When client sends ClientHello with TLS 1.2 in ClientHello.client_version, server may respond with a ServerHello containing an older version number, if it does not support version, suggested by client. If client agrees, the negotiation will proceed as appropriate for the negotiated protocol (according to http://tools.ietf.org/html/rfc5246#appendix-E.1).
But openssl client fails to downgrade tls protocol, if it tries to resume tls1.2 session, even when server responds with new session id and switches to the full handshake. Handshake terminated by client with “protocol_version” alert. Expected behaviour is downgrading to the version suggested by server and continuing with full handshake. How to reproduce: a) create and save tls1.2 session parameters: openssl s_server -cert ./srv.crt -key ./srv.key -no_ssl2 -no_ssl3 -accept 11111 openssl s_client -connect 127.0.0.1:11111 -no_ssl2 -no_ssl3 -debug -sess_out sess.txt -no_ticket b) try to resume saved session with server that does not support tls1.2: openssl s_server -cert ./srv.crt -key ./srv.key -no_ssl2 -no_ssl3 -no_tls1_2 -no_tls1_1 -accept 11111 openssl s_client -connect 127.0.0.1:11111 -no_ssl2 -no_ssl3 -debug -sess_in sees.txt -no_ticket Handshake will fail with: "139874422396744:error:1409442E:SSL routines:SSL3_READ_BYTES:tlsv1 alert protocol version:s3_pkt.c:1257:SSL alert number 70" % openssl version -a OpenSSL 1.0.1e-fips 11 Feb 2013 built on: Wed Aug 13 19:13:02 UTC 2014 platform: linux-x86_64 options: bn(64,64) md2(int) rc4(16x,int) des(idx,cisc,16,int) idea(int) blowfish(idx) compiler: gcc -fPIC -DOPENSSL_PIC -DZLIB -DOPENSSL_THREADS -D_REENTRANT -DDSO_DLFCN -DHAVE_DLFCN_H -DKRB5_MIT -m64 -DL_ENDIAN -DTERMIO -Wall -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -Wa,--noexecstack -DPURIFY -DOPENSSL_IA32_SSE2 -DOPENSSL_BN_ASM_MONT -DOPENSSL_BN_ASM_MONT5 -DOPENSSL_BN_ASM_GF2m -DSHA1_ASM -DSHA256_ASM -DSHA512_ASM -DMD5_ASM -DAES_ASM -DVPAES_ASM -DBSAES_ASM -DWHIRLPOOL_ASM -DGHASH_ASM OPENSSLDIR: "/etc/pki/tls" engines: dynamic ______________________________________________________________________ OpenSSL Project http://www.openssl.org Development Mailing List openssl-dev@openssl.org Automated List Manager majord...@openssl.org
