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diff -up openssl-1.0.1e/doc/ssl/SSL_CTX_set_tmp_dh_callback.pod.logjam openssl-1.0.1e/doc/ssl/SSL_CTX_set_tmp_dh_callback.pod
--- openssl-1.0.1e/doc/ssl/SSL_CTX_set_tmp_dh_callback.pod.logjam	2013-02-11 16:02:48.000000000 +0100
+++ openssl-1.0.1e/doc/ssl/SSL_CTX_set_tmp_dh_callback.pod	2015-05-25 11:37:08.893049771 +0200
@@ -12,12 +12,10 @@ SSL_CTX_set_tmp_dh_callback, SSL_CTX_set
             DH *(*tmp_dh_callback)(SSL *ssl, int is_export, int keylength));
  long SSL_CTX_set_tmp_dh(SSL_CTX *ctx, DH *dh);
- void SSL_set_tmp_dh_callback(SSL_CTX *ctx,
+ void SSL_set_tmp_dh_callback(SSL *ctx,
             DH *(*tmp_dh_callback)(SSL *ssl, int is_export, int keylength));
  long SSL_set_tmp_dh(SSL *ssl, DH *dh)
- DH *(*tmp_dh_callback)(SSL *ssl, int is_export, int keylength));
 SSL_CTX_set_tmp_dh_callback() sets the callback function for B<ctx> to be
@@ -50,24 +48,25 @@ even if he gets hold of the normal (cert
 only used for signing.
 In order to perform a DH key exchange the server must use a DH group
-(DH parameters) and generate a DH key. The server will always generate a new
-DH key during the negotiation, when the DH parameters are supplied via
-callback and/or when the SSL_OP_SINGLE_DH_USE option of
-L<SSL_CTX_set_options(3)|SSL_CTX_set_options(3)> is set. It will
-immediately create a DH key, when DH parameters are supplied via
-SSL_CTX_set_tmp_dh() and SSL_OP_SINGLE_DH_USE is not set. In this case,
+(DH parameters) and generate a DH key.
+The server will always generate a new DH key during the negotiation
+if either the DH parameters are supplied via callback or the
+SSL_OP_SINGLE_DH_USE option of SSL_CTX_set_options(3) is set (or both).
+It will  immediately create a DH key if DH parameters are supplied via
+SSL_CTX_set_tmp_dh() and SSL_OP_SINGLE_DH_USE is not set.
+In this case,
 it may happen that a key is generated on initialization without later
 being needed, while on the other hand the computer time during the
 negotiation is being saved.
 If "strong" primes were used to generate the DH parameters, it is not strictly
 necessary to generate a new key for each handshake but it does improve forward
-secrecy. If it is not assured, that "strong" primes were used (see especially
-the section about DSA parameters below), SSL_OP_SINGLE_DH_USE must be used
-in order to prevent small subgroup attacks. Always using SSL_OP_SINGLE_DH_USE
-has an impact on the computer time needed during negotiation, but it is not
-very large, so application authors/users should consider to always enable
-this option.
+secrecy. If it is not assured that "strong" primes were used,
+SSL_OP_SINGLE_DH_USE must be used in order to prevent small subgroup
+attacks. Always using SSL_OP_SINGLE_DH_USE has an impact on the
+computer time needed during negotiation, but it is not very large, so
+application authors/users should consider always enabling this option.
+The option is required to implement perfect forward secrecy (PFS).
 As generating DH parameters is extremely time consuming, an application
 should not generate the parameters on the fly but supply the parameters.
@@ -75,82 +74,62 @@ DH parameters can be reused, as the actu
 the negotiation. The risk in reusing DH parameters is that an attacker
 may specialize on a very often used DH group. Applications should therefore
 generate their own DH parameters during the installation process using the
-openssl L<dhparam(1)|dhparam(1)> application. In order to reduce the computer
-time needed for this generation, it is possible to use DSA parameters
-instead (see L<dhparam(1)|dhparam(1)>), but in this case SSL_OP_SINGLE_DH_USE
-is mandatory.
+openssl L<dhparam(1)|dhparam(1)> application. This application
+guarantees that "strong" primes are used.
