Additional robustness to SFTP packet parsing and memory allocation.

[u/mdw/putty] / 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"

/*
 * 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 (isspace(*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;
}

/* ----------------------------------------------------------------------
 * 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.
 * 
 *  - 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. It
 *    would be better to use the `va_copy' macro mandated by C99,
 *    but that too is not yet ubiquitous.
 * 
 * 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
        len = vsnprintf(buf, size, fmt, ap);
        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
 *    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_GRANULE  512

struct bufchain_granule {
    struct bufchain_granule *next;
    int buflen, bufpos;
    char buf[BUFFER_GRANULE];
};

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;

    if (ch->tail && ch->tail->buflen < BUFFER_GRANULE) {
        int copylen = min(len, BUFFER_GRANULE - ch->tail->buflen);
        memcpy(ch->tail->buf + ch->tail->buflen, buf, copylen);
        buf += copylen;
        len -= copylen;
        ch->tail->buflen += copylen;
    }
    while (len > 0) {
        int grainlen = min(len, BUFFER_GRANULE);
        struct bufchain_granule *newbuf;
        newbuf = snew(struct bufchain_granule);
        newbuf->bufpos = 0;
        newbuf->buflen = grainlen;
        memcpy(newbuf->buf, buf, grainlen);
        buf += grainlen;
        len -= grainlen;
        if (ch->tail)
            ch->tail->next = newbuf;
        else
            ch->head = ch->tail = newbuf;
        newbuf->next = NULL;
        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->buflen - ch->head->bufpos) {
            remlen = ch->head->buflen - ch->head->bufpos;
            tmp = ch->head;
            ch->head = tmp->next;
            sfree(tmp);
            if (!ch->head)
                ch->tail = NULL;
        } else
            ch->head->bufpos += remlen;
        ch->buffersize -= remlen;
        len -= remlen;
    }
}

void bufchain_prefix(bufchain *ch, void **data, int *len)
{
    *len = ch->head->buflen - ch->head->bufpos;
    *data = ch->head->buf + 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->buflen - tmp->bufpos)
            remlen = tmp->buflen - tmp->bufpos;
        memcpy(data_c, tmp->buf + 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;
#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(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(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(char *);             /* defined in per-platform *misc.c */

void debug_printf(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(void *buf, int len, int L)
{
    int i;
    unsigned char *p = buf;
    char foo[17];
    if (L) {
        int delta;
        debug_printf("\t%d (0x%x) bytes:\n", len, len);
        delta = 15 & (int) 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 */