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Store and verify SSH server fingerprints.
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This also moves thread creation for SSHLogin back into mosh_nacl.cc, which
allows better handing of data communication between MoshClientInstance and
SSHLogin. It also further generalizes SSHLogin; it shouldn't care that it is
run in a thread.
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@rpwoodbu
rpwoodbu committed Mar 10, 2014
1 parent 421582f commit 4b44fab
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Showing 5 changed files with 158 additions and 59 deletions.
33 changes: 30 additions & 3 deletions src/app/mosh_window.js
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Original file line number Diff line number Diff line change
Expand Up @@ -125,11 +125,38 @@ mosh.CommandInstance.prototype.onMessage_ = function(e) {
}
this.io.print(output + '\r\n');
console.error(output);
} else if (type == 'get_ssh_key') {
} else if (type.match(/^get_.+/)) {
var thiz = this;
chrome.storage.local.get('ssh_key', function(o) {
thiz.moshNaCl_.postMessage({'ssh_key': o['ssh_key']});
var name = type.slice(4);
chrome.storage.local.get(name, function(o) {
var result = {};
result[name] = o[name];
thiz.moshNaCl_.postMessage(result);
});
} else if (type.match(/^set_.+/)) {
var name = type.slice(4);
var param = {};
param[name] = data;
// Wash out any string "objects" by going through JSON (hacky).
var j = JSON.stringify(param);
param = JSON.parse(j);
chrome.storage.local.set(param);
} else if (type.match(/^sync_get_.+/)) {
var thiz = this;
var name = type.slice(9);
chrome.storage.sync.get(name, function(o) {
var result = {};
result[name] = o[name];
thiz.moshNaCl_.postMessage(result);
});
} else if (type.match(/^sync_set_.+/)) {
var name = type.slice(9);
var param = {};
param[name] = data;
// Wash out any string "objects" by going through JSON (hacky).
var j = JSON.stringify(param);
param = JSON.parse(j);
chrome.storage.sync.set(param);
} else {
console.log('Unknown message type: ' + JSON.stringify(e.data));
}
Expand Down
60 changes: 50 additions & 10 deletions src/mosh_nacl.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -208,15 +208,23 @@ void MoshClientInstance::HandleMessage(const pp::Var &var) {
if (key.is_undefined() == false) {
ssh_login_.set_key(key.AsString());
}
ssh_login_.set_addr(addr_);
ssh_login_.set_port(port_);
ssh_login_.Launch();
// Now get the known hosts.
Output(TYPE_GET_KNOWN_HOSTS, "");
} else if (dict.HasKey("known_hosts")) {
pp::Var known_hosts = dict.Get("known_hosts");
if (known_hosts.is_undefined() == false) {
ssh_login_.set_known_hosts(known_hosts);
}
// The assumption is that Output(TYPE_GET_SSH_KEY, "") was already
// called, which precipitated Output(TYPE_GET_KNOWN_HOSTS, ""), so now we
// are ready to do the SSH login.
LaunchSSHLogin();
} else {
Log("HandleMessage(): Got a message of an unexpected type.");
}
}

void MoshClientInstance::Output(OutputType t, const string &s) {
void MoshClientInstance::Output(OutputType t, const pp::Var &data) {
string type;
switch (t) {
case TYPE_DISPLAY:
Expand All @@ -231,15 +239,21 @@ void MoshClientInstance::Output(OutputType t, const string &s) {
case TYPE_GET_SSH_KEY:
type = "get_ssh_key";
break;
case TYPE_GET_KNOWN_HOSTS:
type = "sync_get_known_hosts";
break;
case TYPE_SET_KNOWN_HOSTS:
type = "sync_set_known_hosts";
break;
default:
// Bad type.
return;
}

pp::VarDictionary dict;
dict.Set(pp::Var("type"), pp::Var(type));
dict.Set(pp::Var("data"), pp::Var(s));
PostMessage(pp::Var(dict));
dict.Set("type", type);
dict.Set("data", data);
PostMessage(dict);
}

void MoshClientInstance::Logv(OutputType t, const char *format, va_list argp) {
Expand Down Expand Up @@ -343,13 +357,13 @@ void MoshClientInstance::Launch(int32_t result) {
}

void MoshClientInstance::LaunchMosh(int32_t unused) {
int thread_err = pthread_create(&thread_, NULL, Mosh, this);
int thread_err = pthread_create(&thread_, NULL, MoshThread, this);
if (thread_err != 0) {
Error("Failed to create Mosh thread: %s", strerror(thread_err));
}
}

void *MoshClientInstance::Mosh(void *data) {
void *MoshClientInstance::MoshThread(void *data) {
MoshClientInstance *thiz = reinterpret_cast<MoshClientInstance *>(data);

