diff options
| -rw-r--r-- | doc/security.rst | 11 | ||||
| -rw-r--r-- | src/lib/asn1/ber_dec.cpp | 5 | ||||
| -rw-r--r-- | src/lib/utils/info.txt | 3 | ||||
| -rw-r--r-- | src/lib/utils/safeint.h | 39 |
4 files changed, 55 insertions, 3 deletions
diff --git a/doc/security.rst b/doc/security.rst index faefca7d5..151c279f6 100644 --- a/doc/security.rst +++ b/doc/security.rst @@ -21,7 +21,16 @@ Advisories 2016 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -* 2016-10-8871 (CVE-2016-8871) OAEP side channel +* 2016-11-27 (CVE-2016-xxxx) Integer overflow in BER decoder + + While decoding BER length fields, an integer overflow could occur. This could + occur while parsing untrusted inputs such as X.509 certificates. The overflow + does not seem to lead to any obviously exploitable condition, but exploitation + cannot be positively ruled out. Only 32-bit platforms are likely affected; to + cause an overflow on 64-bit the parsed data would have to be many gigabytes. + Bug found by Falko Strenzke, cryptosource GmbH. + +* 2016-10-26 (CVE-2016-8871) OAEP side channel A side channel in OAEP decoding could be used to distinguish RSA ciphertexts that did or did not have a leading 0 byte. For an attacker capable of diff --git a/src/lib/asn1/ber_dec.cpp b/src/lib/asn1/ber_dec.cpp index ac676cd08..81c04aa6a 100644 --- a/src/lib/asn1/ber_dec.cpp +++ b/src/lib/asn1/ber_dec.cpp @@ -9,6 +9,7 @@ #include <botan/ber_dec.h> #include <botan/bigint.h> #include <botan/loadstor.h> +#include <botan/internal/safeint.h> namespace Botan { @@ -126,7 +127,9 @@ size_t find_eoc(DataSource* ber) size_t item_size = decode_length(&source, length_size); source.discard_next(item_size); - length += item_size + length_size + tag_size; + length = BOTAN_CHECKED_ADD(length, item_size); + length = BOTAN_CHECKED_ADD(length, tag_size); + length = BOTAN_CHECKED_ADD(length, length_size); if(type_tag == EOC && class_tag == UNIVERSAL) break; diff --git a/src/lib/utils/info.txt b/src/lib/utils/info.txt index 820dd407d..306e6e9ad 100644 --- a/src/lib/utils/info.txt +++ b/src/lib/utils/info.txt @@ -1,4 +1,4 @@ -define UTIL_FUNCTIONS 20150919 +define UTIL_FUNCTIONS 20161127 load_on always @@ -31,6 +31,7 @@ filesystem.h os_utils.h prefetch.h rounding.h +safeint.h semaphore.h stl_util.h </header:internal> diff --git a/src/lib/utils/safeint.h b/src/lib/utils/safeint.h new file mode 100644 index 000000000..e0bd66232 --- /dev/null +++ b/src/lib/utils/safeint.h @@ -0,0 +1,39 @@ +/* +* Safe(r) Integer Handling +* (C) 2016 Jack Lloyd +* +* Botan is released under the Simplified BSD License (see license.txt) +*/ + +#ifndef BOTAN_UTILS_SAFE_INT_H__ +#define BOTAN_UTILS_SAFE_INT_H__ + +#include <botan/exceptn.h> +#include <string> + +namespace Botan { + +class Integer_Overflow_Detected : public Exception + { + public: + Integer_Overflow_Detected(const std::string& file, int line) : + Exception("Integer overflow detected at " + file + ":" + std::to_string(line)) + {} + }; + +inline size_t checked_add(size_t x, size_t y, const char* file, int line) + { + // TODO: use __builtin_x_overflow on GCC and Clang + size_t z = x + y; + if(z < x) + { + throw Integer_Overflow_Detected(file, line); + } + return z; + } + +#define BOTAN_CHECKED_ADD(x,y) checked_add(x,y,__FILE__,__LINE__) + +} + +#endif |