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putty/scpserver.c

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/*
* Server side of the old-school SCP protocol.
*/
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include "putty.h"
#include "ssh.h"
#include "sshcr.h"
#include "sshchan.h"
#include "sftp.h"
/*
* I think it's worth actually documenting my understanding of what
* this protocol _is_, since I don't know of any other documentation
* of it anywhere.
*
* Format of data stream
* ---------------------
*
* The sending side of an SCP connection - the client, if you're
* uploading files, or the server if you're downloading - sends a data
* stream consisting of a sequence of 'commands', or header records,
* or whatever you want to call them, interleaved with file data.
*
* Each command starts with a letter indicating what type it is, and
* ends with a \n.
*
* The 'C' command introduces an actual file. It is followed by an
* octal file-permissions mask, then a space, then a decimal file
* size, then a space, then the file name up to the termating newline.
* For example, "C0644 12345 filename.txt\n" would be a plausible C
* command.
*
* After the 'C' command, the sending side will transmit exactly as
* many bytes of file data as specified by the size field in the
* header line, followed by a single zero byte.
*
* The 'D' command introduces a subdirectory. Its format is identical
* to 'C', including the size field, but the size field is sent as
* zero.
*
* After the 'D' command, all subsequent C and D commands are taken to
* indicate files that should be placed inside that subdirectory,
* until a terminating 'E' command.
*
* The 'E' command indicates the end of a subdirectory. It has no
* arguments at all (its format is always just "E\n"). After the E
* command, the receiver should revert to placing further downloaded
* files in whatever directory it was placing them before the
* subdirectory opened by the just-closed D.
*
* D and E commands match like parentheses: if you send, say,
*
* C0644 123 foo.txt ( followed by data )
* D0755 0 subdir
* C0644 123 bar.txt ( followed by data )
* D0755 0 subsubdir
* C0644 123 baz.txt ( followed by data )
* E
* C0644 123 quux.txt ( followed by data )
* E
* C0644 123 wibble.txt ( followed by data )
*
* then foo.txt, subdir and wibble.txt go in the top-level destination
* directory; bar.txt, subsubdir and quux.txt go in 'subdir'; and
* baz.txt goes in 'subdir/subsubdir'.
*
* The sender terminates the data stream with EOF when it has no more
* files to send. I believe it is not _required_ for all D to be
* closed by an E before this happens - you can elide a trailing
* sequence of E commands without provoking an error message from the
* receiver.
*
* Finally, the 'T' command is sent immediately before a C or D. It is
* followed by four space-separated decimal integers giving an mtime
* and atime to be applied to the file or directory created by the
* following C or D command. The first two integers give the mtime,
* encoded as seconds and microseconds (respectively) since the Unix
* epoch; the next two give the atime, encoded similarly. So
* "T1540373455 0 1540373457 0\n" is an example of a valid T command.
*
* Acknowledgments
* ---------------
*
* The sending side waits for an ack from the receiving side before
* sending each command; before beginning to send the file data
* following a C command; and before sending the final EOF.
*
* (In particular, the receiving side is expected to send an initial
* ack before _anything_ is sent.)
*
* Normally an ack consists of a single zero byte. It's also allowable
* to send a byte with value 1 or 2 followed by a \n-terminated error
* message (where 1 means a non-fatal error and 2 means a fatal one).
* I have to suppose that sending an error message from client to
* server is of limited use, but apparently it's allowed.
*
* Initiation
* ----------
*
* The protocol is begun by the client sending a command string to the
* server via the SSH-2 "exec" request (or the analogous
* SSH1_CMSG_EXEC_CMD), which indicates that this is an scp session
* rather than any other thing; specifies the direction of transfer;
* says what file(s) are to be sent by the server, or where the server
* should put files that the client is about to send; and a couple of
* other options.
*
* The command string takes the following form:
*
* Start with prefix "scp ", indicating that this is an SCP command at
* all. Otherwise it's a request to run some completely different
* command in the SSH session.
*
* Next the command can contain zero or more of the following options,
* each followed by a space:
*
* "-v" turns on verbose server diagnostics. Of course a server is not
* required to actually produce any, but this is an invitation for it
* to send any it might have available. Diagnostics are free-form, and
* sent as SSH standard-error extended data, so that they are separate
* from the actual data stream as described above.
*
* (Servers can send standard-error output anyway if they like, and in
* case of an actual error, they probably will with or without -v.)
*
* "-r" indicates recursive file transfer, i.e. potentially including
* subdirectories. For a download, this indicates that the client is
* willing to receive subdirectories (a D/E command pair bracketing
* further files and subdirs); without it, the server should only send
* C commands for individual files, followed by EOF.
*
* This flag must also be specified for a recursive upload, because I
* believe at least one server will reject D/E pairs sent by the
* client if the command didn't have -r in it. (Probably a consequence
* of sharing code between download and upload.)
*
* "-p" means preserve file times. In a download, this requests the
* server to send a T command before each C or D. I don't know whether
* any server will insist on having seen this option from the client
* before accepting T commands in an upload, but it is probably
* sensible to send it anyway.
*
* "-d", in an upload, means that the destination pathname (see below)
* is expected to be a directory, and that uploaded files (and
* subdirs) should be put inside it. Without -d, the semantics are
* that _if_ the destination exists and is a directory, then files
* will be put in it, whereas if it is not, then just a single file
* (or subdir) upload is expected, which will be placed at that exact
* pathname.
*
* In a download, I observe that clients tend to send -d if they are
* requesting multiple files or a wildcard, but as far as I know,
* servers ignore it.
