1. openvpn
  2. Commit 480e4cc14ff34fac72406ab1dd66290a91cc09f0
Browse code

Fix console prompts with redirected log

When openvpn needs to prompt user for a password
(for example, to set management interface password),
the prompt is written to standard error device.

When log is redirected to a file, that prompt is written
to that file and not to the "original" stderr. Moreover, on recent
Insider build (21390.2025) openvpn exits with fatal error

get_console_input_win32(): unexpected error: No such device or address
(errno=6)

while attempting to write that prompt.

When redirecting stdout/stderr, we use _dup2() to associate stderr
descriptor with a log file. This call closes file associated
with stderr descriptor, which might explain why it has stopped
working (original stderr is closed and WriteFile() fails) and on
older versions it appears to work "by accident" - not failing
but use redirected stderr instead of original one.

Fix by creating new file descriptor with _dup() for stderr
before redirect and use this descriptor for writing prompts.

While on it, make code a bit more C99-ish by moving variables
declaration from the beginning of the scope to the actual
initialisation.

Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20210625010405.224-1-lstipakov@gmail.com>
URL: https://www.mail-archive.com/search?l=mid&q=20210625010405.224-1-lstipakov@gmail.com
Signed-off-by: Gert Doering <gert@greenie.muc.de>

Lev Stipakov authored on 2021/06/25 10:04:05
Showing 3 changed files
src/openvpn/console_builtin.c
History View file @ 480e4cc
... ... 
@@ -62,23 +62,17 @@
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 static bool
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 get_console_input_win32(const char *prompt, const bool echo, char *input, const int capacity)
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 {
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-    HANDLE in = INVALID_HANDLE_VALUE;
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-    HANDLE err = INVALID_HANDLE_VALUE;
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-    DWORD len = 0;
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-
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     ASSERT(prompt);
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     ASSERT(input);
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     ASSERT(capacity > 0);
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     input[0] = '\0';
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-    in = GetStdHandle(STD_INPUT_HANDLE);
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-    err = get_orig_stderr();
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-
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-    if (in == INVALID_HANDLE_VALUE
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-        || err == INVALID_HANDLE_VALUE
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+    HANDLE in = GetStdHandle(STD_INPUT_HANDLE);
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+    int orig_stderr = get_orig_stderr(); // guaranteed to be always valid
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+    if ((in == INVALID_HANDLE_VALUE)
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         || win32_service_interrupt(&win32_signal)
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-        || !WriteFile(err, prompt, strlen(prompt), &len, NULL))
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+        || (_write(orig_stderr, prompt, strlen(prompt)) == -1))
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     {
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         msg(M_WARN|M_ERRNO, "get_console_input_win32(): unexpected error");
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         return false;
... ... 
@@ -106,6 +100,8 @@ get_console_input_win32(const char *prompt, const bool echo, char *input, const
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         }
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     }
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+    DWORD len = 0;
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+
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     if (is_console)
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     {
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         winput = malloc(capacity * sizeof(WCHAR));
... ... 
@@ -128,7 +124,7 @@ get_console_input_win32(const char *prompt, const bool echo, char *input, const
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     if (!echo)
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     {
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-        WriteFile(err, "\r\n", 2, &len, NULL);
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+        _write(orig_stderr, "\r\n", 2);
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     }
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     if (is_console)
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     {
src/openvpn/error.c
History View file @ 480e4cc
... ... 
@@ -491,22 +491,12 @@ close_syslog(void)
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 }
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 #ifdef _WIN32
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+static int orig_stderr;
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-static HANDLE orig_stderr;
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-
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-HANDLE
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-get_orig_stderr(void)
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+int get_orig_stderr()
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 {
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-    if (orig_stderr)
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-    {
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-        return orig_stderr;
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-    }
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-    else
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-    {
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-        return GetStdHandle(STD_ERROR_HANDLE);
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-    }
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+    return orig_stderr ? orig_stderr : _fileno(stderr);
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 }
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-
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 #endif
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 void
... ... 
@@ -550,16 +540,12 @@ redirect_stdout_stderr(const char *file, bool append)
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         }
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         /* save original stderr for password prompts */
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-        orig_stderr = GetStdHandle(STD_ERROR_HANDLE);
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-
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-#if 0 /* seems not be necessary with stdout/stderr redirection below*/
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-        /* set up for redirection */
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-        if (!SetStdHandle(STD_OUTPUT_HANDLE, log_handle)
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-            || !SetStdHandle(STD_ERROR_HANDLE, log_handle))
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+        orig_stderr = _dup(_fileno(stderr));
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+        if (orig_stderr == -1)
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         {
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-            msg(M_ERR, "Error: cannot redirect stdout/stderr to --log file: %s", file);
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+            msg(M_WARN | M_ERRNO, "Warning: cannot duplicate stderr, password prompts will appear in log file instead of console.");
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+            orig_stderr = _fileno(stderr);
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         }
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-#endif
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         /* direct stdout/stderr to point to log_handle */
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         log_fd = _open_osfhandle((intptr_t)log_handle, _O_TEXT);
src/openvpn/error.h
History View file @ 480e4cc
... ... 
@@ -256,8 +256,8 @@ void close_syslog(void);
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 void redirect_stdout_stderr(const char *file, bool append);
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 #ifdef _WIN32
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-/* get original stderr handle, even if redirected by --log/--log-append */
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-HANDLE get_orig_stderr(void);
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+/* get original stderr fd, even if redirected by --log/--log-append */
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+int get_orig_stderr(void);
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 #endif
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