Allow for dynamically expanded PSK.

When a client connects to a server, the server can now dynamically
determine which PSK to use for that client.

diff --git a/raddb/sites-available/tls b/raddb/sites-available/tls
index 0874951..d62893d 100644 (file)
--- a/raddb/sites-available/tls
+++ b/raddb/sites-available/tls
@@ -421,6 +421,20 @@ home_server tls {
                ca_file = ${cadir}/ca.pem
 
                #
+               #  For TLS-PSK, the key should be specified
+               #  dynamically, instead of using a hard-coded
+               #  psk_identity and psk_hexphrase.
+               #
+               #  The input to the dynamic expansion will be the PSK
+               #  identity supplied by the client, in the
+               #  TLS-PSK-Identity attribute.  The output of the
+               #  expansion should be a hex string, of no more than
+               #  512 characters.  The string should not be prefixed
+               #  with "0x".  e.g. "abcdef" is OK.  "0xabcdef" is not.
+               #
+       #       psk_query = "%{psksql:select hex(key) from psk_keys where keyid = '%{TLS-PSK-Identity}'}"
+
+               #
                #  For DH cipher suites to work, you have to
                #  run OpenSSL to create the DH file first:
                #

diff --git a/share/dictionary.freeradius.internal b/share/dictionary.freeradius.internal
index 3301662..c1e09a8 100644 (file)
--- a/share/dictionary.freeradius.internal
+++ b/share/dictionary.freeradius.internal
@@ -510,8 +510,9 @@ ATTRIBUTE   TLS-Client-Cert-X509v3-Authority-Key-Identifier 1929    string
 ATTRIBUTE      TLS-Client-Cert-X509v3-Basic-Constraints 1930   string
 ATTRIBUTE      TLS-Client-Cert-Subject-Alt-Name-Dns    1931    string
 ATTRIBUTE      TLS-Client-Cert-Subject-Alt-Name-Upn    1932    string
+ATTRIBUTE      TLS-PSK-Identity                        1933    string
 
-# 1933 - 1939: reserved for future cert attributes
+# 1934 - 1939: reserved for future cert attributes
 
 #
 #      Range:  1940-2099

diff --git a/src/include/tls-h b/src/include/tls-h
index 9ae3182..899685a 100644 (file)
--- a/src/include/tls-h
+++ b/src/include/tls-h
@@ -392,6 +392,7 @@ struct fr_tls_server_conf_t {
 #ifdef PSK_MAX_IDENTITY_LEN
        char const      *psk_identity;
        char const      *psk_password;
+       char const      *psk_query;
 #endif
 
 };

diff --git a/src/main/tls.c b/src/main/tls.c
index 59d094c..50b1edc 100644 (file)
--- a/src/main/tls.c
+++ b/src/main/tls.c
@@ -40,6 +40,7 @@ USES_APPLE_DEPRECATED_API     /* OpenSSL API has been deprecated by Apple */
 #ifdef HAVE_UTIME_H
 #include <utime.h>
 #endif
+#include <ctype.h>
 
 #ifdef WITH_TLS
 #ifdef HAVE_OPENSSL_RAND_H
@@ -80,21 +81,92 @@ static unsigned int         record_minus(record_t *buf, void *ptr,
                                     unsigned int size);
 
 #ifdef PSK_MAX_IDENTITY_LEN
-static unsigned int psk_server_callback(SSL *ssl, char const *identity,
+static bool identity_is_safe(const char *identity)
+{
+       char c;
+
+       if (!identity) return true;
+
+       while ((c = *(identity++)) != '\0') {
+               if (isalpha((int) c) || isdigit((int) c) || isspace((int) c) ||
+                   (c == '@') || (c == '-') || (c == '_') || (c == '.')) {
+                       continue;
+               }
+
+               return false;
+       }
+
+       return true;
+}
+
+
+/*
+ *     When a client uses TLS-PSK to talk to a server, this callback
+ *     is used by the server to determine the PSK to use.
+ */
+static unsigned int psk_server_callback(SSL *ssl, const char *identity,
                                        unsigned char *psk,
                                        unsigned int max_psk_len)
 {
-       unsigned int psk_len;
+       unsigned int psk_len = 0;
        fr_tls_server_conf_t *conf;
+       REQUEST *request;
 
        conf = (fr_tls_server_conf_t *)SSL_get_ex_data(ssl,
                                                       FR_TLS_EX_INDEX_CONF);
        if (!conf) return 0;
 
+       request = (REQUEST *)SSL_get_ex_data(ssl,
+                                            FR_TLS_EX_INDEX_REQUEST);
+       if (request && conf->psk_query) {
+               size_t hex_len;
+               VALUE_PAIR *vp;
+               char buffer[2 * PSK_MAX_PSK_LEN + 4]; /* allow for too-long keys */
+
+               /*
+                *      The passed identity is weird.  Deny it.
+                */
+               if (!identity_is_safe(identity)) {
+                       RWDEBUG("Invalid characters in PSK identity %s", identity);
+                       return 0;
+               }
+
+               vp = pairmake_packet("TLS-PSK-Identity", identity, T_OP_SET);
+               if (!vp) return 0;
+
+               hex_len = radius_xlat(buffer, sizeof(buffer), request, conf->psk_query,
+                                     NULL, NULL);
+               if (!hex_len) {
+                       RWDEBUG("PSK expansion returned an empty string.");
+                       return 0;
+               }
+
+               /*
+                *      The returned key is truncated at MORE than
+                *      OpenSSL can handle.  That way we can detect
+                *      the truncation, and complain about it.
+                */
+               if (hex_len > (2 * max_psk_len)) {
+                       RWDEBUG("Returned PSK is too long (%u > %u)",
+                               (unsigned int) hex_len, 2 * max_psk_len);
+                       return 0;
+               }
+
+               /*
+                *      Leave the TLS-PSK-Identity in the request, and
+                *      convert the expansion from printable string
+                *      back to hex.
+                */
+               return fr_hex2bin(psk, max_psk_len, buffer, hex_len);
+       }
+
        /*
-        *      FIXME: Look up the PSK password based on the identity!
+        *      No REQUEST, or no dynamic query.  Just look for a
+        *      static identity.
         */
        if (strcmp(identity, conf->psk_identity) != 0) {
+               ERROR("Supplied PSK identity %s does not match configuration.  Rejecting.",
+                     identity);
                return 0;
        }
 
