src/openvpn/argv.c

/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single TCP/UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2002-2018 OpenVPN Inc <sales@openvpn.net>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 *
 *  A printf-like function (that only recognizes a subset of standard printf
 *  format operators) that prints arguments to an argv list instead
 *  of a standard string.  This is used to build up argv arrays for passing
 *  to execve.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#elif defined(_MSC_VER)
#include "config-msvc.h"
#endif

#include "syshead.h"

#include "argv.h"
#include "integer.h"
#include "env_set.h"
#include "options.h"

/**
 *  Resizes the list of arguments struct argv can carry.  This resize
 *  operation will only increase the size, never decrease the size.
 *
 *  @param *a      Valid pointer to a struct argv to resize
 *  @param newcap  size_t with the new size of the argument list.
 */
static void
argv_extend(struct argv *a, const size_t newcap)
{
    if (newcap > a->capacity)
    {
        char **newargv;
        size_t i;
        ALLOC_ARRAY_CLEAR_GC(newargv, char *, newcap, &a->gc);
        for (i = 0; i < a->argc; ++i)
        {
            newargv[i] = a->argv[i];
        }
        a->argv = newargv;
        a->capacity = newcap;
    }
}

/**
 *  Initialise an already allocated struct argv.
 *  It is expected that the input argument is a valid pointer.
 *
 *  @param *a  Pointer to a struct argv to initialise
 */
static void
argv_init(struct argv *a)
{
    a->capacity = 0;
    a->argc = 0;
    a->argv = NULL;
    a->gc = gc_new();
    argv_extend(a, 8);
}

/**
 *  Allocates a new struct argv and ensures it is initialised.
 *  Note that it does not return a pointer, but a struct argv directly.
 *
 *  @returns Returns an initialised and empty struct argv.
 */
struct argv
argv_new(void)
{
    struct argv ret;
    argv_init(&ret);
    return ret;
}

/**
 *  Frees all memory allocations allocated by the struct argv
 *  related functions.
 *
 *  @param *a  Valid pointer to a struct argv to release memory from
 */
void
argv_free(struct argv *a)
{
    gc_free(&a->gc);
}

/**
 *  Resets the struct argv to an initial state.  No memory buffers
 *  will be released by this call.
 *
 *  @param *a      Valid pointer to a struct argv to resize
 */
static void
argv_reset(struct argv *a)
{
    if (a->argc)
    {
        size_t i;
        for (i = 0; i < a->argc; ++i)
        {
            a->argv[i] = NULL;
        }
        a->argc = 0;
    }
}

/**
 *  Extends an existing struct argv to carry minimum 'add' number
 *  of new arguments.  This builds on argv_extend(), which ensures the
 *  new size will only be higher than the current capacity.
 *
 *  The new size is also calculated based on the result of adjust_power_of_2().
 *  This approach ensures that the list does grow bulks and only when the
 *  current limit is reached.
 *
 *  @param *a   Valid pointer to the struct argv to extend
 *  @param add  size_t with the number of elements to add.
 *
 */
static void
argv_grow(struct argv *a, const size_t add)
{
    const size_t newargc = a->argc + add + 1;
    ASSERT(newargc > a->argc);
    argv_extend(a, adjust_power_of_2(newargc));
}

/**
 *  Appends a string to to the list of arguments stored in a struct argv
 *  This will ensure the list size in struct argv has the needed capacity to
 *  store the value.
 *
 *  @param *a    struct argv where to append the new string value
 *  @param *str  Pointer to string to append.  The provided string *MUST* have
 *               been malloc()ed or NULL.
 */
static void
argv_append(struct argv *a, char *str)
{
    argv_grow(a, 1);
    a->argv[a->argc++] = str;
}

/**
 *  Clones a struct argv with all the contents to a new allocated struct argv.
 *  If 'headroom' is larger than 0, it will create a head-room in front of the
 *  values being copied from the source input.
 *
 *
 *  @param *source   Valid pointer to the source struct argv to clone.  It may
 *                   be NULL.
 *  @param headroom  Number of slots to leave empty in front of the slots
 *                   copied from the source.
 *
 *  @returns Returns a new struct argv containing a copy of the source
 *           struct argv, with the given headroom in front of the copy.
 *
 */
static struct argv
argv_clone(const struct argv *source, const size_t headroom)
{
    struct argv r;
    argv_init(&r);

    for (size_t i = 0; i < headroom; ++i)
    {
        argv_append(&r, NULL);
    }
    if (source)
    {
        for (size_t i = 0; i < source->argc; ++i)
        {
            argv_append(&r, string_alloc(source->argv[i], &r.gc));
        }
    }
    return r;
}

