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Avoid failing s_server when client's psk_identity is unexpected 

s_server has traditionally been very brittle in PSK mode.  If the
client offered any PSK identity other than "Client_identity" s_server
would simply abort.

This is breakage for breakage's sake, and unlike most other parts of
s_server, which tend to allow more flexible connections.

This change accomplishes two things:

 * when the client's psk_identity does *not* match the identity
   expected by the server, just warn, don't fail.

 * allow the server to expect instead a different psk_identity from
   the client besides "Client_identity"

Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>

Reviewed-by: Ben Kaduk <kaduk@mit.edu>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3605)
This commit is contained in:
Daniel Kahn Gillmor 2017-06-01 21:01:27 -04:00 committed by Rich Salz
parent ae269dd8b7
commit 720b6cbe4a
2 changed files with 18 additions and 6 deletions
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18
apps/s_server.c
View File

@ -149,7 +149,7 @@ static int dtlslisten = 0;
static int early_data = 0;
#ifndef OPENSSL_NO_PSK
static const char psk_identity[] = "Client_identity";
static char *psk_identity = "Client_identity";
char *psk_key = NULL; /* by default PSK is not used */
static unsigned int psk_server_cb(SSL *ssl, const char *identity,
@ -171,12 +171,12 @@ static unsigned int psk_server_cb(SSL *ssl, const char *identity,
/* here we could lookup the given identity e.g. from a database */
if (strcmp(identity, psk_identity) != 0) {
BIO_printf(bio_s_out, "PSK error: client identity not found"
BIO_printf(bio_s_out, "PSK warning: client identity not what we expected"
" (got '%s' expected '%s')\n", identity, psk_identity);
goto out_err;
}
if (s_debug)
} else {
if (s_debug)
BIO_printf(bio_s_out, "PSK client identity found\n");
}
/* convert the PSK key to binary */
key = OPENSSL_hexstr2buf(psk_key, &key_len);
@ -715,7 +715,7 @@ typedef enum OPTION_choice {
OPT_STATUS_TIMEOUT, OPT_STATUS_URL, OPT_STATUS_FILE, OPT_MSG, OPT_MSGFILE,
OPT_TRACE, OPT_SECURITY_DEBUG, OPT_SECURITY_DEBUG_VERBOSE, OPT_STATE,
OPT_CRLF, OPT_QUIET, OPT_BRIEF, OPT_NO_DHE,
OPT_NO_RESUME_EPHEMERAL, OPT_PSK_HINT, OPT_PSK, OPT_SRPVFILE,
OPT_NO_RESUME_EPHEMERAL, OPT_PSK_IDENTITY, OPT_PSK_HINT, OPT_PSK, OPT_SRPVFILE,
OPT_SRPUSERSEED, OPT_REV, OPT_WWW, OPT_UPPER_WWW, OPT_HTTP, OPT_ASYNC,
OPT_SSL_CONFIG,
OPT_MAX_SEND_FRAG, OPT_SPLIT_SEND_FRAG, OPT_MAX_PIPELINES, OPT_READ_BUF,
@ -869,6 +869,7 @@ const OPTIONS s_server_options[] = {
OPT_X_OPTIONS,
{"nbio", OPT_NBIO, '-', "Use non-blocking IO"},
#ifndef OPENSSL_NO_PSK
{"psk_identity", OPT_PSK_IDENTITY, 's', "PSK identity to expect"},
{"psk_hint", OPT_PSK_HINT, 's', "PSK identity hint to use"},
{"psk", OPT_PSK, 's', "PSK in hex (without 0x)"},
#endif
@ -1351,6 +1352,11 @@ int s_server_main(int argc, char *argv[])
case OPT_NO_RESUME_EPHEMERAL:
no_resume_ephemeral = 1;
break;
case OPT_PSK_IDENTITY:
#ifndef OPENSSL_NO_PSK
psk_identity = opt_arg();
#endif
break;
case OPT_PSK_HINT:
#ifndef OPENSSL_NO_PSK
psk_identity_hint = opt_arg();

6
doc/man1/s_server.pod
View File

@ -333,6 +333,12 @@ Inhibit printing of session and certificate information.
Use the PSK identity hint B<hint> when using a PSK cipher suite.
=item B<-psk_identity identity>
Expect the client to send PSK identity B<identity> when using a PSK
cipher suite, and warn if they do not. By default, the expected PSK
identity is the string "Client_identity".
=item B<-psk key>
Use the PSK key B<key> when using a PSK cipher suite. The key is