*
* After all those optional options, there is a single mandatory
* option indicating the direction of transfer, which is either "-f"
* or "-t". "-f" indicates a download; "-t" indicates an upload.
*
* After that mandatory option, there is a single space, followed by
* the name(s) of files to transfer.
*
* This file name field is transmitted with NO QUOTING, in spite of
* the fact that a server will typically interpret it as a shell
* command. You'd think this couldn't possibly work, in the face of
* almost any filename with an interesting character in it - and you'd
* be right. Or rather (you might argue), it works 'as designed', but
* it's designed in a weird way, in that it's the user's
* responsibility to apply quoting on the client command line to get
* the filename through the shell that will decode things on the
* server side.
*
* But one effect of this is that if you issue a download command
* including a wildcard, say "scp -f somedir/foo*.txt", then the shell
* will expand the wildcard, and actually run the server-side scp
* program with multiple arguments, say "somedir/foo.txt
* somedir/quux.txt", leading to the download sending multiple C
* commands. This clearly _is_ intended: it's how a command such as
* 'scp server:somedir/foo*.txt destdir' can work at all.
*
* (You would think, given that, that it might also be legal to send
* multiple space-separated filenames in order to trigger a download
* of exactly those files. Given how scp is invoked in practice on a
* typical server, this would surely actually work, but my observation
* is that scp clients don't in fact try this - if you run OpenSSH's
* scp by saying 'scp server:foo server:bar destdir' then it will make
* two separate connections to the server for the two files, rather
* than sending a single space-separated remote command. PSCP won't
* even do that, and will make you do it in two separate runs.)
*
* So, some examples:
*
* - "scp -f filename.txt"
*
* Server should send a single C command (plus data) for that file.
* Client ought to ignore the filename in the C command, in favour
* of saving the file under the name implied by the user's command
* line.
*
* - "scp -f file*.txt"
*
* Server sends zero or more C commands, then EOF. Client will have
* been given a target directory to put them all in, and will name
* each one according to the name in the C command.
*
* (You'd like the client to validate the filenames against the
* wildcard it sent, to ensure a malicious server didn't try to
* overwrite some path like ".bashrc" when you thought you were
* downloading only normal text files. But wildcard semantics are
* chosen by the server, so this is essentially hopeless to do
* rigorously.)
*
* - "scp -f -r somedir"
*
* Assuming somedir is actually a directory, server sends a D/E
* pair, in between which are the contents of the directory
* (perhaps including further nested D/E pairs). Client probably
* ignores the name field of the outermost D
*
* - "scp -f -r some*wild*card*"
*
* Server sends multiple C or D-stuff-E, one for each top-level
* thing matching the wildcard, whether it's a file or a directory.
*
* - "scp -t -d some_dir"
*
* Client sends stuff, and server deposits each file at
* some_dir/<name from the C command>.
*
* - "scp -t some_path_name"
*
* Client sends one C command, and server deposits it at
* some_path_name itself, or in some_path_name/<name from C
* command>, depending whether some_path_name was already a
* directory or not.
*/
/*
* Here's a useful debugging aid: run over a binary file containing
* the complete contents of the sender's data stream (e.g. extracted
* by contrib/logparse.pl -d), it removes the file contents, leaving
* only the list of commands, so you can see what the server sent.
*
* perl -pe 'read ARGV,$x,1+$1 if/^C\S+ (\d+)/'
*/
/* ----------------------------------------------------------------------
* Shared system for receiving replies from the SftpServer, and
* putting them into a set of ordinary variables rather than
* marshalling them into actual SFTP reply packets that we'd only have
* to unmarshal again.
*/
typedef struct ScpReplyReceiver ScpReplyReceiver;
struct ScpReplyReceiver {
bool err;
unsigned code;
char *errmsg;
struct fxp_attrs attrs;
ptrlen name, handle, data;
SftpReplyBuilder srb;
};
static void scp_reply_ok(SftpReplyBuilder *srb)
{
ScpReplyReceiver *reply = container_of(srb, ScpReplyReceiver, srb);
reply->err = false;
}
static void scp_reply_error(
SftpReplyBuilder *srb, unsigned code, const char *msg)
{
ScpReplyReceiver *reply = container_of(srb, ScpReplyReceiver, srb);
reply->err = true;
reply->code = code;
sfree(reply->errmsg);
reply->errmsg = dupstr(msg);
}
static void scp_reply_name_count(SftpReplyBuilder *srb, unsigned count)
{
ScpReplyReceiver *reply = container_of(srb, ScpReplyReceiver, srb);
reply->err = false;
}
static void scp_reply_full_name(
SftpReplyBuilder *srb, ptrlen name,
ptrlen longname, struct fxp_attrs attrs)
{
ScpReplyReceiver *reply = container_of(srb, ScpReplyReceiver, srb);
char *p;
reply->err = false;
sfree((void *)reply->name.ptr);
reply->name.ptr = p = mkstr(name);
reply->name.len = name.len;
reply->attrs = attrs;
}
static void scp_reply_simple_name(SftpReplyBuilder *srb, ptrlen name)
{
ScpReplyReceiver *reply = container_of(srb, ScpReplyReceiver, srb);
reply->err = false;
}
static void scp_reply_handle(SftpReplyBuilder *srb, ptrlen handle)
{
ScpReplyReceiver *reply = container_of(srb, ScpReplyReceiver, srb);
char *p;
reply->err = false;
sfree((void *)reply->handle.ptr);
reply->handle.ptr = p = mkstr(handle);
reply->handle.len = handle.len;
}
static void scp_reply_data(SftpReplyBuilder *srb, ptrlen data)
{
ScpReplyReceiver *reply = container_of(srb, ScpReplyReceiver, srb);
char *p;
reply->err = false;
sfree((void *)reply->data.ptr);
reply->data.ptr = p = mkstr(data);
reply->data.len = data.len;
}
static void scp_reply_attrs(
SftpReplyBuilder *srb, struct fxp_attrs attrs)
{
ScpReplyReceiver *reply = container_of(srb, ScpReplyReceiver, srb);
reply->err = false;
reply->attrs = attrs;
}
static const struct SftpReplyBuilderVtable ScpReplyReceiver_vt = {
scp_reply_ok,
scp_reply_error,
scp_reply_simple_name,
scp_reply_name_count,
scp_reply_full_name,
scp_reply_handle,
scp_reply_data,
scp_reply_attrs,
};
static void scp_reply_setup(ScpReplyReceiver *reply)
{
memset(reply, 0, sizeof(*reply));
reply->srb.vt = &ScpReplyReceiver_vt;
}
static void scp_reply_cleanup(ScpReplyReceiver *reply)
{
sfree(reply->errmsg);
sfree((void *)reply->name.ptr);
sfree((void *)reply->handle.ptr);
sfree((void *)reply->data.ptr);
}
/* ----------------------------------------------------------------------
* Source end of the SCP protocol.
