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[PATCHv2 5/9] add generic terminal prompt function

From
Jeff King <peff@peff.net>
Date
Dec 10, 2011, 10:41 UTC
Message-ID
<20111210104101.GE16648@sigill.intra.peff.net>
In-Reply-To
<20111210103943.GA16478@sigill.intra.peff.net>

When we need to prompt the user for input interactively, we want to access their terminal directly. We can't rely on stdio because it may be connected to pipes or files, rather than the terminal. Instead, we use "getpass()", because it abstracts the idea of prompting and reading from the terminal. However, it has some problems:

  1. It never echoes the typed characters, which makes it OK
     for passwords but annoying for other input (like usernames).
  2. Some implementations of getpass() have an extremely
     small input buffer (e.g., Solaris 8 is reported to
     support only 8 characters).
  3. Some implementations of getpass() will fall back to
     reading from stdin (e.g., glibc). We explicitly don't
     want this, because our stdin may be connected to a pipe
     speaking a particular protocol, and reading will
     disrupt the protocol flow (e.g., the remote-curl
     helper).
  4. Some implementations of getpass() turn off signals, so
     that hitting "^C" on the terminal does not break out of
     the password prompt. This can be a mild annoyance.

Instead, let's provide an abstract "git_terminal_prompt" function that addresses these concerns. This patch includes an implementation based on /dev/tty, enabled by setting HAVE_DEV_TTY. The fallback is to use getpass() as before.

Signed-off-by: Jeff King <peff@peff.net>
---
 Makefile          |    9 ++++++
 compat/terminal.c |   81 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 compat/terminal.h |    6 ++++
 3 files changed, 96 insertions(+), 0 deletions(-)
 create mode 100644 compat/terminal.c
 create mode 100644 compat/terminal.h
diff --git a/Makefile b/Makefile
index 5201bea..4ef6ba5 100644
--- a/Makefile
+++ b/Makefile
@@ -227,6 +227,9 @@ all::
 #
 # Define NO_REGEX if you have no or inferior regex support in your C library.
 #
+# Define HAVE_DEV_TTY if your system can open /dev/tty to interact with the
+# user.
+#
 # Define GETTEXT_POISON if you are debugging the choice of strings marked
 # for translation.  In a GETTEXT_POISON build, you can turn all strings marked
 # for translation into gibberish by setting the GIT_GETTEXT_POISON variable
@@ -523,6 +526,7 @@ LIB_H += compat/bswap.h
 LIB_H += compat/cygwin.h
 LIB_H += compat/mingw.h
 LIB_H += compat/obstack.h
+LIB_H += compat/terminal.h
 LIB_H += compat/win32/pthread.h
 LIB_H += compat/win32/syslog.h
 LIB_H += compat/win32/poll.h
@@ -612,6 +616,7 @@ LIB_OBJS += color.o
 LIB_OBJS += combine-diff.o
 LIB_OBJS += commit.o
 LIB_OBJS += compat/obstack.o
+LIB_OBJS += compat/terminal.o
 LIB_OBJS += config.o
 LIB_OBJS += connect.o
 LIB_OBJS += connected.o
@@ -1642,6 +1647,10 @@ ifdef HAVE_PATHS_H
 	BASIC_CFLAGS += -DHAVE_PATHS_H
 endif
 
+ifdef HAVE_DEV_TTY
+	BASIC_CFLAGS += -DHAVE_DEV_TTY
+endif
+
 ifdef DIR_HAS_BSD_GROUP_SEMANTICS
 	COMPAT_CFLAGS += -DDIR_HAS_BSD_GROUP_SEMANTICS
 endif
diff --git a/compat/terminal.c b/compat/terminal.c
new file mode 100644
index 0000000..6d16c8f
--- /dev/null
+++ b/compat/terminal.c
@@ -0,0 +1,81 @@
+#include "git-compat-util.h"
+#include "compat/terminal.h"
+#include "sigchain.h"
+#include "strbuf.h"
+
+#ifdef HAVE_DEV_TTY
+
+static int term_fd = -1;
+static struct termios old_term;
+
+static void restore_term(void)
+{
+	if (term_fd < 0)
+		return;
+
+	tcsetattr(term_fd, TCSAFLUSH, &old_term);
+	term_fd = -1;
+}
+
+static void restore_term_on_signal(int sig)
+{
+	restore_term();
+	sigchain_pop(sig);
+	raise(sig);
+}
+
+char *git_terminal_prompt(const char *prompt, int echo)
+{
+	static struct strbuf buf = STRBUF_INIT;
+	int r;
+	FILE *fh;
+
+	fh = fopen("/dev/tty", "w+");
+	if (!fh)
+		return NULL;
+
+	if (!echo) {
+		struct termios t;
+
+		if (tcgetattr(fileno(fh), &t) < 0) {
+			fclose(fh);
+			return NULL;
+		}
+
+		old_term = t;
+		term_fd = fileno(fh);
+		sigchain_push_common(restore_term_on_signal);
+
+		t.c_lflag &= ~ECHO;
+		if (tcsetattr(fileno(fh), TCSAFLUSH, &t) < 0) {
+			term_fd = -1;
+			fclose(fh);
+			return NULL;
+		}
+	}
+
+	fputs(prompt, fh);
+	fflush(fh);
+
+	r = strbuf_getline(&buf, fh, '\n');
+	if (!echo) {
+		putc('\n', fh);
+		fflush(fh);
+	}
+
+	restore_term();
+	fclose(fh);
+
+	if (r == EOF)
+		return NULL;
+	return buf.buf;
+}
+
+#else
+
+char *git_terminal_prompt(const char *prompt, int echo)
+{
+	return getpass(prompt);
+}
+
+#endif
diff --git a/compat/terminal.h b/compat/terminal.h
new file mode 100644
index 0000000..97db7cd
--- /dev/null
+++ b/compat/terminal.h
@@ -0,0 +1,6 @@
+#ifndef COMPAT_TERMINAL_H
+#define COMPAT_TERMINAL_H
+
+char *git_terminal_prompt(const char *prompt, int echo);
+
+#endif /* COMPAT_TERMINAL_H */

