share rand_pool between libcrypto and providers

Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/11682)

9 files changed, 523 insertions, 11 deletions

diff --git a/providers/implementations/include/prov/rand_pool.h b/providers/implementations/include/prov/rand_pool.h
new file mode 100644
index 0000000000..f476604770
--- /dev/null
+++ b/providers/implementations/include/prov/rand_pool.h
@@ -0,0 +1,108 @@
+/*
+ * Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#ifndef OSSL_PROVIDER_RAND_POOL_H
+# define OSSL_PROVIDER_RAND_POOL_H
+
+# include <stdio.h>
+# include <openssl/rand_drbg.h>
+
+/*
+ * Maximum allocation size for RANDOM_POOL buffers
+ *
+ * The max_len value for the buffer provided to the rand_drbg_get_entropy()
+ * callback is currently 2^31 bytes (2 gigabytes), if a derivation function
+ * is used. Since this is much too large to be allocated, the rand_pool_new()
+ * function chooses more modest values as default pool length, bounded
+ * by RAND_POOL_MIN_LENGTH and RAND_POOL_MAX_LENGTH
+ *
+ * The choice of the RAND_POOL_FACTOR is large enough such that the
+ * RAND_POOL can store a random input which has a lousy entropy rate of
+ * 8/256 (= 0.03125) bits per byte. This input will be sent through the
+ * derivation function which 'compresses' the low quality input into a
+ * high quality output.
+ *
+ * The factor 1.5 below is the pessimistic estimate for the extra amount
+ * of entropy required when no get_nonce() callback is defined.
+ */
+# define RAND_POOL_FACTOR        256
+# define RAND_POOL_MAX_LENGTH    (RAND_POOL_FACTOR * \
+                                  3 * (RAND_DRBG_STRENGTH / 16))
+/*
+ *                             = (RAND_POOL_FACTOR * \
+ *                                1.5 * (RAND_DRBG_STRENGTH / 8))
+ */
+
+/*
+ * Initial allocation minimum.
+ *
+ * There is a distinction between the secure and normal allocation minimums.
+ * Ideally, the secure allocation size should be a power of two.  The normal
+ * allocation size doesn't have any such restriction.
+ *
+ * The secure value is based on 128 bits of secure material, which is 16 bytes.
+ * Typically, the DRBGs will set a minimum larger than this so optimal
+ * allocation ought to take place (for full quality seed material).
+ *
+ * The normal value has been chosen by noticing that the rand_drbg_get_nonce
+ * function is usually the largest of the built in allocation (twenty four
+ * bytes and then appending another sixteen bytes).  This means the buffer ends
+ * with 40 bytes.  The value of forty eight is comfortably above this which
+ * allows some slack in the platform specific values used.
+ */
+# define RAND_POOL_MIN_ALLOCATION(secure) ((secure) ? 16 : 48)
+
+/*
+ * The 'random pool' acts as a dumb container for collecting random
+ * input from various entropy sources. It is the callers duty to 1) initialize
+ * the random pool, 2) pass it to the polling callbacks, 3) seed the RNG, and
+ * 4) cleanup the random pool again.
+ *
+ * The random pool contains no locking mechanism because its scope and
+ * lifetime is intended to be restricted to a single stack frame.
+ */
+typedef struct rand_pool_st {
+    unsigned char *buffer;  /* points to the beginning of the random pool */
+    size_t len; /* current number of random bytes contained in the pool */
+
+    int attached;  /* true pool was attached to existing buffer */
+    int secure;    /* 1: allocated on the secure heap, 0: otherwise */
+
+    size_t min_len; /* minimum number of random bytes requested */
+    size_t max_len; /* maximum number of random bytes (allocated buffer size) */
+    size_t alloc_len; /* current number of bytes allocated */
+    size_t entropy; /* current entropy count in bits */
+    size_t entropy_requested; /* requested entropy count in bits */
+} RAND_POOL;
+
+RAND_POOL *rand_pool_new(int entropy_requested, int secure,
+                         size_t min_len, size_t max_len);
+RAND_POOL *rand_pool_attach(const unsigned char *buffer, size_t len,
+                            size_t entropy);
+void rand_pool_free(RAND_POOL *pool);
+
+const unsigned char *rand_pool_buffer(RAND_POOL *pool);
+unsigned char *rand_pool_detach(RAND_POOL *pool);
+void rand_pool_reattach(RAND_POOL *pool, unsigned char *buffer);
+
+size_t rand_pool_entropy(RAND_POOL *pool);
+size_t rand_pool_length(RAND_POOL *pool);
+
+size_t rand_pool_entropy_available(RAND_POOL *pool);
+size_t rand_pool_entropy_needed(RAND_POOL *pool);
+/* |entropy_factor| expresses how many bits of data contain 1 bit of entropy */
+size_t rand_pool_bytes_needed(RAND_POOL *pool, unsigned int entropy_factor);
+size_t rand_pool_bytes_remaining(RAND_POOL *pool);
+
+int rand_pool_add(RAND_POOL *pool,
+                  const unsigned char *buffer, size_t len, size_t entropy);
+unsigned char *rand_pool_add_begin(RAND_POOL *pool, size_t len);
+int rand_pool_add_end(RAND_POOL *pool, size_t len, size_t entropy);
+
+#endif /* OSSL_PROVIDER_RAND_POOL_H */
diff --git a/providers/implementations/rands/seeding/seeding.h b/providers/implementations/include/prov/seeding.h
index bd0a57a769..bd0a57a769 100644
--- a/providers/implementations/rands/seeding/seeding.h
+++ b/providers/implementations/include/prov/seeding.h
diff --git a/providers/implementations/rands/rand_pool.c b/providers/implementations/rands/rand_pool.c
index 71b71190e8..cf0e6774a5 100644
--- a/providers/implementations/rands/rand_pool.c
+++ b/providers/implementations/rands/rand_pool.c
@@ -1,5 +1,5 @@
 /*
- * Copyright 2020 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the Apache License 2.0 (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
@@ -7,3 +7,406 @@
  * https://www.openssl.org/source/license.html
  */
 
