From: Todd C. Miller <Todd.Miller@sudo.ws>
Date: Tue, 27 Aug 2019 01:30:11 +0000 (-0600)
Subject: Use the SUDO_CONV_PREFER_TTY flag during authentication.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=972670bfca64423488928bc7e482645d9c440080;p=sudo

Use the SUDO_CONV_PREFER_TTY flag during authentication.
This prevents the password and PAM prompts from being redirected.
Bug #895
---

diff --git a/plugins/sudoers/auth/aix_auth.c b/plugins/sudoers/auth/aix_auth.c
index b40382c52..bb62612e2 100644
--- a/plugins/sudoers/auth/aix_auth.c
+++ b/plugins/sudoers/auth/aix_auth.c
@@ -256,7 +256,8 @@ sudo_aix_verify(struct passwd *pw, char *prompt, sudo_auth *auth, struct sudo_co
     if (result != 0) {
 	/* Display error message, if any. */
 	if (sudo_aix_valid_message(message))
-	    sudo_printf(SUDO_CONV_ERROR_MSG, "%s", message);
+	    sudo_printf(SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY,
+		"%s", message);
 	ret = pass ? AUTH_FAILURE : AUTH_INTR;
     }
     free(message);
@@ -266,8 +267,9 @@ sudo_aix_verify(struct passwd *pw, char *prompt, sudo_auth *auth, struct sudo_co
     if (ret == AUTH_SUCCESS) {
 	result = passwdexpired(pw->pw_name, &message);
 	if (message != NULL && message[0] != '\0') {
-	    sudo_printf(result ? SUDO_CONV_ERROR_MSG : SUDO_CONV_INFO_MSG,
-		"%s", message);
+	    int msg_type = SUDO_CONV_PREFER_TTY;
+	    msg_type |= result ? SUDO_CONV_ERROR_MSG : SUDO_CONV_INFO_MSG,
+	    sudo_printf(msg_type, "%s", message);
 	    free(message);
 	    message = NULL;
 	}
diff --git a/plugins/sudoers/auth/dce.c b/plugins/sudoers/auth/dce.c
index 2f88b4b1c..27bd059fc 100644
--- a/plugins/sudoers/auth/dce.c
+++ b/plugins/sudoers/auth/dce.c
@@ -103,7 +103,7 @@ sudo_dce_verify(struct passwd *pw, char *plain_pw, sudo_auth *auth, struct sudo_
 	     * sure that we didn't get spoofed by another DCE server.
 	     */
 	    if (!sec_login_certify_identity(login_context, &status)) {
-		sudo_printf(SUDO_CONV_ERROR_MSG,
+		sudo_printf(SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY,
 		    "Whoa! Bogus authentication server!\n");
 		(void) check_dce_status(status,"sec_login_certify_identity(1):");
 		debug_return_int(AUTH_FAILURE);
@@ -125,13 +125,13 @@ sudo_dce_verify(struct passwd *pw, char *plain_pw, sudo_auth *auth, struct sudo_
 	     * DCE client and DCE security server...
 	     */
 	    if (auth_src != sec_login_auth_src_network) {
-		    sudo_printf(SUDO_CONV_ERROR_MSG,
+		    sudo_printf(SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY,
 			"You have no network credentials.\n");
 		    debug_return_int(AUTH_FAILURE);
 	    }
 	    /* Check if the password has aged and is thus no good */
 	    if (reset_passwd) {
-		    sudo_printf(SUDO_CONV_ERROR_MSG,
+		    sudo_printf(SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY,
 			"Your DCE password needs resetting.\n");
 		    debug_return_int(AUTH_FAILURE);
 	    }
@@ -191,7 +191,8 @@ check_dce_status(error_status_t input_status, char *comment)
     if (input_status == rpc_s_ok)
 	debug_return_int(0);
     dce_error_inq_text(input_status, error_string, &error_stat);
-    sudo_printf(SUDO_CONV_ERROR_MSG, "%s %s\n", comment, error_string);
+    sudo_printf(SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY,
+	"%s %s\n", comment, error_string);
     debug_return_int(1);
 }
 
