genfile.c

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/*-------------------------------------------------------------------------
 *
 * genfile.c
 *      Functions for direct access to files
 *
 *
 * Copyright (c) 2004-2020, PostgreSQL Global Development Group
 *
 * Author: Andreas Pflug <pgadmin@pse-consulting.de>
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/genfile.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <sys/file.h>
#include <sys/stat.h>
#include <unistd.h>
#include <dirent.h>

#include "access/htup_details.h"
#include "access/xlog_internal.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_tablespace_d.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "postmaster/syslogger.h"
#include "storage/fd.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/memutils.h"
#include "utils/syscache.h"
#include "utils/timestamp.h"


/*
 * Convert a "text" filename argument to C string, and check it's allowable.
 *
 * Filename may be absolute or relative to the DataDir, but we only allow
 * absolute paths that match DataDir or Log_directory.
 *
 * This does a privilege check against the 'pg_read_server_files' role, so
 * this function is really only appropriate for callers who are only checking
 * 'read' access.  Do not use this function if you are looking for a check
 * for 'write' or 'program' access without updating it to access the type
 * of check as an argument and checking the appropriate role membership.
 */
static char *
convert_and_check_filename(text *arg)
{
    char       *filename;

    filename = text_to_cstring(arg);
    canonicalize_path(filename);    /* filename can change length here */

    /*
     * Members of the 'pg_read_server_files' role are allowed to access any
     * files on the server as the PG user, so no need to do any further checks
     * here.
     */
    if (is_member_of_role(GetUserId(), DEFAULT_ROLE_READ_SERVER_FILES))
        return filename;

    /* User isn't a member of the default role, so check if it's allowable */
    if (is_absolute_path(filename))
    {
        /* Disallow '/a/b/data/..' */
        if (path_contains_parent_reference(filename))
            ereport(ERROR,
                    (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                     errmsg("reference to parent directory (\"..\") not allowed")));

        /*
         * Allow absolute paths if within DataDir or Log_directory, even
         * though Log_directory might be outside DataDir.
         */
        if (!path_is_prefix_of_path(DataDir, filename) &&
            (!is_absolute_path(Log_directory) ||
             !path_is_prefix_of_path(Log_directory, filename)))
            ereport(ERROR,
                    (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                     errmsg("absolute path not allowed")));
    }
    else if (!path_is_relative_and_below_cwd(filename))
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("path must be in or below the current directory")));

    return filename;
}


/*
 * Read a section of a file, returning it as bytea
 *
 * Caller is responsible for all permissions checking.
 *
 * We read the whole of the file when bytes_to_read is negative.
 */
static bytea *
read_binary_file(const char *filename, int64 seek_offset, int64 bytes_to_read,
                 bool missing_ok)
{
    bytea      *buf;
    size_t      nbytes = 0;
    FILE       *file;

    /* clamp request size to what we can actually deliver */
    if (bytes_to_read > (int64) (MaxAllocSize - VARHDRSZ))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("requested length too large")));

    if ((file = AllocateFile(filename, PG_BINARY_R)) == NULL)
    {
        if (missing_ok && errno == ENOENT)
            return NULL;
        else
            ereport(ERROR,
                    (errcode_for_file_access(),
                     errmsg("could not open file \"%s\" for reading: %m",
                            filename)));
    }

    if (fseeko(file, (off_t) seek_offset,
               (seek_offset >= 0) ? SEEK_SET : SEEK_END) != 0)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not seek in file \"%s\": %m", filename)));

    if (bytes_to_read >= 0)
    {
        /* If passed explicit read size just do it */
        buf = (bytea *) palloc((Size) bytes_to_read + VARHDRSZ);

        nbytes = fread(VARDATA(buf), 1, (size_t) bytes_to_read, file);
    }
    else
    {
        /* Negative read size, read rest of file */
        StringInfoData sbuf;

        initStringInfo(&sbuf);
        /* Leave room in the buffer for the varlena length word */
        sbuf.len += VARHDRSZ;
        Assert(sbuf.len < sbuf.maxlen);

        while (!(feof(file) || ferror(file)))
        {
            size_t      rbytes;

