lib/agetpass.[ch]: add function ro read from pipe

Add alternative function to agetpass for reading password
from stdin or pipe.

Signed-off-by: Tomas Halman <tomas@halman.net>

lib/agetpass.c

@@ -33,6 +33,7 @@
  * SYNOPSIS
  *	[[gnu::malloc(erase_pass)]]
  *	char *agetpass(const char *prompt);
+ *	char *agetpass_stdin();
  *
  *	void erase_pass(char *pass);
  *
@@ -65,6 +66,10 @@
  *	erased by calling erase_pass(), to avoid possibly leaking the
  *	password.
  *
+ *   agetpass_stdin()
+ *	This function is the same as previous one (agetpass). Just the
+ *	password is read from stdin and terminal is not required.
+ *
  *   erase_pass()
  *	This function first clears the password, by calling
  *	explicit_bzero(3) (or an equivalent call), and then frees the
@@ -93,8 +98,8 @@
  */
 
 
-char *
-agetpass(const char *prompt)
+static char *
+agetpass_internal(const char *prompt, int flags)
 {
 	char    *pass;
 	size_t  len;
@@ -111,7 +116,7 @@ agetpass(const char *prompt)
 	if (pass == NULL)
 		return NULL;
 
-	if (readpassphrase(prompt, pass, PASS_MAX + 2, RPP_REQUIRE_TTY) == NULL)
+	if (readpassphrase(prompt, pass, PASS_MAX + 2, flags) == NULL)
 		goto fail;
 
 	len = strlen(pass);
@@ -127,6 +132,17 @@ fail:
 	return NULL;
 }
 
+char *
+agetpass(const char *prompt)
+{
+	return agetpass_internal(prompt, RPP_REQUIRE_TTY);
+}
+
+char *
+agetpass_stdin()
+{
+	return agetpass_internal(NULL, RPP_STDIN);
+}
 
 void
 erase_pass(char *pass)

lib/agetpass.h

@@ -17,6 +17,7 @@
 void erase_pass(char *pass);
 ATTR_MALLOC(erase_pass)
 char *agetpass(const char *prompt);
+char *agetpass_stdin();
 
 
 #endif  // include guard