misc.c

/*
 * Platform-independent routines shared between all PuTTY programs.
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <limits.h>
#include <ctype.h>
#include <assert.h>
#include "putty.h"
#include "misc.h"

/*
 * Parse a string block size specification. This is approximately a
 * subset of the block size specs supported by GNU fileutils:
 *  "nk" = n kilobytes
 *  "nM" = n megabytes
 *  "nG" = n gigabytes
 * All numbers are decimal, and suffixes refer to powers of two.
 * Case-insensitive.
 */
unsigned long parse_blocksize(const char *bs)
{
  char *suf;
  unsigned long r = strtoul(bs, &suf, 10);
  if (*suf != '\0') {
    while (*suf && isspace((unsigned char)*suf))
      suf++;
    switch (*suf) {
    case 'k':
    case 'K':
      r *= 1024ul;
      break;
    case 'm':
    case 'M':
      r *= 1024ul * 1024ul;
      break;
    case 'g':
    case 'G':
      r *= 1024ul * 1024ul * 1024ul;
      break;
    case '\0':
    default:
      break;
    }
  }
  return r;
}

/*
 * Parse a ^C style character specification.
 * Returns NULL in `next' if we didn't recognise it as a control character,
 * in which case `c' should be ignored.
 * The precise current parsing is an oddity inherited from the terminal
 * answerback-string parsing code. All sequences start with ^; all except
 * ^<123> are two characters. The ones that are worth keeping are probably:
 *   ^?		    127
 *   ^@A-Z[\]^_	    0-31
 *   a-z	    1-26
 *   <num>	    specified by number (decimal, 0octal, 0xHEX)
 *   ~		    ^ escape
 */
char ctrlparse(char *s, char **next)
{
  char c = 0;
  if (*s != '^') {
    *next = NULL;
  } else {
    s++;
    if (*s == '\0') {
      *next = NULL;
    } else if (*s == '<') {
      s++;
      c = (char)strtol(s, next, 0);
      if ((*next == s) || (**next != '>')) {
        c = 0;
        *next = NULL;
      } else
        (*next)++;
    } else if (*s >= 'a' && *s <= 'z') {
      c = (*s - ('a' - 1));
      *next = s + 1;
    } else if ((*s >= '@' && *s <= '_') || *s == '?' || (*s & 0x80)) {
      c = ('@' ^ *s);
      *next = s + 1;
    } else if (*s == '~') {
      c = '^';
      *next = s + 1;
    }
  }
  return c;
}

/*
 * Find a character in a string, unless it's a colon contained within
 * square brackets. Used for untangling strings of the form
 * 'host:port', where host can be an IPv6 literal.
 *
 * We provide several variants of this function, with semantics like
 * various standard string.h functions.
 */
static const char *host_strchr_internal(const char *s,
                                        const char *set,
                                        int first)
{
  int brackets = 0;
  const char *ret = NULL;

  while (1) {
    if (!*s)
      return ret;

    if (*s == '[')
      brackets++;
    else if (*s == ']' && brackets > 0)
      brackets--;
    else if (brackets && *s == ':')
      /* never match */;
    else if (strchr(set, *s)) {
      ret = s;
      if (first)
        return ret;
    }

    s++;
  }
}
size_t host_strcspn(const char *s, const char *set)
{
  const char *answer = host_strchr_internal(s, set, TRUE);
  if (answer)
    return answer - s;
  else
    return strlen(s);
}
char *host_strchr(const char *s, int c)
{
  char set[2];
  set[0] = c;
  set[1] = '\0';
  return (char *)host_strchr_internal(s, set, TRUE);
}
char *host_strrchr(const char *s, int c)
{
  char set[2];
  set[0] = c;
  set[1] = '\0';
  return (char *)host_strchr_internal(s, set, FALSE);
}

#ifdef TEST_HOST_STRFOO
int main(void)
{
  int passes = 0, fails = 0;

#define TEST1(func, string, arg2, suffix, result)                              \
  do {                                                                         \
    const char *str = string;                                                  \
    unsigned ret = func(string, arg2) suffix;                                  \
    if (ret == result) {                                                       \
      passes++;                                                                \
    } else {                                                                   \
      printf("fail: %s(%s,%s)%s = %u, expected %u\n",                          \
             #func,                                                            \
             #string,                                                          \
             #arg2,                                                            \
             #suffix,                                                          \
             ret,                                                              \
             (unsigned)result);                                                \
      fails++;                                                                 \
    }                                                                          \
  } while (0)

  TEST1(host_strchr, "[1:2:3]:4:5", ':', -str, 7);
  TEST1(host_strrchr, "[1:2:3]:4:5", ':', -str, 9);
  TEST1(host_strcspn, "[1:2:3]:4:5", "/:", , 7);
  TEST1(host_strchr, "[1:2:3]", ':', == NULL, 1);
  TEST1(host_strrchr, "[1:2:3]", ':', == NULL, 1);
  TEST1(host_strcspn, "[1:2:3]", "/:", , 7);
  TEST1(host_strcspn, "[1:2/3]", "/:", , 4);
  TEST1(host_strcspn, "[1:2:3]/", "/:", , 7);

  printf("passed %d failed %d total %d\n", passes, fails, passes + fails);
  return fails != 0 ? 1 : 0;
}
/* Stubs to stop the rest of this module causing compile failures. */
void modalfatalbox(const char *fmt, ...)
{
}
int conf_get_int(Conf *conf, int primary)
{
  return 0;
}
char *conf_get_str(Conf *conf, int primary)
{
  return NULL;
}
#endif /* TEST_HOST_STRFOO */

/*
 * Trim square brackets off the outside of an IPv6 address literal.
 * Leave all other strings unchanged. Returns a fresh dynamically
 * allocated string.
 */
char *host_strduptrim(const char *s)
{
  if (s[0] == '[') {
    const char *p = s + 1;
    int colons = 0;
    while (*p && *p != ']') {
      if (isxdigit((unsigned char)*p))
        /* OK */;
      else if (*p == ':')
        colons++;
      else
        break;
      p++;
    }
    if (*p == ']' && !p[1] && colons > 1) {
      /*
       * This looks like an IPv6 address literal (hex digits and
       * at least two colons, contained in square brackets).
       * Trim off the brackets.
       */
      return dupprintf("%.*s", (int)(p - (s + 1)), s + 1);
    }
  }

  /*
   * Any other shape of string is simply duplicated.
   */
  return dupstr(s);
}

prompts_t *new_prompts(void *frontend)
{
  prompts_t *p = snew(prompts_t);
  p->prompts = NULL;
  p->n_prompts = 0;
  p->frontend = frontend;
  p->data = NULL;
  p->to_server = TRUE; /* to be on the safe side */
  p->name = p->instruction = NULL;
  p->name_reqd = p->instr_reqd = FALSE;
  return p;
}
void add_prompt(prompts_t *p, char *promptstr, int echo)
{
  prompt_t *pr = snew(prompt_t);
  pr->prompt = promptstr;
  pr->echo = echo;
  pr->result = NULL;
  pr->resultsize = 0;
  p->n_prompts++;
  p->prompts = sresize(p->prompts, p->n_prompts, prompt_t *);
  p->prompts[p->n_prompts - 1] = pr;
}
void prompt_ensure_result_size(prompt_t *pr, int newlen)
{
  if ((int)pr->resultsize < newlen) {
    char *newbuf;
    newlen = newlen * 5 / 4 + 512; /* avoid too many small allocs */

    /*
     * We don't use sresize / realloc here, because we will be
     * storing sensitive stuff like passwords in here, and we want
     * to make sure that the data doesn't get copied around in
     * memory without the old copy being destroyed.
     */
    newbuf = snewn(newlen, char);
    memcpy(newbuf, pr->result, pr->resultsize);
    smemclr(pr->result, pr->resultsize);
    sfree(pr->result);
    pr->result = newbuf;
    pr->resultsize = newlen;
  }
}
void prompt_set_result(prompt_t *pr, const char *newstr)
{
  prompt_ensure_result_size(pr, strlen(newstr) + 1);
  strcpy(pr->result, newstr);
}
void free_prompts(prompts_t *p)
{
  size_t i;
  for (i = 0; i < p->n_prompts; i++) {
    prompt_t *pr = p->prompts[i];
    smemclr(pr->result, pr->resultsize); /* burn the evidence */
    sfree(pr->result);
    sfree(pr->prompt);
    sfree(pr);
  }
  sfree(p->prompts);
  sfree(p->name);
  sfree(p->instruction);
  sfree(p);
}

/* ----------------------------------------------------------------------
 * String handling routines.
 */

char *dupstr(const char *s)
{
  char *p = NULL;
  if (s) {
    int len = strlen(s);
    p = snewn(len + 1, char);
    strcpy(p, s);
  }
  return p;
}

