char *X509_NAME_oneline(X509_NAME *a, char *buf, int len)
{
    X509_NAME_ENTRY *ne;
    int i;
    int n, lold, l, l1, l2, num, j, type;
    const char *s;
    char *p;
    unsigned char *q;
    BUF_MEM *b = NULL;
    static const char hex[17] = "0123456789ABCDEF";
    int gs_doit[4];
    char tmp_buf[80];
#ifdef CHARSET_EBCDIC
    char ebcdic_buf[1024];
#endif

    if (buf == NULL) {
        if ((b = BUF_MEM_new()) == NULL)
            goto err;
        if (!BUF_MEM_grow(b, 200))
            goto err;
        b->data[0] = '\0';
        len = 200;
    } else if (len == 0) {
        return NULL;
    }
    if (a == NULL) {
        if (b) {
            buf = b->data;
            OPENSSL_free(b);
        }
        strncpy(buf, "NO X509_NAME", len);
        buf[len - 1] = '\0';
        return buf;
    }

    len--;                      /* space for '\0' */
    l = 0;
    for (i = 0; i < sk_X509_NAME_ENTRY_num(a->entries); i++) {
        ne = sk_X509_NAME_ENTRY_value(a->entries, i);
        n = OBJ_obj2nid(ne->object);
        if ((n == NID_undef) || ((s = OBJ_nid2sn(n)) == NULL)) {
            i2t_ASN1_OBJECT(tmp_buf, sizeof(tmp_buf), ne->object);
            s = tmp_buf;
        }
        l1 = strlen(s);

        type = ne->value->type;
        num = ne->value->length;
        if (num > NAME_ONELINE_MAX) {
            X509err(X509_F_X509_NAME_ONELINE, X509_R_NAME_TOO_LONG);
            goto end;
        }
        q = ne->value->data;
#ifdef CHARSET_EBCDIC
        if (type == V_ASN1_GENERALSTRING ||
            type == V_ASN1_VISIBLESTRING ||
             type == V_ASN1_PRINTABLESTRING ||
             type == V_ASN1_TELETEXSTRING ||
             type == V_ASN1_VISIBLESTRING || type == V_ASN1_IA5STRING) {
            ascii2ebcdic(ebcdic_buf, q, (num > sizeof ebcdic_buf)
                         ? sizeof ebcdic_buf : num);
             q = ebcdic_buf;
         }
 #endif
        if ((type == V_ASN1_GENERALSTRING) && ((num % 4) == 0)) {
            gs_doit[0] = gs_doit[1] = gs_doit[2] = gs_doit[3] = 0;
            for (j = 0; j < num; j++)
                if (q[j] != 0)
                    gs_doit[j & 3] = 1;

            if (gs_doit[0] | gs_doit[1] | gs_doit[2])
                gs_doit[0] = gs_doit[1] = gs_doit[2] = gs_doit[3] = 1;
            else {
                gs_doit[0] = gs_doit[1] = gs_doit[2] = 0;
                gs_doit[3] = 1;
            }
        } else
            gs_doit[0] = gs_doit[1] = gs_doit[2] = gs_doit[3] = 1;

        for (l2 = j = 0; j < num; j++) {
            if (!gs_doit[j & 3])
                continue;
            l2++;
#ifndef CHARSET_EBCDIC
            if ((q[j] < ' ') || (q[j] > '~'))
                l2 += 3;
#else
            if ((os_toascii[q[j]] < os_toascii[' ']) ||
                (os_toascii[q[j]] > os_toascii['~']))
                l2 += 3;
#endif
        }

        lold = l;
        l += 1 + l1 + 1 + l2;
        if (l > NAME_ONELINE_MAX) {
            X509err(X509_F_X509_NAME_ONELINE, X509_R_NAME_TOO_LONG);
            goto end;
        }
        if (b != NULL) {
            if (!BUF_MEM_grow(b, l + 1))
                goto err;
            p = &(b->data[lold]);
        } else if (l > len) {
            break;
        } else
            p = &(buf[lold]);
        *(p++) = '/';
        memcpy(p, s, (unsigned int)l1);
        p += l1;
        *(p++) = '=';

#ifndef CHARSET_EBCDIC          /* q was assigned above already. */
        q = ne->value->data;
#endif

        for (j = 0; j < num; j++) {
            if (!gs_doit[j & 3])
                continue;
#ifndef CHARSET_EBCDIC
            n = q[j];
            if ((n < ' ') || (n > '~')) {
                *(p++) = '\\';
                *(p++) = 'x';
                *(p++) = hex[(n >> 4) & 0x0f];
                *(p++) = hex[n & 0x0f];
            } else
                *(p++) = n;
#else
            n = os_toascii[q[j]];
            if ((n < os_toascii[' ']) || (n > os_toascii['~'])) {
                *(p++) = '\\';
                *(p++) = 'x';
                *(p++) = hex[(n >> 4) & 0x0f];
                *(p++) = hex[n & 0x0f];
            } else
                *(p++) = q[j];
#endif
        }
        *p = '\0';
    }
    if (b != NULL) {
        p = b->data;
        OPENSSL_free(b);
    } else
        p = buf;
    if (i == 0)
        *p = '\0';
    return (p);
 err:
    X509err(X509_F_X509_NAME_ONELINE, ERR_R_MALLOC_FAILURE);
 end:
    BUF_MEM_free(b);
    return (NULL);
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.