如何存储公钥为C数组 [英] how to store public key as c array

问题描述

我一直在寻找这个答案了一段时间，所以我虽然我可能藏汉寄我已经找到了。

I've been looking for an answer for this for a while so i though i might aswell post what I've found.

我使用OpenSSL的签署和使用私钥签名和公钥来验证验证许可证。

I'm using openssl to sign and verify license using private key to sign and public key to verify.

因为我发送公钥到客户端进行验证，我不能给他，并要求路径关键，因为他可以改变公共密钥，并使用自己的私人/公共密钥加密邮件

since I'm sending the public key to the client for verification, I can't give it to him and ask for path to key, because he can change the public key and encrypt the message using his own private/public keys.

解决方案：存储C程序中作为一个数组公钥

the solution: store the public key inside the C program as an array.

现在我需要改变从阅读公钥我的code：

now i need to change my code of reading the public key from:

EVP_PKEY   *public_key = NULL;

public_key_fd = fopen( public_key_path, "r" );
if ( !public_key_fd )
     // something went wrong
PEM_read_PUBKEY( public_key_fd, &public_key, NULL, NULL );
fclose( public_key_path );

要使用字符串而不是一个文件的东西。

to something that uses a string instead of a file.

推荐答案

首先，我们需要了解什么是什么样子，使用cat：

first we need to understand what does the look like, using cat:

cat public_key.pem

我们得到

---- BEGIN PUBLIC KEY ----
AAAAB3NzaC1yc2EAAAABJQAAAQB/nAmOjTmezNUDKYvEeIRf2YnwM9/uUG1d0BYs
c8/tRtx+RGi7N2lUbp728MXGwdnL9od4cItzky/zVdLZE2cycOa18xBK9cOWmcKS
0A8FYBxEQWJ/q9YVUgZbFKfYGaGQxsER+A0w/fX8ALuk78ktP31K69LcQgxIsl7r
NzxsoOQKJ/CIxOGMMxczYTiEoLvQhapFQMs3FL96didKr/QbrfB1WT6s3838SEaX
fgZvLef1YB2xmfhbT9OXFE3FXvh2UPBfN+ffE7iiayQf/2XR+8j4N4bW30DiPtOQ
LGUrH1y5X/rpNZNlWW2+jGIxqZtgWg7lTy3mXy5x836Sj/6L
---- END PUBLIC KEY ----

我读过此CHAR成炭来理解是'\\ n'以及其他不可见字符和我所发现的是，每一行的'\\ n'

I've read this char by char to understand where are the '\n' and other invisible characters and what I've found is that each line ends with '\n'

让我们得到什么作为对C将是一个数组：

so what we get as an array for C will be:

char *key_string = "---- BEGIN PUBLIC KEY ----\nAAAAB3NzaC1yc2EAAAABJQAAAQB/nAmOjTmezNUDKYvEeIRf2YnwM9/uUG1d0BYs\nc8/tRtx+RGi7N2lUbp728MXGwdnL9od4cItzky/zVdLZE2cycOa18xBK9cOWmcKS\n0A8FYBxEQWJ/q9YVUgZbFKfYGaGQxsER+A0w/fX8ALuk78ktP31K69LcQgxIsl7r\nNzxsoOQKJ/CIxOGMMxczYTiEoLvQhapFQMs3FL96didKr/QbrfB1WT6s3838SEaX\nfgZvLef1YB2xmfhbT9OXFE3FXvh2UPBfN+ffE7iiayQf/2XR+8j4N4bW30DiPtOQ\nLGUrH1y5X/rpNZNlWW2+jGIxqZtgWg7lTy3mXy5x836Sj/6L\n---- END PUBLIC KEY ----\n";

和读取字符数组的一个关键所需的code是：

and The code needed to read a key from a char array is:

EVP_PKEY    *public_key = NULL;
BIO         *bio;

bio = BIO_num_mem_buf( key_string, strlen( key_string ) );
PEM_read_bio_PUBKEY( bio, &public_key, NULL, NULL );

的解释： PEM_read_PrivateKey（）约为PEM_ASN1_read（）（包装从一个读取任意ASN.1对象
PEM-CN codeD BLOB）和d2i_PrivateKey（）（它知道如何读的私人密钥blob明确）。

explaination: PEM_read_PrivateKey() is a wrapper around PEM_ASN1_read() (which reads an arbitrary ASN.1 object from a PEM-encoded blob) and d2i_PrivateKey() (which knows how to read a private key blob specifically).

PEM_ASN1_read（）只是简单地创建从你给它FILE *生物，并调用PEM_ASN1_read_bio（）。如果
你想，你可以改为创建使用类似BIO_new_mem_buf（）的字符串，并呼叫BIO
PEM_ASN1_read_bio（）自己。 （生物是OpenSSL的对象，像一个更通用的FILE *）。

PEM_ASN1_read() simply creates a BIO from the FILE* that you give it, and calls PEM_ASN1_read_bio(). If you want, you can instead create a BIO from your string using something like BIO_new_mem_buf() and call PEM_ASN1_read_bio() yourself. (A BIO is an openssl object that's like a more general-purpose FILE*.)

顺便说一句，如果你的密钥存储在数据库中，有大概没有需要他们是PEM-CN codeD;你可以节省
在DER格式存储它们和（）直接调用d2i_PrivateKey的空间和时间位。 （PEM格式
或多或少只是基于64位带codeD DER）有一个FAQ条目在此：
     http://www.openssl.org/support/faq.html#PROG3

BTW, if your keys are stored in a database, there's probably no need for them to be PEM-encoded; you can save a bit of space and time by storing them in DER format and calling d2i_PrivateKey() directly. (PEM format is more or less just base64-encoded DER.) There's a FAQ entry on this: http://www.openssl.org/support/faq.html#PROG3

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