/* Allocate the concatenation of N strings. Terminate arg list with NULL. */
char *dupcat(const char *s1, ...)
{
  int len;
  char *p, *q, *sn;
  va_list ap;

  len = strlen(s1);
  va_start(ap, s1);
  while (1) {
    sn = va_arg(ap, char *);
    if (!sn)
      break;
    len += strlen(sn);
  }
  va_end(ap);

  p = snewn(len + 1, char);
  strcpy(p, s1);
  q = p + strlen(p);

  va_start(ap, s1);
  while (1) {
    sn = va_arg(ap, char *);
    if (!sn)
      break;
    strcpy(q, sn);
    q += strlen(q);
  }
  va_end(ap);

  return p;
}

void burnstr(char *string) /* sfree(str), only clear it first */
{
  if (string) {
    smemclr(string, strlen(string));
    sfree(string);
  }
}

int toint(unsigned u)
{
  /*
   * Convert an unsigned to an int, without running into the
   * undefined behaviour which happens by the strict C standard if
   * the value overflows. You'd hope that sensible compilers would
   * do the sensible thing in response to a cast, but actually I
   * don't trust modern compilers not to do silly things like
   * assuming that _obviously_ you wouldn't have caused an overflow
   * and so they can elide an 'if (i < 0)' test immediately after
   * the cast.
   *
   * Sensible compilers ought of course to optimise this entire
   * function into 'just return the input value'!
   */
  if (u <= (unsigned)INT_MAX)
    return (int)u;
  else if (u >= (unsigned)INT_MIN) /* wrap in cast _to_ unsigned is OK */
    return INT_MIN + (int)(u - (unsigned)INT_MIN);
  else
    return INT_MIN; /* fallback; should never occur on binary machines */
}

/*
 * Do an sprintf(), but into a custom-allocated buffer.
 *
 * Currently I'm doing this via vsnprintf. This has worked so far,
 * but it's not good, because vsnprintf is not available on all
 * platforms. There's an ifdef to use `_vsnprintf', which seems
 * to be the local name for it on Windows. Other platforms may
 * lack it completely, in which case it'll be time to rewrite
 * this function in a totally different way.
 *
 * The only `properly' portable solution I can think of is to
 * implement my own format string scanner, which figures out an
 * upper bound for the length of each formatting directive,
 * allocates the buffer as it goes along, and calls sprintf() to
 * actually process each directive. If I ever need to actually do
 * this, some caveats:
 *
 *  - It's very hard to find a reliable upper bound for
 *    floating-point values. %f, in particular, when supplied with
 *    a number near to the upper or lower limit of representable
 *    numbers, could easily take several hundred characters. It's
 *    probably feasible to predict this statically using the
 *    constants in <float.h>, or even to predict it dynamically by
 *    looking at the exponent of the specific float provided, but
 *    it won't be fun.
 *
 *  - Don't forget to _check_, after calling sprintf, that it's
 *    used at most the amount of space we had available.
 *
 *  - Fault any formatting directive we don't fully understand. The
 *    aim here is to _guarantee_ that we never overflow the buffer,
 *    because this is a security-critical function. If we see a
 *    directive we don't know about, we should panic and die rather
 *    than run any risk.
 */
static char *dupvprintf_inner(
    char *buf, int oldlen, int *oldsize, const char *fmt, va_list ap)
{
  int len, size, newsize;

  assert(*oldsize >= oldlen);
  size = *oldsize - oldlen;
  if (size == 0) {
    size = 512;
    newsize = oldlen + size;
    buf = sresize(buf, newsize, char);
  } else {
    newsize = *oldsize;
  }

  while (1) {
#if defined _WINDOWS && !defined __WINE__ &&                                   \
    _MSC_VER < 1900 /* 1900 == VS2015 has real snprintf */
#define vsnprintf _vsnprintf
#endif
#ifdef va_copy
    /* Use the `va_copy' macro mandated by C99, if present.
     * XXX some environments may have this as __va_copy() */
    va_list aq;
    va_copy(aq, ap);
    len = vsnprintf(buf + oldlen, size, fmt, aq);
    va_end(aq);
#else
    /* Ugh. No va_copy macro, so do something nasty.
     * Technically, you can't reuse a va_list like this: it is left
     * unspecified whether advancing a va_list pointer modifies its
     * value or something it points to, so on some platforms calling
     * vsnprintf twice on the same va_list might fail hideously
     * (indeed, it has been observed to).
     * XXX the autoconf manual suggests that using memcpy() will give
     *     "maximum portability". */
    len = vsnprintf(buf + oldlen, size, fmt, ap);
#endif
    if (len >= 0 && len < size) {
      /* This is the C99-specified criterion for snprintf to have
       * been completely successful. */
      *oldsize = newsize;
      return buf;
    } else if (len > 0) {
      /* This is the C99 error condition: the returned length is
       * the required buffer size not counting the NUL. */
      size = len + 1;
    } else {
      /* This is the pre-C99 glibc error condition: <0 means the
       * buffer wasn't big enough, so we enlarge it a bit and hope. */
      size += 512;
    }
    newsize = oldlen + size;
    buf = sresize(buf, newsize, char);
  }
}