diff --git a/plugins/sudoers/auth/fwtk.c b/plugins/sudoers/auth/fwtk.c
index 2291ff921..c1784b3e3 100644
--- a/plugins/sudoers/auth/fwtk.c
+++ b/plugins/sudoers/auth/fwtk.c
@@ -109,7 +109,7 @@ restart:
     } else if (strncmp(resp, "password", 8) == 0) {
 	pass = auth_getpass(prompt, SUDO_CONV_PROMPT_ECHO_OFF, callback);
     } else if (strncmp(resp, "display ", 8) == 0) {
-	sudo_printf(SUDO_CONV_INFO_MSG, "%s\n", &resp[8]);
+	sudo_printf(SUDO_CONV_INFO_MSG|SUDO_CONV_PREFER_TTY, "%s\n", &resp[8]);
 	strlcpy(buf, "response dummy", sizeof(buf));
 	goto restart;
     } else {
diff --git a/plugins/sudoers/auth/pam.c b/plugins/sudoers/auth/pam.c
index 03bdfeaeb..db342b0f6 100644
--- a/plugins/sudoers/auth/pam.c
+++ b/plugins/sudoers/auth/pam.c
@@ -696,11 +696,13 @@ converse(int num_msg, PAM_CONST struct pam_message **msg,
 		break;
 	    case PAM_TEXT_INFO:
 		if (pm->msg != NULL && !is_filtered(pm->msg))
-		    sudo_printf(SUDO_CONV_INFO_MSG, "%s\n", pm->msg);
+		    sudo_printf(SUDO_CONV_INFO_MSG|SUDO_CONV_PREFER_TTY,
+			"%s\n", pm->msg);
 		break;
 	    case PAM_ERROR_MSG:
 		if (pm->msg != NULL)
-		    sudo_printf(SUDO_CONV_ERROR_MSG, "%s\n", pm->msg);
+		    sudo_printf(SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY,
+			"%s\n", pm->msg);
 		break;
 	    default:
 		sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
diff --git a/plugins/sudoers/auth/securid5.c b/plugins/sudoers/auth/securid5.c
index 64fd978bf..9f1ab3b16 100644
--- a/plugins/sudoers/auth/securid5.c
+++ b/plugins/sudoers/auth/securid5.c
@@ -206,9 +206,9 @@ then enter the new token code.\n", \
 		 */
 		/* XXX - Is setting up a new PIN within sudo's scope? */
 		SD_Pin(*sd, "");
-		sudo_printf(SUDO_CONV_ERROR_MSG, 
+		sudo_printf(SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY, 
 		    "Your SecurID access has not yet been set up.\n");
-		sudo_printf(SUDO_CONV_ERROR_MSG, 
+		sudo_printf(SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY, 
 		    "Please set up a PIN before you try to authenticate.\n");
 		ret = AUTH_FATAL;
 		break;
diff --git a/plugins/sudoers/auth/sudo_auth.c b/plugins/sudoers/auth/sudo_auth.c
index 0d8d99341..bae41a20d 100644
--- a/plugins/sudoers/auth/sudo_auth.c
+++ b/plugins/sudoers/auth/sudo_auth.c
@@ -227,7 +227,7 @@ pass_warn(void)
     if (def_insults)
 	warning = INSULT;
 #endif
-    sudo_printf(SUDO_CONV_ERROR_MSG, "%s\n", warning);
+    sudo_printf(SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY, "%s\n", warning);
 