            /* Minimum amount to read at a time */
#define MIN_READ_SIZE 4096

            /*
             * If not at end of file, and sbuf.len is equal to
             * MaxAllocSize - 1, then either the file is too large, or
             * there is nothing left to read. Attempt to read one more
             * byte to see if the end of file has been reached. If not,
             * the file is too large; we'd rather give the error message
             * for that ourselves.
             */
            if (sbuf.len == MaxAllocSize - 1)
            {
                char    rbuf[1]; 

                if (fread(rbuf, 1, 1, file) != 0 || !feof(file))
                    ereport(ERROR,
                            (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                             errmsg("file length too large")));
                else
                    break;
            }

            /* OK, ensure that we can read at least MIN_READ_SIZE */
            enlargeStringInfo(&sbuf, MIN_READ_SIZE);

            /*
             * stringinfo.c likes to allocate in powers of 2, so it's likely
             * that much more space is available than we asked for.  Use all
             * of it, rather than making more fread calls than necessary.
             */
            rbytes = fread(sbuf.data + sbuf.len, 1,
                           (size_t) (sbuf.maxlen - sbuf.len - 1), file);
            sbuf.len += rbytes;
            nbytes += rbytes;
        }

        /* Now we can commandeer the stringinfo's buffer as the result */
        buf = (bytea *) sbuf.data;
    }

    if (ferror(file))
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not read file \"%s\": %m", filename)));

    SET_VARSIZE(buf, nbytes + VARHDRSZ);

    FreeFile(file);

    return buf;
}

/*
 * Similar to read_binary_file, but we verify that the contents are valid
 * in the database encoding.
 */
static text *
read_text_file(const char *filename, int64 seek_offset, int64 bytes_to_read,
               bool missing_ok)
{
    bytea      *buf;

    buf = read_binary_file(filename, seek_offset, bytes_to_read, missing_ok);

    if (buf != NULL)
    {
        /* Make sure the input is valid */
        pg_verifymbstr(VARDATA(buf), VARSIZE(buf) - VARHDRSZ, false);

        /* OK, we can cast it to text safely */
        return (text *) buf;
    }
    else
        return NULL;
}

/*
 * Read a section of a file, returning it as text
 *
 * This function is kept to support adminpack 1.0.
 */
Datum
pg_read_file(PG_FUNCTION_ARGS)
{
    text       *filename_t = PG_GETARG_TEXT_PP(0);
    int64       seek_offset = 0;
    int64       bytes_to_read = -1;
    bool        missing_ok = false;
    char       *filename;
    text       *result;

    if (!superuser())
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("must be superuser to read files with adminpack 1.0"),
        /* translator: %s is a SQL function name */
                 errhint("Consider using %s, which is part of core, instead.",
                         "pg_file_read()")));

    /* handle optional arguments */
    if (PG_NARGS() >= 3)
    {
        seek_offset = PG_GETARG_INT64(1);
        bytes_to_read = PG_GETARG_INT64(2);

        if (bytes_to_read < 0)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("requested length cannot be negative")));
    }
    if (PG_NARGS() >= 4)
        missing_ok = PG_GETARG_BOOL(3);

    filename = convert_and_check_filename(filename_t);

    result = read_text_file(filename, seek_offset, bytes_to_read, missing_ok);
    if (result)
        PG_RETURN_TEXT_P(result);
    else
        PG_RETURN_NULL();
}

/*
 * Read a section of a file, returning it as text
 *
 * No superuser check done here- instead privileges are handled by the
 * GRANT system.
 */
Datum
pg_read_file_v2(PG_FUNCTION_ARGS)
{
    text       *filename_t = PG_GETARG_TEXT_PP(0);
    int64       seek_offset = 0;
    int64       bytes_to_read = -1;
    bool        missing_ok = false;
    char       *filename;
    text       *result;

    /* handle optional arguments */
    if (PG_NARGS() >= 3)
    {
        seek_offset = PG_GETARG_INT64(1);
        bytes_to_read = PG_GETARG_INT64(2);

        if (bytes_to_read < 0)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("requested length cannot be negative")));
    }
    if (PG_NARGS() >= 4)
        missing_ok = PG_GETARG_BOOL(3);

    filename = convert_and_check_filename(filename_t);

    result = read_text_file(filename, seek_offset, bytes_to_read, missing_ok);
    if (result)
        PG_RETURN_TEXT_P(result);
    else
        PG_RETURN_NULL();
}

