strtol不要求您指定要处理的字节数，因此理论上它可以处理包含无尽数字序列的字符串，从而导致拒绝服务攻击。当然，只要一旦long数据类型的精度已经耗尽（实际上不能超过二进制数的65个字符），就没有必要再读取任何内容，因此可以轻松地避免这种攻击。strtol也需要丢弃多余的空格字符，直到遇到第一个非空格字符。所以，即使它在读取数字时很聪明，如果输入一个无尽的空格字符串，它是否也会受到攻击呢？strtol 没有单一的实现。我怀疑任何实现都不容易受到您所描述的攻击；显而易见的实现只需遍历数字序列，而无需一次性存储所有数字。（请注意，由于前导的 0，数字序列可以是任意长的。）
如果您想查看实现的代码，可以在此处下载 glibc 版本 here；strtol() 在 stdlib/strtol.c 中。
p[1]或类似的东西），所以理论上你可以将其转换为从流中读取的内容（例如，调用getc()来获取字符的get_long()）。#include <errno.h>
#define LONG_MAX ((long)(~0UL>>1))
#define LONG_MIN (~LONG_MAX)
int isspace(int c); /* <-- Forward declare from <ctype.h> */
long strtol(const char *restrict nptr, char **restrict endptr, int base) {
const char *p = nptr, *endp;
_Bool is_neg = 0, overflow = 0;
/* Need unsigned so (-LONG_MIN) can fit in these: */
unsigned long n = 0UL, cutoff;
int cutlim;
if (base < 0 || base == 1 || base > 36) {
#ifdef EINVAL /* errno value defined by POSIX */
errno = EINVAL;
#endif
return 0L;
}
endp = nptr;
while (isspace(*p))
p++;
if (*p == '+') {
p++;
} else if (*p == '-') {
is_neg = 1, p++;
}
if (*p == '0') {
p++;
/* For strtol(" 0xZ", &endptr, 16), endptr should point to 'x';
* pointing to ' ' or '0' is non-compliant.
* (Many implementations do this wrong.) */
endp = p;
if (base == 16 && (*p == 'X' || *p == 'x')) {
p++;
} else if (base == 2 && (*p == 'B' || *p == 'b')) {
/* C23 standard supports "0B" and "0b" prefixes. */
p++;
} else if (base == 0) {
if (*p == 'X' || *p == 'x') {
base = 16, p++;
} else if (*p == 'B' || *p == 'b') {
base = 2, p++;
} else {
base = 8;
}
}
} else if (base == 0) {
base = 10;
}
cutoff = (is_neg) ? -(LONG_MIN / base) : LONG_MAX / base;
cutlim = (is_neg) ? -(LONG_MIN % base) : LONG_MAX % base;
while (1) {
int c;
if (*p >= 'A')
c = ((*p - 'A') & (~('a' ^ 'A'))) + 10;
else if (*p <= '9')
c = *p - '0';
else
break;
if (c < 0 || c >= base) break;
endp = ++p;
if (overflow) {
/* endptr should go forward and point to the non-digit character
* (of the given base); required by ANSI standard. */
if (endptr) continue;
break;
}
if (n > cutoff || (n == cutoff && c > cutlim)) {
overflow = 1; continue;
}
n = n * base + c;
}
if (endptr) *endptr = (char *)endp;
if (overflow) {
errno = ERANGE; return ((is_neg) ? LONG_MIN : LONG_MAX);
}
return (long)((is_neg) ? -n : n);
}
如果你想查看strtol，你可以查看加州大学的相关资料。
/*
* strtol.c --
*
* Source code for the "strtol" library procedure.
*
* Copyright (c) 1988 The Regents of the University of California.
* All rights reserved.
*
* Permission is hereby granted, without written agreement and without
* license or royalty fees, to use, copy, modify, and distribute this
* software and its documentation for any purpose, provided that the
* above copyright notice and the following two paragraphs appear in
* all copies of this software.
*
* IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
* OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF
* CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
* ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO
* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
*/
static const char rcsid[] = "$Header$ SPRITE (Berkeley)";
#include <ctype.h>
extern unsigned long int strtoul(char *string, char **endPtr, int base);
/*
*----------------------------------------------------------------------
*
* strtol --
*
* Convert an ASCII string into an integer.
*
* Results:
* The return value is the integer equivalent of string. If endPtr
* is non-NULL, then *endPtr is filled in with the character
* after the last one that was part of the integer. If string
* doesn't contain a valid integer value, then zero is returned
* and *endPtr is set to string.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
long int
strtol(
char *string, /* String of ASCII digits, possibly
* preceded by white space. For bases
* greater than 10, either lower- or
* upper-case digits may be used.
*/
char **endPtr, /* Where to store address of terminating
* character, or NULL. */
int base /* Base for conversion. Must be less
* than 37. If 0, then the base is chosen
* from the leading characters of string:
* "0x" means hex, "0" means octal, anything
* else means decimal.
*/
)
{
register char *p;
int result;
/*
* Skip any leading blanks.
*/
p = string;
while (isspace(*p)) {
p += 1;
}
/*
* Check for a sign.
*/
if (*p == '-') {
p += 1;
result = -1*(strtoul(p, endPtr, base));
} else {
if (*p == '+') {
p += 1;
}
result = strtoul(p, endPtr, base);
}
if ((result == 0) && (endPtr != 0) && (*endPtr == p)) {
*endPtr = string;
}
return result;
}
strtol() 在溢出时不像 C 规范中指定的那样返回 INT_MAX 或 INT_MIN。 - chux - Reinstate Monicastrtoul 的源代码在哪里？ - user3064538
fgets()（和sscanf()）来读取用户输入！ - pmgstrtol来进行DOS攻击。 - Blastfurnace