diff --git a/ChangeLog b/ChangeLog
index e85af2e9d..ac0e32a9d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -22,11 +22,16 @@ Bugfix
      enabled unless others were also present. Found by David Fernandez. #428
    * Fixed cert_app sample program for debug output and for use when no root
      certificates are provided.
+   * Fix conditional statement that would cause a 1 byte overread in
+     mbedtls_asn1_get_int(). Found and fixed by Guido Vranken. #599
+   * Fixed pthread implementation to avoid unintended double initialisations
+     and double frees. (found by Niklas Amnebratt)
    * Fixed the sample applications gen_key.c, cert_req.c and cert_write.c for
      builds where the configuration MBEDTLS_PEM_WRITE_C is not defined. Found
      by inestlerode. #559.
-   * Fixed pthread implementation to avoid unintended double initialisations
-     and double frees. (found by Niklas Amnebratt)
+   * Fix documentation and implementation missmatch for function arguments of
+     mbedtls_gcm_finish(). Found by cmiatpaar. #602
+   * Guarantee that P>Q at RSA key generation. Found by inestlerode. #558
 
 = mbed TLS 2.1.5 branch released 2016-06-28
 
diff --git a/include/mbedtls/gcm.h b/include/mbedtls/gcm.h
index 6743ac9a5..1b77aaedd 100644
--- a/include/mbedtls/gcm.h
+++ b/include/mbedtls/gcm.h
@@ -190,8 +190,8 @@ int mbedtls_gcm_update( mbedtls_gcm_context *ctx,
  *                  16 bytes.
  *
  * \param ctx       GCM context
- * \param tag       buffer for holding the tag (may be NULL if tag_len is 0)
- * \param tag_len   length of the tag to generate
+ * \param tag       buffer for holding the tag
+ * \param tag_len   length of the tag to generate (must be at least 4)
  *
  * \return          0 if successful or MBEDTLS_ERR_GCM_BAD_INPUT
  */
diff --git a/include/mbedtls/x509_csr.h b/include/mbedtls/x509_csr.h
index 34998a3a5..65187f38b 100644
--- a/include/mbedtls/x509_csr.h
+++ b/include/mbedtls/x509_csr.h
@@ -276,7 +276,7 @@ int mbedtls_x509write_csr_der( mbedtls_x509write_csr *ctx, unsigned char *buf, s
  *
  * \note            f_rng may be NULL if RSA is used for signature and the
  *                  signature is made offline (otherwise f_rng is desirable
- *                  for couermeasures against timing attacks).
+ *                  for countermeasures against timing attacks).
  *                  ECDSA signatures always require a non-NULL f_rng.
  */
 int mbedtls_x509write_csr_pem( mbedtls_x509write_csr *ctx, unsigned char *buf, size_t size,
diff --git a/library/asn1parse.c b/library/asn1parse.c
index b37523def..36aff6ed5 100644
--- a/library/asn1parse.c
+++ b/library/asn1parse.c
@@ -153,7 +153,7 @@ int mbedtls_asn1_get_int( unsigned char **p,
     if( ( ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_INTEGER ) ) != 0 )
         return( ret );
 
-    if( len > sizeof( int ) || ( **p & 0x80 ) != 0 )
+    if( len == 0 || len > sizeof( int ) || ( **p & 0x80 ) != 0 )
         return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
 
     *val = 0;
diff --git a/library/gcm.c b/library/gcm.c
index aaacf97d6..f1210c52c 100644
--- a/library/gcm.c
+++ b/library/gcm.c
@@ -415,8 +415,7 @@ int mbedtls_gcm_finish( mbedtls_gcm_context *ctx,
     if( tag_len > 16 || tag_len < 4 )
         return( MBEDTLS_ERR_GCM_BAD_INPUT );
 
-    if( tag_len != 0 )
-        memcpy( tag, ctx->base_ectr, tag_len );
+    memcpy( tag, ctx->base_ectr, tag_len );
 
     if( orig_len || orig_add_len )
     {
diff --git a/library/rsa.c b/library/rsa.c
index 119431d8f..76e35dea3 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -96,7 +96,10 @@ int mbedtls_rsa_gen_key( mbedtls_rsa_context *ctx,
     if( f_rng == NULL || nbits < 128 || exponent < 3 )
         return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
 
-    mbedtls_mpi_init( &P1 ); mbedtls_mpi_init( &Q1 ); 
+    if( nbits % 2 )
+        return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
+
+    mbedtls_mpi_init( &P1 ); mbedtls_mpi_init( &Q1 );
     mbedtls_mpi_init( &H ); mbedtls_mpi_init( &G );
 
     /*
@@ -110,16 +113,8 @@ int mbedtls_rsa_gen_key( mbedtls_rsa_context *ctx,
         MBEDTLS_MPI_CHK( mbedtls_mpi_gen_prime( &ctx->P, nbits >> 1, 0,
                                 f_rng, p_rng ) );
 
-        if( nbits % 2 )
-        {
-            MBEDTLS_MPI_CHK( mbedtls_mpi_gen_prime( &ctx->Q, ( nbits >> 1 ) + 1, 0,
+        MBEDTLS_MPI_CHK( mbedtls_mpi_gen_prime( &ctx->Q, nbits >> 1, 0,
                                 f_rng, p_rng ) );
-        }
-        else
-        {
-            MBEDTLS_MPI_CHK( mbedtls_mpi_gen_prime( &ctx->Q, nbits >> 1, 0,
-                                f_rng, p_rng ) );
-        }
 
         if( mbedtls_mpi_cmp_mpi( &ctx->P, &ctx->Q ) == 0 )
             continue;
@@ -128,6 +123,9 @@ int mbedtls_rsa_gen_key( mbedtls_rsa_context *ctx,
         if( mbedtls_mpi_bitlen( &ctx->N ) != nbits )
             continue;
 
+        if( mbedtls_mpi_cmp_mpi( &ctx->P, &ctx->Q ) < 0 )
+                                mbedtls_mpi_swap( &ctx->P, &ctx->Q );
+
         MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &P1, &ctx->P, 1 ) );
         MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &Q1, &ctx->Q, 1 ) );
         MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &H, &P1, &Q1 ) );
diff --git a/tests/suites/test_suite_rsa.data b/tests/suites/test_suite_rsa.data
index d522332a2..af168805f 100644
--- a/tests/suites/test_suite_rsa.data
+++ b/tests/suites/test_suite_rsa.data
@@ -361,7 +361,7 @@ RSA Generate Key - 2048 bit key
 mbedtls_rsa_gen_key:2048:3:0
 
 RSA Generate Key - 1025 bit key
-mbedtls_rsa_gen_key:1025:3:0
+mbedtls_rsa_gen_key:1025:3:MBEDTLS_ERR_RSA_BAD_INPUT_DATA
 
 RSA PKCS1 Encrypt Bad RNG
 depends_on:MBEDTLS_PKCS1_V15
diff --git a/tests/suites/test_suite_rsa.function b/tests/suites/test_suite_rsa.function
index 59cbb5c97..b1bc19ea7 100644
--- a/tests/suites/test_suite_rsa.function
+++ b/tests/suites/test_suite_rsa.function
@@ -678,6 +678,7 @@ void mbedtls_rsa_gen_key( int nrbits, int exponent, int result)
     if( result == 0 )
     {
         TEST_ASSERT( mbedtls_rsa_check_privkey( &ctx ) == 0 );
+        TEST_ASSERT( mbedtls_mpi_cmp_mpi( &ctx.P, &ctx.Q ) > 0 );
     }
 
 exit: