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adds fallback to posix-rename@openssh.com extension if possible and c… (#827)

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* adds fallback to posix-rename@openssh.com extension if possible and communicates possible problems with flags to the developer

* Adds '{}' around if/else statements

* adds basic tests for file rename

* fix comments

* fixes indentation

* adds helper methods to make existing sftp rename tests more concise

* adds basic test for atomic rewrite

* adds possibility to request a specific client version (e.g. for testing purposes)

* adds testcases for SFTP rename flags fallback behaviour

* refactoring to make SFTPEngine.init(int requestedVersion) protected

---------

Co-authored-by: Florian Klemenz <florian.klemenz@fau.de>
Co-authored-by: Jeroen van Erp <jeroen@hierynomus.com>
This commit is contained in:
Florian Klemenz
2023-10-23 10:46:14 +02:00
committed by GitHub
parent 542bb35bda
commit 4774721b49
2 changed files with 321 additions and 9 deletions
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93
src/main/java/net/schmizz/sshj/sftp/SFTPEngine.java
View File

@@ -81,7 +81,23 @@ public class SFTPEngine
public SFTPEngine init()
throws IOException {
transmit(new SFTPPacket<Request>(PacketType.INIT).putUInt32(MAX_SUPPORTED_VERSION));
return init(MAX_SUPPORTED_VERSION);
}
/**
* Introduced for internal use by testcases.
* @param requestedVersion
* @throws IOException
*/
protected SFTPEngine init(int requestedVersion)
throws IOException {
if (requestedVersion > MAX_SUPPORTED_VERSION)
throw new SFTPException("You requested an unsupported protocol version: " + requestedVersion + " (requested) > " + MAX_SUPPORTED_VERSION + " (supported)");
if (requestedVersion < MAX_SUPPORTED_VERSION)
log.debug("Client version {} is smaller than MAX_SUPPORTED_VERSION {}", requestedVersion, MAX_SUPPORTED_VERSION);
transmit(new SFTPPacket<Request>(PacketType.INIT).putUInt32(requestedVersion));
final SFTPPacket<Response> response = reader.readPacket();
@@ -91,7 +107,7 @@ public class SFTPEngine
operativeVersion = response.readUInt32AsInt();
log.debug("Server version {}", operativeVersion);
if (MAX_SUPPORTED_VERSION < operativeVersion)
if (requestedVersion < operativeVersion)
throw new SFTPException("Server reported incompatible protocol version: " + operativeVersion);
while (response.available() > 0)
@@ -234,16 +250,75 @@ public class SFTPEngine
public void rename(String oldPath, String newPath, Set<RenameFlags> flags)
throws IOException {
if (operativeVersion < 1)
if (operativeVersion < 1) {
throw new SFTPException("RENAME is not supported in SFTPv" + operativeVersion);
}
final Request request = newRequest(PacketType.RENAME).putString(oldPath, sub.getRemoteCharset()).putString(newPath, sub.getRemoteCharset());
// SFTP Version 5 introduced rename flags according to Section 6.5 of the specification
if (operativeVersion >= 5) {
long renameFlagMask = 0L;
for (RenameFlags flag : flags) {
renameFlagMask = renameFlagMask | flag.longValue();
// request variables to be determined
PacketType type = PacketType.RENAME; // Default
long renameFlagMask = 0L;
String serverExtension = null;
if (!flags.isEmpty()) {
// SFTP Version 5 introduced rename flags according to Section 6.5 of the specification
if (operativeVersion >= 5) {
for (RenameFlags flag : flags) {
renameFlagMask = renameFlagMask | flag.longValue();
}
}
// Try to find a fallback solution if flags are not supported by the server.
// "posix-rename@openssh.com" provides ATOMIC and OVERWRITE behaviour.
// From the SFTP-spec, Section 6.5:
// "If SSH_FXP_RENAME_OVERWRITE is specified, the server MAY perform an atomic rename even if it is
// not requested."
// So, if overwrite is allowed we can always use the posix-rename as a fallback.
else if (flags.contains(RenameFlags.OVERWRITE) &&
supportsServerExtension("posix-rename","openssh.com")) {
type = PacketType.EXTENDED;
serverExtension = "posix-rename@openssh.com";
}
// Because the OVERWRITE flag changes the behaviour in a possibly unintended way, it has to be
// explicitly requested for the above fallback to be applicable.
// Tell this to the developer if ATOMIC is requested without OVERWRITE.
else if (flags.contains(RenameFlags.ATOMIC) &&
!flags.contains(RenameFlags.OVERWRITE) &&
!flags.contains(RenameFlags.NATIVE) && // see next case below
supportsServerExtension("posix-rename","openssh.com")) {
throw new SFTPException("RENAME-FLAGS are not supported in SFTPv" + operativeVersion + " but " +
"the \"posix-rename@openssh.com\" extension could be used as fallback if OVERWRITE " +
"behaviour is acceptable (needs to be activated via RenameFlags.OVERWRITE).");
}
// From the SFTP-spec, Section 6.5:
// "If flags includes SSH_FXP_RENAME_NATIVE, the server is free to do the rename operation in whatever
// fashion it deems appropriate. Other flag values are considered hints as to desired behavior, but not
// requirements."
else if (flags.contains(RenameFlags.NATIVE)) {
log.debug("Flags are not supported but NATIVE-flag allows to ignore other requested flags: " +
flags.toString());
}
// finally: let the user know that the server does not support what was asked
else {
throw new SFTPException("RENAME-FLAGS are not supported in SFTPv" + operativeVersion + " and no " +
"supported server extension could be found to achieve a similar result.");
}
}
// build and send request
final Request request = newRequest(type);
if (serverExtension != null) {
request.putString(serverExtension);
}
request.putString(oldPath, sub.getRemoteCharset())
.putString(newPath, sub.getRemoteCharset());
if (renameFlagMask != 0L) {
request.putUInt32(renameFlagMask);
}