diff --git a/changes/bug17404 b/changes/bug17404
new file mode 100644
index 000000000..d524f6662
--- /dev/null
+++ b/changes/bug17404
@@ -0,0 +1,6 @@
+ o Major bugfixes (security, correctness):
+ - Fix a programming error that could cause us to read 4 bytes before
+ the beginning of an openssl string. This could be used to provoke
+ a crash on systems with an unusual malloc implementation, or
+ systems with unsual hardening installed. Fixes bug 17404; bugfix
+ on 0.2.3.6-alpha.
diff --git a/changes/bug18089 b/changes/bug18089
new file mode 100644
index 000000000..c1fb342f7
--- /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 f4e86683d..43bf5bd6b 100644
--- a/src/common/crypto.c
+++ b/src/common/crypto.c
@@ -3056,6 +3056,7 @@ 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
@@ -3073,6 +3074,15 @@ 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 (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);
+
/* 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. */
diff --git a/src/common/tortls.c b/src/common/tortls.c
index d637a8e4d..221b47e00 100644
--- a/src/common/tortls.c
+++ b/src/common/tortls.c
@@ -2708,6 +2708,10 @@ dn_indicates_v3_cert(X509_NAME *name)
len = ASN1_STRING_to_UTF8(&s, str);
if (len < 0)
return 0;
+ if (len < 4) {
+ OPENSSL_free(s);
+ return 1;
+ }
r = fast_memneq(s + len - 4, ".net", 4);
OPENSSL_free(s);
return r;