/*
 * Read a section of a file, returning it as bytea
 */
Datum
pg_read_binary_file(PG_FUNCTION_ARGS)
{
    text       *filename_t = PG_GETARG_TEXT_PP(0);
    int64       seek_offset = 0;
    int64       bytes_to_read = -1;
    bool        missing_ok = false;
    char       *filename;
    bytea      *result;

    /* handle optional arguments */
    if (PG_NARGS() >= 3)
    {
        seek_offset = PG_GETARG_INT64(1);
        bytes_to_read = PG_GETARG_INT64(2);

        if (bytes_to_read < 0)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("requested length cannot be negative")));
    }
    if (PG_NARGS() >= 4)
        missing_ok = PG_GETARG_BOOL(3);

    filename = convert_and_check_filename(filename_t);

    result = read_binary_file(filename, seek_offset,
                              bytes_to_read, missing_ok);
    if (result)
        PG_RETURN_BYTEA_P(result);
    else
        PG_RETURN_NULL();
}


/*
 * Wrapper functions for the 1 and 3 argument variants of pg_read_file_v2()
 * and pg_read_binary_file().
 *
 * These are necessary to pass the sanity check in opr_sanity, which checks
 * that all built-in functions that share the implementing C function take
 * the same number of arguments.
 */
Datum
pg_read_file_off_len(PG_FUNCTION_ARGS)
{
    return pg_read_file_v2(fcinfo);
}

Datum
pg_read_file_all(PG_FUNCTION_ARGS)
{
    return pg_read_file_v2(fcinfo);
}

Datum
pg_read_binary_file_off_len(PG_FUNCTION_ARGS)
{
    return pg_read_binary_file(fcinfo);
}

Datum
pg_read_binary_file_all(PG_FUNCTION_ARGS)
{
    return pg_read_binary_file(fcinfo);
}

/*
 * stat a file
 */
Datum
pg_stat_file(PG_FUNCTION_ARGS)
{
    text       *filename_t = PG_GETARG_TEXT_PP(0);
    char       *filename;
    struct stat fst;
    Datum       values[6];
    bool        isnull[6];
    HeapTuple   tuple;
    TupleDesc   tupdesc;
    bool        missing_ok = false;

    /* check the optional argument */
    if (PG_NARGS() == 2)
        missing_ok = PG_GETARG_BOOL(1);

    filename = convert_and_check_filename(filename_t);

    if (stat(filename, &fst) < 0)
    {
        if (missing_ok && errno == ENOENT)
            PG_RETURN_NULL();
        else
            ereport(ERROR,
                    (errcode_for_file_access(),
                     errmsg("could not stat file \"%s\": %m", filename)));
    }

    /*
     * This record type had better match the output parameters declared for me
     * in pg_proc.h.
     */
    tupdesc = CreateTemplateTupleDesc(6);
    TupleDescInitEntry(tupdesc, (AttrNumber) 1,
                       "size", INT8OID, -1, 0);
    TupleDescInitEntry(tupdesc, (AttrNumber) 2,
                       "access", TIMESTAMPTZOID, -1, 0);
    TupleDescInitEntry(tupdesc, (AttrNumber) 3,
                       "modification", TIMESTAMPTZOID, -1, 0);
    TupleDescInitEntry(tupdesc, (AttrNumber) 4,
                       "change", TIMESTAMPTZOID, -1, 0);
    TupleDescInitEntry(tupdesc, (AttrNumber) 5,
                       "creation", TIMESTAMPTZOID, -1, 0);
    TupleDescInitEntry(tupdesc, (AttrNumber) 6,
                       "isdir", BOOLOID, -1, 0);
    BlessTupleDesc(tupdesc);

    memset(isnull, false, sizeof(isnull));

    values[0] = Int64GetDatum((int64) fst.st_size);
    values[1] = TimestampTzGetDatum(time_t_to_timestamptz(fst.st_atime));
    values[2] = TimestampTzGetDatum(time_t_to_timestamptz(fst.st_mtime));
    /* Unix has file status change time, while Win32 has creation time */
#if !defined(WIN32) && !defined(__CYGWIN__)
    values[3] = TimestampTzGetDatum(time_t_to_timestamptz(fst.st_ctime));
    isnull[4] = true;
#else
    isnull[3] = true;
    values[4] = TimestampTzGetDatum(time_t_to_timestamptz(fst.st_ctime));
#endif
    values[5] = BoolGetDatum(S_ISDIR(fst.st_mode));

    tuple = heap_form_tuple(tupdesc, values, isnull);

    pfree(filename);

    PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
}

/*
 * stat a file (1 argument version)
 *
 * note: this wrapper is necessary to pass the sanity check in opr_sanity,
 * which checks that all built-in functions that share the implementing C
 * function take the same number of arguments
 */
Datum
pg_stat_file_1arg(PG_FUNCTION_ARGS)
{
    return pg_stat_file(fcinfo);
}

/*
 * List a directory (returns the filenames only)
 */
Datum
pg_ls_dir(PG_FUNCTION_ARGS)
{
    ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
    char       *location;
    bool        missing_ok = false;
    bool        include_dot_dirs = false;
    bool        randomAccess;
    TupleDesc   tupdesc;
    Tuplestorestate *tupstore;
    DIR        *dirdesc;
    struct dirent *de;
    MemoryContext oldcontext;

    location = convert_and_check_filename(PG_GETARG_TEXT_PP(0));

    /* check the optional arguments */
    if (PG_NARGS() == 3)
    {
        if (!PG_ARGISNULL(1))
            missing_ok = PG_GETARG_BOOL(1);
        if (!PG_ARGISNULL(2))
            include_dot_dirs = PG_GETARG_BOOL(2);
    }

    /* check to see if caller supports us returning a tuplestore */
    if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("set-valued function called in context that cannot accept a set")));
    if (!(rsinfo->allowedModes & SFRM_Materialize))
        ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                 errmsg("materialize mode required, but it is not allowed in this context")));

    /* The tupdesc and tuplestore must be created in ecxt_per_query_memory */
    oldcontext = MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);

    tupdesc = CreateTemplateTupleDesc(1);
    TupleDescInitEntry(tupdesc, (AttrNumber) 1, "pg_ls_dir", TEXTOID, -1, 0);

    randomAccess = (rsinfo->allowedModes & SFRM_Materialize_Random) != 0;
    tupstore = tuplestore_begin_heap(randomAccess, false, work_mem);
    rsinfo->returnMode = SFRM_Materialize;
    rsinfo->setResult = tupstore;
    rsinfo->setDesc = tupdesc;

    MemoryContextSwitchTo(oldcontext);

    dirdesc = AllocateDir(location);
    if (!dirdesc)
    {
        /* Return empty tuplestore if appropriate */
        if (missing_ok && errno == ENOENT)
            return (Datum) 0;
        /* Otherwise, we can let ReadDir() throw the error */
    }

    while ((de = ReadDir(dirdesc, location)) != NULL)
    {
        Datum       values[1];
        bool        nulls[1];

        if (!include_dot_dirs &&
            (strcmp(de->d_name, ".") == 0 ||
             strcmp(de->d_name, "..") == 0))
            continue;

        values[0] = CStringGetTextDatum(de->d_name);
        nulls[0] = false;

        tuplestore_putvalues(tupstore, tupdesc, values, nulls);
    }

    FreeDir(dirdesc);
    return (Datum) 0;
}

/*
 * List a directory (1 argument version)
 *
 * note: this wrapper is necessary to pass the sanity check in opr_sanity,
 * which checks that all built-in functions that share the implementing C
 * function take the same number of arguments.
 */
Datum
pg_ls_dir_1arg(PG_FUNCTION_ARGS)
{
    return pg_ls_dir(fcinfo);
}

/*
 * Generic function to return a directory listing of files.
 *
 * If the directory isn't there, silently return an empty set if missing_ok.
 * Other unreadable-directory cases throw an error.
 */
static Datum
pg_ls_dir_files(FunctionCallInfo fcinfo, const char *dir, bool missing_ok)
{
    ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
    bool        randomAccess;
    TupleDesc   tupdesc;
    Tuplestorestate *tupstore;
    DIR        *dirdesc;
    struct dirent *de;
    MemoryContext oldcontext;

