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tls: command-line switch and envar cipher-list override
Add command line switches and environment variables to override the default cipher suite in tls.js `--cipher-list` and `NODE_CIPHER_LIST` can be used to completely override the default cipher list with a given value. `--enable-legacy-cipher-list` and `NODE_LEGACY_CIPHER_LIST` can be used to reset the default cipher list back to a known legacy value shipped in prior Node.js releases A new `getLegacyCiphers` method on the tis module allows programmatic access to the old cipher list defaults.
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‎doc/api/tls.markdown

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@@ -136,6 +136,81 @@ the character "E" appended to the traditional abbreviations):
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Ephemeral methods may have some performance drawbacks, because key generation
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is expensive.
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## Modifying the Default Cipher Suite
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Node.js is built with a default suite of enabled and disabled ciphers.
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Currently, the default cipher suite is:
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ECDHE-RSA-AES256-SHA384:DHE-RSA-AES256-SHA384:ECDHE-RSA-AES256-SHA256:
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DHE-RSA-AES256-SHA256:ECDHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA256:
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HIGH:!aNULL:!eNULL:!EXPORT:!DES:!RC4:!MD5:!PSK:!SRP:!CAMELLIA
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This default can be overridden entirely using the `--cipher-list` command line
149+
switch or `NODE_CIPHER_LIST` environment variable. For instance:
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node --cipher-list=ECDHE-RSA-AES256-SHA384:DHE-RSA-AES256-SHA384
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Setting the environment variable would have the same effect:
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NODE_CIPHER_LIST=ECDHE-RSA-AES256-SHA384:DHE-RSA-AES256-SHA384
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CAUTION: The default cipher suite has been carefully selected to reflect current
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security best practices and risk mitigation. Changing the default cipher suite
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can have a significant impact on the security of an application. The
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`--cipher-list` and `NODE_CIPHER_LIST` options should only be used if
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absolutely necessary.
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### Using Legacy Default Cipher Suite ###
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It is possible for the built-in default cipher suite to change from one release
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of Node.js to another. For instance, v0.10.38 uses a different default than
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v0.12.2. Such changes can cause issues with applications written to assume
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certain specific defaults. To help buffer applications against such changes,
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the `--enable-legacy-cipher-list` command line switch or `NODE_LEGACY_CIPHER_LIST`
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environment variable can be set to specify a specific preset default:
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# Use the v0.10.38 defaults
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node --enable-legacy-cipher-list=v0.10.38
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// or
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NODE_LEGACY_CIPHER_LIST=v0.10.38
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# Use the v0.12.2 defaults
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node --enable-legacy-cipher-list=v0.12.2
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// or
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NODE_LEGACY_CIPHER_LIST=v0.12.2
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Currently, the values supported for the `enable-legacy-cipher-list` switch and
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`NODE_LEGACY_CIPHER_LIST` environment variable include:
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v0.10.38 - To enable the default cipher suite used in v0.10.38
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ECDHE-RSA-AES128-SHA256:AES128-GCM-SHA256:RC4:HIGH:!MD5:!aNULL:!EDH
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v0.10.39 - To enable the default cipher suite used in v0.10.39
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ECDHE-RSA-AES128-SHA256:AES128-GCM-SHA256:HIGH:!RC4:!MD5:!aNULL:!EDH
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v0.12.2 - To enable the default cipher suite used in v0.12.2
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ECDHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA256:AES128-GCM-SHA256:RC4:
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HIGH:!MD5:!aNULL
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v.0.12.3 - To enable the default cipher suite used in v0.12.3
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ECDHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA256:AES128-GCM-SHA256:HIGH:
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!RC4:!MD5:!aNULL
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These legacy cipher suites are also made available for use via the
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`getLegacyCiphers()` method:
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var tls = require('tls');
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console.log(tls.getLegacyCiphers('v0.10.38'));
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CAUTION: Changes to the default cipher suite are typically made in order to
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strengthen the default security for applications running within Node.js.
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Reverting back to the defaults used by older releases can weaken the security
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of your applications. The legacy cipher suites should only be used if absolutely
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necessary.
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## tls.getCiphers()
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@@ -146,6 +221,12 @@ Example:
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var ciphers = tls.getCiphers();
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console.log(ciphers); // ['AES128-SHA', 'AES256-SHA', ...]
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224+
## tls.getLegacyCiphers(version)
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Returns the legacy default cipher suite for the specified Node.js release.
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Example:
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var cipher_suite = tls.getLegacyCiphers('v0.10.38');
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## tls.createServer(options[, secureConnectionListener])
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‎lib/tls.js