-- 
1.7.8.rc2.40.gaf387
Previous: Jeff KingNext: Pete Wyckoff
Message 36 of 54 in “[PATCHv3 0/13] credential helpers”
  1. Jeff KingDec 10, 2011
  2. 01/13 test-lib: add test_config_global variantJeff King, Dec 10, 2011
  3. 02/13 t5550: fix typoJeff King, Dec 10, 2011
  4. 03/13 introduce credentials APIJeff King, Dec 10, 2011
  5. Jakub NarebskiDec 10, 2011
  6. Jeff KingDec 10, 2011
  7. 04/13 credential: add function for parsing url componentsJeff King, Dec 10, 2011
  8. 05/13 http: use credential API to get passwordsJeff King, Dec 10, 2011
  9. 06/13 credential: apply helper configJeff King, Dec 10, 2011
  10. 07/13 credential: add credential.*.usernameJeff King, Dec 10, 2011
  11. 08/13 credential: make relevance of http path configurableJeff King, Dec 10, 2011
  12. Jakub NarebskiDec 10, 2011
  13. Jeff KingDec 10, 2011
  14. 09/13 docs: end-user documentation for the credential subsystemJeff King, Dec 10, 2011
  15. 10/13 credentials: add "cache" helperJeff King, Dec 10, 2011
  16. Jonathan NiederJan 10, 2012
  17. Jeff KingJan 10, 2012
  18. Jeff KingJan 10, 2012
  19. Junio C HamanoJan 10, 2012
  20. Jeff KingJan 17, 2012
  21. Junio C HamanoJan 17, 2012
  22. Jonathan NiederJan 10, 2012
  23. Jeff KingJan 10, 2012
  24. Jonathan NiederJan 11, 2012
  25. Jeff KingJan 12, 2012
  26. 11/13 strbuf: add strbuf_add*_urlencodeJeff King, Dec 10, 2011
  27. Jakub NarebskiDec 10, 2011
  28. Jeff KingDec 10, 2011
  29. 12/13 credentials: add "store" helperJeff King, Dec 10, 2011
  30. 13/13 t: add test harness for external credential helpersJeff King, Dec 10, 2011
  31. 0/9 echo characters in username promptJeff King, Dec 10, 2011
  32. 1/9 imap-send: avoid buffer overflowJeff King, Dec 10, 2011
  33. 2/9 imap-send: don't check return value of git_getpassJeff King, Dec 10, 2011
  34. 3/9 move git_getpass to its own source fileJeff King, Dec 10, 2011
  35. 4/9 refactor git_getpass into generic prompt functionJeff King, Dec 10, 2011
  36. 5/9 add generic terminal prompt functionJeff King, Dec 10, 2011
  37. Pete WyckoffDec 15, 2011
  38. Jeff KingDec 15, 2011
  39. Pete WyckoffDec 15, 2011
  40. 6/9 prompt: use git_terminal_promptJeff King, Dec 10, 2011
  41. 7/9 credential: use git_prompt instead of git_getpassJeff King, Dec 10, 2011
  42. 8/9 Makefile: linux has /dev/ttyJeff King, Dec 10, 2011
  43. 9/9 Makefile: OS X has /dev/ttyJeff King, Dec 10, 2011
  44. 1/2 Makefile: Windows lacks /dev/ttyJohannes Sixt, Dec 12, 2011
  45. 2/2 Makefile: optionally exclude code that needs Unix socketsJohannes Sixt, Dec 12, 2011
  46. Jeff KingDec 12, 2011
  47. Junio C HamanoDec 12, 2011
  48. Junio C HamanoDec 13, 2011
  49. Jeff KingDec 13, 2011
  50. Johannes SixtDec 13, 2011
  51. Junio C HamanoDec 14, 2011
  52. Jeff KingDec 12, 2011
  53. Johannes SixtDec 12, 2011
  54. 1/1 contrib: add credential helper for OS X KeychainJeff King, Dec 10, 2011

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