@@ -826,6 +898,7 @@ static CONF_PARSER tls_server_config[] = {
 #ifdef PSK_MAX_IDENTITY_LEN
        { "psk_identity", FR_CONF_OFFSET(PW_TYPE_STRING, fr_tls_server_conf_t, psk_identity), NULL },
        { "psk_hexphrase", FR_CONF_OFFSET(PW_TYPE_STRING | PW_TYPE_SECRET, fr_tls_server_conf_t, psk_password), NULL },
+       { "psk_query", FR_CONF_OFFSET(PW_TYPE_STRING, fr_tls_server_conf_t, psk_query), NULL },
 #endif
        { "dh_file", FR_CONF_OFFSET(PW_TYPE_STRING, fr_tls_server_conf_t, dh_file), NULL },
        { "random_file", FR_CONF_OFFSET(PW_TYPE_STRING, fr_tls_server_conf_t, random_file), NULL },
@@ -1997,7 +2070,7 @@ void tls_global_cleanup(void)
  *     - Load the Private key & the certificate
  *     - Set the Context options & Verify options
  */
-static SSL_CTX *init_tls_ctx(fr_tls_server_conf_t *conf, int client)
+static SSL_CTX *tls_init_ctx(fr_tls_server_conf_t *conf, int client)
 {
        SSL_CTX *ctx;
        X509_STORE *certstore;
@@ -2096,6 +2169,26 @@ static SSL_CTX *init_tls_ctx(fr_tls_server_conf_t *conf, int client)
        }
 
 #ifdef PSK_MAX_IDENTITY_LEN
+       if (!client) {
+               /*
+                *      No dynamic query exists.  There MUST be a
+                *      statically configured identity and password.
+                */
+               if (conf->psk_query && !*conf->psk_query) {
+                       ERROR("Invalid PSK Configuration: psk_query cannot be empty");
+                       return NULL;
+               }
+
+               SSL_CTX_set_psk_server_callback(ctx, psk_server_callback);
+
+       } else if (conf->psk_query) {
+               ERROR("Invalid PSK Configuration: psk_query cannot be used for outgoing connections");
+               return NULL;
+       }
+
+       /*
+        *      Now check that if PSK is being used, the config is valid.
+        */
        if ((conf->psk_identity && !conf->psk_password) ||
            (!conf->psk_identity && conf->psk_password) ||
            (conf->psk_identity && !*conf->psk_identity) ||
@@ -2106,7 +2199,7 @@ static SSL_CTX *init_tls_ctx(fr_tls_server_conf_t *conf, int client)
 
        if (conf->psk_identity) {
                size_t psk_len, hex_len;
-               char buffer[PSK_MAX_PSK_LEN];
+               uint8_t buffer[PSK_MAX_PSK_LEN];
 
                if (conf->certificate_file ||
                    conf->private_key_password || conf->private_key_file ||
@@ -2118,9 +2211,6 @@ static SSL_CTX *init_tls_ctx(fr_tls_server_conf_t *conf, int client)
                if (client) {
                        SSL_CTX_set_psk_client_callback(ctx,
                                                        psk_client_callback);
-               } else {
-                       SSL_CTX_set_psk_server_callback(ctx,
-                                                       psk_server_callback);
                }
 
                psk_len = strlen(conf->psk_password);
@@ -2130,7 +2220,11 @@ static SSL_CTX *init_tls_ctx(fr_tls_server_conf_t *conf, int client)
                        return NULL;
                }
 
-               hex_len = fr_hex2bin((uint8_t *) buffer, sizeof(buffer), conf->psk_password, psk_len);
+               /*
+                *      Check the password now, so that we don't have
+                *      errors at run-time.
+                */
+               hex_len = fr_hex2bin(buffer, sizeof(buffer), conf->psk_password, psk_len);
                if (psk_len != (2 * hex_len)) {
                        ERROR("psk_hexphrase is not all hex");
                        return NULL;
@@ -2443,7 +2537,7 @@ fr_tls_server_conf_t *tls_server_conf_parse(CONF_SECTION *cs)
        /*
         *      Initialize TLS
         */
-       conf->ctx = init_tls_ctx(conf, 0);
+       conf->ctx = tls_init_ctx(conf, 0);
        if (conf->ctx == NULL) {
                goto error;
        }
@@ -2516,7 +2610,7 @@ fr_tls_server_conf_t *tls_client_conf_parse(CONF_SECTION *cs)
        /*
         *      Initialize TLS
         */
-       conf->ctx = init_tls_ctx(conf, 1);
+       conf->ctx = tls_init_ctx(conf, 1);
        if (conf->ctx == NULL) {
                goto error;
        }