---

static char bit_string[MAX_PRINT_STRING_LEN + 1];

static uint8_t srtp_nibble_to_hex_char(uint8_t nibble)
{
    static const char buf[16] = { '0', '1', '2', '3', '4', '5', '6', '7',
                                  '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
    return buf[nibble & 0xF];
}

char *srtp_octet_string_hex_string(const void *s, int length)
{
    const uint8_t *str = (const uint8_t *)s;
    int i;

    /* double length, since one octet takes two hex characters */
    length *= 2;

    /* truncate string if it would be too long */
    if (length > MAX_PRINT_STRING_LEN)
        length = MAX_PRINT_STRING_LEN - 2;

    for (i = 0; i < length; i += 2) {
        bit_string[i] = srtp_nibble_to_hex_char(*str >> 4);
        bit_string[i + 1] = srtp_nibble_to_hex_char(*str++ & 0xF);
    }
    bit_string[i] = 0; /* null terminate string */
    return bit_string;
}

char *v128_hex_string(v128_t *x)
{
    int i, j;

    for (i = j = 0; i < 16; i++) {
        bit_string[j++] = srtp_nibble_to_hex_char(x->v8[i] >> 4);
        bit_string[j++] = srtp_nibble_to_hex_char(x->v8[i] & 0xF);
    }

    bit_string[j] = 0; /* null terminate string */
    return bit_string;
}

char *v128_bit_string(v128_t *x)
{
    int j, i;
    uint32_t mask;

    for (j = i = 0; j < 4; j++) {
        for (mask = 0x80000000; mask > 0; mask >>= 1) {
            if (x->v32[j] & mask)
                bit_string[i] = '1';
            else
                bit_string[i] = '0';
            ++i;
        }
    }
    bit_string[128] = 0; /* null terminate string */

    return bit_string;
}

void v128_copy_octet_string(v128_t *x, const uint8_t s[16])
{
#ifdef ALIGNMENT_32BIT_REQUIRED
    if ((((uint32_t)&s[0]) & 0x3) != 0)
#endif
    {
        x->v8[0] = s[0];
        x->v8[1] = s[1];
        x->v8[2] = s[2];
        x->v8[3] = s[3];
        x->v8[4] = s[4];
        x->v8[5] = s[5];
        x->v8[6] = s[6];
        x->v8[7] = s[7];
        x->v8[8] = s[8];
        x->v8[9] = s[9];
        x->v8[10] = s[10];
        x->v8[11] = s[11];
        x->v8[12] = s[12];
        x->v8[13] = s[13];
        x->v8[14] = s[14];
        x->v8[15] = s[15];
    }
#ifdef ALIGNMENT_32BIT_REQUIRED
    else {
        v128_t *v = (v128_t *)&s[0];

        v128_copy(x, v);
    }
#endif
}

void v128_left_shift(v128_t *x, int shift)
{
    int i;
    const int base_index = shift >> 5;
    const int bit_index = shift & 31;

    if (shift > 127) {
        v128_set_to_zero(x);
        return;
    }

    if (bit_index == 0) {
        for (i = 0; i < 4 - base_index; i++)
            x->v32[i] = x->v32[i + base_index];
    } else {
        for (i = 0; i < 4 - base_index - 1; i++)
            x->v32[i] = (x->v32[i + base_index] >> bit_index) ^
                        (x->v32[i + base_index + 1] << (32 - bit_index));
        x->v32[4 - base_index - 1] = x->v32[4 - 1] >> bit_index;
    }

    /* now wrap up the final portion */
    for (i = 4 - base_index; i < 4; i++)
        x->v32[i] = 0;
}

/* functions manipulating bitvector_t */

int bitvector_alloc(bitvector_t *v, unsigned long length)
{
    unsigned long l;

    /* Round length up to a multiple of bits_per_word */
    length =
        (length + bits_per_word - 1) & ~(unsigned long)((bits_per_word - 1));

    l = length / bits_per_word * bytes_per_word;

    /* allocate memory, then set parameters */
    if (l == 0) {
        v->word = NULL;
        v->length = 0;
        return -1;
    } else {
        v->word = (uint32_t *)srtp_crypto_alloc(l);
        if (v->word == NULL) {
            v->length = 0;
            return -1;
        }
    }
    v->length = length;

    /* initialize bitvector to zero */
    bitvector_set_to_zero(v);

    return 0;
}

void bitvector_dealloc(bitvector_t *v)
{
    if (v->word != NULL)
        srtp_crypto_free(v->word);
    v->word = NULL;
    v->length = 0;
}

void bitvector_set_to_zero(bitvector_t *x)
{
    /* C99 guarantees that memset(0) will set the value 0 for uint32_t */
    memset(x->word, 0, x->length >> 3);
}

void bitvector_left_shift(bitvector_t *x, int shift)
{
    int i;
    const int base_index = shift >> 5;
    const int bit_index = shift & 31;
    const int word_length = x->length >> 5;

    if (shift >= (int)x->length) {
        bitvector_set_to_zero(x);
        return;
    }

    if (bit_index == 0) {
        for (i = 0; i < word_length - base_index; i++)
            x->word[i] = x->word[i + base_index];
    } else {
        for (i = 0; i < word_length - base_index - 1; i++)
            x->word[i] = (x->word[i + base_index] >> bit_index) ^
                         (x->word[i + base_index + 1] << (32 - bit_index));
        x->word[word_length - base_index - 1] =
            x->word[word_length - 1] >> bit_index;
    }

    /* now wrap up the final portion */
    for (i = word_length - base_index; i < word_length; i++)
        x->word[i] = 0;
}

int srtp_octet_string_is_eq(uint8_t *a, uint8_t *b, int len)
{
    uint8_t *end = b + len;
    uint8_t accumulator = 0;

    /*
     * We use this somewhat obscure implementation to try to ensure the running
     * time only depends on len, even accounting for compiler optimizations.
     * The accumulator ends up zero iff the strings are equal.
     */
    while (b < end)
        accumulator |= (*a++ ^ *b++);

    /* Return 1 if *not* equal. */
    return accumulator != 0;
}

void srtp_cleanse(void *s, size_t len)
{
    volatile unsigned char *p = (volatile unsigned char *)s;
    while (len--)
        *p++ = 0;
}

void octet_string_set_to_zero(void *s, size_t len)
{
#if defined(OPENSSL)
    OPENSSL_cleanse(s, len);
#else
    srtp_cleanse(s, len);
#endif
}
Найди уязвимости в коде с bit_string. Возможно это:     if (length > MAX_PRINT_STRING_LEN)
        length = MAX_PRINT_STRING_LEN - 2;
если length = MAX_PRINT_STRING_LEN - будет переполнения дальше в цикле?