*/
#define SCP_MAX_BACKLOG 65536
typedef struct ScpSource ScpSource;
typedef struct ScpSourceStackEntry ScpSourceStackEntry;
struct ScpSource {
SftpServer *sf;
int acks;
bool expect_newline, eof, throttled, finished;
SshChannel *sc;
ScpSourceStackEntry *head;
bool recursive;
bool send_file_times;
strbuf *pending_commands[3];
int n_pending_commands;
uint64_t file_offset, file_size;
ScpReplyReceiver reply;
ScpServer scpserver;
};
typedef enum ScpSourceNodeType ScpSourceNodeType;
enum ScpSourceNodeType { SCP_ROOTPATH, SCP_NAME, SCP_READDIR, SCP_READFILE };
struct ScpSourceStackEntry {
ScpSourceStackEntry *next;
ScpSourceNodeType type;
ptrlen pathname, handle;
const char *wildcard;
struct fxp_attrs attrs;
};
static void scp_source_push(ScpSource *scp, ScpSourceNodeType type,
ptrlen pathname, ptrlen handle,
const struct fxp_attrs *attrs, const char *wc)
{
size_t wc_len = wc ? strlen(wc)+1 : 0;
ScpSourceStackEntry *node = snew_plus(
ScpSourceStackEntry, pathname.len + handle.len + wc_len);
char *namebuf = snew_plus_get_aux(node);
memcpy(namebuf, pathname.ptr, pathname.len);
node->pathname = make_ptrlen(namebuf, pathname.len);
memcpy(namebuf + pathname.len, handle.ptr, handle.len);
node->handle = make_ptrlen(namebuf + pathname.len, handle.len);
if (wc) {
strcpy(namebuf + pathname.len + handle.len, wc);
node->wildcard = namebuf + pathname.len + handle.len;
} else {
node->wildcard = NULL;
}
node->attrs = attrs ? *attrs : no_attrs;
node->type = type;
node->next = scp->head;
scp->head = node;
}
static char *scp_source_err_base(ScpSource *scp, const char *fmt, va_list ap)
{
char *msg = dupvprintf(fmt, ap);
sshfwd_write_ext(scp->sc, true, msg, strlen(msg));
sshfwd_write_ext(scp->sc, true, "\012", 1);
return msg;
}
static void scp_source_err(ScpSource *scp, const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
sfree(scp_source_err_base(scp, fmt, ap));
va_end(ap);
}
static void scp_source_abort(ScpSource *scp, const char *fmt, ...)