    /* check to see if caller supports us returning a tuplestore */
    if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("set-valued function called in context that cannot accept a set")));
    if (!(rsinfo->allowedModes & SFRM_Materialize))
        ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                 errmsg("materialize mode required, but it is not allowed in this context")));

    /* The tupdesc and tuplestore must be created in ecxt_per_query_memory */
    oldcontext = MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);

    if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
        elog(ERROR, "return type must be a row type");

    randomAccess = (rsinfo->allowedModes & SFRM_Materialize_Random) != 0;
    tupstore = tuplestore_begin_heap(randomAccess, false, work_mem);
    rsinfo->returnMode = SFRM_Materialize;
    rsinfo->setResult = tupstore;
    rsinfo->setDesc = tupdesc;

    MemoryContextSwitchTo(oldcontext);

    /*
     * Now walk the directory.  Note that we must do this within a single SRF
     * call, not leave the directory open across multiple calls, since we
     * can't count on the SRF being run to completion.
     */
    dirdesc = AllocateDir(dir);
    if (!dirdesc)
    {
        /* Return empty tuplestore if appropriate */
        if (missing_ok && errno == ENOENT)
            return (Datum) 0;
        /* Otherwise, we can let ReadDir() throw the error */
    }

    while ((de = ReadDir(dirdesc, dir)) != NULL)
    {
        Datum       values[3];
        bool        nulls[3];
        char        path[MAXPGPATH * 2];
        struct stat attrib;

        /* Skip hidden files */
        if (de->d_name[0] == '.')
            continue;

        /* Get the file info */
        snprintf(path, sizeof(path), "%s/%s", dir, de->d_name);
        if (stat(path, &attrib) < 0)
        {
            /* Ignore concurrently-deleted files, else complain */
            if (errno == ENOENT)
                continue;
            ereport(ERROR,
                    (errcode_for_file_access(),
                     errmsg("could not stat file \"%s\": %m", path)));
        }

        /* Ignore anything but regular files */
        if (!S_ISREG(attrib.st_mode))
            continue;

        values[0] = CStringGetTextDatum(de->d_name);
        values[1] = Int64GetDatum((int64) attrib.st_size);
        values[2] = TimestampTzGetDatum(time_t_to_timestamptz(attrib.st_mtime));
        memset(nulls, 0, sizeof(nulls));

        tuplestore_putvalues(tupstore, tupdesc, values, nulls);
    }

    FreeDir(dirdesc);
    return (Datum) 0;
}

/* Function to return the list of files in the log directory */
Datum
pg_ls_logdir(PG_FUNCTION_ARGS)
{
    return pg_ls_dir_files(fcinfo, Log_directory, false);
}

/* Function to return the list of files in the WAL directory */
Datum
pg_ls_waldir(PG_FUNCTION_ARGS)
{
    return pg_ls_dir_files(fcinfo, XLOGDIR, false);
}

/*
 * Generic function to return the list of files in pgsql_tmp
 */
static Datum
pg_ls_tmpdir(FunctionCallInfo fcinfo, Oid tblspc)
{
    char        path[MAXPGPATH];

    if (!SearchSysCacheExists1(TABLESPACEOID, ObjectIdGetDatum(tblspc)))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("tablespace with OID %u does not exist",
                        tblspc)));

    TempTablespacePath(path, tblspc);
    return pg_ls_dir_files(fcinfo, path, true);
}

/*
 * Function to return the list of temporary files in the pg_default tablespace's
 * pgsql_tmp directory
 */
Datum
pg_ls_tmpdir_noargs(PG_FUNCTION_ARGS)
{
    return pg_ls_tmpdir(fcinfo, DEFAULTTABLESPACE_OID);
}

/*
 * Function to return the list of temporary files in the specified tablespace's
 * pgsql_tmp directory
 */
Datum
pg_ls_tmpdir_1arg(PG_FUNCTION_ARGS)
{
    return pg_ls_tmpdir(fcinfo, PG_GETARG_OID(0));
}

/*
 * Function to return the list of files in the WAL archive status directory.
 */
Datum
pg_ls_archive_statusdir(PG_FUNCTION_ARGS)
{
    return pg_ls_dir_files(fcinfo, XLOGDIR "/archive_status", true);
}