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@@ -21,6 +21,8 @@
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'use strict';
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var _crypto = process.binding('crypto');
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var net = require('net');
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var url = require('url');
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var util = require('util');
@@ -35,29 +37,14 @@ exports.CLIENT_RENEG_WINDOW = 600;
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exports.SLAB_BUFFER_SIZE = 10 * 1024 * 1024;
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38-
exports.DEFAULT_CIPHERS = [
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'ECDHE-RSA-AES256-SHA384',
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'DHE-RSA-AES256-SHA384',
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'ECDHE-RSA-AES256-SHA256',
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'DHE-RSA-AES256-SHA256',
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'ECDHE-RSA-AES128-SHA256',
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'DHE-RSA-AES128-SHA256',
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'HIGH',
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'!aNULL',
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'!eNULL',
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'!EXPORT',
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'!DES',
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'!RC4',
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'!MD5',
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'!PSK',
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'!SRP',
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'!CAMELLIA'
55-
].join(':');
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exports.DEFAULT_CIPHERS = _crypto.DEFAULT_CIPHER_LIST;
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exports.DEFAULT_ECDH_CURVE = 'prime256v1';
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exports.getLegacyCiphers = _crypto.getLegacyCiphers;
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exports.getCiphers = function() {
60-
var names = process.binding('crypto').getSSLCiphers();
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var names = _crypto.getSSLCiphers();
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// Drop all-caps names in favor of their lowercase aliases,
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var ctx = {};
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names.forEach(function(name) {

‎src/node.cc

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@@ -2929,6 +2929,12 @@ static void PrintHelp() {
29292929
#endif
29302930
" --enable-ssl2 enable ssl2\n"
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" --enable-ssl3 enable ssl3\n"
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" --cipher-list=val specify the default TLS cipher list\n"
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" --enable-legacy-cipher-list=val \n"
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" set to v0.10.38 to use the v0.10.38 list,\n"
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" set to v0.10.39 to use the v0.10.39 list.\n"
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" set to v0.12.2 to use the v0.12.2 list.\n"
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" set to v0.12.3 to use the v0.12.3 list.\n"
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"\n"
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"Environment variables:\n"
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#ifdef _WIN32
@@ -2946,6 +2952,12 @@ static void PrintHelp() {
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" (will extend linked-in data)\n"
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#endif
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#endif
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"NODE_CIPHER_LIST Override the default TLS cipher list\n"
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"NODE_LEGACY_CIPHER_LIST\n"
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" Set to v0.10.38 to use the v0.10.38 list,\n"
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" Set to v0.10.39 to use the v0.10.39 list.\n"
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" Set to v0.12.2 to use the v0.12.2 list.\n"
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" Set to v0.12.3 to use the v0.12.3 list.\n"
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"\n"
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"Documentation can be found at http://nodejs.org/\n");
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}
@@ -2985,6 +2997,7 @@ static void ParseArgs(int* argc,
29852997
unsigned int new_argc = 1;
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new_v8_argv[0] = argv[0];
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new_argv[0] = argv[0];
3000+
bool using_legacy_cipher_list = false;
29883001

29893002
unsigned int index = 1;
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while (index < nargs && argv[index][0] == '-') {
@@ -3040,6 +3053,17 @@ static void ParseArgs(int* argc,
30403053
} else if (strcmp(arg, "--v8-options") == 0) {
30413054
new_v8_argv[new_v8_argc] = "--help";
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new_v8_argc += 1;
3056+
} else if (strncmp(arg, "--cipher-list=", 14) == 0) {
3057+
if (!using_legacy_cipher_list) {
3058+
DEFAULT_CIPHER_LIST = arg + 14;
3059+
}
3060+
} else if (strncmp(arg, "--enable-legacy-cipher-list=", 28) == 0) {
3061+
using_legacy_cipher_list = true;
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// use the original v0.10.x/v0.12.x cipher lists
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const char * legacy_list = legacy_cipher_list(arg+28);
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if (legacy_list != NULL) {
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DEFAULT_CIPHER_LIST = legacy_list;
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}
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#if defined(NODE_HAVE_I18N_SUPPORT)
30443068
} else if (strncmp(arg, "--icu-data-dir=", 15) == 0) {
30453069
icu_data_dir = arg + 15;
@@ -3402,6 +3426,23 @@ void Init(int* argc,
34023426
}
34033427
}
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3429+
// if parseargs didn't come up with a cipher_list,
3430+
// try the NODE_CIPHER_LIST env variable to grab the
3431+
// list.
3432+
const char * cipher_list = getenv("NODE_CIPHER_LIST");
3433+
if (cipher_list != NULL) {
3434+
DEFAULT_CIPHER_LIST = cipher_list;
3435+
}
3436+
// Allow the NODE_LEGACY_CIPHER_LIST envar to override the other
3437+
// cipher list options. NODE_LEGACY_CIPHER_LIST=v0.10.x will use
3438+
// the cipher list from v0.10.x, NODE_LEGACY_CIPHER_LIST=v0.12.x will
3439+
// use the cipher list from v0.12.x
3440+
const char * leg_cipher_list =
3441+
legacy_cipher_list(getenv("NODE_LEGACY_CIPHER_LIST"));
3442+
if (leg_cipher_list != NULL) {
3443+
DEFAULT_CIPHER_LIST = leg_cipher_list;
3444+
}
3445+
34053446
#if defined(NODE_HAVE_I18N_SUPPORT)
34063447
if (icu_data_dir == NULL) {
34073448
// if the parameter isn't given, use the env variable.

‎src/node.h

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@@ -223,6 +223,18 @@ NODE_EXTERN void RunAtExit(Environment* env);
223223
} \
224224
while (0)
225225

226+
#define NODE_DEFINE_STRING_CONSTANT(target, constant) \
227+
do { \
228+
v8::Isolate* isolate = v8::Isolate::GetCurrent(); \
229+
v8::Local<v8::String> constant_name = \
230+
v8::String::NewFromUtf8(isolate, #constant); \
231+
v8::Local<v8::String> constant_value = \
232+
v8::String::NewFromUtf8(isolate, constant); \
233+
v8::PropertyAttribute constant_attributes = \
234+
static_cast<v8::PropertyAttribute>(v8::ReadOnly | v8::DontDelete); \
235+
(target)->ForceSet(constant_name, constant_value, constant_attributes); \
236+
} while (0)
237+
226238
// Used to be a macro, hence the uppercase name.
227239
template <typename TypeName>
228240
inline void NODE_SET_METHOD(const TypeName& recv,

‎src/node_crypto.cc

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@@ -77,6 +77,7 @@ namespace node {
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7878
bool SSL2_ENABLE = false;
7979
bool SSL3_ENABLE = false;
80+
const char * DEFAULT_CIPHER_LIST = DEFAULT_CIPHER_LIST_HEAD;
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8182
namespace crypto {
8283

@@ -4851,6 +4852,26 @@ static void array_push_back(const TypeName* md,
48514852
ctx->arr->Set(ctx->arr->Length(), OneByteString(ctx->env()->isolate(), from));
48524853
}
48534854

4855+
// borrowed from v8
4856+
// (see http://v8.googlecode.com/svn/trunk/samples/shell.cc)
4857+
const char* ToCString(const String::Utf8Value& value) {
4858+
return *value ? *value : "<string conversion failed>";
4859+
}
4860+
4861+
void DefaultCiphers(const v8::FunctionCallbackInfo<v8::Value>& args) {
4862+
Environment* env = Environment::GetCurrent(args.GetIsolate());
4863+
HandleScope scope(env->isolate());
4864+
v8::String::Utf8Value key(args[0]);
4865+
const char * list = legacy_cipher_list(ToCString(key));
4866+
if (list != NULL) {
4867+
args.GetReturnValue().Set(
4868+
v8::String::NewFromUtf8(args.GetIsolate(), list));
4869+
} else {
4870+
args.GetReturnValue().Set(
4871+
v8::String::NewFromUtf8(args.GetIsolate(),
4872+
DEFAULT_CIPHER_LIST_HEAD));
4873+
}
4874+
}
48544875

