When a stdio stream is opened in update mode (e.g., "w+"),
the C standard forbids switching between reading or writing
without an intervening positioning function. Many
implementations are lenient about this, but Solaris libc
will flush the recently-read contents to the output buffer.
In this instance, that meant writing the non-echoed password
that the user just typed to the terminal.
Fix it by inserting a no-op fseek between the read and
write.
The opposite direction (writing followed by reading) is also
disallowed, but our intervening fflush is an acceptable
positioning function for that alternative.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
