/*
 * sftp.h: definitions for SFTP and the sftp.c routines.
 */

#include "defs.h"

#define SSH_FXP_INIT                              1     /* 0x1 */
#define SSH_FXP_VERSION                           2     /* 0x2 */
#define SSH_FXP_OPEN                              3     /* 0x3 */
#define SSH_FXP_CLOSE                             4     /* 0x4 */
#define SSH_FXP_READ                              5     /* 0x5 */
#define SSH_FXP_WRITE                             6     /* 0x6 */
#define SSH_FXP_LSTAT                             7     /* 0x7 */
#define SSH_FXP_FSTAT                             8     /* 0x8 */
#define SSH_FXP_SETSTAT                           9     /* 0x9 */
#define SSH_FXP_FSETSTAT                          10    /* 0xa */
#define SSH_FXP_OPENDIR                           11    /* 0xb */
#define SSH_FXP_READDIR                           12    /* 0xc */
#define SSH_FXP_REMOVE                            13    /* 0xd */
#define SSH_FXP_MKDIR                             14    /* 0xe */
#define SSH_FXP_RMDIR                             15    /* 0xf */
#define SSH_FXP_REALPATH                          16    /* 0x10 */
#define SSH_FXP_STAT                              17    /* 0x11 */
#define SSH_FXP_RENAME                            18    /* 0x12 */
#define SSH_FXP_STATUS                            101   /* 0x65 */
#define SSH_FXP_HANDLE                            102   /* 0x66 */
#define SSH_FXP_DATA                              103   /* 0x67 */
#define SSH_FXP_NAME                              104   /* 0x68 */
#define SSH_FXP_ATTRS                             105   /* 0x69 */
#define SSH_FXP_EXTENDED                          200   /* 0xc8 */
#define SSH_FXP_EXTENDED_REPLY                    201   /* 0xc9 */

#define SSH_FX_OK                                 0
#define SSH_FX_EOF                                1
#define SSH_FX_NO_SUCH_FILE                       2
#define SSH_FX_PERMISSION_DENIED                  3
#define SSH_FX_FAILURE                            4
#define SSH_FX_BAD_MESSAGE                        5
#define SSH_FX_NO_CONNECTION                      6
#define SSH_FX_CONNECTION_LOST                    7
#define SSH_FX_OP_UNSUPPORTED                     8

#define SSH_FILEXFER_ATTR_SIZE                    0x00000001
#define SSH_FILEXFER_ATTR_UIDGID                  0x00000002
#define SSH_FILEXFER_ATTR_PERMISSIONS             0x00000004
#define SSH_FILEXFER_ATTR_ACMODTIME               0x00000008
#define SSH_FILEXFER_ATTR_EXTENDED                0x80000000

#define SSH_FXF_READ                              0x00000001
#define SSH_FXF_WRITE                             0x00000002
#define SSH_FXF_APPEND                            0x00000004
#define SSH_FXF_CREAT                             0x00000008
#define SSH_FXF_TRUNC                             0x00000010
#define SSH_FXF_EXCL                              0x00000020

#define SFTP_PROTO_VERSION 3

#define PERMS_DIRECTORY   040000

/*
 * External references. The sftp client module sftp.c expects to be
 * able to get at these functions.
 *
 * sftp_recvdata must never return less than len. It either blocks
 * until len is available and then returns true, or it returns false
 * for failure.
 *
 * sftp_senddata returns true on success, false on failure.
 *
 * sftp_sendbuffer returns the size of the backlog of data in the
 * transmit queue.
 */
bool sftp_senddata(const char *data, size_t len);
size_t sftp_sendbuffer(void);
bool sftp_recvdata(char *data, size_t len);

/*
 * Free sftp_requests
 */
void sftp_cleanup_request(void);

struct fxp_attrs {
    unsigned long flags;
    uint64_t size;
    unsigned long uid;
    unsigned long gid;
    unsigned long permissions;
    unsigned long atime;
    unsigned long mtime;
};
extern const struct fxp_attrs no_attrs;

