;
    size_t size = 0;
    if (in_str == NULL || out_str == NULL)
        return -1;
    b64 = BIO_new(BIO_f_base64());
    bio = BIO_new(BIO_s_mem());
    bio = BIO_push(b64, bio);
    BIO_write(bio, in_str, in_len);
    BIO_flush(bio);
    BIO_get_mem_ptr(bio, &bptr);
    memcpy(out_str, bptr->data, bptr->length);
    out_str[bptr->length] = '\0';
    size = bptr->length;
    BIO_free_all(bio);
    return size;
}
int base64_decode(char* in_str, int in_len, char* out_str) {//解码
    BIO* b64, * bio;
    BUF_MEM* bptr = NULL;
    int counts;
    int size = 0;
    if (in_str == NULL || out_str == NULL)
        return -1;
    b64 = BIO_new(BIO_f_base64());
    BIO_set_flags(b64, BIO_FLAGS_BASE64_NO_NL);
    bio = BIO_new_mem_buf(in_str, in_len);
    bio = BIO_push(b64, bio);
    size = BIO_read(bio, out_str, in_len);
    out_str[size] = '\0';
    BIO_free_all(bio);
    return size;
}
int main(){
    char instr[512] = "";
    char outstr1[1024] = { 0 };
    puts("enter plain text:");
    scanf_s("%s", instr, 512);
    base64_encode(instr, strlen(instr), outstr1);
    printf("base64:%s", outstr1);  //末尾并没有\n，但实际输出回车换行了。
    char outstr2[1024] = { 0 };
    base64_decode(outstr1, strlen(outstr1), outstr2);
    printf("base64 -d:%s\n", outstr2);
    return 0;
}

PEM文件

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openssl genrsa -out RSA私钥文件名.pem 1024 #密钥长度1024

ASN.1

下载ASN1C编译器并安装：http://lionet.info/asn1c/download.html 。新建.asn1文件：

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RetangleTest DEFINITIONS::=BEGIN
Rectangle::=SEQUENCE{
    height INTEGER, --Height of the rectangle
    width INTEGER --Width of the rectangle
}
END

生成：

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asn1c -S skeletons -fskeletons-copy -fnative-types try.asn1

之后会生成一堆文件。在Visual Studio工程目录下新建inc文件夹并添加到附加包含目录中，把生成的.h文件复制进去，再把生成的.c文件复制到工程目录下，删除converter-sample.c。

Windows上的编译器最新的只有2006年的，只支持x86下编译。代码实现为：

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#include <iostream>
#include <stdio.h>
#include <sys/types.h>
#include <Rectangle.h>
char tab[8];
static int decode_callback(const void* buffer, size_t size, void* app_key) {
    static int i = 0;
    memcpy(&tab[i], buffer, size);
    i += size;
    return 0;
}
int main() {
    Rectangle_t* rectangle; /* Type to encode */
    asn_enc_rval_t ec; /* Encoder return value */
    /* Allocate the Rectangle_t */
    rectangle = (Rectangle_t*)calloc(1, sizeof(Rectangle_t)); /* not */
    if (!rectangle) {
        perror("calloc() failed");
        exit(71); /* better, EX_OSERR */
    }
    /* Initialize the Rectangle members */
    rectangle->height = 42; /* any random value */
    rectangle->width = 23; /* any random value */
    /* Encode the Rectangle type as BER (DER) */
    ec = der_encode(&asn_DEF_Rectangle, rectangle, decode_callback, tab);
    if (ec.encoded == -1) {
        fprintf(stderr, "Could not encode Rectangle (at %s)\n", ec.failed_type ? ec.failed_type->name : "unknown");
        exit(65); /* better, EX_DATAERR */
    }
    else
        fprintf(stderr, "Created %s with BER encoded Rectangle\n", "");
    /* Also print the constructed Rectangle XER encoded (XML) */
    xer_fprint(stdout, &asn_DEF_Rectangle, rectangle);
    return 0;
}