allowing users to configure the default shell through windows registry (#215)

contrib/win32/win32compat/shell-host.c

@@ -255,8 +255,11 @@ struct key_translation keys[] = {
 
 static SHORT lastX = 0;
 static SHORT lastY = 0;
-static wchar_t system32_path[PATH_MAX];
+static wchar_t system32_path[PATH_MAX + 1] = { 0, };
-static wchar_t cmd_exe_path[PATH_MAX];
+static wchar_t cmd_exe_path[PATH_MAX + 1] = { 0, };
+static wchar_t default_shell_path[PATH_MAX + 3] = { 0, }; /* 2 - quotes, 1 - Null terminator */
+static wchar_t default_shell_cmd_option[10] = { 0, }; /* for cmd.exe/powershell it is "/c", for bash.exe it is "-c" */
+static BOOL is_default_shell_configured = FALSE;
 
 SHORT currentLine = 0;
 consoleEvent* head = NULL;
@@ -1192,19 +1195,70 @@ cleanup:
 }
 
 wchar_t *
-w32_cmd_path()
+get_default_shell_path()
 {
+	HKEY reg_key = 0;
+	int tmp_len = PATH_MAX;
 	errno_t r = 0;
-	if ((r = wcsncpy_s(cmd_exe_path, _countof(cmd_exe_path), system32_path, wcsnlen(system32_path, _countof(system32_path)) + 1)) != 0) {
+	REGSAM mask = STANDARD_RIGHTS_READ | KEY_QUERY_VALUE | KEY_WOW64_64KEY;
-		printf_s("wcsncpy_s failed with error: %d.", r);
+	wchar_t *tmp = malloc(PATH_MAX + 1);
+
+	if (!tmp) {
+		printf_s("get_default_shell_path(),  Unable to allocate memory");
 		exit(255);
 	}
 
-	if ((r = wcscat_s(cmd_exe_path, _countof(cmd_exe_path), L"\\cmd.exe")) != 0) {
+	memset(tmp, 0, PATH_MAX + 1);
-		printf_s("wcscat_s failed with error: %d.", r);
+	memset(default_shell_path, 0, _countof(default_shell_path));
+
+	if ((RegOpenKeyExW(HKEY_LOCAL_MACHINE, L"SOFTWARE\\OpenSSH", 0, mask, &reg_key) == ERROR_SUCCESS) &&
+	    (RegQueryValueExW(reg_key, L"DefaultShell", 0, NULL, (LPBYTE)tmp, &tmp_len) == ERROR_SUCCESS) &&
+	    (tmp)) {
+		is_default_shell_configured = TRUE;
+
+		/* If required, add quotes to the default shell. */
+		if (tmp[0] != L'"') {
+			default_shell_path[0] = L'\"';
+			wcscat_s(default_shell_path, _countof(default_shell_path), tmp);
+			wcscat_s(default_shell_path, _countof(default_shell_path), L"\"");
+		} else
+			wcscat_s(default_shell_path, _countof(default_shell_path), tmp);
+		
+		/* Fetch the default shell command option.
+		 * For cmd.exe/powershell.exe it is "/c", for bash.exe it is "-c".
+		 * For cmd.exe/powershell.exe/bash.exe, verify if present otherwise auto-populate.
+		 */
+		memset(tmp, 0, PATH_MAX + 1);
+		
+		if ((RegQueryValueExW(reg_key, L"DefaultShellCommandOption", 0, NULL, (LPBYTE)tmp, &tmp_len) == ERROR_SUCCESS)) {
+			wcscat_s(default_shell_cmd_option, _countof(default_shell_cmd_option), L" ");
+			wcscat_s(default_shell_cmd_option, _countof(default_shell_cmd_option), tmp);
+			wcscat_s(default_shell_cmd_option, _countof(default_shell_cmd_option), L" ");
+		}
+	}
+
+	if (((r = wcsncpy_s(cmd_exe_path, _countof(cmd_exe_path), system32_path, wcsnlen(system32_path, _countof(system32_path)) + 1)) != 0) ||
+	    ((r = wcscat_s(cmd_exe_path, _countof(cmd_exe_path), L"\\cmd.exe")) != 0)) {
+		printf_s("get_default_shell_path(), wcscat_s failed with error: %d.", r);
 		exit(255);
 	}
-	return cmd_exe_path;
+
+	/* if default shell is not configured then use cmd.exe as the default shell */
+	if (!is_default_shell_configured)
+		wcscat_s(default_shell_path, _countof(default_shell_path), cmd_exe_path);
+
+	memset(default_shell_cmd_option, 0, _countof(default_shell_cmd_option));
+	if (!default_shell_cmd_option[0]) {
+		if (wcsstr(default_shell_path, L"cmd.exe") || wcsstr(default_shell_path, L"powershell.exe"))
+			wcscat_s(default_shell_cmd_option, _countof(default_shell_cmd_option), L" /c ");
+		else if (wcsstr(default_shell_path, L"bash.exe"))
+			wcscat_s(default_shell_cmd_option, _countof(default_shell_cmd_option), L" -c ");
+	}
+
+	if (tmp)
+		free(tmp);
+
+	return default_shell_path;
 }
 
 int 
@@ -1280,10 +1334,24 @@ start_with_pty(wchar_t *command)
 	GOTO_CLEANUP_ON_FALSE(SetHandleInformation(pipe_in, HANDLE_FLAG_INHERIT, 0));
 	