/*
 * Copy between the possibly-unused permissions field in an fxp_attrs
 * and a possibly-negative integer containing the same permissions.
 */
#define PUT_PERMISSIONS(attrs, perms)                   \
    ((perms) >= 0 ?                                     \
     ((attrs).flags |= SSH_FILEXFER_ATTR_PERMISSIONS,   \
      (attrs).permissions = (perms)) :                  \
     ((attrs).flags &= ~SSH_FILEXFER_ATTR_PERMISSIONS))
#define GET_PERMISSIONS(attrs, defaultperms)            \
    ((attrs).flags & SSH_FILEXFER_ATTR_PERMISSIONS ?    \
     (attrs).permissions : defaultperms)

struct fxp_handle {
    char *hstring;
    int hlen;
};

struct fxp_name {
    char *filename, *longname;
    struct fxp_attrs attrs;
};

struct fxp_names {
    int nnames;
    struct fxp_name *names;
};

struct sftp_request;

/*
 * Packet-manipulation functions.
 */

struct sftp_packet {
    char *data;
    size_t length, maxlen, savedpos;
    int type;
    BinarySink_IMPLEMENTATION;
    BinarySource_IMPLEMENTATION;
};

/* When sending a packet, create it with sftp_pkt_init, then add
 * things to it by treating it as a BinarySink. When it's done, call
 * sftp_send_prepare, and then pkt->data and pkt->length describe its
 * wire format. */
struct sftp_packet *sftp_pkt_init(int pkt_type);
void sftp_send_prepare(struct sftp_packet *pkt);

/* When receiving a packet, create it with sftp_recv_prepare once you
 * decode its length from the first 4 bytes of wire data. Then write
 * that many bytes into pkt->data, and call sftp_recv_finish to set up
 * the type code and BinarySource. */
struct sftp_packet *sftp_recv_prepare(unsigned length);
bool sftp_recv_finish(struct sftp_packet *pkt);

/* Either kind of packet can be freed afterwards with sftp_pkt_free. */
void sftp_pkt_free(struct sftp_packet *pkt);

void BinarySink_put_fxp_attrs(BinarySink *bs, struct fxp_attrs attrs);
bool BinarySource_get_fxp_attrs(BinarySource *src, struct fxp_attrs *attrs);
#define put_fxp_attrs(bs, attrs) \
    BinarySink_put_fxp_attrs(BinarySink_UPCAST(bs), attrs)
#define get_fxp_attrs(bs, attrs) \
    BinarySource_get_fxp_attrs(BinarySource_UPCAST(bs), attrs)

/*
 * Error handling.
 */

const char *fxp_error(void);
int fxp_error_type(void);

/*
 * Perform exchange of init/version packets. Return false on failure.
 */
bool fxp_init(void);

/*
 * Canonify a pathname. Concatenate the two given path elements
 * with a separating slash, unless the second is NULL.
 */
struct sftp_request *fxp_realpath_send(const char *path);
char *fxp_realpath_recv(struct sftp_packet *pktin, struct sftp_request *req);

/*
 * Open a file. 'attrs' contains attributes to be applied to the file
 * if it's being created.
 */
struct sftp_request *fxp_open_send(const char *path, int type,
                                   const struct fxp_attrs *attrs);
struct fxp_handle *fxp_open_recv(struct sftp_packet *pktin,
                                 struct sftp_request *req);

/*
 * Open a directory.
 */
struct sftp_request *fxp_opendir_send(const char *path);
struct fxp_handle *fxp_opendir_recv(struct sftp_packet *pktin,
                                    struct sftp_request *req);

/*
 * Close a file/dir. Returns true on success, false on error.
 */
struct sftp_request *fxp_close_send(struct fxp_handle *handle);
bool fxp_close_recv(struct sftp_packet *pktin, struct sftp_request *req);

