random: Add support for maintaining internal entropy store over restarts

[thirdparty/hostap.git] / src / crypto / random.c

diff --git a/src/crypto/random.c b/src/crypto/random.c
index a30afde1156e584e6adf8675371313d224f3e028..f545917a73396204246f2b1dbe0d4d1651e35678 100644 (file)
--- a/src/crypto/random.c
+++ b/src/crypto/random.c
@@ -57,12 +57,18 @@ static size_t dummy_key_avail = 0;
 static int random_fd = -1;
 #endif /* __linux__ */
 static unsigned int own_pool_ready = 0;
+#define RANDOM_ENTROPY_SIZE 20
+static char *random_entropy_file = NULL;
+static int random_entropy_file_read = 0;
 
 #define MIN_COLLECT_ENTROPY 1000
 static unsigned int entropy = 0;
 static unsigned int total_collected = 0;
 
 
+static void random_write_entropy(void);
+
+
 static u32 __ROL32(u32 x, u32 y)
 {
        return (x << (y & 31)) | (x >> (32 - (y & 31)));
@@ -232,8 +238,12 @@ int random_pool_ready(void)
        dummy_key_avail += res;
        close(fd);
 
-       if (dummy_key_avail == sizeof(dummy_key))
+       if (dummy_key_avail == sizeof(dummy_key)) {
+               if (own_pool_ready < MIN_READY_MARK)
+                       own_pool_ready = MIN_READY_MARK;
+               random_write_entropy();
                return 1;
+       }
 
        wpa_printf(MSG_INFO, "random: Only %u/%u bytes of strong "
                   "random data available from /dev/random",
@@ -261,6 +271,7 @@ void random_mark_pool_ready(void)
        own_pool_ready++;
        wpa_printf(MSG_DEBUG, "random: Mark internal entropy pool to be "
                   "ready (count=%u/%u)", own_pool_ready, MIN_READY_MARK);
+       random_write_entropy();
 }
 
 
@@ -298,15 +309,84 @@ static void random_read_fd(int sock, void *eloop_ctx, void *sock_ctx)
                   (unsigned) (sizeof(dummy_key) - dummy_key_avail));
        dummy_key_avail += res;
 
-       if (dummy_key_avail == sizeof(dummy_key))
+       if (dummy_key_avail == sizeof(dummy_key)) {
                random_close_fd();
+               if (own_pool_ready < MIN_READY_MARK)
+                       own_pool_ready = MIN_READY_MARK;
+               random_write_entropy();
+       }
 }
 
 #endif /* __linux__ */
 
 
-void random_init(void)
+static void random_read_entropy(void)
+{
+       char *buf;
+       size_t len;
+
+       if (!random_entropy_file)
+               return;
+
+       buf = os_readfile(random_entropy_file, &len);
+       if (buf == NULL)
+               return; /* entropy file not yet available */
+
+       if (len != 1 + RANDOM_ENTROPY_SIZE) {
+               wpa_printf(MSG_DEBUG, "random: Invalid entropy file %s",
+                          random_entropy_file);
+               os_free(buf);
+               return;
+       }
+
+       own_pool_ready = (u8) buf[0];
+       random_add_randomness(buf + 1, RANDOM_ENTROPY_SIZE);
+       random_entropy_file_read = 1;
+       os_free(buf);
+       wpa_printf(MSG_DEBUG, "random: Added entropy from %s "
+                  "(own_pool_ready=%u)",
+                  random_entropy_file, own_pool_ready);
+}
+
+
+static void random_write_entropy(void)
 {
+       char buf[RANDOM_ENTROPY_SIZE];
+       FILE *f;
+       u8 opr;
+
+       if (!random_entropy_file)
+               return;
+
+       random_get_bytes(buf, RANDOM_ENTROPY_SIZE);
+
+       f = fopen(random_entropy_file, "wb");
+       if (f == NULL) {
+               wpa_printf(MSG_ERROR, "random: Could not write %s",
+                          random_entropy_file);
+               return;
+       }
+
+       opr = own_pool_ready > 0xff ? 0xff : own_pool_ready;
+       fwrite(&opr, 1, 1, f);
+       fwrite(buf, RANDOM_ENTROPY_SIZE, 1, f);
+       fclose(f);
+
+       wpa_printf(MSG_DEBUG, "random: Updated entropy file %s "
+                  "(own_pool_ready=%u)",
+                  random_entropy_file, own_pool_ready);
+}
+
+
+void random_init(const char *entropy_file)
+{
+       os_free(random_entropy_file);
+       if (entropy_file)
+               random_entropy_file = os_strdup(entropy_file);
+       else
+               random_entropy_file = NULL;
+       random_read_entropy();
+
 #ifdef __linux__
        if (random_fd >= 0)
                return;
@@ -326,6 +406,8 @@ void random_init(void)
 
        eloop_register_read_sock(random_fd, random_read_fd, NULL, NULL);
 #endif /* __linux__ */
+
+       random_write_entropy();
 }
 
 
@@ -334,4 +416,7 @@ void random_deinit(void)
 #ifdef __linux__
        random_close_fd();
 #endif /* __linux__ */
+       random_write_entropy();
+       os_free(random_entropy_file);
+       random_entropy_file = NULL;
 }