char *dupvprintf(const char *fmt, va_list ap)
{
  int size = 0;
  return dupvprintf_inner(NULL, 0, &size, fmt, ap);
}
char *dupprintf(const char *fmt, ...)
{
  char *ret;
  va_list ap;
  va_start(ap, fmt);
  ret = dupvprintf(fmt, ap);
  va_end(ap);
  return ret;
}

struct strbuf {
  char *s;
  int len, size;
};
strbuf *strbuf_new(void)
{
  strbuf *buf = snew(strbuf);
  buf->len = 0;
  buf->size = 512;
  buf->s = snewn(buf->size, char);
  *buf->s = '\0';
  return buf;
}
void strbuf_free(strbuf *buf)
{
  sfree(buf->s);
  sfree(buf);
}
char *strbuf_str(strbuf *buf)
{
  return buf->s;
}
char *strbuf_to_str(strbuf *buf)
{
  char *ret = buf->s;
  sfree(buf);
  return ret;
}
void strbuf_catfv(strbuf *buf, const char *fmt, va_list ap)
{
  buf->s = dupvprintf_inner(buf->s, buf->len, &buf->size, fmt, ap);
  buf->len += strlen(buf->s + buf->len);
}
void strbuf_catf(strbuf *buf, const char *fmt, ...)
{
  va_list ap;
  va_start(ap, fmt);
  strbuf_catfv(buf, fmt, ap);
  va_end(ap);
}

/*
 * Read an entire line of text from a file. Return a buffer
 * malloced to be as big as necessary (caller must free).
 */
char *fgetline(FILE *fp)
{
  char *ret = snewn(512, char);
  int size = 512, len = 0;
  while (fgets(ret + len, size - len, fp)) {
    len += strlen(ret + len);
    if (len > 0 && ret[len - 1] == '\n')
      break; /* got a newline, we're done */
    size = len + 512;
    ret = sresize(ret, size, char);
  }
  if (len == 0) { /* first fgets returned NULL */
    sfree(ret);
    return NULL;
  }
  ret[len] = '\0';
  return ret;
}

/*
 * Perl-style 'chomp', for a line we just read with fgetline. Unlike
 * Perl chomp, however, we're deliberately forgiving of strange
 * line-ending conventions. Also we forgive NULL on input, so you can
 * just write 'line = chomp(fgetline(fp));' and not bother checking
 * for NULL until afterwards.
 */
char *chomp(char *str)
{
  if (str) {
    int len = strlen(str);
    while (len > 0 && (str[len - 1] == '\r' || str[len - 1] == '\n'))
      len--;
    str[len] = '\0';
  }
  return str;
}

/* ----------------------------------------------------------------------
 * Core base64 encoding and decoding routines.
 */

void base64_encode_atom(const unsigned char *data, int n, char *out)
{
  static const char base64_chars[] =
      "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

  unsigned word;

  word = data[0] << 16;
  if (n > 1)
    word |= data[1] << 8;
  if (n > 2)
    word |= data[2];
  out[0] = base64_chars[(word >> 18) & 0x3F];
  out[1] = base64_chars[(word >> 12) & 0x3F];
  if (n > 1)
    out[2] = base64_chars[(word >> 6) & 0x3F];
  else
    out[2] = '=';
  if (n > 2)
    out[3] = base64_chars[word & 0x3F];
  else
    out[3] = '=';
}

int base64_decode_atom(const char *atom, unsigned char *out)
{
  int vals[4];
  int i, v, len;
  unsigned word;
  char c;

  for (i = 0; i < 4; i++) {
    c = atom[i];
    if (c >= 'A' && c <= 'Z')
      v = c - 'A';
    else if (c >= 'a' && c <= 'z')
      v = c - 'a' + 26;
    else if (c >= '0' && c <= '9')
      v = c - '0' + 52;
    else if (c == '+')
      v = 62;
    else if (c == '/')
      v = 63;
    else if (c == '=')
      v = -1;
    else
      return 0; /* invalid atom */
    vals[i] = v;
  }

  if (vals[0] == -1 || vals[1] == -1)
    return 0;
  if (vals[2] == -1 && vals[3] != -1)
    return 0;

  if (vals[3] != -1)
    len = 3;
  else if (vals[2] != -1)
    len = 2;
  else
    len = 1;

  word = ((vals[0] << 18) | (vals[1] << 12) | ((vals[2] & 0x3F) << 6) |
          (vals[3] & 0x3F));
  out[0] = (word >> 16) & 0xFF;
  if (len > 1)
    out[1] = (word >> 8) & 0xFF;
  if (len > 2)
    out[2] = word & 0xFF;
  return len;
}