+#include <stdio.h>
+#include <time.h>
+#include "internal/cryptlib.h"
+#include <openssl/opensslconf.h>
+#include "crypto/rand.h"
+#include <openssl/engine.h>
+#include "internal/thread_once.h"
+#include "prov/rand_pool.h"
+
+/*
+ * Allocate memory and initialize a new random pool
+ */
+RAND_POOL *rand_pool_new(int entropy_requested, int secure,
+                         size_t min_len, size_t max_len)
+{
+    RAND_POOL *pool = OPENSSL_zalloc(sizeof(*pool));
+    size_t min_alloc_size = RAND_POOL_MIN_ALLOCATION(secure);
+
+    if (pool == NULL) {
+        RANDerr(RAND_F_RAND_POOL_NEW, ERR_R_MALLOC_FAILURE);
+        return NULL;
+    }
+
+    pool->min_len = min_len;
+    pool->max_len = (max_len > RAND_POOL_MAX_LENGTH) ?
+        RAND_POOL_MAX_LENGTH : max_len;
+    pool->alloc_len = min_len < min_alloc_size ? min_alloc_size : min_len;
+    if (pool->alloc_len > pool->max_len)
+        pool->alloc_len = pool->max_len;
+
+    if (secure)
+        pool->buffer = OPENSSL_secure_zalloc(pool->alloc_len);
+    else
+        pool->buffer = OPENSSL_zalloc(pool->alloc_len);
+
+    if (pool->buffer == NULL) {
+        RANDerr(RAND_F_RAND_POOL_NEW, ERR_R_MALLOC_FAILURE);
+        goto err;
+    }
+
+    pool->entropy_requested = entropy_requested;
+    pool->secure = secure;
+    return pool;
+
+err:
+    OPENSSL_free(pool);
+    return NULL;
+}
+
+/*
+ * Attach new random pool to the given buffer
+ *
+ * This function is intended to be used only for feeding random data
+ * provided by RAND_add() and RAND_seed() into the <master> DRBG.
+ */
+RAND_POOL *rand_pool_attach(const unsigned char *buffer, size_t len,
+                            size_t entropy)
+{
+    RAND_POOL *pool = OPENSSL_zalloc(sizeof(*pool));
+
+    if (pool == NULL) {
+        RANDerr(RAND_F_RAND_POOL_ATTACH, ERR_R_MALLOC_FAILURE);
+        return NULL;
+    }
+
+    /*
+     * The const needs to be cast away, but attached buffers will not be
+     * modified (in contrary to allocated buffers which are zeroed and
+     * freed in the end).
+     */
+    pool->buffer = (unsigned char *) buffer;
+    pool->len = len;
+
+    pool->attached = 1;
+
+    pool->min_len = pool->max_len = pool->alloc_len = pool->len;
+    pool->entropy = entropy;
+
+    return pool;
+}
+
+/*
+ * Free |pool|, securely erasing its buffer.
+ */
+void rand_pool_free(RAND_POOL *pool)
+{
+    if (pool == NULL)
+        return;
+
+    /*
+     * Although it would be advisable from a cryptographical viewpoint,
+     * we are not allowed to clear attached buffers, since they are passed
+     * to rand_pool_attach() as `const unsigned char*`.
+     * (see corresponding comment in rand_pool_attach()).
+     */
+    if (!pool->attached) {
+        if (pool->secure)
+            OPENSSL_secure_clear_free(pool->buffer, pool->alloc_len);
+        else
+            OPENSSL_clear_free(pool->buffer, pool->alloc_len);
+    }
+
+    OPENSSL_free(pool);
+}
+
+/*
+ * Return the |pool|'s buffer to the caller (readonly).
+ */
+const unsigned char *rand_pool_buffer(RAND_POOL *pool)
+{
+    return pool->buffer;
+}
+
+/*