/**
 *  Inserts an argument string in front of all other argument slots.
 *
 *  @param  *a     Valid pointer to the struct argv to insert the argument into
 *  @param  *head  Pointer to the char * string with the argument to insert
 *
 *  @returns Returns a new struct argv with the inserted argument in front
 */
struct argv
argv_insert_head(const struct argv *a, const char *head)
{
    struct argv r;
    r = argv_clone(a, 1);
    r.argv[0] = string_alloc(head, &r.gc);
    return r;
}

/**
 *  Generate a single string with all the arguments in a struct argv
 *  concatenated.
 *
 *  @param *a    Valid pointer to the struct argv with the arguments to list
 *  @param *gc   Pointer to a struct gc_arena managed buffer
 *  @param flags Flags passed to the print_argv() function.
 *
 *  @returns Returns a string generated by print_argv() with all the arguments
 *           concatenated.  If the argument count is 0, it will return an empty
 *           string.  The return string is allocated in the gc_arena managed
 *           buffer.  If the gc_arena pointer is NULL, the returned string
 *           must be free()d explicitly to avoid memory leaks.
 */
const char *
argv_str(const struct argv *a, struct gc_arena *gc, const unsigned int flags)
{
    return print_argv((const char **)a->argv, gc, flags);
}

/**
 *  Write the arguments stored in a struct argv via the msg() command.
 *
 *  @param msglev  Integer with the message level used by msg().
 *  @param *a      Valid pointer to the struct argv with the arguments to write.
 */
void
argv_msg(const int msglev, const struct argv *a)
{
    struct gc_arena gc = gc_new();
    msg(msglev, "%s", argv_str(a, &gc, 0));
    gc_free(&gc);
}

/**
 *  Similar to argv_msg() but prefixes the messages being written with a
 *  given string.
 *
 *  @param msglev   Integer with the message level used by msg().
 *  @param *a       Valid pointer to the struct argv with the arguments to write
 *  @param *prefix  Valid char * pointer to the prefix string
 *
 */
void
argv_msg_prefix(const int msglev, const struct argv *a, const char *prefix)
{
    struct gc_arena gc = gc_new();
    msg(msglev, "%s: %s", prefix, argv_str(a, &gc, 0));
    gc_free(&gc);
}

/**
 *  Prepares argv format string for further processing
 *
 *  Individual argument must be separated by space. Ignores leading and
 *  trailing spaces.  Consecutive spaces count as one. Returns prepared
 *  format string, with space replaced by delim and adds the number of
 *  arguments to the count parameter.
 *
 *  @param *format  Pointer to a the format string to process
 *  @param delim    Char with the delimiter to use
 *  @param *count   size_t pointer used to return the number of
 *                  tokens (argument slots) found in the format string.
 *  @param *gc      Pointer to a gc_arena managed buffer.
 *
 *  @returns Returns a parsed format string (char *), together with the
 *           number of tokens parts found (via *count).  The result string
 *           is allocated within the gc_arena managed buffer.  If the
 *           gc_arena pointer is NULL, the returned string must be explicitly
 *           free()d to avoid memory leaks.
 */
static char *
argv_prep_format(const char *format, const char delim, size_t *count,
                 struct gc_arena *gc)
{
    if (format == NULL)
    {
        return NULL;
    }

    bool in_token = false;
    char *f = gc_malloc(strlen(format) + 1, true, gc);
    for (int i = 0, j = 0; i < strlen(format); i++)
    {
        if (format[i] == ' ')
        {
            in_token = false;
            continue;
        }

        if (!in_token)
        {
            (*count)++;

            /*
             * We don't add any delimiter to the output string if
             * the string is empty; the resulting format string
             * will never start with a delimiter.
             */
            if (j > 0)  /* Has anything been written to the output string? */
            {
                f[j++] = delim;
            }
        }

        f[j++] = format[i];
        in_token = true;
    }

    return f;
}

/**
 *  Create a struct argv based on a format string
 *
 *  Instead of parsing the format string ourselves place delimiters via
 *  argv_prep_format() before we let libc's printf() do the parsing.
 *  Then split the resulting string at the injected delimiters.
 *
 *  @param *argres  Valid pointer to a struct argv where the resulting parsed
 *                  arguments, based on the format string.
 *  @param *format  Char* string with a printf() compliant format string
 *  @param arglist  A va_list with the arguments to be consumed by the format
 *                  string
 *
 *  @returns Returns true if the parsing and processing was successfully.  If
 *           the resulting number of arguments does not match the expected
 *           number of arguments (based on the format string), it is
 *           considered a failure, which returns false.  This can happen if
 *           the ASCII Group Separator (GS - 0x1D) is put into the arguments
 *           list or format string.
 */
static bool
argv_printf_arglist(struct argv *argres, const char *format, va_list arglist)
{
    const char delim = 0x1D;  /* ASCII Group Separator (GS) */
    bool res = false;