{
va_list ap;
char *msg;
va_start(ap, fmt);
msg = scp_source_err_base(scp, fmt, ap);
va_end(ap);
sshfwd_send_exit_status(scp->sc, 1);
sshfwd_write_eof(scp->sc);
sshfwd_initiate_close(scp->sc, msg);
scp->finished = true;
}
static void scp_source_push_name(
ScpSource *scp, ptrlen pathname, struct fxp_attrs attrs, const char *wc)
{
if (!(attrs.flags & SSH_FILEXFER_ATTR_PERMISSIONS)) {
scp_source_err(scp, "unable to read file permissions for %.*s",
PTRLEN_PRINTF(pathname));
return;
}
if (attrs.permissions & PERMS_DIRECTORY) {
if (!scp->recursive && !wc) {
scp_source_err(scp, "%.*s: is a directory",
PTRLEN_PRINTF(pathname));
return;
}
} else {
if (!(attrs.flags & SSH_FILEXFER_ATTR_SIZE)) {
scp_source_err(scp, "unable to read file size for %.*s",
PTRLEN_PRINTF(pathname));
return;
}
}
scp_source_push(scp, SCP_NAME, pathname, PTRLEN_LITERAL(""), &attrs, wc);
}
static void scp_source_free(ScpServer *s);
static int scp_source_send(ScpServer *s, const void *data, size_t length);
static void scp_source_eof(ScpServer *s);
static void scp_source_throttle(ScpServer *s, bool throttled);
static struct ScpServerVtable ScpSource_ScpServer_vt = {
scp_source_free,
scp_source_send,
scp_source_throttle,
scp_source_eof,
};
static ScpSource *scp_source_new(
SshChannel *sc, const SftpServerVtable *sftpserver_vt, ptrlen pathname)
{
ScpSource *scp = snew(ScpSource);
memset(scp, 0, sizeof(*scp));
scp->scpserver.vt = &ScpSource_ScpServer_vt;
scp_reply_setup(&scp->reply);
scp->sc = sc;
scp->sf = sftpsrv_new(sftpserver_vt);
scp->n_pending_commands = 0;
scp_source_push(scp, SCP_ROOTPATH, pathname, PTRLEN_LITERAL(""),
NULL, NULL);
return scp;
}
static void scp_source_free(ScpServer *s)
{
ScpSource *scp = container_of(s, ScpSource, scpserver);
scp_reply_cleanup(&scp->reply);
while (scp->n_pending_commands > 0)
strbuf_free(scp->pending_commands[--scp->n_pending_commands]);
while (scp->head) {
ScpSourceStackEntry *node = scp->head;
scp->head = node->next;
sfree(node);
}
sfree(scp);
}
static void scp_source_send_E(ScpSource *scp)
{
strbuf *cmd;
assert(scp->n_pending_commands == 0);
scp->pending_commands[scp->n_pending_commands++] = cmd = strbuf_new();
strbuf_catf(cmd, "E\012");
}
static void scp_source_send_CD(
ScpSource *scp, char cmdchar,
struct fxp_attrs attrs, uint64_t size, ptrlen name)
{
strbuf *cmd;
assert(scp->n_pending_commands == 0);
if (scp->send_file_times && (attrs.flags & SSH_FILEXFER_ATTR_ACMODTIME)) {
scp->pending_commands[scp->n_pending_commands++] = cmd = strbuf_new();
/* Our SFTP-based filesystem API doesn't support microsecond times */
strbuf_catf(cmd, "T%lu 0 %lu 0\012", attrs.mtime, attrs.atime);
}
const char *slash;
while ((slash = memchr(name.ptr, '/', name.len)) != NULL)
name = make_ptrlen(
slash+1, name.len - (slash+1 - (const char *)name.ptr));
scp->pending_commands[scp->n_pending_commands++] = cmd = strbuf_new();
strbuf_catf(cmd, "%c%04o %"PRIu64" %.*s\012", cmdchar,
(unsigned)(attrs.permissions & 07777),
size, PTRLEN_PRINTF(name));
if (cmdchar == 'C') {
/* We'll also wait for an ack before sending the file data,
* which we record by saving a zero-length 'command' to be
* sent after the C. */
scp->pending_commands[scp->n_pending_commands++] = cmd = strbuf_new();
}
}
static void scp_source_process_stack(ScpSource *scp);
static void scp_source_process_stack_cb(void *vscp)
{
ScpSource *scp = (ScpSource *)vscp;
if (scp->finished)
return; /* this callback is out of date */
scp_source_process_stack(scp);
}
static void scp_requeue(ScpSource *scp)
{
queue_toplevel_callback(scp_source_process_stack_cb, scp);
}
static void scp_source_process_stack(ScpSource *scp)
{
if (scp->throttled)
return;
while (scp->n_pending_commands > 0) {
/* Expect an ack, and consume it */
if (scp->eof) {
scp_source_abort(
scp, "scp: received client EOF, abandoning transfer");
return;
}
if (scp->acks == 0)
return;
scp->acks--;
/*
* Now send the actual command (unless it was the phony
* zero-length one that indicates our need for an ack before
* beginning to send file data).
*/
if (scp->pending_commands[0]->len)
sshfwd_write(scp->sc, scp->pending_commands[0]->s,
scp->pending_commands[0]->len);
strbuf_free(scp->pending_commands[0]);
scp->n_pending_commands--;
if (scp->n_pending_commands > 0) {
/*
* We still have at least one pending command to send, so
* move up the queue.
*
* (We do that with a bodgy memmove, because there are at
* most a bounded number of commands ever pending at once,
* so no need to worry about quadratic time.)
*/
memmove(scp->pending_commands, scp->pending_commands+1,
scp->n_pending_commands * sizeof(*scp->pending_commands));
}
}
/*
* Mostly, we start by waiting for an ack byte from the receiver.
*/
if (scp->head && scp->head->type == SCP_READFILE && scp->file_offset) {
/*
* Exception: if we're already in the middle of transferring a
* file, we'll be called back here because the channel backlog
* has cleared; we don't need to wait for an ack.
*/
} else if (scp->head && scp->head->type == SCP_ROOTPATH) {
/*
* Another exception: the initial action node that makes us
* stat the root path. We'll translate it into an SCP_NAME,
* and _that_ will require an ack.
*/
ScpSourceStackEntry *node = scp->head;
scp->head = node->next;
/*
* Start by checking if there's a wildcard involved in the
* root path.
*/
char *rootpath_str = mkstr(node->pathname);
char *rootpath_unesc = snewn(1+node->pathname.len, char);
ptrlen pathname;
const char *wildcard;
if (wc_unescape(rootpath_unesc, rootpath_str)) {
/*
* We successfully removed instances of the escape
* character used in our wildcard syntax, without
* encountering any actual wildcard chars - i.e. this is
* not a wildcard, just a single file. The simple case.
*/
pathname = ptrlen_from_asciz(rootpath_str);
wildcard = NULL;
} else {
/*
* This is a wildcard. Separate it into a directory name
* (which we enforce mustn't contain wc characters, for
* simplicity) and a wildcard to match leaf names.