 	cmd[0] = L'\0';
-	GOTO_CLEANUP_ON_ERR(wcscat_s(cmd, MAX_CMD_LEN, w32_cmd_path()));	
+	GOTO_CLEANUP_ON_ERR(wcscat_s(cmd, MAX_CMD_LEN, get_default_shell_path()));
 	if (command) {
-		GOTO_CLEANUP_ON_ERR(wcscat_s(cmd, MAX_CMD_LEN, L" /c "));		
+		if(default_shell_cmd_option[0])
+			GOTO_CLEANUP_ON_ERR(wcscat_s(cmd, MAX_CMD_LEN, default_shell_cmd_option));
+
 		GOTO_CLEANUP_ON_ERR(wcscat_s(cmd, MAX_CMD_LEN, command));
+	} else {
+		/* Launch the default shell through cmd.exe.
+		 * If we don't launch default shell through cmd.exe then the powershell colors are rendered badly to the ssh client.
+		 */
+		if (is_default_shell_configured) {
+			wchar_t tmp_cmd[PATH_MAX + 1] = {0,};
+			wcscat_s(tmp_cmd, _countof(tmp_cmd), cmd);
+			cmd[0] = L'\0';
+			GOTO_CLEANUP_ON_ERR(wcscat_s(cmd, MAX_CMD_LEN, cmd_exe_path));
+			GOTO_CLEANUP_ON_ERR(wcscat_s(cmd, MAX_CMD_LEN, L" /c "));
+			GOTO_CLEANUP_ON_ERR(wcscat_s(cmd, MAX_CMD_LEN, tmp_cmd));
+		}
 	}
 
 	SetConsoleCtrlHandler(NULL, FALSE);
@@ -1454,9 +1522,11 @@ start_withno_pty(wchar_t *command)
 	/* if above failed with FILE_NOT_FOUND, try running the provided command under cmd*/
 	if (run_under_cmd) {
 		cmd[0] = L'\0';
-		GOTO_CLEANUP_ON_ERR(wcscat_s(cmd, MAX_CMD_LEN, w32_cmd_path()));
+		GOTO_CLEANUP_ON_ERR(wcscat_s(cmd, MAX_CMD_LEN, get_default_shell_path()));
 		if (command) {
-			GOTO_CLEANUP_ON_ERR(wcscat_s(cmd, MAX_CMD_LEN, L" /c "));
+			if (default_shell_cmd_option[0])
+				GOTO_CLEANUP_ON_ERR(wcscat_s(cmd, MAX_CMD_LEN, default_shell_cmd_option));
+
 			GOTO_CLEANUP_ON_ERR(wcscat_s(cmd, MAX_CMD_LEN, command));
 		}
 	

regress/pesterTests/SSH.Tests.ps1

@@ -67,7 +67,19 @@ Describe "E2E scenarios for ssh client" -Tags "CI" {
                 Options = '-i $identifyFile -l $($server.localAdminUserName)'
             }
         )#>
-        
+        $defaultRegistryPath = "HKLM:\Software\OpenSSH"
+        $registryKeyName = "DefaultShell"
+
+        function ConfigureDefaultShell {
+            param([string]$default_shell_path)
+            
+            if (!(Test-Path $defaultRegistryPath)) {
+                New-Item -Path $defaultRegistryPath -Force | Out-Null
+                New-ItemProperty -Path $defaultRegistryPath -Name $registryKeyName -Value $default_shell_path -PropertyType String -Force
+            } else {
+                New-ItemProperty -Path $defaultRegistryPath -Name $registryKeyName -Value $default_shell_path -PropertyType String -Force
+            }
+        }
     }
 
     BeforeEach {
@@ -98,7 +110,7 @@ Describe "E2E scenarios for ssh client" -Tags "CI" {
         }
 
     }
-
+    
     Context "$tC - exit code (exit-status.sh)" {
         BeforeAll {$tI=1}
         AfterAll{$tC++}
@@ -131,8 +143,36 @@ Describe "E2E scenarios for ssh client" -Tags "CI" {
             0 | ssh -p $port $ssouser@$server pause
             $true | Should Be $true
         }#>
-    }
+    }    
+    
+    Context "$tC - configure default shell Scenarios" {
+        BeforeAll {$tI=1}
+        AfterAll{$tC++}
+        AfterEach {
+            Remove-ItemProperty -Name $registryKeyName -Path $defaultRegistryPath -ErrorAction SilentlyContinue
+        }
 
+        It "$tC.$tI - default shell as powershell" {
+            $shell_path = (Get-Command powershell.exe -ErrorAction SilentlyContinue).path
+            if($shell_path -ne $null) {
+                ConfigureDefaultShell -default_shell_path $shell_path
+
+                $o = ssh test_target Write-Output 1234
+                $o | Should Be "1234"
+            }
+        }
+
+        It "$tC.$tI - default shell as cmd" {
+            $shell_path = (Get-Command cmd.exe -ErrorAction SilentlyContinue).path
+            if($shell_path -ne $null) {
+                ConfigureDefaultShell -default_shell_path $shell_path
+
+                $o = ssh test_target where cmd
+                $o | Should Contain "cmd"
+            }
+        }
+    }
+    
     Context "$tC - cmdline parameters" {
         
         BeforeAll {$tI=1}