/* ----------------------------------------------------------------------
 * Generic routines to deal with send buffers: a linked list of
 * smallish blocks, with the operations
 *
 *  - add an arbitrary amount of data to the end of the list
 *  - remove the first N bytes from the list
 *  - return a (pointer,length) pair giving some initial data in
 *    the list, suitable for passing to a send or write system
 *    call
 *  - retrieve a larger amount of initial data from the list
 *  - return the current size of the buffer chain in bytes
 */

#define BUFFER_MIN_GRANULE 512

struct bufchain_granule {
  struct bufchain_granule *next;
  char *bufpos, *bufend, *bufmax;
};

void bufchain_init(bufchain *ch)
{
  ch->head = ch->tail = NULL;
  ch->buffersize = 0;
}

void bufchain_clear(bufchain *ch)
{
  struct bufchain_granule *b;
  while (ch->head) {
    b = ch->head;
    ch->head = ch->head->next;
    sfree(b);
  }
  ch->tail = NULL;
  ch->buffersize = 0;
}

int bufchain_size(bufchain *ch)
{
  return ch->buffersize;
}

void bufchain_add(bufchain *ch, const void *data, int len)
{
  const char *buf = (const char *)data;

  if (len == 0)
    return;

  ch->buffersize += len;

  while (len > 0) {
    if (ch->tail && ch->tail->bufend < ch->tail->bufmax) {
      int copylen = min(len, ch->tail->bufmax - ch->tail->bufend);
      memcpy(ch->tail->bufend, buf, copylen);
      buf += copylen;
      len -= copylen;
      ch->tail->bufend += copylen;
    }
    if (len > 0) {
      int grainlen =
          max(sizeof(struct bufchain_granule) + len, BUFFER_MIN_GRANULE);
      struct bufchain_granule *newbuf;
      newbuf = smalloc(grainlen);
      newbuf->bufpos = newbuf->bufend =
          (char *)newbuf + sizeof(struct bufchain_granule);
      newbuf->bufmax = (char *)newbuf + grainlen;
      newbuf->next = NULL;
      if (ch->tail)
        ch->tail->next = newbuf;
      else
        ch->head = newbuf;
      ch->tail = newbuf;
    }
  }
}

void bufchain_consume(bufchain *ch, int len)
{
  struct bufchain_granule *tmp;

  assert(ch->buffersize >= len);
  while (len > 0) {
    int remlen = len;
    assert(ch->head != NULL);
    if (remlen >= ch->head->bufend - ch->head->bufpos) {
      remlen = ch->head->bufend - ch->head->bufpos;
      tmp = ch->head;
      ch->head = tmp->next;
      if (!ch->head)
        ch->tail = NULL;
      sfree(tmp);
    } else
      ch->head->bufpos += remlen;
    ch->buffersize -= remlen;
    len -= remlen;
  }
}

void bufchain_prefix(bufchain *ch, void **data, int *len)
{
  *len = ch->head->bufend - ch->head->bufpos;
  *data = ch->head->bufpos;
}

void bufchain_fetch(bufchain *ch, void *data, int len)
{
  struct bufchain_granule *tmp;
  char *data_c = (char *)data;

  tmp = ch->head;

  assert(ch->buffersize >= len);
  while (len > 0) {
    int remlen = len;

    assert(tmp != NULL);
    if (remlen >= tmp->bufend - tmp->bufpos)
      remlen = tmp->bufend - tmp->bufpos;
    memcpy(data_c, tmp->bufpos, remlen);

    tmp = tmp->next;
    len -= remlen;
    data_c += remlen;
  }
}

/* ----------------------------------------------------------------------
 * My own versions of malloc, realloc and free. Because I want
 * malloc and realloc to bomb out and exit the program if they run
 * out of memory, realloc to reliably call malloc if passed a NULL
 * pointer, and free to reliably do nothing if passed a NULL
 * pointer. We can also put trace printouts in, if we need to; and
 * we can also replace the allocator with an ElectricFence-like
 * one.
 */

#ifdef MINEFIELD
void *minefield_c_malloc(size_t size);
void minefield_c_free(void *p);
void *minefield_c_realloc(void *p, size_t size);
#endif