/*
 * Make a directory.
 */
struct sftp_request *fxp_mkdir_send(const char *path,
                                    const struct fxp_attrs *attrs);
bool fxp_mkdir_recv(struct sftp_packet *pktin, struct sftp_request *req);

/*
 * Remove a directory.
 */
struct sftp_request *fxp_rmdir_send(const char *path);
bool fxp_rmdir_recv(struct sftp_packet *pktin, struct sftp_request *req);

/*
 * Remove a file.
 */
struct sftp_request *fxp_remove_send(const char *fname);
bool fxp_remove_recv(struct sftp_packet *pktin, struct sftp_request *req);

/*
 * Rename a file.
 */
struct sftp_request *fxp_rename_send(const char *srcfname,
                                     const char *dstfname);
bool fxp_rename_recv(struct sftp_packet *pktin, struct sftp_request *req);

/*
 * Return file attributes.
 */
struct sftp_request *fxp_stat_send(const char *fname);
bool fxp_stat_recv(struct sftp_packet *pktin, struct sftp_request *req,
                   struct fxp_attrs *attrs);
struct sftp_request *fxp_fstat_send(struct fxp_handle *handle);
bool fxp_fstat_recv(struct sftp_packet *pktin, struct sftp_request *req,
                    struct fxp_attrs *attrs);

/*
 * Set file attributes.
 */
struct sftp_request *fxp_setstat_send(const char *fname,
                                      struct fxp_attrs attrs);
bool fxp_setstat_recv(struct sftp_packet *pktin, struct sftp_request *req);
struct sftp_request *fxp_fsetstat_send(struct fxp_handle *handle,
                                       struct fxp_attrs attrs);
bool fxp_fsetstat_recv(struct sftp_packet *pktin, struct sftp_request *req);

/*
 * Read from a file.
 */
struct sftp_request *fxp_read_send(struct fxp_handle *handle,
                                   uint64_t offset, int len);
int fxp_read_recv(struct sftp_packet *pktin, struct sftp_request *req,
                  char *buffer, int len);

/*
 * Write to a file.
 */
struct sftp_request *fxp_write_send(struct fxp_handle *handle,
                                    void *buffer, uint64_t offset, int len);
bool fxp_write_recv(struct sftp_packet *pktin, struct sftp_request *req);

/*
 * Read from a directory.
 */
struct sftp_request *fxp_readdir_send(struct fxp_handle *handle);
struct fxp_names *fxp_readdir_recv(struct sftp_packet *pktin,
                                   struct sftp_request *req);

/*
 * Free up an fxp_names structure.
 */
void fxp_free_names(struct fxp_names *names);

/*
 * Duplicate and free fxp_name structures.
 */
struct fxp_name *fxp_dup_name(struct fxp_name *name);
void fxp_free_name(struct fxp_name *name);

/*
 * Store user data in an sftp_request structure.
 */
void *fxp_get_userdata(struct sftp_request *req);
void fxp_set_userdata(struct sftp_request *req, void *data);

/*
 * These functions might well be temporary placeholders to be
 * replaced with more useful similar functions later. They form the
 * main dispatch loop for processing incoming SFTP responses.
 */
void sftp_register(struct sftp_request *req);
struct sftp_request *sftp_find_request(struct sftp_packet *pktin);
struct sftp_packet *sftp_recv(void);

/*
 * A wrapper to go round fxp_read_* and fxp_write_*, which manages
 * the queueing of multiple read/write requests.
 */

struct fxp_xfer;

struct fxp_xfer *xfer_download_init(struct fxp_handle *fh, uint64_t offset);
void xfer_download_queue(struct fxp_xfer *xfer);
int xfer_download_gotpkt(struct fxp_xfer *xfer, struct sftp_packet *pktin);
bool xfer_download_data(struct fxp_xfer *xfer, void **buf, int *len);

struct fxp_xfer *xfer_upload_init(struct fxp_handle *fh, uint64_t offset);
bool xfer_upload_ready(struct fxp_xfer *xfer);
void xfer_upload_data(struct fxp_xfer *xfer, char *buffer, int len);
int xfer_upload_gotpkt(struct fxp_xfer *xfer, struct sftp_packet *pktin);

bool xfer_done(struct fxp_xfer *xfer);
void xfer_set_error(struct fxp_xfer *xfer);
void xfer_cleanup(struct fxp_xfer *xfer);

