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shared: add NM_HASH_OBFUSCATE_PTR() macro

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We want to log pointer values to indicate the related parties of a
log message. But we should not, because plain pointer values can be
used to defeat ASLR.

Instead, we have nm_hash_obfuscate_ptr() to managle a pointer and give
a distinct (albeit not 100% unique) 64 bit integer for logging.

But for the logging messages to be meaning-full, all related parties
must use the same static-seed.

Add a macro NM_HASH_OBFUSCATE_PTR() that uses a particular seed.
This commit is contained in:
Thomas Haller 2019-05-10 07:42:00 +02:00
parent 156f4ee53f
commit 78999f9b61
1 changed files with 12 additions and 2 deletions
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14
shared/nm-glib-aux/nm-hash-utils.h
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@ -291,7 +291,7 @@ gboolean nm_pstr_equal (gconstpointer a, gconstpointer b);
/*****************************************************************************/
#define NM_HASH_OBFUSCATE_PTR_FMT "%016llx"
#define NM_HASH_OBFUSCATE_PTR_FMT "%016" G_GINT64_MODIFIER "x"
/* sometimes we want to log a pointer directly, for providing context/information about
* the message that get logged. Logging pointer values directly defeats ASLR, so we should
@ -307,9 +307,19 @@ gboolean nm_pstr_equal (gconstpointer a, gconstpointer b);
\
nm_hash_init (&_h, (static_seed)); \
nm_hash_update_val (&_h, _val_obf_ptr); \
(unsigned long long) nm_hash_complete_u64 (&_h); \
nm_hash_complete_u64 (&_h); \
})
/* if you want to log obfuscated pointer for a certain context (like, NMPRuleManager
* logging user-tags), then you are advised to use nm_hash_obfuscate_ptr() with your
* own, unique static-seed.
*
* However, for example the singleton constructors log the obfuscated pointer values
* for all singletons, so they must all be obfuscated with the same seed. So, this
* macro uses a particular static seed that should be used by when comparing pointer
* values in a global context. */
#define NM_HASH_OBFUSCATE_PTR(ptr) (nm_hash_obfuscate_ptr (1678382159u, ptr))
/*****************************************************************************/
#endif /* __NM_HASH_UTILS_H__ */