From 1d11e79fefea34b4395043e8e951414c5b7817ba Mon Sep 17 00:00:00 2001

From: Lennart Poettering <lennart@poettering.net>

Date: Mon, 1 Jun 2020 17:06:19 +0200

Subject: [PATCH] parse-util: allow tweaking how to parse integers

This allows disabling a few alternative ways to decode integers

formatted as strings, for safety reasons.

See: #15991

(cherry picked from commit 707e93aff8f358f8a62117e54b857530d6594e4b)

Related: #1848373

---

 src/basic/parse-util.c | 65 +++++++++++++++++++++++++++++++++---------

 src/basic/parse-util.h |  6 ++++

 2 files changed, 58 insertions(+), 13 deletions(-)

diff --git a/src/basic/parse-util.c b/src/basic/parse-util.c

index 67056c0434..6cc4fc3e57 100644

--- a/src/basic/parse-util.c

+++ b/src/basic/parse-util.c

@@ -383,20 +383,35 @@ 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)

@@ -438,11 +453,24 @@ 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)

@@ -504,13 +532,24 @@ 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)

diff --git a/src/basic/parse-util.h b/src/basic/parse-util.h

index 8a49257050..c6bbc98dff 100644

--- a/src/basic/parse-util.h

+++ b/src/basic/parse-util.h

@@ -26,6 +26,12 @@ int parse_syscall_and_errno(const char *in, char **name, int *error);

 #define FORMAT_BYTES_MAX 8

 char *format_bytes(char *buf, size_t l, uint64_t t);

+#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) {