如何在openssl中禁用特定的密码套件? [英] How do I disable a particular cipher suite in openssl?

问题描述

我想保护服务器免受FREAK攻击，因此我想禁用所有使用Openssl出口级RSA密钥的密码套件.有没有办法在openssl中禁用特定的密码套件?如果是，我该怎么办?

I want to secure my server from FREAK attack so I want to disable all the cipher suites that uses export grade RSA key from Openssl. Is there a way to disable a particular cipher suite in openssl? If yes, how do i do it?

推荐答案

有没有办法禁用openssl中的特定密码套件?如果是，我该怎么办?

Is there a way to disable a particular cipher suite in openssl? If yes, how do i do it?

要回答禁用特定密码套件的直接问题，可以通过将其从传递给SSL_CTX_set_cipher_list或SSL_CTX_set_cipher_list的密码套件列表中删除来实现:

To answer the direct question of disabling a particular cipher suite, do so by removing it from the cipher suite list passed to SSL_CTX_set_cipher_list or SSL_CTX_set_cipher_list:

int rc = SSL_CTX_set_cipher_list(ctx, "ALL:!NULL-MD5:!NULL-SHA");
assert(0 != rc);

您可以在SSL*上执行以下操作:

You can do it on a SSL* with:

int rc = SSL_set_cipher_list(ssl, "ALL:!NULL-MD5:!NULL-SHA");
assert(0 != rc);

在上面，NULL-MD5是SSL_RSA_WITH_NULL_MD5，NULL-SHA是SSL_RSA_WITH_NULL_SHA.您可以通过 openssl ciphers 命令获取映射列表.

In the above, NULL-MD5 is SSL_RSA_WITH_NULL_MD5 and NULL-SHA is SSL_RSA_WITH_NULL_SHA. You can get the list of mappings from the openssl ciphers command.

您还可以使用!EXP禁用导出密码:

You can also disable export ciphers with !EXP:

int rc = SSL_CTX_set_cipher_list(ctx, "ALL:!EXP");
assert(0 != rc);

您可以在SSL*上执行以下操作:

And you can do it on a SSL* with:

int rc = SSL_set_cipher_list(ssl, "ALL:!EXP");
assert(0 != rc);

---

您可以看到"ALL:!EXP"等同于OpenSSL命令(请注意单引号，这样外壳程序就不会发生爆炸):

---

You can see what "ALL:!EXP" equates to with the OpenSSL command (note the single quote so the shell does not get a hold of the bang):

$ openssl ciphers 'ALL:!EXP'
ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-SHA384:
ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:SRP-DSS-AES-256-CBC-SHA:
SRP-RSA-AES-256-CBC-SHA:SRP-AES-256-CBC-SHA:DH-DSS-AES256-GCM-SHA384...

您可以使用以下方法计算密码套件的数量:

You can count the number of cipher suites with:

$ openssl ciphers 'ALL:!EXP' | tr ':' ' ' | wc -w
     124

这告诉您，由于有124个密码套件，您的ClientHello将至少使用248个字节.理想情况下，您应该广告您真正想要的16个左右的套房.

That tells you your ClientHello will use at least 248 bytes due to the 124 cipher suites. Ideally, you should advertise the 16 or so suites you really want.

通常只使用"HIGH"配置密码套件.它不包括"MEDIUM"，"LOW"和"EXP".有时我的电话看起来像这样:

You usually configure your cipher suites using "HIGH" only. It excludes "MEDIUM", "LOW" and "EXP". Here's how my call sometimes look:

int rc = SSL_CTX_set_cipher_list(ctx, "HIGH:!ADH:!MD5:!RC4:!SRP:!PSK:!DSS");
assert(0 != rc);

请确保排除匿名齿轮(!ADH)，因为默认情况下已将其包括在内.使用!MD5和!RC4是因为它们很弱/很受伤. !SRP，!PSK和!DSS用于进一步修剪密码列表，因为它们通常不使用.

Be sure to exclude the anonymous gear (!ADH) because its included by default. !MD5 and !RC4 are used because they are weak/wounded. !SRP, !PSK, and !DSS are used to trim the list of ciphers further because they are not usually used.

您也可以对SSL*和SSL_set_cipher_list进行同样的操作.

You can also do the same with a SSL* and SSL_set_cipher_list.

如果您在服务器上调用SSL_CTX_set_cipher_list和SSL_set_cipher_list，则密码套件列表将根据证书中密钥的类型进一步调整.

If you call SSL_CTX_set_cipher_list and SSL_set_cipher_list on a server, the the cipher suite list will be trimmed further depending on the type of key in the certificate.

在上一个区块中，我说了 ...有时候我的电话看起来如何.通常，我想指定16个左右的位置，以配合使用:

In the previous block, I said ... how my call sometimes look. Usually, I like to specify the 16 or so I want to use with:

string GetCipherSuites()
{
    static string ciphers = ""

#if defined(ALLOW_ECDSA)
    "ECDHE-ECDSA-AES256-GCM-SHA384:"
    "ECDHE-ECDSA-AES128-GCM-SHA256:"
#endif

    "ECDHE-RSA-AES256-GCM-SHA384:"
    "ECDHE-RSA-AES128-GCM-SHA256:"

#if defined(ALLOW_DSA)
    "DHE-DSS-AES256-GCM-SHA384:"
#endif

    "DHE-RSA-AES256-GCM-SHA384:"

#if defined(ALLOW_DSA)
    "DHE-DSS-AES128-GCM-SHA256:"
#endif

    "DHE-RSA-AES128-GCM-SHA256:"

#if defined(ALLOW_DSA)
    "DHE-DSS-AES256-SHA:"
#endif

    "DHE-RSA-AES256-SHA:"

#if defined(ALLOW_DSA)
    "DHE-DSS-AES128-SHA:"
#endif

    "DHE-RSA-AES128-SHA:"

#if defined(ALLOW_DSA)
    "EDH-DSS-DES-CBC3-SHA:"
#endif

    "EDH-RSA-DES-CBC3-SHA:"

#if defined(ALLOW_DSA)
    "DH-DSS-DES-CBC3-SHA:"
#endif

    "DH-RSA-DES-CBC3-SHA:";

    return ciphers;
}

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