+ * Return the |pool|'s entropy to the caller.
+ */
+size_t rand_pool_entropy(RAND_POOL *pool)
+{
+    return pool->entropy;
+}
+
+/*
+ * Return the |pool|'s buffer length to the caller.
+ */
+size_t rand_pool_length(RAND_POOL *pool)
+{
+    return pool->len;
+}
+
+/*
+ * Detach the |pool| buffer and return it to the caller.
+ * It's the responsibility of the caller to free the buffer
+ * using OPENSSL_secure_clear_free() or to re-attach it
+ * again to the pool using rand_pool_reattach().
+ */
+unsigned char *rand_pool_detach(RAND_POOL *pool)
+{
+    unsigned char *ret = pool->buffer;
+    pool->buffer = NULL;
+    pool->entropy = 0;
+    return ret;
+}
+
+/*
+ * Re-attach the |pool| buffer. It is only allowed to pass
+ * the |buffer| which was previously detached from the same pool.
+ */
+void rand_pool_reattach(RAND_POOL *pool, unsigned char *buffer)
+{
+    pool->buffer = buffer;
+    OPENSSL_cleanse(pool->buffer, pool->len);
+    pool->len = 0;
+}
+
+/*
+ * If |entropy_factor| bits contain 1 bit of entropy, how many bytes does one
+ * need to obtain at least |bits| bits of entropy?
+ */
+#define ENTROPY_TO_BYTES(bits, entropy_factor) \
+    (((bits) * (entropy_factor) + 7) / 8)
+
+
+/*
+ * Checks whether the |pool|'s entropy is available to the caller.
+ * This is the case when entropy count and buffer length are high enough.
+ * Returns
+ *
+ *  |entropy|  if the entropy count and buffer size is large enough
+ *      0      otherwise
+ */
+size_t rand_pool_entropy_available(RAND_POOL *pool)
+{
+    if (pool->entropy < pool->entropy_requested)
+        return 0;
+
+    if (pool->len < pool->min_len)
+        return 0;
+
+    return pool->entropy;
+}
+
+/*
+ * Returns the (remaining) amount of entropy needed to fill
+ * the random pool.
+ */
+
+size_t rand_pool_entropy_needed(RAND_POOL *pool)
+{
+    if (pool->entropy < pool->entropy_requested)
+        return pool->entropy_requested - pool->entropy;
+
+    return 0;
+}
+
+/* Increase the allocation size -- not usable for an attached pool */
+static int rand_pool_grow(RAND_POOL *pool, size_t len)
+{
+    if (len > pool->alloc_len - pool->len) {
+        unsigned char *p;
+        const size_t limit = pool->max_len / 2;
+        size_t newlen = pool->alloc_len;
+
+        if (pool->attached || len > pool->max_len - pool->len) {
+            RANDerr(RAND_F_RAND_POOL_GROW, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
+
+        do
+            newlen = newlen < limit ? newlen * 2 : pool->max_len;
+        while (len > newlen - pool->len);
+
+        if (pool->secure)
+            p = OPENSSL_secure_zalloc(newlen);
+        else
+            p = OPENSSL_zalloc(newlen);
+        if (p == NULL) {
+            RANDerr(RAND_F_RAND_POOL_GROW, ERR_R_MALLOC_FAILURE);
+            return 0;
+        }
+        memcpy(p, pool->buffer, pool->len);
+        if (pool->secure)
+            OPENSSL_secure_clear_free(pool->buffer, pool->alloc_len);
+        else
+            OPENSSL_clear_free(pool->buffer, pool->alloc_len);
+        pool->buffer = p;
+        pool->alloc_len = newlen;
+    }