-Application authors may compile in DH parameters. Files dh512.pem,
-dh1024.pem, dh2048.pem, and dh4096 in the 'apps' directory of current
+Files dh2048.pem, and dh4096.pem in the 'apps' directory of the current
 version of the OpenSSL distribution contain the 'SKIP' DH parameters,
 which use safe primes and were generated verifiably pseudo-randomly.
 These files can be converted into C code using the B<-C> option of the
-L<dhparam(1)|dhparam(1)> application.
-Authors may also generate their own set of parameters using
-L<dhparam(1)|dhparam(1)>, but a user may not be sure how the parameters were
-generated. The generation of DH parameters during installation is therefore
+L<dhparam(1)|dhparam(1)> application. Generation of custom DH
+parameters during installation should still be preferred to stop an
+attacker from specializing on a commonly used group. Files dh1024.pem
+and dh512.pem contain old parameters that must not be used by
 An application may either directly specify the DH parameters or
-can supply the DH parameters via a callback function. The callback approach
-has the advantage, that the callback may supply DH parameters for different
-key lengths.
-The B<tmp_dh_callback> is called with the B<keylength> needed and
-the B<is_export> information. The B<is_export> flag is set, when the
-ephemeral DH key exchange is performed with an export cipher.
+can supply the DH parameters via a callback function.
+Previous versions of the callback used B<is_export> and B<keylength>
+parameters to control parameter generation for export and non-export
+cipher suites. Modern servers that do not support export ciphersuites
+are advised to either use SSL_CTX_set_tmp_dh() in combination with
+SSL_OP_SINGLE_DH_USE, or alternatively, use the callback but ignore
+B<keylength> and B<is_export> and simply supply at least 2048-bit
+parameters in the callback.
 =head1 EXAMPLES
-Handle DH parameters for key lengths of 512 and 1024 bits. (Error handling
+Setup DH parameters with a key length of 2048 bits. (Error handling
 partly left out.)
- ...
- /* Set up ephemeral DH stuff */
- DH *dh_512 = NULL;
- DH *dh_1024 = NULL;
- FILE *paramfile;
+ Command-line parameter generation:
+ $ openssl dhparam -out dh_param_2048.pem 2048
+ Code for setting up parameters during server initialization:
+ ...
+ SSL_CTX ctx = SSL_CTX_new();
- /* "openssl dhparam -out dh_param_512.pem -2 512" */
- paramfile = fopen("dh_param_512.pem", "r");
+ /* Set up ephemeral DH parameters. */
+ DH *dh_2048 = NULL;
+ FILE *paramfile;
+ paramfile = fopen("dh_param_2048.pem", "r");
  if (paramfile) {
-   dh_512 = PEM_read_DHparams(paramfile, NULL, NULL, NULL);
+   dh_2048 = PEM_read_DHparams(paramfile, NULL, NULL, NULL);
+ } else {
+   /* Error. */
- /* "openssl dhparam -out dh_param_1024.pem -2 1024" */
- paramfile = fopen("dh_param_1024.pem", "r");
- if (paramfile) {
-   dh_1024 = PEM_read_DHparams(paramfile, NULL, NULL, NULL);
-   fclose(paramfile);
+ if (dh_2048 == NULL) {
+  /* Error. */
- ...
- /* "openssl dhparam -C -2 512" etc... */
- DH *get_dh512() { ... }
- DH *get_dh1024() { ... }
- DH *tmp_dh_callback(SSL *s, int is_export, int keylength)
- {
-    DH *dh_tmp=NULL;
-    switch (keylength) {
-    case 512:
-      if (!dh_512)
-        dh_512 = get_dh512();
-      dh_tmp = dh_512;
-      break;
-    case 1024:
-      if (!dh_1024) 
-        dh_1024 = get_dh1024();
-      dh_tmp = dh_1024;
-      break;
-    default:
-      /* Generating a key on the fly is very costly, so use what is there */
-      setup_dh_parameters_like_above();
-    }
-    return(dh_tmp);
+ if (SSL_CTX_set_tmp_dh(ctx, dh_2048) != 1) {
+   /* Error. */
+ SSL_CTX_set_options(ctx, SSL_OP_SINGLE_DH_USE);
+ ...