#ifdef MALLOC_LOG
static FILE *fp = NULL;

static char *mlog_file = NULL;
static int mlog_line = 0;

void mlog(char *file, int line)
{
  mlog_file = file;
  mlog_line = line;
  if (!fp) {
    fp = fopen("putty_mem.log", "w");
    setvbuf(fp, NULL, _IONBF, BUFSIZ);
  }
  if (fp)
    fprintf(fp, "%s:%d: ", file, line);
}
#endif

void *safemalloc(size_t n, size_t size)
{
  void *p;

  if (n > INT_MAX / size) {
    p = NULL;
  } else {
    size *= n;
    if (size == 0)
      size = 1;
#ifdef MINEFIELD
    p = minefield_c_malloc(size);
#else
    p = malloc(size);
#endif
  }

  if (!p) {
    char str[200];
#ifdef MALLOC_LOG
    sprintf(str, "Out of memory! (%s:%d, size=%d)", mlog_file, mlog_line, size);
    fprintf(fp, "*** %s\n", str);
    fclose(fp);
#else
    strcpy(str, "Out of memory!");
#endif
    modalfatalbox("%s", str);
  }
#ifdef MALLOC_LOG
  if (fp)
    fprintf(fp, "malloc(%d) returns %p\n", size, p);
#endif
  return p;
}

void *saferealloc(void *ptr, size_t n, size_t size)
{
  void *p;

  if (n > INT_MAX / size) {
    p = NULL;
  } else {
    size *= n;
    if (!ptr) {
#ifdef MINEFIELD
      p = minefield_c_malloc(size);
#else
      p = malloc(size);
#endif
    } else {
#ifdef MINEFIELD
      p = minefield_c_realloc(ptr, size);
#else
      p = realloc(ptr, size);
#endif
    }
  }

  if (!p) {
    char str[200];
#ifdef MALLOC_LOG
    sprintf(str, "Out of memory! (%s:%d, size=%d)", mlog_file, mlog_line, size);
    fprintf(fp, "*** %s\n", str);
    fclose(fp);
#else
    strcpy(str, "Out of memory!");
#endif
    modalfatalbox("%s", str);
  }
#ifdef MALLOC_LOG
  if (fp)
    fprintf(fp, "realloc(%p,%d) returns %p\n", ptr, size, p);
#endif
  return p;
}

void safefree(void *ptr)
{
  if (ptr) {
#ifdef MALLOC_LOG
    if (fp)
      fprintf(fp, "free(%p)\n", ptr);
#endif
#ifdef MINEFIELD
    minefield_c_free(ptr);
#else
    free(ptr);
#endif
  }
#ifdef MALLOC_LOG
  else if (fp)
    fprintf(fp, "freeing null pointer - no action taken\n");
#endif
}

/* ----------------------------------------------------------------------
 * Debugging routines.
 */

#ifdef DEBUG
extern void dputs(const char *); /* defined in per-platform *misc.c */

void debug_printf(const char *fmt, ...)
{
  char *buf;
  va_list ap;

  va_start(ap, fmt);
  buf = dupvprintf(fmt, ap);
  dputs(buf);
  sfree(buf);
  va_end(ap);
}

void debug_memdump(const void *buf, int len, int L)
{
  int i;
  const unsigned char *p = buf;
  char foo[17];
  if (L) {
    int delta;
    debug_printf("\t%d (0x%x) bytes:\n", len, len);
    delta = 15 & (uintptr_t)p;
    p -= delta;
    len += delta;
  }
  for (; 0 < len; p += 16, len -= 16) {
    dputs("  ");
    if (L)
      debug_printf("%p: ", p);
    strcpy(foo, "................"); /* sixteen dots */
    for (i = 0; i < 16 && i < len; ++i) {
      if (&p[i] < (unsigned char *)buf) {
        dputs("   "); /* 3 spaces */
        foo[i] = ' ';
      } else {
        debug_printf("%c%02.2x",
                     &p[i] != (unsigned char *)buf && i % 4 ? '.' : ' ',
                     p[i]);
        if (p[i] >= ' ' && p[i] <= '~')
          foo[i] = (char)p[i];
      }
    }
    foo[i] = '\0';
    debug_printf("%*s%s\n", (16 - i) * 3 + 2, "", foo);
  }
}

#endif /* def DEBUG */

/*
 * Determine whether or not a Conf represents a session which can
 * sensibly be launched right now.
 */
int conf_launchable(Conf *conf)
{
  if (conf_get_int(conf, CONF_protocol) == PROT_SERIAL)
    return conf_get_str(conf, CONF_serline)[0] != 0;
  else
    return conf_get_str(conf, CONF_host)[0] != 0;
}

char const *conf_dest(Conf *conf)
{
  if (conf_get_int(conf, CONF_protocol) == PROT_SERIAL)
    return conf_get_str(conf, CONF_serline);
  else
    return conf_get_str(conf, CONF_host);
}

#ifndef PLATFORM_HAS_SMEMCLR
/*
 * Securely wipe memory.
 *
 * The actual wiping is no different from what memset would do: the
 * point of 'securely' is to try to be sure over-clever compilers
 * won't optimise away memsets on variables that are about to be freed
 * or go out of scope. See
 * https://buildsecurityin.us-cert.gov/bsi-rules/home/g1/771-BSI.html
 *
 * Some platforms (e.g. Windows) may provide their own version of this
 * function.
 */
void smemclr(void *b, size_t n)
{
  volatile char *vp;

  if (b && n > 0) {
    /*
     * Zero out the memory.
     */
    memset(b, 0, n);

