If we're printing password prompts to /dev/tty rather than standard

error, we should also read the corresponding password inputs from
/dev/tty. That way, redirection of Plink's standard input will play
nicely with SSH sessions that need interactive login.

(This is what we get for disdaining getpass(3) and going it alone, of
course. But we had no choice, due to the extra output part way through
keyboard-interactive.)

[originally from svn r9262]

unix/uxcons.c

@@ -7,8 +7,10 @@
 #include <stdlib.h>
 #include <stdarg.h>
 #include <assert.h>
+
 #include <termios.h>
 #include <unistd.h>
+#include <fcntl.h>
 
 #include "putty.h"
 #include "storage.h"
@@ -326,31 +328,45 @@ void logevent(void *frontend, const char *string)
 }
 
 /*
- * Special function to print text to the console for password
- * prompts and the like. Uses /dev/tty or stderr, in that order of
- * preference; also sanitises escape sequences out of the text, on
+ * Special functions to read and print to the console for password
+ * prompts and the like. Uses /dev/tty or stdin/stderr, in that order
+ * of preference; also sanitises escape sequences out of the text, on
  * the basis that it might have been sent by a hostile SSH server
  * doing malicious keyboard-interactive.
  */
-static void console_prompt_text(FILE **confp, const char *data, int len)
+static void console_open(FILE **outfp, int *infd)
+{
+    int fd;
+
+    if ((fd = open("/dev/tty", O_RDWR)) >= 0) {
+        *infd = fd;
+        *outfp = fdopen(*infd, "w");
+    } else {
+        *infd = 0;
+        *outfp = stderr;
+    }
+}
+static void console_close(FILE *outfp, int infd)
+{
+    if (outfp != stderr)
+        fclose(outfp);             /* will automatically close infd too */
+}
+
+static void console_prompt_text(FILE *outfp, const char *data, int len)
 {
     int i;
 
-    if (!*confp) {
-	if ((*confp = fopen("/dev/tty", "w")) == NULL)
-	    *confp = stderr;
-    }
-
     for (i = 0; i < len; i++)
 	if ((data[i] & 0x60) || (data[i] == '\n'))
-	    fputc(data[i], *confp);
-    fflush(*confp);
+	    fputc(data[i], outfp);
+    fflush(outfp);
 }
 
 int console_get_userpass_input(prompts_t *p, unsigned char *in, int inlen)
 {
     size_t curr_prompt;
-    FILE *confp = NULL;
+    FILE *outfp = NULL;
+    int infd;
 
     /*
      * Zero all the results, in case we abort half-way through.
@@ -364,22 +380,24 @@ int console_get_userpass_input(prompts_t *p, unsigned char *in, int inlen)
     if (p->n_prompts && console_batch_mode)
 	return 0;
 
+    console_open(&outfp, &infd);
+
     /*
      * Preamble.
      */
     /* We only print the `name' caption if we have to... */
     if (p->name_reqd && p->name) {
 	size_t l = strlen(p->name);
-	console_prompt_text(&confp, p->name, l);
+	console_prompt_text(outfp, p->name, l);
 	if (p->name[l-1] != '\n')
-	    console_prompt_text(&confp, "\n", 1);
+	    console_prompt_text(outfp, "\n", 1);
     }
     /* ...but we always print any `instruction'. */
     if (p->instruction) {
 	size_t l = strlen(p->instruction);
-	console_prompt_text(&confp, p->instruction, l);
+	console_prompt_text(outfp, p->instruction, l);
 	if (p->instruction[l-1] != '\n')
-	    console_prompt_text(&confp, "\n", 1);
+	    console_prompt_text(outfp, "\n", 1);
     }
 
     for (curr_prompt = 0; curr_prompt < p->n_prompts; curr_prompt++) {
@@ -388,32 +406,31 @@ int console_get_userpass_input(prompts_t *p, unsigned char *in, int inlen)
 	int i;
 	prompt_t *pr = p->prompts[curr_prompt];
 
-	tcgetattr(0, &oldmode);
+	tcgetattr(infd, &oldmode);
 	newmode = oldmode;
 	newmode.c_lflag |= ISIG | ICANON;
 	if (!pr->echo)
 	    newmode.c_lflag &= ~ECHO;
 	else
 	    newmode.c_lflag |= ECHO;
-	tcsetattr(0, TCSANOW, &newmode);
+	tcsetattr(infd, TCSANOW, &newmode);
 
-	console_prompt_text(&confp, pr->prompt, strlen(pr->prompt));
+	console_prompt_text(outfp, pr->prompt, strlen(pr->prompt));
 
-	i = read(0, pr->result, pr->result_len - 1);
+	i = read(infd, pr->result, pr->result_len - 1);
 
-	tcsetattr(0, TCSANOW, &oldmode);
+	tcsetattr(infd, TCSANOW, &oldmode);
 
 	if (i > 0 && pr->result[i-1] == '\n')
 	    i--;
 	pr->result[i] = '\0';
 
 	if (!pr->echo)
-	    console_prompt_text(&confp, "\n", 1);
+	    console_prompt_text(outfp, "\n", 1);
 
     }
 
-    if (confp && confp != stderr)
-	fclose(confp);
+    console_close(outfp, infd);
 
     return 1; /* success */
 }