*/
char *last_slash = strrchr(rootpath_str, '/');
if (last_slash) {
wildcard = last_slash + 1;
*last_slash = '\0';
if (!wc_unescape(rootpath_unesc, rootpath_str)) {
scp_source_abort(scp, "scp: wildcards in path components "
"before the file name not supported");
sfree(rootpath_str);
sfree(rootpath_unesc);
return;
}
pathname = ptrlen_from_asciz(rootpath_unesc);
} else {
pathname = PTRLEN_LITERAL(".");
wildcard = rootpath_str;
}
}
/*
* Now we know what directory we're scanning, and what
* wildcard (if any) we're using to match the filenames we get
* back.
*/
sftpsrv_stat(scp->sf, &scp->reply.srb, pathname, true);
if (scp->reply.err) {
scp_source_abort(
scp, "%.*s: unable to access: %s",
PTRLEN_PRINTF(pathname), scp->reply.errmsg);
sfree(rootpath_str);
sfree(rootpath_unesc);
sfree(node);
return;
}
scp_source_push_name(scp, pathname, scp->reply.attrs, wildcard);
sfree(rootpath_str);
sfree(rootpath_unesc);
sfree(node);
scp_requeue(scp);
return;
} else {
}
if (scp->head && scp->head->type == SCP_READFILE) {
/*
* Transfer file data if our backlog hasn't filled up.
*/
int backlog;
uint64_t limit = scp->file_size - scp->file_offset;
if (limit > 4096)
limit = 4096;
if (limit > 0) {
sftpsrv_read(scp->sf, &scp->reply.srb, scp->head->handle,
scp->file_offset, limit);
if (scp->reply.err) {
scp_source_abort(
scp, "%.*s: unable to read: %s",
PTRLEN_PRINTF(scp->head->pathname), scp->reply.errmsg);
return;
}
backlog = sshfwd_write(
scp->sc, scp->reply.data.ptr, scp->reply.data.len);
scp->file_offset += scp->reply.data.len;
if (backlog < SCP_MAX_BACKLOG)
scp_requeue(scp);
return;
}
/*
* If we're done, send a terminating zero byte, close our file
* handle, and pop the stack.
*/
sshfwd_write(scp->sc, "\0", 1);
sftpsrv_close(scp->sf, &scp->reply.srb, scp->head->handle);
ScpSourceStackEntry *node = scp->head;
scp->head = node->next;
sfree(node);
scp_requeue(scp);
return;
}
/*
* If our queue is actually empty, send outgoing EOF.
*/
if (!scp->head) {
sshfwd_send_exit_status(scp->sc, 0);
sshfwd_write_eof(scp->sc);
sshfwd_initiate_close(scp->sc, NULL);
scp->finished = true;
return;
}
/*
* Otherwise, handle a command.
*/
ScpSourceStackEntry *node = scp->head;
scp->head = node->next;
if (node->type == SCP_READDIR) {
sftpsrv_readdir(scp->sf, &scp->reply.srb, node->handle, 1, true);
if (scp->reply.err) {
if (scp->reply.code != SSH_FX_EOF)
scp_source_err(scp, "%.*s: unable to list directory: %s",
PTRLEN_PRINTF(node->pathname),
scp->reply.errmsg);
sftpsrv_close(scp->sf, &scp->reply.srb, node->handle);
if (!node->wildcard) {
/*
* Send 'pop stack' or 'end of directory' command,
* unless this was the topmost READDIR in a
* wildcard-based retrieval (in which case we didn't
* send a D command to start, so an E now would have
* no stack entry to pop).
*/
scp_source_send_E(scp);
}
} else if (ptrlen_eq_string(scp->reply.name, ".") ||
ptrlen_eq_string(scp->reply.name, "..") ||
(node->wildcard &&
!wc_match_pl(node->wildcard, scp->reply.name))) {
/* Skip special directory names . and .., and anything
* that doesn't match our wildcard (if we have one). */
scp->head = node; /* put back the unfinished READDIR */
node = NULL; /* and prevent it being freed */
} else {
ptrlen subpath;
subpath.len = node->pathname.len + 1 + scp->reply.name.len;
char *subpath_space = snewn(subpath.len, char);
subpath.ptr = subpath_space;
memcpy(subpath_space, node->pathname.ptr, node->pathname.len);
subpath_space[node->pathname.len] = '/';
memcpy(subpath_space + node->pathname.len + 1,
scp->reply.name.ptr, scp->reply.name.len);
scp->head = node; /* put back the unfinished READDIR */
node = NULL; /* and prevent it being freed */
scp_source_push_name(scp, subpath, scp->reply.attrs, NULL);
sfree(subpath_space);
}
} else if (node->attrs.permissions & PERMS_DIRECTORY) {
assert(scp->recursive || node->wildcard);
if (!node->wildcard)
scp_source_send_CD(scp, 'D', node->attrs, 0, node->pathname);
sftpsrv_opendir(scp->sf, &scp->reply.srb, node->pathname);
if (scp->reply.err) {
scp_source_err(
scp, "%.*s: unable to access: %s",
PTRLEN_PRINTF(node->pathname), scp->reply.errmsg);
if (!node->wildcard) {
/* Send 'pop stack' or 'end of directory' command. */
scp_source_send_E(scp);
}
} else {
scp_source_push(
scp, SCP_READDIR, node->pathname,
scp->reply.handle, NULL, node->wildcard);
}
} else {
sftpsrv_open(scp->sf, &scp->reply.srb,