    /*
     * Perform a volatile access to the object, forcing the
     * compiler to admit that the previous memset was important.
     *
     * This while loop should in practice run for zero iterations
     * (since we know we just zeroed the object out), but in
     * theory (as far as the compiler knows) it might range over
     * the whole object. (If we had just written, say, '*vp =
     * *vp;', a compiler could in principle have 'helpfully'
     * optimised the memset into only zeroing out the first byte.
     * This should be robust.)
     */
    vp = b;
    while (*vp)
      vp++;
  }
}
#endif

/*
 * Validate a manual host key specification (either entered in the
 * GUI, or via -hostkey). If valid, we return TRUE, and update 'key'
 * to contain a canonicalised version of the key string in 'key'
 * (which is guaranteed to take up at most as much space as the
 * original version), suitable for putting into the Conf. If not
 * valid, we return FALSE.
 */
int validate_manual_hostkey(char *key)
{
  char *p, *q, *r, *s;

  /*
   * Step through the string word by word, looking for a word that's
   * in one of the formats we like.
   */
  p = key;
  while ((p += strspn(p, " \t"))[0]) {
    q = p;
    p += strcspn(p, " \t");
    if (*p)
      *p++ = '\0';

    /*
     * Now q is our word.
     */

    if (strlen(q) == 16 * 3 - 1 &&
        q[strspn(q, "0123456789abcdefABCDEF:")] == 0) {
      /*
       * Might be a key fingerprint. Check the colons are in the
       * right places, and if so, return the same fingerprint
       * canonicalised into lowercase.
       */
      int i;
      for (i = 0; i < 16; i++)
        if (q[3 * i] == ':' || q[3 * i + 1] == ':')
          goto not_fingerprint; /* sorry */
      for (i = 0; i < 15; i++)
        if (q[3 * i + 2] != ':')
          goto not_fingerprint; /* sorry */
      for (i = 0; i < 16 * 3 - 1; i++)
        key[i] = tolower(q[i]);
      key[16 * 3 - 1] = '\0';
      return TRUE;
    }
  not_fingerprint:;

    /*
     * Before we check for a public-key blob, trim newlines out of
     * the middle of the word, in case someone's managed to paste
     * in a public-key blob _with_ them.
     */
    for (r = s = q; *r; r++)
      if (*r != '\n' && *r != '\r')
        *s++ = *r;
    *s = '\0';

    if (strlen(q) % 4 == 0 && strlen(q) > 2 * 4 &&
        q[strspn(q,
                 "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                 "abcdefghijklmnopqrstuvwxyz+/=")] == 0) {
      /*
       * Might be a base64-encoded SSH-2 public key blob. Check
       * that it starts with a sensible algorithm string. No
       * canonicalisation is necessary for this string type.
       *
       * The algorithm string must be at most 64 characters long
       * (RFC 4251 section 6).
       */
      unsigned char decoded[6];
      unsigned alglen;
      int minlen;
      int len = 0;

      len += base64_decode_atom(q, decoded + len);
      if (len < 3)
        goto not_ssh2_blob; /* sorry */
      len += base64_decode_atom(q + 4, decoded + len);
      if (len < 4)
        goto not_ssh2_blob; /* sorry */

      alglen = GET_32BIT_MSB_FIRST(decoded);
      if (alglen > 64)
        goto not_ssh2_blob; /* sorry */

      minlen = ((alglen + 4) + 2) / 3;
      if (strlen(q) < minlen)
        goto not_ssh2_blob; /* sorry */

      strcpy(key, q);
      return TRUE;
    }
  not_ssh2_blob:;
  }

  return FALSE;
}

int smemeq(const void *av, const void *bv, size_t len)
{
  const unsigned char *a = (const unsigned char *)av;
  const unsigned char *b = (const unsigned char *)bv;
  unsigned val = 0;

  while (len-- > 0) {
    val |= *a++ ^ *b++;
  }
  /* Now val is 0 iff we want to return 1, and in the range
   * 0x01..0xFF iff we want to return 0. So subtracting from 0x100
   * will clear bit 8 iff we want to return 0, and leave it set iff
   * we want to return 1, so then we can just shift down. */
  return (0x100 - val) >> 8;
}

int match_ssh_id(int stringlen, const void *string, const char *id)
{
  int idlen = strlen(id);
  return (idlen == stringlen && !memcmp(string, id, idlen));
}