48554876
void GetCiphers(const FunctionCallbackInfo<Value>& args) {
48564877
Environment* env = Environment::GetCurrent(args.GetIsolate());
@@ -5171,6 +5192,8 @@ void InitCrypto(Handle<Object> target,
51715192

51725193
NODE_DEFINE_CONSTANT(target, SSL3_ENABLE);
51735194
NODE_DEFINE_CONSTANT(target, SSL2_ENABLE);
5195+
NODE_DEFINE_STRING_CONSTANT(target, DEFAULT_CIPHER_LIST);
5196+
NODE_SET_METHOD(target, "getLegacyCiphers", DefaultCiphers);
51745197
}
51755198

51765199
} // namespace crypto

‎src/node_crypto.h

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@@ -38,6 +38,7 @@
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3939
#include "v8.h"
4040

41+
#include <string.h>
4142
#include <openssl/ssl.h>
4243
#include <openssl/ec.h>
4344
#include <openssl/ecdh.h>
@@ -59,10 +60,51 @@
5960
# define NODE__HAVE_TLSEXT_STATUS_CB
6061
#endif // !defined(OPENSSL_NO_TLSEXT) && defined(SSL_CTX_set_tlsext_status_cb)
6162

63+
#define DEFAULT_CIPHER_LIST_V10_38 "ECDHE-RSA-AES128-SHA256:" \
64+
"AES128-GCM-SHA256:RC4:HIGH:!MD5:!aNULL:!EDH"
65+
66+
#define DEFAULT_CIPHER_LIST_V10_39 "ECDHE-RSA-AES128-SHA256:" \
67+
"AES128-GCM-SHA256:HIGH:!RC4:!MD5:!aNULL:!EDH"
68+
69+
#define DEFAULT_CIPHER_LIST_V12_2 "ECDHE-RSA-AES128-SHA256:" \
70+
"DHE-RSA-AES128-SHA256:AES128-GCM-SHA256:RC4:" \
71+
"HIGH:!MD5:!aNULL"
72+
73+
#define DEFAULT_CIPHER_LIST_V12_3 "ECDHE-RSA-AES128-SHA256:" \
74+
"DHE-RSA-AES128-SHA256:AES128-GCM-SHA256:HIGH:"\
75+
"!RC4:!MD5:!aNULL"
76+
77+
#define DEFAULT_CIPHER_LIST_HEAD "ECDHE-RSA-AES256-SHA384:" \
78+
"DHE-RSA-AES256-SHA384:" \
79+
"ECDHE-RSA-AES256-SHA256:" \
80+
"DHE-RSA-AES256-SHA256:" \
81+
"ECDHE-RSA-AES128-SHA256:" \
82+
"DHE-RSA-AES128-SHA256:" \
83+
"HIGH:!aNULL:!eNULL:!EXPORT:!DES:!RC4:!MD5:" \
84+
"!PSK:!SRP:!CAMELLIA"
85+
86+
static inline const char * legacy_cipher_list(const char * ver) {
87+
if (ver == NULL) {
88+
return NULL;
89+
}
90+
if (strncmp(ver, "v0.10.38", 8) == 0) {
91+
return DEFAULT_CIPHER_LIST_V10_38;
92+
} else if (strncmp(ver, "v0.10.39", 8) == 0) {
93+
return DEFAULT_CIPHER_LIST_V10_39;
94+
} else if (strncmp(ver, "v0.12.2", 7) == 0) {
95+
return DEFAULT_CIPHER_LIST_V12_2;
96+
} else if (strncmp(ver, "v0.12.3", 7) == 0) {
97+
return DEFAULT_CIPHER_LIST_V12_3;
98+
} else {
99+
return NULL;
100+
}
101+
}
102+
62103
namespace node {
63104

64105
extern bool SSL2_ENABLE;
65106
extern bool SSL3_ENABLE;
107+
extern const char * DEFAULT_CIPHER_LIST;
66108

67109
namespace crypto {
68110

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