     debug_return;
 }
diff --git a/plugins/sudoers/check.c b/plugins/sudoers/check.c
index 74c8f2f43..db8e05161 100644
--- a/plugins/sudoers/check.c
+++ b/plugins/sudoers/check.c
@@ -259,13 +259,13 @@ display_lecture(int status)
     if (def_lecture_file && (fp = fopen(def_lecture_file, "r")) != NULL) {
 	while ((nread = fread(buf, sizeof(char), sizeof(buf) - 1, fp)) != 0) {
 	    buf[nread] = '\0';
-	    msg.msg_type = SUDO_CONV_ERROR_MSG;
+	    msg.msg_type = SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY;
 	    msg.msg = buf;
 	    sudo_conv(1, &msg, &repl, NULL);
 	}
 	fclose(fp);
     } else {
-	msg.msg_type = SUDO_CONV_ERROR_MSG;
+	msg.msg_type = SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY;
 	msg.msg = _("\n"
 	    "We trust you have received the usual lecture from the local System\n"
 	    "Administrator. It usually boils down to these three things:\n\n"
diff --git a/plugins/sudoers/sudo_printf.c b/plugins/sudoers/sudo_printf.c
index 9e6a3d9b1..fd21e4b9e 100644
--- a/plugins/sudoers/sudo_printf.c
+++ b/plugins/sudoers/sudo_printf.c
@@ -32,22 +32,28 @@
 #include "sudo_compat.h"
 #include "sudo_plugin.h"
 #include "sudo_debug.h"
+#include "pathnames.h"
 
 static int
 sudo_printf_int(int msg_type, const char *fmt, ...)
 {
+    FILE *fp = stdout;
+    FILE *ttyfp = NULL;
     va_list ap;
     int len;
 
-    switch (msg_type) {
-    case SUDO_CONV_INFO_MSG:
-	va_start(ap, fmt);
-	len = vfprintf(stdout, fmt, ap);
-	va_end(ap);
-	break;
+    if (ISSET(msg_type, SUDO_CONV_PREFER_TTY)) {
+	/* Try writing to /dev/tty first. */
+	ttyfp = fopen(_PATH_TTY, "w");
+    }
+
+    switch (msg_type & 0xff) {
     case SUDO_CONV_ERROR_MSG:
+	fp = stderr;
+	/* FALLTHROUGH */
+    case SUDO_CONV_INFO_MSG:
 	va_start(ap, fmt);
-	len = vfprintf(stderr, fmt, ap);
+	len = vfprintf(ttyfp ? ttyfp : fp, fmt, ap);
 	va_end(ap);
 	break;
     default:
@@ -56,6 +62,9 @@ sudo_printf_int(int msg_type, const char *fmt, ...)
 	break;
     }
 
+    if (ttyfp != NULL)
+	fclose(ttyfp);
+
     return len;
 }
 
diff --git a/src/conversation.c b/src/conversation.c
index d78e1b89f..1e20215d0 100644
--- a/src/conversation.c
+++ b/src/conversation.c
@@ -140,21 +140,26 @@ sudo_conversation_1_7(int num_msgs, const struct sudo_conv_message msgs[],
 int
 sudo_conversation_printf(int msg_type, const char *fmt, ...)
 {
+    FILE *fp = stdout;
+    FILE *ttyfp = NULL;
     va_list ap;
     int len;
     const int conv_debug_instance = sudo_debug_get_active_instance();
 
     sudo_debug_set_active_instance(sudo_debug_instance);
 
-    switch (msg_type) {
-    case SUDO_CONV_INFO_MSG:
-	va_start(ap, fmt);
-	len = vfprintf(stdout, fmt, ap);
-	va_end(ap);
-	break;
+    if (ISSET(msg_type, SUDO_CONV_PREFER_TTY)) {
+	/* Try writing to /dev/tty first. */
+	ttyfp = fopen(_PATH_TTY, "w");
+    }
+
+    switch (msg_type & 0xff) {
     case SUDO_CONV_ERROR_MSG:
+	fp = stderr;
+	/* FALLTHROUGH */
+    case SUDO_CONV_INFO_MSG:
 	va_start(ap, fmt);
-	len = vfprintf(stderr, fmt, ap);
+	len = vfprintf(ttyfp ? ttyfp : fp, fmt, ap);
 	va_end(ap);
 	break;
     default:
@@ -163,6 +168,9 @@ sudo_conversation_printf(int msg_type, const char *fmt, ...)
 	break;
     }
 
+    if (ttyfp != NULL)
+	fclose(ttyfp);
+
     sudo_debug_set_active_instance(conv_debug_instance);
     return len;
 }