293 lines
8.9 KiB
Diff
293 lines
8.9 KiB
Diff
From 8ca4c61dfa5832e02a86e555d26ce4c31bac9a2a Mon Sep 17 00:00:00 2001
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From: "Richard W.M. Jones" <rjones@redhat.com>
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Date: Fri, 15 Apr 2022 12:08:37 +0100
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Subject: [PATCH] ssh: Allow the remote file to be created
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This adds new parameters, create=(true|false), create-size=SIZE and
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create-mode=MODE to create and truncate the remote file.
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Reviewed-by: Laszlo Ersek <lersek@redhat.com>
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(cherry picked from commit 0793f30b1071753532362b2ebf9cb8156a88c3c3)
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---
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plugins/ssh/nbdkit-ssh-plugin.pod | 34 ++++++++-
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plugins/ssh/ssh.c | 112 +++++++++++++++++++++++++++---
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tests/test-ssh.sh | 13 +++-
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3 files changed, 146 insertions(+), 13 deletions(-)
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diff --git a/plugins/ssh/nbdkit-ssh-plugin.pod b/plugins/ssh/nbdkit-ssh-plugin.pod
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index 3f401c15..2bc2c4a7 100644
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--- a/plugins/ssh/nbdkit-ssh-plugin.pod
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+++ b/plugins/ssh/nbdkit-ssh-plugin.pod
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@@ -5,8 +5,10 @@ nbdkit-ssh-plugin - access disk images over the SSH protocol
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=head1 SYNOPSIS
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nbdkit ssh host=HOST [path=]PATH
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- [compression=true] [config=CONFIG_FILE] [identity=FILENAME]
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- [known-hosts=FILENAME] [password=PASSWORD|-|+FILENAME]
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+ [compression=true] [config=CONFIG_FILE]
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+ [create=true] [create-mode=MODE] [create-size=SIZE]
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+ [identity=FILENAME] [known-hosts=FILENAME]
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+ [password=PASSWORD|-|+FILENAME]
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[port=PORT] [timeout=SECS] [user=USER]
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[verify-remote-host=false]
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@@ -62,6 +64,34 @@ The C<config> parameter is optional. If it is I<not> specified at all
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then F<~/.ssh/config> and F</etc/ssh/ssh_config> are both read.
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Missing or unreadable files are ignored.
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+=item B<create=true>
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+
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+(nbdkit E<ge> 1.32)
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+
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+If set, the remote file will be created. The remote file is created
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+on the first NBD connection to nbdkit, not when nbdkit starts up. If
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+the file already exists, it will be replaced and any existing content
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+lost.
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+
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+If using this option, you must use C<create-size>. C<create-mode> can
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+be used to control the permissions of the new file.
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+
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+=item B<create-mode=>MODE
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+
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+(nbdkit E<ge> 1.32)
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+
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+If using C<create=true> specify the default permissions of the new
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+remote file. You can use octal modes like C<create-mode=0777> or
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+C<create-mode=0644>. The default is C<0600>, ie. only readable and
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+writable by the remote user.
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+
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+=item B<create-size=>SIZE
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+
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+(nbdkit E<ge> 1.32)
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+
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+If using C<create=true>, specify the virtual size of the new disk.
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+C<SIZE> can use modifiers like C<100M> etc.
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+
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=item B<host=>HOST
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Specify the name or IP address of the remote host.
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diff --git a/plugins/ssh/ssh.c b/plugins/ssh/ssh.c
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index 77cfcf6c..ac9cc230 100644
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--- a/plugins/ssh/ssh.c
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+++ b/plugins/ssh/ssh.c
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@@ -44,12 +44,15 @@
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#include <fcntl.h>
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#include <sys/stat.h>
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+#include <pthread.h>
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+
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#include <libssh/libssh.h>
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#include <libssh/sftp.h>
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#include <libssh/callbacks.h>
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#include <nbdkit-plugin.h>
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+#include "cleanup.h"
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#include "const-string-vector.h"
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#include "minmax.h"
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@@ -63,6 +66,9 @@ static const char *known_hosts = NULL;
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static const_string_vector identities = empty_vector;
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static uint32_t timeout = 0;
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static bool compression = false;
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+static bool create = false;
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+static int64_t create_size = -1;
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+static unsigned create_mode = S_IRUSR | S_IWUSR /* 0600 */;
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/* config can be:
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* NULL => parse options from default file
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@@ -167,6 +173,27 @@ ssh_config (const char *key, const char *value)
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return -1;
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compression = r;
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}
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+ else if (strcmp (key, "create") == 0) {
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+ r = nbdkit_parse_bool (value);
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+ if (r == -1)
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+ return -1;
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+ create = r;
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+ }
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+ else if (strcmp (key, "create-size") == 0) {
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+ create_size = nbdkit_parse_size (value);
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+ if (create_size == -1)
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+ return -1;
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+ }
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+ else if (strcmp (key, "create-mode") == 0) {
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+ r = nbdkit_parse_unsigned (key, value, &create_mode);
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+ if (r == -1)
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+ return -1;
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+ /* OpenSSH checks this too. */
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+ if (create_mode > 0777) {
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+ nbdkit_error ("create-mode must be <= 0777");
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+ return -1;
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+ }
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+ }
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else {
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nbdkit_error ("unknown parameter '%s'", key);
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@@ -186,6 +213,13 @@ ssh_config_complete (void)
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return -1;
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}
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+ /* If create=true, create-size must be supplied. */
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+ if (create && create_size == -1) {
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+ nbdkit_error ("if using create=true, you must specify the size "
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+ "of the new remote file using create-size=SIZE");
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+ return -1;
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+ }
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+
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return 0;
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}
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@@ -200,7 +234,10 @@ ssh_config_complete (void)
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"identity=<FILENAME> Prepend private key (identity) file.\n" \
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"timeout=SECS Set SSH connection timeout.\n" \
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"verify-remote-host=false Ignore known_hosts.\n" \
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- "compression=true Enable compression."
