misc.c

putty

/*
 * 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"

/*
 * 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;
}

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, size_t len)
{
    prompt_t *pr = snew(prompt_t);
    char *result = snewn(len, char);
    pr->prompt = promptstr;
    pr->echo = echo;
    pr->result = result;
    pr->result_len = len;
    p->n_prompts++;
    p->prompts = sresize(p->prompts, p->n_prompts, prompt_t *);
    p->prompts[p->n_prompts-1] = pr;
}
void free_prompts(prompts_t *p)
{
    size_t i;
    for (i=0; i < p->n_prompts; i++) {
	prompt_t *pr = p->prompts[i];
	memset(pr->result, 0, pr->result_len); /* 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;
}

/*
 * 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.
 */
char *dupprintf(const char *fmt, ...)
{
    char *ret;
    va_list ap;
    va_start(ap, fmt);
    ret = dupvprintf(fmt, ap);
    va_end(ap);
    return ret;
}
char *dupvprintf(const char *fmt, va_list ap)
{
    char *buf;
    int len, size;

    buf = snewn(512, char);
    size = 512;

    while (1) {
#ifdef _WINDOWS
#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, 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, size, fmt, ap);
#endif
	if (len >= 0 && len < size) {
	    /* This is the C99-specified criterion for snprintf to have
	     * been completely successful. */
	    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;
	}
	buf = sresize(buf, size, char);
    }
}

/*
 * 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 (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;
}

/* ----------------------------------------------------------------------
 * Base64 encoding routine. This is required in public-key writing
 * but also in HTTP proxy handling, so it's centralised here.
 */

void base64_encode_atom(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] = '=';
}

/* ----------------------------------------------------------------------
 * 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