    /*
     * Prepare a format string which will be used by vsnprintf() later on.
     *
     * This means all space separators in the input format string will be
     * replaced by the GS (0x1D), so we can split this up again after the
     * the vsnprintf() call into individual arguments again which will be
     * saved in the struct argv.
     *
     */
    size_t argc = argres->argc;
    char *f = argv_prep_format(format, delim, &argc, &argres->gc);
    if (f == NULL)
    {
        goto out;
    }

    /*
     * Determine minimum buffer size.
     *
     * With C99, vsnprintf(NULL, 0, ...) will return the number of bytes
     * it would have written, had the buffer been large enough.
     */
    va_list tmplist;
    va_copy(tmplist, arglist);
    int len = vsnprintf(NULL, 0, f, tmplist);
    va_end(tmplist);
    if (len < 0)
    {
        goto out;
    }

    /*
     *  Do the actual vsnprintf() operation, which expands the format
     *  string with the provided arguments.
     */
    size_t size = len + 1;
    char *buf = gc_malloc(size, false, &argres->gc);
    len = vsnprintf(buf, size, f, arglist);
    if (len < 0 || len >= size)
    {
        goto out;
    }

    /*
     * Split the string at the GS (0x1D) delimiters and put each elemen
     * into the struct argv being returned to the caller.
     */
    char *end = strchr(buf, delim);
    while (end)
    {
        *end = '\0';
        argv_append(argres, buf);
        buf = end + 1;
        end = strchr(buf, delim);
    }
    argv_append(argres, buf);

    if (argres->argc != argc)
    {
        /* Someone snuck in a GS (0x1D), fail gracefully */
        argv_reset(argres);
        goto out;
    }
    res = true;

out:
    return res;
}

/**
 *  printf() variant which populates a struct argv.  It processes the
 *  format string with the provided arguments.  For each space separator found
 *  in the format string, a new argument will be added to the resulting
 *  struct argv.
 *
 *  This will always reset and ensure the result is based on a pristine
 *  struct argv.
 *
 *  @param *argres  Valid pointer to a struct argv where the result will be put.
 *  @param *format  printf() compliant (char *) format string.
 *
 *  @returns Returns true if the parsing was successful.  See
 *           argv_printf_arglist() for more details.  The parsed result will
 *           be put into argres.
 */
bool
argv_printf(struct argv *argres, const char *format, ...)
{
    va_list arglist;
    va_start(arglist, format);

    argv_reset(argres);
    bool res = argv_printf_arglist(argres, format, arglist);
    va_end(arglist);
    return res;
}

/**
 *  printf() inspired argv concatenation.  Adds arguments to an existing
 *  struct argv and populets the argument slots based on the printf() based
 *  format string.
 *
 *  @param *argres  Valid pointer to a struct argv where the result will be put.
 *  @param *format  printf() compliant (char *) format string.
 *
 *  @returns Returns true if the parsing was successful.  See
 *           argv_printf_arglist() for more details.  The parsed result will
 *           be put into argres.
 */
bool
argv_printf_cat(struct argv *argres, const char *format, ...)
{
    va_list arglist;
    va_start(arglist, format);
    bool res = argv_printf_arglist(argres, format, arglist);
    va_end(arglist);
    return res;
}

/**
 *  Parses a command string, tokenizes it and puts each element into a separate
 *  struct argv argument slot.
 *
 *  @params *argres  Valid pointer to a struct argv where the parsed result
 *                   will be found.
 *  @params *cmdstr  Char * based string to parse
 *
 */
void
argv_parse_cmd(struct argv *argres, const char *cmdstr)
{
    argv_reset(argres);

    char *parms[MAX_PARMS + 1] = { 0 };
    int nparms = parse_line(cmdstr, parms, MAX_PARMS, "SCRIPT-ARGV", 0,
                            D_ARGV_PARSE_CMD, &argres->gc);
    if (nparms)
    {
        int i;
        for (i = 0; i < nparms; ++i)
        {
            argv_append(argres, parms[i]);
        }
    }
    else
    {
        argv_append(argres, string_alloc(cmdstr, &argres->gc));
    }
}