使用 OpenSSL 库在 C++ 中生成 SHA 哈希
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Generate SHA hash in C++ using OpenSSL library
提问by brianegge
回答by brianegge
From the command line, it's simply:
从命令行，它很简单：
printf "compute sha1" | openssl sha1
You can invoke the library like this:
您可以像这样调用库：
#include <stdio.h>
#include <string.h>
#include <openssl/sha.h>
int main()
{
unsigned char ibuf[] = "compute sha1";
unsigned char obuf[20];
SHA1(ibuf, strlen(ibuf), obuf);
int i;
for (i = 0; i < 20; i++) {
printf("%02x ", obuf[i]);
}
printf("\n");
return 0;
}
回答by AndiDog
OpenSSL has a horrible documentationwith no code examples, but here you are:
OpenSSL 有一个糟糕的文档，没有代码示例，但你在这里：
#include <openssl/sha.h>
bool simpleSHA256(void* input, unsigned long length, unsigned char* md)
{
SHA256_CTX context;
if(!SHA256_Init(&context))
return false;
if(!SHA256_Update(&context, (unsigned char*)input, length))
return false;
if(!SHA256_Final(md, &context))
return false;
return true;
}
Usage:
用法：
unsigned char md[SHA256_DIGEST_LENGTH]; // 32 bytes
if(!simpleSHA256(<data buffer>, <data length>, md))
{
// handle error
}
Afterwards, mdwill contain the binary SHA-256 message digest. Similar code can be used for the other SHA family members, just replace "256" in the code.
之后，md将包含二进制 SHA-256 消息摘要。类似的代码可用于其他 SHA 系列成员，只需替换代码中的“256”即可。
If you have larger data, you of course should feed data chunks as they arrive (multiple SHA256_Updatecalls).
如果您有更大的数据，您当然应该在数据块到达时提供数据块（多次SHA256_Update调用）。
回答by mecano
correct syntax at command line should be
命令行中的正确语法应该是
echo -n "compute sha1" | openssl sha1
otherwise you'll hash the trailing newline character as well.
否则你也会散列尾随的换行符。
回答by Nayfe
Adaptation of @AndiDog version for big file:
大文件@AndiDog 版本的适配：
static const int K_READ_BUF_SIZE{ 1024 * 16 };
std::optional<std::string> CalcSha256(std::string filename)
{
// Initialize openssl
SHA256_CTX context;
if(!SHA256_Init(&context))
{
return std::nullopt;
}
// Read file and update calculated SHA
char buf[K_READ_BUF_SIZE];
std::ifstream file(filename, std::ifstream::binary);
while (file.good())
{
file.read(buf, sizeof(buf));
if(!SHA256_Update(&context, buf, file.gcount()))
{
return std::nullopt;
}
}
// Get Final SHA
unsigned char result[SHA256_DIGEST_LENGTH];
if(!SHA256_Final(result, &context))
{
return std::nullopt;
}
// Transform byte-array to string
std::stringstream shastr;
shastr << std::hex << std::setfill('0');
for (const auto &byte: result)
{
shastr << std::setw(2) << (int)byte;
}
return shastr.str();
}
回答by anton_rh
Here is OpenSSLexample of calculating sha-1digest using BIO:
这是使用BIO计算sha-1摘要的OpenSSL示例：
#include <openssl/bio.h>
#include <openssl/evp.h>
std::string sha1(const std::string &input)
{
BIO * p_bio_md = nullptr;
BIO * p_bio_mem = nullptr;
try
{
// make chain: p_bio_md <-> p_bio_mem
p_bio_md = BIO_new(BIO_f_md());
if (!p_bio_md) throw std::bad_alloc();
BIO_set_md(p_bio_md, EVP_sha1());
p_bio_mem = BIO_new_mem_buf((void*)input.c_str(), input.length());
if (!p_bio_mem) throw std::bad_alloc();
BIO_push(p_bio_md, p_bio_mem);
// read through p_bio_md
// read sequence: buf <<-- p_bio_md <<-- p_bio_mem
std::vector<char> buf(input.size());
for (;;)
{
auto nread = BIO_read(p_bio_md, buf.data(), buf.size());
if (nread < 0) { throw std::runtime_error("BIO_read failed"); }
if (nread == 0) { break; } // eof
}
// get result
char md_buf[EVP_MAX_MD_SIZE];
auto md_len = BIO_gets(p_bio_md, md_buf, sizeof(md_buf));
if (md_len <= 0) { throw std::runtime_error("BIO_gets failed"); }
std::string result(md_buf, md_len);
// clean
BIO_free_all(p_bio_md);
return result;
}
catch (...)
{
if (p_bio_md) { BIO_free_all(p_bio_md); }
throw;
}
}
Though it's longer than just calling SHA1function from OpenSSL, but it's more universal and can be reworked for using with file streams (thus processing data of any length).
虽然它比仅仅SHA1从OpenSSL调用函数要长，但它更通用，可以重新设计以用于文件流（从而处理任何长度的数据）。
回答by Alan CN
C versionof @Nayfe code, generating SHA1 hash from file:
@Nayfe 代码的C 版本，从文件生成 SHA1 哈希：
#include <stdio.h>
#include <openssl/sha.h>
static const int K_READ_BUF_SIZE = { 1024 * 16 };
unsigned char* calculateSHA1(char *filename)
{
if (!filename) {
return NULL;
}
FILE *fp = fopen(filename, "rb");
if (fp == NULL) {
return NULL;
}
unsigned char* sha1_digest = malloc(sizeof(char)*SHA_DIGEST_LENGTH);
SHA_CTX context;
if(!SHA1_Init(&context))
return NULL;
unsigned char buf[K_READ_BUF_SIZE];
while (!feof(fp))
{
size_t total_read = fread(buf, 1, sizeof(buf), fp);
if(!SHA1_Update(&context, buf, total_read))
{
return NULL;
}
}
fclose(fp);
if(!SHA1_Final(sha1_digest, &context))
return NULL;
return sha1_digest;
}
It can be used as follows:
它可以按如下方式使用：
unsigned char *sha1digest = calculateSHA1("/tmp/file1");
The resvariable contains the sha1 hash.
该水库变量包含SHA1哈希。
You can print it on the screen using the following for-loop:
您可以使用以下 for 循环将其打印在屏幕上：
char *sha1hash = (char *)malloc(sizeof(char) * 41);
sha1hash[41] = '##代码##';
int i;
for (i = 0; i < SHA_DIGEST_LENGTH; i++)
{
sprintf(&sha1hash[i*2], "%02x", sha1digest[i]);
}
printf("SHA1 HASH: %s\n", sha1hash);