node->pathname, SSH_FXF_READ, no_attrs);
if (scp->reply.err) {
scp_source_err(
scp, "%.*s: unable to open: %s",
PTRLEN_PRINTF(node->pathname), scp->reply.errmsg);
scp_requeue(scp);
return;
}
sftpsrv_fstat(scp->sf, &scp->reply.srb, scp->reply.handle);
if (scp->reply.err) {
scp_source_err(
scp, "%.*s: unable to stat: %s",
PTRLEN_PRINTF(node->pathname), scp->reply.errmsg);
sftpsrv_close(scp->sf, &scp->reply.srb, scp->reply.handle);
scp_requeue(scp);
return;
}
scp->file_offset = 0;
scp->file_size = scp->reply.attrs.size;
scp_source_send_CD(scp, 'C', node->attrs,
scp->file_size, node->pathname);
scp_source_push(
scp, SCP_READFILE, node->pathname, scp->reply.handle, NULL, NULL);
}
sfree(node);
scp_requeue(scp);
}
static int scp_source_send(ScpServer *s, const void *vdata, size_t length)
{
ScpSource *scp = container_of(s, ScpSource, scpserver);
const char *data = (const char *)vdata;
size_t i;
if (scp->finished)
return 0;
for (i = 0; i < length; i++) {
if (scp->expect_newline) {
if (data[i] == '\012') {
/* End of an error message following a 1 byte */
scp->expect_newline = false;
scp->acks++;
}
} else {
switch (data[i]) {
case 0: /* ordinary ack */
scp->acks++;
break;
case 1: /* non-fatal error; consume it */
scp->expect_newline = true;
break;
case 2:
scp_source_abort(
scp, "terminating on fatal error from client");
return 0;
default:
scp_source_abort(
scp, "unrecognised response code from client");
return 0;
}
}
}
scp_source_process_stack(scp);
return 0;
}
static void scp_source_throttle(ScpServer *s, bool throttled)
{
ScpSource *scp = container_of(s, ScpSource, scpserver);
if (scp->finished)
return;
scp->throttled = throttled;
if (!throttled)
scp_source_process_stack(scp);
}
static void scp_source_eof(ScpServer *s)
{
ScpSource *scp = container_of(s, ScpSource, scpserver);
if (scp->finished)
return;
scp->eof = true;
scp_source_process_stack(scp);
}
/* ----------------------------------------------------------------------
* Sink end of the SCP protocol.
*/
typedef struct ScpSink ScpSink;
typedef struct ScpSinkStackEntry ScpSinkStackEntry;
struct ScpSink {
SftpServer *sf;
SshChannel *sc;
ScpSinkStackEntry *head;
uint64_t file_offset, file_size;
unsigned long atime, mtime;
bool got_file_times;
bufchain data;
bool input_eof;
strbuf *command;
char command_chr;
strbuf *filename_sb;
ptrlen filename;
struct fxp_attrs attrs;
char *errmsg;
int crState;
ScpReplyReceiver reply;
ScpServer scpserver;
};
struct ScpSinkStackEntry {
ScpSinkStackEntry *next;
ptrlen destpath;
/*
* If isdir is true, then destpath identifies a directory that the
* files we receive should be created inside. If it's false, then
* it identifies the exact pathname the next file we receive
* should be created _as_ - regardless of the filename in the 'C'
* command.
*/
bool isdir;
};
static void scp_sink_push(ScpSink *scp, ptrlen pathname, bool isdir)
{
ScpSinkStackEntry *node = snew_plus(ScpSinkStackEntry, pathname.len);
char *p = snew_plus_get_aux(node);
node->destpath.ptr = p;
node->destpath.len = pathname.len;
memcpy(p, pathname.ptr, pathname.len);
node->isdir = isdir;
node->next = scp->head;
scp->head = node;
}
static void scp_sink_pop(ScpSink *scp)
{
ScpSinkStackEntry *node = scp->head;
scp->head = node->next;
sfree(node);
}
static void scp_sink_free(ScpServer *s);
static int scp_sink_send(ScpServer *s, const void *data, size_t length);
static void scp_sink_eof(ScpServer *s);
static void scp_sink_throttle(ScpServer *s, bool throttled) {}
static struct ScpServerVtable ScpSink_ScpServer_vt = {
scp_sink_free,
scp_sink_send,
scp_sink_throttle,
scp_sink_eof,
};
static void scp_sink_coroutine(ScpSink *scp);
static void scp_sink_start_callback(void *vscp)
{
scp_sink_coroutine((ScpSink *)vscp);
}
static ScpSink *scp_sink_new(
SshChannel *sc, const SftpServerVtable *sftpserver_vt, ptrlen pathname,
bool pathname_is_definitely_dir)
{
ScpSink *scp = snew(ScpSink);
memset(scp, 0, sizeof(*scp));
scp->scpserver.vt = &ScpSink_ScpServer_vt;
scp_reply_setup(&scp->reply);
scp->sc = sc;
scp->sf = sftpsrv_new(sftpserver_vt);
bufchain_init(&scp->data);
scp->command = strbuf_new();
scp->filename_sb = strbuf_new();
if (!pathname_is_definitely_dir) {
/*
* If our root pathname is not already expected to be a
* directory because of the -d option in the command line,
* test it ourself to see whether it is or not.