+    return 1;
+}
+
+/*
+ * Returns the number of bytes needed to fill the pool, assuming
+ * the input has 1 / |entropy_factor| entropy bits per data bit.
+ * In case of an error, 0 is returned.
+ */
+
+size_t rand_pool_bytes_needed(RAND_POOL *pool, unsigned int entropy_factor)
+{
+    size_t bytes_needed;
+    size_t entropy_needed = rand_pool_entropy_needed(pool);
+
+    if (entropy_factor < 1) {
+        RANDerr(RAND_F_RAND_POOL_BYTES_NEEDED, RAND_R_ARGUMENT_OUT_OF_RANGE);
+        return 0;
+    }
+
+    bytes_needed = ENTROPY_TO_BYTES(entropy_needed, entropy_factor);
+
+    if (bytes_needed > pool->max_len - pool->len) {
+        /* not enough space left */
+        RANDerr(RAND_F_RAND_POOL_BYTES_NEEDED, RAND_R_RANDOM_POOL_OVERFLOW);
+        return 0;
+    }
+
+    if (pool->len < pool->min_len &&
+        bytes_needed < pool->min_len - pool->len)
+        /* to meet the min_len requirement */
+        bytes_needed = pool->min_len - pool->len;
+
+    /*
+     * Make sure the buffer is large enough for the requested amount
+     * of data. This guarantees that existing code patterns where
+     * rand_pool_add_begin, rand_pool_add_end or rand_pool_add
+     * are used to collect entropy data without any error handling
+     * whatsoever, continue to be valid.
+     * Furthermore if the allocation here fails once, make sure that
+     * we don't fall back to a less secure or even blocking random source,
+     * as that could happen by the existing code patterns.
+     * This is not a concern for additional data, therefore that
+     * is not needed if rand_pool_grow fails in other places.
+     */
+    if (!rand_pool_grow(pool, bytes_needed)) {
+        /* persistent error for this pool */
+        pool->max_len = pool->len = 0;
+        return 0;
+    }
+
+    return bytes_needed;
+}
+
+/* Returns the remaining number of bytes available */
+size_t rand_pool_bytes_remaining(RAND_POOL *pool)
+{
+    return pool->max_len - pool->len;
+}
+
+/*
+ * Add random bytes to the random pool.
+ *
+ * It is expected that the |buffer| contains |len| bytes of
+ * random input which contains at least |entropy| bits of
+ * randomness.
+ *
+ * Returns 1 if the added amount is adequate, otherwise 0
+ */
+int rand_pool_add(RAND_POOL *pool,
+                  const unsigned char *buffer, size_t len, size_t entropy)
+{
+    if (len > pool->max_len - pool->len) {
+        RANDerr(RAND_F_RAND_POOL_ADD, RAND_R_ENTROPY_INPUT_TOO_LONG);
+        return 0;
+    }
+
+    if (pool->buffer == NULL) {
+        RANDerr(RAND_F_RAND_POOL_ADD, ERR_R_INTERNAL_ERROR);
+        return 0;
+    }
+
+    if (len > 0) {
+        /*
+         * This is to protect us from accidentally passing the buffer
+         * returned from rand_pool_add_begin.
+         * The check for alloc_len makes sure we do not compare the
+         * address of the end of the allocated memory to something
+         * different, since that comparison would have an
+         * indeterminate result.
+         */
+        if (pool->alloc_len > pool->len && pool->buffer + pool->len == buffer) {
