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parse-util: allow tweaking how to parse integers

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This allows disabling a few alternative ways to decode integers
formatted as strings, for safety reasons.

See: #15991
This commit is contained in:
Lennart Poettering 2020-06-01 17:06:19 +02:00
parent 0ce8092109
commit 707e93aff8
2 changed files with 58 additions and 13 deletions
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65
src/basic/parse-util.c
View file

@ -359,20 +359,35 @@ int safe_atou_full(const char *s, unsigned base, unsigned *ret_u) {
unsigned long l;
assert(s);
assert(base <= 16);
assert(SAFE_ATO_MASK_FLAGS(base) <= 16);
/* strtoul() is happy to parse negative values, and silently
* converts them to unsigned values without generating an
* error. We want a clean error, hence let's look for the "-"
* prefix on our own, and generate an error. But let's do so
* only after strtoul() validated that the string is clean
* otherwise, so that we return EINVAL preferably over
* ERANGE. */
/* strtoul() is happy to parse negative values, and silently converts them to unsigned values without
* generating an error. We want a clean error, hence let's look for the "-" prefix on our own, and
* generate an error. But let's do so only after strtoul() validated that the string is clean
* otherwise, so that we return EINVAL preferably over ERANGE. */
if (FLAGS_SET(base, SAFE_ATO_REFUSE_LEADING_WHITESPACE) &&
strchr(WHITESPACE, s[0]))
return -EINVAL;
s += strspn(s, WHITESPACE);
if (FLAGS_SET(base, SAFE_ATO_REFUSE_PLUS_MINUS) &&
IN_SET(s[0], '+', '-'))
return -EINVAL; /* Note that we check the "-" prefix again a second time below, but return a
* different error. I.e. if the SAFE_ATO_REFUSE_PLUS_MINUS flag is set we
* blanket refuse +/- prefixed integers, while if it is missing we'll just
* return ERANGE, because the string actually parses correctly, but doesn't
* fit in the return type. */
if (FLAGS_SET(base, SAFE_ATO_REFUSE_LEADING_ZERO) &&
s[0] == '0' && !streq(s, "0"))
return -EINVAL; /* This is particularly useful to avoid ambiguities between C's octal
* notation and assumed-to-be-decimal integers with a leading zero. */
errno = 0;
l = strtoul(s, &x, base);
l = strtoul(s, &x, SAFE_ATO_MASK_FLAGS(base) /* Let's mask off the flags bits so that only the actual
* base is left */);
if (errno > 0)
return -errno;
if (!x || x == s || *x != 0)
@ -414,11 +429,24 @@ int safe_atollu_full(const char *s, unsigned base, long long unsigned *ret_llu)
unsigned long long l;
assert(s);
assert(SAFE_ATO_MASK_FLAGS(base) <= 16);
if (FLAGS_SET(base, SAFE_ATO_REFUSE_LEADING_WHITESPACE) &&
strchr(WHITESPACE, s[0]))
return -EINVAL;
s += strspn(s, WHITESPACE);
if (FLAGS_SET(base, SAFE_ATO_REFUSE_PLUS_MINUS) &&
IN_SET(s[0], '+', '-'))
return -EINVAL;
if (FLAGS_SET(base, SAFE_ATO_REFUSE_LEADING_ZERO) &&
s[0] == '0' && s[1] != 0)
return -EINVAL;
errno = 0;
l = strtoull(s, &x, base);
l = strtoull(s, &x, SAFE_ATO_MASK_FLAGS(base));
if (errno > 0)
return -errno;
if (!x || x == s || *x != 0)
@ -480,13 +508,24 @@ int safe_atou16_full(const char *s, unsigned base, uint16_t *ret) {
unsigned long l;
assert(s);
assert(ret);
assert(base <= 16);
assert(SAFE_ATO_MASK_FLAGS(base) <= 16);
if (FLAGS_SET(base, SAFE_ATO_REFUSE_LEADING_WHITESPACE) &&
strchr(WHITESPACE, s[0]))
return -EINVAL;
s += strspn(s, WHITESPACE);
if (FLAGS_SET(base, SAFE_ATO_REFUSE_PLUS_MINUS) &&
IN_SET(s[0], '+', '-'))
return -EINVAL;
if (FLAGS_SET(base, SAFE_ATO_REFUSE_LEADING_ZERO) &&
s[0] == '0' && s[1] != 0)
return -EINVAL;
errno = 0;
l = strtoul(s, &x, base);
l = strtoul(s, &x, SAFE_ATO_MASK_FLAGS(base));
if (errno > 0)
return -errno;
if (!x || x == s || *x != 0)

6
src/basic/parse-util.h
View file

@ -21,6 +21,12 @@ int parse_range(const char *t, unsigned *lower, unsigned *upper);
int parse_errno(const char *t);
int parse_syscall_and_errno(const char *in, char **name, int *error);
#define SAFE_ATO_REFUSE_PLUS_MINUS (1U << 30)
#define SAFE_ATO_REFUSE_LEADING_ZERO (1U << 29)
#define SAFE_ATO_REFUSE_LEADING_WHITESPACE (1U << 28)
#define SAFE_ATO_ALL_FLAGS (SAFE_ATO_REFUSE_PLUS_MINUS|SAFE_ATO_REFUSE_LEADING_ZERO|SAFE_ATO_REFUSE_LEADING_WHITESPACE)
#define SAFE_ATO_MASK_FLAGS(base) ((base) & ~SAFE_ATO_ALL_FLAGS)
int safe_atou_full(const char *s, unsigned base, unsigned *ret_u);
static inline int safe_atou(const char *s, unsigned *ret_u) {