void *get_ssh_string(int *datalen, const void **data, int *stringlen)
{
  void *ret;
  unsigned int len;

  if (*datalen < 4)
    return NULL;
  len = GET_32BIT_MSB_FIRST((const unsigned char *)*data);
  if (*datalen - 4 < len)
    return NULL;
  ret = (void *)((const char *)*data + 4);
  *datalen -= len + 4;
  *data = (const char *)*data + len + 4;
  *stringlen = len;
  return ret;
}

int get_ssh_uint32(int *datalen, const void **data, unsigned *ret)
{
  if (*datalen < 4)
    return FALSE;
  *ret = GET_32BIT_MSB_FIRST((const unsigned char *)*data);
  *datalen -= 4;
  *data = (const char *)*data + 4;
  return TRUE;
}

int strstartswith(const char *s, const char *t)
{
  return !memcmp(s, t, strlen(t));
}

int strendswith(const char *s, const char *t)
{
  size_t slen = strlen(s), tlen = strlen(t);
  return slen >= tlen && !strcmp(s + (slen - tlen), t);
}

char *buildinfo(const char *newline)
{
  strbuf *buf = strbuf_new();
  extern const char commitid[]; /* in commitid.c */

  strbuf_catf(buf,
              "Build platform: %d-bit %s",
              (int)(CHAR_BIT * sizeof(void *)),
              BUILDINFO_PLATFORM);

#ifdef __clang_version__
#define FOUND_COMPILER
  strbuf_catf(buf, "%sCompiler: clang %s", newline, __clang_version__);
#elif defined __GNUC__ && defined __VERSION__
#define FOUND_COMPILER
  strbuf_catf(buf, "%sCompiler: gcc %s", newline, __VERSION__);
#endif

#if defined _MSC_VER
#ifndef FOUND_COMPILER
#define FOUND_COMPILER
  strbuf_catf(buf, "%sCompiler: ", newline);
#else
  strbuf_catf(buf, ", emulating ");
#endif
  strbuf_catf(buf, "Visual Studio", newline);
#if _MSC_VER == 1900
  strbuf_catf(buf, " 2015 / MSVC++ 14.0");
#elif _MSC_VER == 1800
  strbuf_catf(buf, " 2013 / MSVC++ 12.0");
#elif _MSC_VER == 1700
  strbuf_catf(buf, " 2012 / MSVC++ 11.0");
#elif _MSC_VER == 1600
  strbuf_catf(buf, " 2010 / MSVC++ 10.0");
#elif _MSC_VER == 1500
  strbuf_catf(buf, " 2008 / MSVC++ 9.0");
#elif _MSC_VER == 1400
  strbuf_catf(buf, " 2005 / MSVC++ 8.0");
#elif _MSC_VER == 1310
  strbuf_catf(buf, " 2003 / MSVC++ 7.1");
#elif _MSC_VER == 1300
  strbuf_catf(buf, " 2003 / MSVC++ 7.0");
#else
  strbuf_catf(buf, ", unrecognised version");
#endif
  strbuf_catf(buf, " (_MSC_VER=%d)", (int)_MSC_VER);
#endif

#ifdef BUILDINFO_GTK
  {
    char *gtk_buildinfo = buildinfo_gtk_version();
    if (gtk_buildinfo) {
      strbuf_catf(
          buf, "%sCompiled against GTK version %s", newline, gtk_buildinfo);
      sfree(gtk_buildinfo);
    }
  }
#endif

#if defined _WINDOWS && defined MINEFIELD
  strbuf_catf(buf, "%sBuild option: MINEFIELD", newline);
#endif
#ifdef NO_SECURITY
  strbuf_catf(buf, "%sBuild option: NO_SECURITY", newline);
#endif
#ifdef NO_SECUREZEROMEMORY
  strbuf_catf(buf, "%sBuild option: NO_SECUREZEROMEMORY", newline);
#endif
#ifdef NO_IPV6
  strbuf_catf(buf, "%sBuild option: NO_IPV6", newline);
#endif
#ifdef NO_GSSAPI
  strbuf_catf(buf, "%sBuild option: NO_GSSAPI", newline);
#endif
#ifdef STATIC_GSSAPI
  strbuf_catf(buf, "%sBuild option: STATIC_GSSAPI", newline);
#endif
#ifdef UNPROTECT
  strbuf_catf(buf, "%sBuild option: UNPROTECT", newline);
#endif
#ifdef FUZZING
  strbuf_catf(buf, "%sBuild option: FUZZING", newline);
#endif
#ifdef DEBUG
  strbuf_catf(buf, "%sBuild option: DEBUG", newline);
#endif

  strbuf_catf(buf, "%sSource commit: %s", newline, commitid);

  return strbuf_to_str(buf);
}