*/
sftpsrv_stat(scp->sf, &scp->reply.srb, pathname, true);
if (!scp->reply.err &&
(scp->reply.attrs.flags & SSH_FILEXFER_ATTR_PERMISSIONS) &&
(scp->reply.attrs.permissions & PERMS_DIRECTORY))
pathname_is_definitely_dir = true;
}
scp_sink_push(scp, pathname, pathname_is_definitely_dir);
queue_toplevel_callback(scp_sink_start_callback, scp);
return scp;
}
static void scp_sink_free(ScpServer *s)
{
ScpSink *scp = container_of(s, ScpSink, scpserver);
scp_reply_cleanup(&scp->reply);
bufchain_clear(&scp->data);
strbuf_free(scp->command);
strbuf_free(scp->filename_sb);
while (scp->head)
scp_sink_pop(scp);
sfree(scp->errmsg);
delete_callbacks_for_context(scp);
sfree(scp);
}
static void scp_sink_coroutine(ScpSink *scp)
{
crBegin(scp->crState);
while (1) {
/*
* Send an ack, and read a command.
*/
sshfwd_write(scp->sc, "\0", 1);
scp->command->len = 0;
while (1) {
crMaybeWaitUntilV(scp->input_eof || bufchain_size(&scp->data) > 0);
if (scp->input_eof)
goto done;
void *vdata;
int len;
const char *cdata, *newline;
bufchain_prefix(&scp->data, &vdata, &len);
cdata = vdata;
newline = memchr(cdata, '\012', len);
if (newline)
len = (int)(newline+1 - cdata);
put_data(scp->command, cdata, len);
bufchain_consume(&scp->data, len);
if (newline)
break;
}
/*
* Parse the command.
*/
scp->command->len--; /* chomp the newline */
scp->command_chr = scp->command->len > 0 ? scp->command->s[0] : '\0';
if (scp->command_chr == 'T') {
unsigned long dummy1, dummy2;
if (sscanf(scp->command->s, "T%lu %lu %lu %lu",
&scp->mtime, &dummy1, &scp->atime, &dummy2) != 4)
goto parse_error;
scp->got_file_times = true;
} else if (scp->command_chr == 'C' || scp->command_chr == 'D') {
/*
* Common handling of the start of this case, because the
* messages are parsed similarly. We diverge later.
*/
const char *q, *p = scp->command->s + 1; /* skip the 'C' */
scp->attrs.flags = SSH_FILEXFER_ATTR_PERMISSIONS;
scp->attrs.permissions = 0;
while (*p >= '0' && *p <= '7') {
scp->attrs.permissions =
scp->attrs.permissions * 8 + (*p - '0');
p++;
}
if (*p != ' ')
goto parse_error;
p++;
q = p;
while (*p >= '0' && *p <= '9')
p++;
if (*p != ' ')
goto parse_error;
p++;
scp->file_size = strtoull(q, NULL, 10);
ptrlen leafname = make_ptrlen(
p, scp->command->len - (p - scp->command->s));
scp->filename_sb->len = 0;
put_datapl(scp->filename_sb, scp->head->destpath);
if (scp->head->isdir) {
if (scp->filename_sb->len > 0 &&
scp->filename_sb->s[scp->filename_sb->len-1]
!= '/')
put_byte(scp->filename_sb, '/');
put_datapl(scp->filename_sb, leafname);
}
scp->filename = ptrlen_from_strbuf(scp->filename_sb);
if (scp->got_file_times) {
scp->attrs.mtime = scp->mtime;
scp->attrs.atime = scp->atime;
scp->attrs.flags |= SSH_FILEXFER_ATTR_ACMODTIME;
}
scp->got_file_times = false;
if (scp->command_chr == 'D') {
sftpsrv_mkdir(scp->sf, &scp->reply.srb,
scp->filename, scp->attrs);
if (scp->reply.err) {
scp->errmsg = dupprintf(
"'%.*s': unable to create directory: %s",
PTRLEN_PRINTF(scp->filename), scp->reply.errmsg);
goto done;
}
scp_sink_push(scp, scp->filename, true);
} else {
sftpsrv_open(scp->sf, &scp->reply.srb, scp->filename,
SSH_FXF_WRITE | SSH_FXF_CREAT | SSH_FXF_TRUNC,
scp->attrs);
if (scp->reply.err) {
scp->errmsg = dupprintf(
"'%.*s': unable to open file: %s",
PTRLEN_PRINTF(scp->filename), scp->reply.errmsg);
goto done;
}
/*
* Now send an ack, and read the file data.
*/
sshfwd_write(scp->sc, "\0", 1);
scp->file_offset = 0;
while (scp->file_offset < scp->file_size) {
void *vdata;
int len;
uint64_t this_len, remaining;
crMaybeWaitUntilV(
scp->input_eof || bufchain_size(&scp->data) > 0);
if (scp->input_eof) {
sftpsrv_close(scp->sf, &scp->reply.srb,
scp->reply.handle);
goto done;
}
bufchain_prefix(&scp->data, &vdata, &len);
this_len = len;
remaining = scp->file_size - scp->file_offset;
if (this_len > remaining)
this_len = remaining;
sftpsrv_write(scp->sf, &scp->reply.srb,
scp->reply.handle, scp->file_offset,
make_ptrlen(vdata, this_len));
if (scp->reply.err) {
scp->errmsg = dupprintf(
"'%.*s': unable to write to file: %s",
PTRLEN_PRINTF(scp->filename), scp->reply.errmsg);
goto done;
}
bufchain_consume(&scp->data, this_len);
scp->file_offset += this_len;
}
/*
* Wait for the trailing NUL byte.
