From fb7d1f41b409761be3381efaeec0f56d2a470a9f Mon Sep 17 00:00:00 2001 From: "teor (Tim Wilson-Brown)" Date: Tue, 19 Jan 2016 11:22:58 +1100 Subject: Make memwipe() do nothing when passed a NULL pointer or zero size Check size argument to memwipe() for underflow. Closes bug #18089. Reported by "gk", patch by "teor". Bugfix on 0.2.3.25 and 0.2.4.6-alpha (#7352), commit 49dd5ef3 on 7 Nov 2012. --- changes/bug18089 | 6 ++++++ src/common/crypto.c | 8 ++++++++ 2 files changed, 14 insertions(+) create mode 100644 changes/bug18089 diff --git a/changes/bug18089 b/changes/bug18089 new file mode 100644 index 0000000000..c1fb342f77 --- /dev/null +++ b/changes/bug18089 @@ -0,0 +1,6 @@ + o Minor fixes (security): + - Make memwipe() do nothing when passed a NULL pointer + or zero size. Check size argument to memwipe() for underflow. + Closes bug #18089. Reported by "gk", patch by "teor". + Bugfix on 0.2.3.25 and 0.2.4.6-alpha (#7352), + commit 49dd5ef3 on 7 Nov 2012. diff --git a/src/common/crypto.c b/src/common/crypto.c index 925beb3529..f91391780a 100644 --- a/src/common/crypto.c +++ b/src/common/crypto.c @@ -2972,6 +2972,7 @@ secret_to_key(char *key_out, size_t key_out_len, const char *secret, /** * Destroy the sz bytes of data stored at mem, setting them to * the value byte. + * If mem is NULL or sz is zero, nothing happens. * * This function is preferable to memset, since many compilers will happily * optimize out memset() when they can convince themselves that the data being @@ -2989,6 +2990,13 @@ secret_to_key(char *key_out, size_t key_out_len, const char *secret, void memwipe(void *mem, uint8_t byte, size_t sz) { + if (mem == NULL || sz == 0) { + return; + } + + /* Data this large is likely to be an underflow. */ + tor_assert(sz < SIZE_T_CEILING); + /* Because whole-program-optimization exists, we may not be able to just * have this function call "memset". A smart compiler could inline it, then * eliminate dead memsets, and declare itself to be clever. */ -- cgit v1.2.3-54-g00ecf From 6cb8c0fd4e9c544710b1ad72a695feb87a1d7ee7 Mon Sep 17 00:00:00 2001 From: Nick Mathewson Date: Tue, 19 Jan 2016 08:28:58 -0500 Subject: Refine the memwipe() arguments check for 18089 a little more. We still silently ignore memwipe(NULL, ch, 0); and memwipe(ptr, ch, 0); /* for ptr != NULL */ But we now assert on: memwipe(NULL, ch, 30); --- src/common/crypto.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/common/crypto.c b/src/common/crypto.c index f91391780a..522c1375c9 100644 --- a/src/common/crypto.c +++ b/src/common/crypto.c @@ -2990,9 +2990,11 @@ secret_to_key(char *key_out, size_t key_out_len, const char *secret, void memwipe(void *mem, uint8_t byte, size_t sz) { - if (mem == NULL || sz == 0) { + if (sz == 0) { return; } + /* If sz is nonzero, then mem must not be NULL. */ + tor_assert(mem != NULL); /* Data this large is likely to be an underflow. */ tor_assert(sz < SIZE_T_CEILING); -- cgit v1.2.3-54-g00ecf