There is only one length byte but for some reason we skipped two, resulting in
reading one byte past the end of the extension. Fortunately, even if that
extension is at the very end of the ClientHello, it can't be at the end of the
buffer since the ClientHello length is at most SSL_MAX_CONTENT_LEN and the
buffer has some more room after that for MAC and so on. So there is no
buffer overread.
Possible consequences are:
- nothing, if the next byte is 0x00, which is a comment first byte for other
extensions, which is why the bug remained unnoticed
- using a point format that was not offered by the peer if next byte is 0x01.
In that case the peer will reject our ServerKeyExchange message and the
handshake will fail.
- thinking that we don't have a common point format even if we do, which will
cause us to immediately abort the handshake.
None of these are a security issue.
The same bug was fixed client-side in fd35af15
Backport of f7022d1
This helps in the case where an intermediate certificate is directly trusted.
In that case we want to ignore what comes after it in the chain, not only for
performance but also to avoid false negatives (eg an old root being no longer
trusted while the newer intermediate is directly trusted).
see #220
backport of fdbdd72
This causes a compile-time error:
platform.c(157): error: #147: declaration is incompatible with "void (*polarssl_exit)(int)" (declared at line 179 of "platform.h")
If the top certificate occurs twice in trust_ca (for example) it would
not be good for the second instance to be checked with check_path_cnt
reduced twice!
library/dhm.c: accept (and ignore) optional privateValueLength for
PKCS#3 DH parameters.
PKCS#3 defines the ASN.1 encoding of a DH parameter set like this:
----------------
DHParameter ::= SEQUENCE {
prime INTEGER, -- p
base INTEGER, -- g
privateValueLength INTEGER OPTIONAL }
The fields of type DHParameter have the following meanings:
o prime is the prime p.
o base is the base g.
o privateValueLength is the optional private-value
length l.
----------------
See: ftp://ftp.rsasecurity.com/pub/pkcs/ascii/pkcs-3.asc
This optional parameter was added in PKCS#3 version 1.4, released
November 1, 1993.
dhm.c currently doesn't cope well with PKCS#3 files that have this
optional final parameter included. i see errors like:
------------
dhm_parse_dhmfile returned -0x33E6
Last error was: -0x33E6 - DHM - The ASN.1 data is not formatted correctly : ASN1 - Actual length differs from expected lengt
------------
You can generate PKCS#3 files with this final parameter with recent
versions of certtool from GnuTLS:
certtool --generate-dh-params > dh.pem
The race was due to mpi_exp_mod storing a Montgomery coefficient in the
context (RM, RP, RQ).
The fix was verified with -fsanitize-thread using ssl_pthread_server and two
concurrent clients.
A more fine-grained fix should be possible, locking just enough time to check
if those values are OK and set them if not, rather than locking for the whole
mpi_exp_mod() operation, but it will be for later.