/*
 * Vtable for the platform-specific filesystem implementation that
 * answers requests in an SFTP server.
 */
typedef struct SftpReplyBuilder SftpReplyBuilder;
struct SftpServer {
    const SftpServerVtable *vt;
};
struct SftpServerVtable {
    SftpServer *(*new)(const SftpServerVtable *vt);
    void (*free)(SftpServer *srv);

    /*
     * Handle actual filesystem requests.
     *
     * Each of these functions replies by calling an appropiate
     * sftp_reply_foo() function on the given reply packet.
     */

    /* Should call fxp_reply_error or fxp_reply_simple_name */
    void (*realpath)(SftpServer *srv, SftpReplyBuilder *reply,
                     ptrlen path);

    /* Should call fxp_reply_error or fxp_reply_handle */
    void (*open)(SftpServer *srv, SftpReplyBuilder *reply,
                 ptrlen path, unsigned flags, struct fxp_attrs attrs);

    /* Should call fxp_reply_error or fxp_reply_handle */
    void (*opendir)(SftpServer *srv, SftpReplyBuilder *reply,
                    ptrlen path);

    /* Should call fxp_reply_error or fxp_reply_ok */
    void (*close)(SftpServer *srv, SftpReplyBuilder *reply, ptrlen handle);

    /* Should call fxp_reply_error or fxp_reply_ok */
    void (*mkdir)(SftpServer *srv, SftpReplyBuilder *reply,
                  ptrlen path, struct fxp_attrs attrs);

    /* Should call fxp_reply_error or fxp_reply_ok */
    void (*rmdir)(SftpServer *srv, SftpReplyBuilder *reply, ptrlen path);

    /* Should call fxp_reply_error or fxp_reply_ok */
    void (*remove)(SftpServer *srv, SftpReplyBuilder *reply, ptrlen path);

    /* Should call fxp_reply_error or fxp_reply_ok */
    void (*rename)(SftpServer *srv, SftpReplyBuilder *reply,
                   ptrlen srcpath, ptrlen dstpath);

    /* Should call fxp_reply_error or fxp_reply_attrs */
    void (*stat)(SftpServer *srv, SftpReplyBuilder *reply, ptrlen path,
                 bool follow_symlinks);

    /* Should call fxp_reply_error or fxp_reply_attrs */
    void (*fstat)(SftpServer *srv, SftpReplyBuilder *reply, ptrlen handle);

    /* Should call fxp_reply_error or fxp_reply_ok */
    void (*setstat)(SftpServer *srv, SftpReplyBuilder *reply,
                    ptrlen path, struct fxp_attrs attrs);

    /* Should call fxp_reply_error or fxp_reply_ok */
    void (*fsetstat)(SftpServer *srv, SftpReplyBuilder *reply,
                     ptrlen handle, struct fxp_attrs attrs);

    /* Should call fxp_reply_error or fxp_reply_data */
    void (*read)(SftpServer *srv, SftpReplyBuilder *reply,
                 ptrlen handle, uint64_t offset, unsigned length);

    /* Should call fxp_reply_error or fxp_reply_ok */
    void (*write)(SftpServer *srv, SftpReplyBuilder *reply,
                  ptrlen handle, uint64_t offset, ptrlen data);

