commit 35bf07b8d67d018f7740ca195cf8c7c86b1b4ef9 Author: Nick Mathewson nickm@torproject.org Date: Wed Oct 21 11:44:43 2015 -0400

Check for len < 4 in dn_indicates_v3_cert

Without this check, we potentially look up to 3 characters before the start of a malloc'd segment, which could provoke a crash under certain (weird afaik) circumstances.

Fixes 17404; bugfix on 0.2.6.3-alpha. --- changes/bug17404 | 6 ++++++ src/common/tortls.c | 4 ++++ 2 files changed, 10 insertions(+)

diff --git a/changes/bug17404 b/changes/bug17404 new file mode 100644 index 0000000..d524f66 --- /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/src/common/tortls.c b/src/common/tortls.c index 4222f6d..75ca47d 100644 --- a/src/common/tortls.c +++ b/src/common/tortls.c @@ -2676,6 +2676,10 @@ 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 0; + } r = fast_memneq(s + len - 4, ".net", 4); OPENSSL_free(s); return r;