+            RANDerr(RAND_F_RAND_POOL_ADD, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
+        /*
+         * We have that only for cases when a pool is used to collect
+         * additional data.
+         * For entropy data, as long as the allocation request stays within
+         * the limits given by rand_pool_bytes_needed this rand_pool_grow
+         * below is guaranteed to succeed, thus no allocation happens.
+         */
+        if (!rand_pool_grow(pool, len))
+            return 0;
+        memcpy(pool->buffer + pool->len, buffer, len);
+        pool->len += len;
+        pool->entropy += entropy;
+    }
+
+    return 1;
+}
+
+/*
+ * Start to add random bytes to the random pool in-place.
+ *
+ * Reserves the next |len| bytes for adding random bytes in-place
+ * and returns a pointer to the buffer.
+ * The caller is allowed to copy up to |len| bytes into the buffer.
+ * If |len| == 0 this is considered a no-op and a NULL pointer
+ * is returned without producing an error message.
+ *
+ * After updating the buffer, rand_pool_add_end() needs to be called
+ * to finish the update operation (see next comment).
+ */
+unsigned char *rand_pool_add_begin(RAND_POOL *pool, size_t len)
+{
+    if (len == 0)
+        return NULL;
+
+    if (len > pool->max_len - pool->len) {
+        RANDerr(RAND_F_RAND_POOL_ADD_BEGIN, RAND_R_RANDOM_POOL_OVERFLOW);
+        return NULL;
+    }
+
+    if (pool->buffer == NULL) {
+        RANDerr(RAND_F_RAND_POOL_ADD_BEGIN, ERR_R_INTERNAL_ERROR);
+        return NULL;
+    }
+
+    /*
+     * As long as the allocation request stays within the limits given
+     * by rand_pool_bytes_needed this rand_pool_grow below is guaranteed
+     * to succeed, thus no allocation happens.
+     * We have that only for cases when a pool is used to collect
+     * additional data. Then the buffer might need to grow here,
+     * and of course the caller is responsible to check the return
+     * value of this function.
+     */
+    if (!rand_pool_grow(pool, len))
+        return NULL;
+
+    return pool->buffer + pool->len;
+}
+
+/*
+ * Finish to add random bytes to the random pool in-place.
+ *
+ * Finishes an in-place update of the random pool started by
+ * rand_pool_add_begin() (see previous comment).
+ * It is expected that |len| bytes of random input have been added
+ * to the buffer which contain at least |entropy| bits of randomness.
+ * It is allowed to add less bytes than originally reserved.
+ */
+int rand_pool_add_end(RAND_POOL *pool, size_t len, size_t entropy)
+{
+    if (len > pool->alloc_len - pool->len) {
+        RANDerr(RAND_F_RAND_POOL_ADD_END, RAND_R_RANDOM_POOL_OVERFLOW);
+        return 0;
+    }
+
+    if (len > 0) {
+        pool->len += len;
+        pool->entropy += entropy;
+    }
+
+    return 1;
+}
diff --git a/providers/implementations/rands/seeding/rand_cpu_x86.c b/providers/implementations/rands/seeding/rand_cpu_x86.c
index 3b276c8f54..ba0f716426 100644
--- a/providers/implementations/rands/seeding/rand_cpu_x86.c
+++ b/providers/implementations/rands/seeding/rand_cpu_x86.c
@@ -9,7 +9,7 @@
 