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+ "compression=true Enable compression.\n" \
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+ "create=true Create the remote file.\n" \
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+ "create-mode=MODE Set the permissions of the remote file.\n" \
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+ "create-size=SIZE Set the size of the remote file."
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/* Since we must simulate atomic pread and pwrite using seek +
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* read/write, calls on each handle must be serialized.
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@@ -329,6 +366,65 @@ authenticate (struct ssh_handle *h)
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return -1;
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}
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+/* This function opens or creates the remote file (depending on
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+ * create=false|true). Parallel connections might call this function
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+ * at the same time, and so we must hold a lock to ensure that the
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+ * file is created at most once.
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+ */
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+static pthread_mutex_t create_lock = PTHREAD_MUTEX_INITIALIZER;
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+
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+static sftp_file
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+open_or_create_path (ssh_session session, sftp_session sftp, int readonly)
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+{
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+ ACQUIRE_LOCK_FOR_CURRENT_SCOPE (&create_lock);
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+ int access_type;
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+ int r;
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+ sftp_file file;
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+
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+ access_type = readonly ? O_RDONLY : O_RDWR;
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+ if (create) access_type |= O_CREAT | O_TRUNC;
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+
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+ file = sftp_open (sftp, path, access_type, S_IRWXU);
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+ if (!file) {
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+ nbdkit_error ("cannot %s file for %s: %s",
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+ create ? "create" : "open",
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+ readonly ? "reading" : "writing",
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+ ssh_get_error (session));
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+ return NULL;
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+ }
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+
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+ if (create) {
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+ /* There's no sftp_truncate call. However OpenSSH lets you call
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+ * SSH_FXP_SETSTAT + SSH_FILEXFER_ATTR_SIZE which invokes
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+ * truncate(2) on the server. Libssh doesn't provide a binding
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+ * for SSH_FXP_FSETSTAT so we have to pass the session + path.
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+ */
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+ struct sftp_attributes_struct attrs = {
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+ .flags = SSH_FILEXFER_ATTR_SIZE |
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+ SSH_FILEXFER_ATTR_PERMISSIONS,
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+ .size = create_size,
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+ .permissions = create_mode,
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+ };
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+
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+ r = sftp_setstat (sftp, path, &attrs);
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+ if (r != SSH_OK) {
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+ nbdkit_error ("setstat failed: %s", ssh_get_error (session));
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+
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+ /* Best-effort attempt to delete the remote file on failure. */
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+ r = sftp_unlink (sftp, path);
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+ if (r != SSH_OK)
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+ nbdkit_debug ("unlink failed: %s", ssh_get_error (session));
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+
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+ return NULL;
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+ }
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+ }
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+
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+ /* On the next connection, don't create or truncate the file. */
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+ create = false;
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+
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+ return file;
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+}
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+
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/* Create the per-connection handle. */
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static void *
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ssh_open (int readonly)
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@@ -337,7 +433,6 @@ ssh_open (int readonly)
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const int set = 1;
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size_t i;
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int r;
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- int access_type;
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h = calloc (1, sizeof *h);
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if (h == NULL) {
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@@ -471,7 +566,7 @@ ssh_open (int readonly)
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if (authenticate (h) == -1)
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goto err;
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- /* Open the SFTP connection and file. */
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+ /* Open the SFTP connection. */
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h->sftp = sftp_new (h->session);
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if (!h->sftp) {
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nbdkit_error ("failed to allocate sftp session: %s",
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@@ -484,14 +579,11 @@ ssh_open (int readonly)
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ssh_get_error (h->session));
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goto err;
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}
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- access_type = readonly ? O_RDONLY : O_RDWR;
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- h->file = sftp_open (h->sftp, path, access_type, S_IRWXU);
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- if (!h->file) {
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- nbdkit_error ("cannot open file for %s: %s",
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- readonly ? "reading" : "writing",
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- ssh_get_error (h->session));
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+
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+ /* Open or create the remote file. */
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+ h->file = open_or_create_path (h->session, h->sftp, readonly);
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+ if (!h->file)
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goto err;
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- }
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nbdkit_debug ("opened libssh handle");
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diff --git a/tests/test-ssh.sh b/tests/test-ssh.sh
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index 6c0ce410..f04b4488 100755
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--- a/tests/test-ssh.sh
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+++ b/tests/test-ssh.sh
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@@ -36,6 +36,7 @@ set -x
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requires test -f disk
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requires nbdcopy --version
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+requires stat --version
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# Check that ssh to localhost will work without any passwords or phrases.
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#
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@@ -48,7 +49,7 @@ then
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exit 77
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fi
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-files="ssh.img"
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+files="ssh.img ssh2.img"
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rm -f $files
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cleanup_fn rm -f $files
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@@ -59,3 +60,13 @@ nbdkit -v -D ssh.log=2 -U - \
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# The output should be identical.
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cmp disk ssh.img
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+
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+# Copy local file 'ssh.img' to newly created "remote" 'ssh2.img'
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+size="$(stat -c %s disk)"
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+nbdkit -v -D ssh.log=2 -U - \
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+ ssh host=localhost $PWD/ssh2.img \
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+ create=true create-size=$size \
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+ --run 'nbdcopy ssh.img "$uri"'
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+
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+# The output should be identical.
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+cmp disk ssh2.img
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--
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2.31.1
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