    /* Should call fxp_reply_error, or fxp_reply_name_count once and
     * then fxp_reply_full_name that many times */
    void (*readdir)(SftpServer *srv, SftpReplyBuilder *reply, ptrlen handle,
                    int max_entries, bool omit_longname);
};

static inline SftpServer *sftpsrv_new(const SftpServerVtable *vt)
{ return vt->new(vt); }
static inline void sftpsrv_free(SftpServer *srv)
{ srv->vt->free(srv); }
static inline void sftpsrv_realpath(SftpServer *srv, SftpReplyBuilder *reply,
                                    ptrlen path)
{ srv->vt->realpath(srv, reply, path); }
static inline void sftpsrv_open(
    SftpServer *srv, SftpReplyBuilder *reply,
    ptrlen path, unsigned flags, struct fxp_attrs attrs)
{ srv->vt->open(srv, reply, path, flags, attrs); }
static inline void sftpsrv_opendir(
    SftpServer *srv, SftpReplyBuilder *reply, ptrlen path)
{ srv->vt->opendir(srv, reply, path); }
static inline void sftpsrv_close(
    SftpServer *srv, SftpReplyBuilder *reply, ptrlen handle)
{ srv->vt->close(srv, reply, handle); }
static inline void sftpsrv_mkdir(SftpServer *srv, SftpReplyBuilder *reply,
                                 ptrlen path, struct fxp_attrs attrs)
{ srv->vt->mkdir(srv, reply, path, attrs); }
static inline void sftpsrv_rmdir(
    SftpServer *srv, SftpReplyBuilder *reply, ptrlen path)
{ srv->vt->rmdir(srv, reply, path); }
static inline void sftpsrv_remove(
    SftpServer *srv, SftpReplyBuilder *reply, ptrlen path)
{ srv->vt->remove(srv, reply, path); }
static inline void sftpsrv_rename(SftpServer *srv, SftpReplyBuilder *reply,
                                  ptrlen srcpath, ptrlen dstpath)
{ srv->vt->rename(srv, reply, srcpath, dstpath); }
static inline void sftpsrv_stat(
    SftpServer *srv, SftpReplyBuilder *reply, ptrlen path, bool follow)
{ srv->vt->stat(srv, reply, path, follow); }
static inline void sftpsrv_fstat(
    SftpServer *srv, SftpReplyBuilder *reply, ptrlen handle)
{ srv->vt->fstat(srv, reply, handle); }
static inline void sftpsrv_setstat(SftpServer *srv, SftpReplyBuilder *reply,
                                   ptrlen path, struct fxp_attrs attrs)
{ srv->vt->setstat(srv, reply, path, attrs); }
static inline void sftpsrv_fsetstat(SftpServer *srv, SftpReplyBuilder *reply,
                                    ptrlen handle, struct fxp_attrs attrs)
{ srv->vt->fsetstat(srv, reply, handle, attrs); }
static inline void sftpsrv_read(
    SftpServer *srv, SftpReplyBuilder *reply,
    ptrlen handle, uint64_t offset, unsigned length)
{ srv->vt->read(srv, reply, handle, offset, length); }
static inline void sftpsrv_write(SftpServer *srv, SftpReplyBuilder *reply,
                                 ptrlen handle, uint64_t offset, ptrlen data)
{ srv->vt->write(srv, reply, handle, offset, data); }
static inline void sftpsrv_readdir(
    SftpServer *srv, SftpReplyBuilder *reply, ptrlen handle,
    int max_entries, bool omit_longname)
{ srv->vt->readdir(srv, reply, handle, max_entries, omit_longname); }

typedef struct SftpReplyBuilderVtable SftpReplyBuilderVtable;
struct SftpReplyBuilder {
    const SftpReplyBuilderVtable *vt;
};
struct SftpReplyBuilderVtable {
    void (*reply_ok)(SftpReplyBuilder *reply);
    void (*reply_error)(SftpReplyBuilder *reply, unsigned code,
                        const char *msg);
    void (*reply_simple_name)(SftpReplyBuilder *reply, ptrlen name);
    void (*reply_name_count)(SftpReplyBuilder *reply, unsigned count);
    void (*reply_full_name)(SftpReplyBuilder *reply, ptrlen name,
                            ptrlen longname, struct fxp_attrs attrs);
    void (*reply_handle)(SftpReplyBuilder *reply, ptrlen handle);
    void (*reply_data)(SftpReplyBuilder *reply, ptrlen data);
    void (*reply_attrs)(SftpReplyBuilder *reply, struct fxp_attrs attrs);
};