*/
crMaybeWaitUntilV(
scp->input_eof || bufchain_size(&scp->data) > 0);
if (scp->input_eof) {
sftpsrv_close(scp->sf, &scp->reply.srb,
scp->reply.handle);
goto done;
}
bufchain_consume(&scp->data, 1);
}
} else if (scp->command_chr == 'E') {
if (!scp->head) {
scp->errmsg = dupstr("received E command without matching D");
goto done;
}
scp_sink_pop(scp);
scp->got_file_times = false;
} else {
ptrlen cmd_pl;
/*
* Also come here if any of the above cases run into
* parsing difficulties.
*/
parse_error:
cmd_pl = ptrlen_from_strbuf(scp->command);
scp->errmsg = dupprintf("unrecognised scp command '%.*s'",
PTRLEN_PRINTF(cmd_pl));
goto done;
}
}
done:
if (scp->errmsg) {
sshfwd_write_ext(scp->sc, true, scp->errmsg, strlen(scp->errmsg));
sshfwd_write_ext(scp->sc, true, "\012", 1);
sshfwd_send_exit_status(scp->sc, 1);
} else {
sshfwd_send_exit_status(scp->sc, 0);
}
sshfwd_write_eof(scp->sc);
sshfwd_initiate_close(scp->sc, scp->errmsg);
while (1) crReturnV;
crFinishV;
}
static int scp_sink_send(ScpServer *s, const void *data, size_t length)
{
ScpSink *scp = container_of(s, ScpSink, scpserver);
if (!scp->input_eof) {
bufchain_add(&scp->data, data, length);
scp_sink_coroutine(scp);
}
return 0;
}
static void scp_sink_eof(ScpServer *s)
{
ScpSink *scp = container_of(s, ScpSink, scpserver);
scp->input_eof = true;
scp_sink_coroutine(scp);
}
/* ----------------------------------------------------------------------
* Top-level error handler, instantiated in the case where the user
* sent a command starting with "scp " that we couldn't make sense of.
*/
typedef struct ScpError ScpError;
struct ScpError {
SshChannel *sc;
char *message;
ScpServer scpserver;
};
static void scp_error_free(ScpServer *s);
static int scp_error_send(ScpServer *s, const void *data, size_t length)
{ return 0; }
static void scp_error_eof(ScpServer *s) {}
static void scp_error_throttle(ScpServer *s, bool throttled) {}
static struct ScpServerVtable ScpError_ScpServer_vt = {
scp_error_free,
scp_error_send,
scp_error_throttle,
scp_error_eof,
};
static void scp_error_send_message_cb(void *vscp)
{
ScpError *scp = (ScpError *)vscp;
sshfwd_write_ext(scp->sc, true, scp->message, strlen(scp->message));
sshfwd_write_ext(scp->sc, true, "\n", 1);
sshfwd_send_exit_status(scp->sc, 1);
sshfwd_write_eof(scp->sc);
sshfwd_initiate_close(scp->sc, scp->message);
}
static ScpError *scp_error_new(SshChannel *sc, const char *fmt, ...)
{
va_list ap;
ScpError *scp = snew(ScpError);
memset(scp, 0, sizeof(*scp));
scp->scpserver.vt = &ScpError_ScpServer_vt;
scp->sc = sc;
va_start(ap, fmt);
scp->message = dupvprintf(fmt, ap);
va_end(ap);
queue_toplevel_callback(scp_error_send_message_cb, scp);
return scp;
}
static void scp_error_free(ScpServer *s)
{
ScpError *scp = container_of(s, ScpError, scpserver);
sfree(scp->message);
delete_callbacks_for_context(scp);
sfree(scp);
}
/* ----------------------------------------------------------------------
* Top-level entry point, which parses a command sent from the SSH
* client, and if it recognises it as an scp command, instantiates an
* appropriate ScpServer implementation and returns it.
*/
ScpServer *scp_recognise_exec(
SshChannel *sc, const SftpServerVtable *sftpserver_vt, ptrlen command)
{
bool recursive = false, preserve = false;
bool targetshouldbedirectory = false;
ptrlen command_orig = command;
if (!ptrlen_startswith(command, PTRLEN_LITERAL("scp "), &command))
return NULL;
while (1) {
if (ptrlen_startswith(command, PTRLEN_LITERAL("-v "), &command)) {
/* Enable verbose mode in the server, which we ignore */
continue;
}
if (ptrlen_startswith(command, PTRLEN_LITERAL("-r "), &command)) {
recursive = true;
continue;
}
if (ptrlen_startswith(command, PTRLEN_LITERAL("-p "), &command)) {
preserve = true;
continue;
}
if (ptrlen_startswith(command, PTRLEN_LITERAL("-d "), &command)) {
targetshouldbedirectory = true;
continue;
}
break;
}
if (ptrlen_startswith(command, PTRLEN_LITERAL("-t "), &command)) {
ScpSink *scp = scp_sink_new(sc, sftpserver_vt, command,
targetshouldbedirectory);
return &scp->scpserver;
} else if (ptrlen_startswith(command, PTRLEN_LITERAL("-f "), &command)) {
ScpSource *scp = scp_source_new(sc, sftpserver_vt, command);
scp->recursive = recursive;
scp->send_file_times = preserve;
return &scp->scpserver;
} else {
ScpError *scp = scp_error_new(
sc, "Unable to parse scp command: '%.*s'",
PTRLEN_PRINTF(command_orig));
return &scp->scpserver;
}
}
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