diff -up openssl-1.0.1e/ssl/ssl_err.c.logjam openssl-1.0.1e/ssl/ssl_err.c
--- openssl-1.0.1e/ssl/ssl_err.c.logjam	2015-05-25 11:38:29.834858712 +0200
+++ openssl-1.0.1e/ssl/ssl_err.c	2015-05-25 11:42:01.041578905 +0200
@@ -361,6 +361,7 @@ static ERR_STRING_DATA SSL_str_reasons[]
 {ERR_REASON(SSL_R_DATA_LENGTH_TOO_LONG)  ,"data length too long"},
 {ERR_REASON(SSL_R_DECRYPTION_FAILED)     ,"decryption failed"},
 {ERR_REASON(SSL_R_DECRYPTION_FAILED_OR_BAD_RECORD_MAC),"decryption failed or bad record mac"},
+{ERR_REASON(SSL_R_DH_KEY_TOO_SMALL)      ,"dh key too small"},
 {ERR_REASON(SSL_R_DH_PUBLIC_VALUE_LENGTH_IS_WRONG),"dh public value length is wrong"},
 {ERR_REASON(SSL_R_DIGEST_CHECK_FAILED)   ,"digest check failed"},
 {ERR_REASON(SSL_R_DTLS_MESSAGE_TOO_BIG)  ,"dtls message too big"},
diff -up openssl-1.0.1e/ssl/ssl.h.logjam openssl-1.0.1e/ssl/ssl.h
--- openssl-1.0.1e/ssl/ssl.h.logjam	2015-05-25 11:38:29.834858712 +0200
+++ openssl-1.0.1e/ssl/ssl.h	2015-05-25 11:40:42.482823220 +0200
@@ -2289,6 +2289,7 @@ void ERR_load_SSL_strings(void);
 #define SSL_R_DATA_LENGTH_TOO_LONG			 146
 #define SSL_R_DECRYPTION_FAILED				 147
+#define SSL_R_DH_KEY_TOO_SMALL                           372
 #define SSL_R_DTLS_MESSAGE_TOO_BIG			 334
diff -up openssl-1.0.1e/ssl/s3_clnt.c.logjam openssl-1.0.1e/ssl/s3_clnt.c
--- openssl-1.0.1e/ssl/s3_clnt.c.logjam	2015-05-25 11:38:29.833858690 +0200
+++ openssl-1.0.1e/ssl/s3_clnt.c	2015-05-25 11:51:05.845754562 +0200
@@ -3277,24 +3277,34 @@ int ssl3_check_cert_and_algorithm(SSL *s
 #ifndef OPENSSL_NO_DH
-	if ((alg_k & SSL_kEDH) &&
-		!(has_bits(i,EVP_PK_DH|EVP_PKT_EXCH) || (dh != NULL)))
+	if ((alg_k & SSL_kEDH) && dh == NULL)
 		goto f_err;
-	else if ((alg_k & SSL_kDHr) && !has_bits(i,EVP_PK_DH|EVP_PKS_RSA))
+	if ((alg_k & SSL_kDHr) && !has_bits(i,EVP_PK_DH|EVP_PKS_RSA))
 		goto f_err;
-	else if ((alg_k & SSL_kDHd) && !has_bits(i,EVP_PK_DH|EVP_PKS_DSA))
+	if ((alg_k & SSL_kDHd) && !has_bits(i,EVP_PK_DH|EVP_PKS_DSA))
 		goto f_err;
+	/* Check DHE only: static DH not implemented. */
+	if (alg_k & SSL_kEDH)
+		{
+		int dh_size = BN_num_bits(dh->p);
+		if ((!SSL_C_IS_EXPORT(s->s3->tmp.new_cipher) && dh_size < 768)
+		    || (SSL_C_IS_EXPORT(s->s3->tmp.new_cipher) && dh_size < 512))
+			{
+			goto f_err;
+			}
+		}
 	if (SSL_C_IS_EXPORT(s->s3->tmp.new_cipher) && !has_bits(i,EVP_PKT_EXP))