static inline void fxp_reply_ok(SftpReplyBuilder *reply)
{ reply->vt->reply_ok(reply); }
static inline void fxp_reply_error(SftpReplyBuilder *reply, unsigned code,
                                   const char *msg)
{ reply->vt->reply_error(reply, code, msg); }
static inline void fxp_reply_simple_name(SftpReplyBuilder *reply, ptrlen name)
{ reply->vt->reply_simple_name(reply, name); }
static inline void fxp_reply_name_count(
    SftpReplyBuilder *reply, unsigned count)
{ reply->vt->reply_name_count(reply, count); }
static inline void fxp_reply_full_name(SftpReplyBuilder *reply, ptrlen name,
                                       ptrlen longname, struct fxp_attrs attrs)
{ reply->vt->reply_full_name(reply, name, longname, attrs); }
static inline void fxp_reply_handle(SftpReplyBuilder *reply, ptrlen handle)
{ reply->vt->reply_handle(reply, handle); }
static inline void fxp_reply_data(SftpReplyBuilder *reply, ptrlen data)
{ reply->vt->reply_data(reply, data); }
static inline void fxp_reply_attrs(
    SftpReplyBuilder *reply, struct fxp_attrs attrs)
{ reply->vt->reply_attrs(reply, attrs); }

/*
 * The usual implementation of an SftpReplyBuilder, containing a
 * 'struct sftp_packet' which is assumed to be already initialised
 * before one of the above request methods is called.
 */
extern const struct SftpReplyBuilderVtable DefaultSftpReplyBuilder_vt;
typedef struct DefaultSftpReplyBuilder DefaultSftpReplyBuilder;
struct DefaultSftpReplyBuilder {
    SftpReplyBuilder rb;
    struct sftp_packet *pkt;
};

/*
 * The top-level function that handles an SFTP request, given an
 * implementation of the above SftpServer abstraction to do the actual
 * filesystem work. It handles all the marshalling and unmarshalling
 * of packets, and the copying of request ids into the responses.
 */
struct sftp_packet *sftp_handle_request(
    SftpServer *srv, struct sftp_packet *request);

/* ----------------------------------------------------------------------
 * Not exactly SFTP-related, but here's a system that implements an
 * old-fashioned SCP server module, given an SftpServer vtable to use
 * as its underlying filesystem access.
 */

typedef struct ScpServer ScpServer;
typedef struct ScpServerVtable ScpServerVtable;
struct ScpServer {
    const struct ScpServerVtable *vt;
};
struct ScpServerVtable {
    void (*free)(ScpServer *s);

    size_t (*send)(ScpServer *s, const void *data, size_t length);
    void (*throttle)(ScpServer *s, bool throttled);
    void (*eof)(ScpServer *s);
};

static inline void scp_free(ScpServer *s)
{ s->vt->free(s); }
static inline size_t scp_send(ScpServer *s, const void *data, size_t length)
{ return s->vt->send(s, data, length); }
static inline void scp_throttle(ScpServer *s, bool throttled)
{ s->vt->throttle(s, throttled); }
static inline void scp_eof(ScpServer *s)
{ s->vt->eof(s); }

/*
 * Create an ScpServer by calling this function, giving it the command
 * you received from the SSH client to execute. If that command is
 * recognised as an scp command, it will construct an ScpServer object
 * and return it; otherwise, it will return NULL, and you should
 * execute the command in whatever way you normally would.
 *
 * The ScpServer will generate output for the client by writing it to
 * the provided SshChannel using sshfwd_write; you pass it input using
 * the send method in its own vtable.
 */
ScpServer *scp_recognise_exec(
    SshChannel *sc, const SftpServerVtable *sftpserver_vt, ptrlen command);