setenv("TERM", "xterm-256color", 1);
Expand All @@ -366,7 +380,33 @@ void *MoshClientInstance::Mosh(void *data) {

delete[] argv0;
exit(0);
return 0;
return NULL;
}

void MoshClientInstance::LaunchSSHLogin() {
ssh_login_.set_addr(addr_);
ssh_login_.set_port(port_);

int thread_err = pthread_create(&thread_, NULL, SSHLoginThread, this);
if (thread_err != 0) {
Error("Failed to create SSHLogin thread: %s", strerror(thread_err));
}
}

void *MoshClientInstance::SSHLoginThread(void *data) {
MoshClientInstance *thiz = reinterpret_cast<MoshClientInstance *>(data);

if (thiz->ssh_login_.Start() == false) {
thiz->Error("SSH Login failed.");
exit(1);
}

thiz->Output(TYPE_SET_KNOWN_HOSTS, thiz->ssh_login_.known_hosts());

pp::Module::Get()->core()->CallOnMainThread(
0, thiz->cc_factory_.NewCallback(&MoshClientInstance::LaunchMosh));

return NULL;
}

// Initialize static data for MoshClientInstance.
Expand Down
28 changes: 17 additions & 11 deletions src/mosh_nacl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -52,10 +52,12 @@ class MoshClientInstance : public pp::Instance {
TYPE_LOG,
TYPE_ERROR,
TYPE_GET_SSH_KEY,
TYPE_GET_KNOWN_HOSTS,
TYPE_SET_KNOWN_HOSTS,
};

// Low-level function to output data to Javascript.
void Output(OutputType t, const string &s);
void Output(OutputType t, const pp::Var &data);

// Sends messages to the Javascript console log.
void Logv(OutputType t, const char *format, va_list argp);
Expand All @@ -66,28 +68,31 @@ class MoshClientInstance : public pp::Instance {
// Sends error messages to the Javascript console log and terminal.
void Error(const char *format, ...);

// Launches Mosh in a new thread. Must be visible to SSHLogin. Must take one
// argument to be used as a completion callback.
void LaunchMosh(int32_t unused);

// Allow SSHLogin to set the port based on its findings. Takes ownership.
void set_port(char *port) { delete port_; port_ = port; }

// Pepper POSIX emulation.
PepperPOSIX::POSIX *posix_;

// Window change "file"; must be visible to sigaction().
class WindowChange *window_change_;

// Must be visible to SSHLogin.
// TODO: Clean up the interface between this class and SSHLogin.
pp::CompletionCallbackFactory<MoshClientInstance> cc_factory_;

private:
// Launcher that can be a callback.
void Launch(int32_t result);

// New thread entry point for Mosh.
static void *Mosh(void *data);
// Launches Mosh in a new thread. Must take one argument to be used as a
// completion callback.
void LaunchMosh(int32_t unused);

// New thread entry point for Mosh. |data| is |this|.
static void *MoshThread(void *data);

// Launches SSHLogin in a new thread.
void LaunchSSHLogin();

// New thread entry point for SSHLogin. |data| is |this|.
static void *SSHLoginThread(void *data);

static int num_instances_; // This needs to be a singleton.
pthread_t thread_;
Expand All @@ -102,6 +107,7 @@ class MoshClientInstance : public pp::Instance {
pp::InstanceHandle instance_handle_;
class Keyboard *keyboard_;
pp::HostResolver resolver_;
pp::CompletionCallbackFactory<MoshClientInstance> cc_factory_;

// Disable copy and assignment.
MoshClientInstance(const MoshClientInstance&);
Expand Down
73 changes: 49 additions & 24 deletions src/ssh_login.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -31,19 +31,6 @@ SSHLogin::~SSHLogin() {
delete session_;
}

void *SSHLogin::ThreadEntry(void *data) {
SSHLogin *thiz = reinterpret_cast<SSHLogin *>(data);
thiz->Start();
return NULL;
}

void SSHLogin::Launch() {
int thread_err = pthread_create(&thread_, NULL, ThreadEntry, this);
if (thread_err != 0) {
mosh_->Error("Failed to create SSH login thread: %s", strerror(thread_err));
}
}

void SSHLogin::GetKeyboardLine(char *buf, size_t len, bool echo) {
int i = 0;
while (i < len) {
Expand Down Expand Up @@ -73,17 +60,27 @@ void SSHLogin::GetKeyboardLine(char *buf, size_t len, bool echo) {
buf[i] = 0;
}