 #include "internal/cryptlib.h"
 #include <openssl/opensslconf.h>
-#include "crypto/rand_pool.h"
+#include "prov/rand_pool.h"
 
 #ifdef OPENSSL_RAND_SEED_RDCPU
 size_t OPENSSL_ia32_rdseed_bytes(unsigned char *buf, size_t len);
diff --git a/providers/implementations/rands/seeding/rand_tsc.c b/providers/implementations/rands/seeding/rand_tsc.c
index 2121abe499..dd69aa438f 100644
--- a/providers/implementations/rands/seeding/rand_tsc.c
+++ b/providers/implementations/rands/seeding/rand_tsc.c
@@ -9,7 +9,7 @@
 
 #include "internal/cryptlib.h"
 #include <openssl/opensslconf.h>
-#include "crypto/rand_pool.h"
+#include "prov/rand_pool.h"
 
 #ifdef OPENSSL_RAND_SEED_RDTSC
 /*
diff --git a/providers/implementations/rands/seeding/rand_unix.c b/providers/implementations/rands/seeding/rand_unix.c
index 050b3e9a18..77c5d26142 100644
--- a/providers/implementations/rands/seeding/rand_unix.c
+++ b/providers/implementations/rands/seeding/rand_unix.c
@@ -15,11 +15,11 @@
 #include "internal/cryptlib.h"
 #include <openssl/rand.h>
 #include <openssl/crypto.h>
-#include "crypto/rand_pool.h"
+#include "prov/rand_pool.h"
 #include "crypto/rand.h"
 #include <stdio.h>
 #include "internal/dso.h"
-#include "seeding.h"
+#include "prov/seeding.h"
 
 #ifdef __linux
 # include <sys/syscall.h>
diff --git a/providers/implementations/rands/seeding/rand_vms.c b/providers/implementations/rands/seeding/rand_vms.c
index 761dad1168..7adf3e718a 100644
--- a/providers/implementations/rands/seeding/rand_vms.c
+++ b/providers/implementations/rands/seeding/rand_vms.c
@@ -14,8 +14,8 @@
 #include "internal/cryptlib.h"
 #include <openssl/rand.h>
 #include "crypto/rand.h"
-#include "crypto/rand_pool.h"
-#include "seeding.h"
+#include "prov/rand_pool.h"
+#include "prov/seeding.h"
 #include <descrip.h>
 #include <dvidef.h>
 #include <jpidef.h>
diff --git a/providers/implementations/rands/seeding/rand_vxworks.c b/providers/implementations/rands/seeding/rand_vxworks.c
index ec9004c06c..f601f77a47 100644
--- a/providers/implementations/rands/seeding/rand_vxworks.c
+++ b/providers/implementations/rands/seeding/rand_vxworks.c
@@ -10,10 +10,10 @@
 #include <openssl/opensslconf.h>
 
 #include <openssl/rand.h>
-#include "crypto/rand_pool.h"
+#include "prov/rand_pool.h"
 #include "crypto/rand.h"
 #include "internal/cryptlib.h"
-#include "seeding.h"
+#include "prov/seeding.h"
 #include <version.h>
 #include <taskLib.h>
 
diff --git a/providers/implementations/rands/seeding/rand_win.c b/providers/implementations/rands/seeding/rand_win.c
index d5c5b59269..605ac6cfe1 100644
--- a/providers/implementations/rands/seeding/rand_win.c
+++ b/providers/implementations/rands/seeding/rand_win.c
@@ -9,9 +9,10 @@
 
 #include "internal/cryptlib.h"
 #include <openssl/rand.h>
-#include "crypto/rand_pool.h"
+#include "prov/rand_pool.h"
 #include "crypto/rand.h"
-#include "seeding.h"
+#include "prov/seeding.h"
+
 #if defined(OPENSSL_SYS_WINDOWS) || defined(OPENSSL_SYS_WIN32)
 
 # ifndef OPENSSL_RAND_SEED_OS