void SSHLogin::Start() {
if (!RealStart()) {
// TODO: Propagate errors more cleanly.
exit(1);
bool SSHLogin::AskYesNo(const string &prompt) {
for (int i = 0; i < RETRIES; ++i) {
mosh_->Output(MoshClientInstance::TYPE_DISPLAY, prompt + " (Yes/No): ");
char input_buf[INPUT_SIZE];
GetKeyboardLine(input_buf, sizeof(input_buf), true);
mosh_->Output(MoshClientInstance::TYPE_DISPLAY, "\r\n");
string input = input_buf;
if (input == "yes" || input == "Yes") {
return true;
}
if (input == "no" || input == "No") {
return false;
}
mosh_->Output(MoshClientInstance::TYPE_DISPLAY,
"Please specify Yes or No.\r\n");
}

pp::Module::Get()->core()->CallOnMainThread(
0, mosh_->cc_factory_.NewCallback(&MoshClientInstance::LaunchMosh));
return false;
}

bool SSHLogin::RealStart() {
bool SSHLogin::Start() {
setenv("HOME", "dummy", 1); // To satisfy libssh.

delete session_;
Expand Down Expand Up @@ -149,11 +146,39 @@ bool SSHLogin::RealStart() {
}

bool SSHLogin::CheckFingerprint() {
// TODO: Actually track known hosts and check with the user if unknown.
const string server_name = addr_ + ":" + port_;
const string server_fp = session_->GetPublicKey()->MD5();

mosh_->Output(MoshClientInstance::TYPE_DISPLAY,
"Fingerprint of remote ssh host (MD5): " +
session_->GetPublicKey()->MD5() + "\r\n");
return true;
"Fingerprint of remote ssh host (MD5):\r\n " + server_fp + "\r\n");

const pp::Var stored_fp_var = known_hosts_.Get(server_name);
if (stored_fp_var.is_undefined()) {
bool result = AskYesNo("Server fingerprint unknown. Store and continue?");
if (result == true) {
known_hosts_.Set(server_name, server_fp);
return true;
}
} else {
string stored_fp = stored_fp_var.AsString();
if (stored_fp == server_fp) {
return true;
}
mosh_->Output(MoshClientInstance::TYPE_DISPLAY,
"WARNING!!! Server fingerprint differs! "
"Possible man-in-the-middle attack.\r\n"
"Stored fingerprint (MD5):\r\n " + stored_fp + "\r\n");
bool result = AskYesNo("Connect anyway, and store new fingerprint?");
if (result == true) {
result = AskYesNo("Don't take this lightly. Are you really sure?");
if (result == true) {
known_hosts_.Set(server_name, server_fp);
return true;
}
}
}

return false;
}

vector<ssh::AuthenticationType> *SSHLogin::GetAuthTypes() {
Expand Down
23 changes: 12 additions & 11 deletions src/ssh_login.h
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Original file line number Diff line number Diff line change
Expand Up @@ -21,12 +21,13 @@
#ifndef SSH_LOGIN_H
#define SSH_LOGIN_H

#include <pthread.h>
#include <stddef.h>
#include <string>
#include <vector>

#include "ssh.h"
#include "ppapi/cpp/var.h"
#include "ppapi/cpp/var_dictionary.h"

using ::std::string;
using ::std::vector;
Expand All @@ -40,8 +41,8 @@ class SSHLogin {
explicit SSHLogin(MoshClientInstance *mosh);
~SSHLogin();

// Launch login in new thread.
void Launch();
// Begin the SSH login session. Returns true iff SSH Login succeeded.
bool Start();

string addr() const { return addr_; }
void set_addr(const string &addr) { addr_ = addr; }
Expand All @@ -55,14 +56,10 @@ class SSHLogin {
string key() const { return key_; }
void set_key(const string &key) { key_ = key; }

private:
// Entry point after thread is created. Handles communication of the
// disposition of SSHLogin to MoshClientInstance.
void Start();

// The real work of the SSHLogin begins here; called from Start().
bool RealStart();
pp::VarDictionary known_hosts() const { return known_hosts_; }
void set_known_hosts(const pp::Var &var) { known_hosts_ = var; }

private:
// Passed as function pointer to pthread_create(). |data| is |this|.
static void *ThreadEntry(void *data);

Expand All @@ -77,6 +74,10 @@ class SSHLogin {
// caller.
vector<ssh::AuthenticationType> *GetAuthTypes();

// Ask a yes/no question to the user, and return the answer as a bool.
// Prefers to return false if input is not parseable.
bool AskYesNo(const string &prompt);

bool DoPasswordAuth();
bool DoInteractiveAuth();
bool DoPublicKeyAuth();
Expand All @@ -86,8 +87,8 @@ class SSHLogin {
string port_;
string user_;
string key_;
pp::VarDictionary known_hosts_;
MoshClientInstance *mosh_;
pthread_t thread_;
ssh::Session *session_;

// Disable copy and assignment.
Expand Down

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