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RAND_load_file(): avoid adding small chunks to RAND_add()

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Increase the load buffer size such that it exceeds the chunk
size by a comfortable amount. This is done to avoid calling
RAND_add() with a small final chunk. Instead, such a small
final chunk will be added together with the previous chunk
(unless it's the only one).

Related-to: #7449

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/7456)
This commit is contained in:
Dr. Matthias St. Pierre 2018-10-21 18:49:19 +02:00
parent 13ce86259e
commit 1d0671b81f
1 changed files with 23 additions and 9 deletions
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32
crypto/rand/randfile.c
View file

@ -16,6 +16,7 @@
#include <openssl/crypto.h>
#include <openssl/rand.h>
#include <openssl/rand_drbg.h>
#include <openssl/buffer.h>
#ifdef OPENSSL_SYS_VMS
@ -48,7 +49,7 @@
# define S_ISREG(m) ((m) & S_IFREG)
# endif
#define RAND_FILE_SIZE 1024
#define RAND_BUF_SIZE 1024
#define RFILE ".rnd"
#ifdef OPENSSL_SYS_VMS
@ -74,7 +75,16 @@ static __FILE_ptr32 (*const vms_fopen)(const char *, const char *, ...) =
*/
int RAND_load_file(const char *file, long bytes)
{
unsigned char buf[RAND_FILE_SIZE];
/*
* The load buffer size exceeds the chunk size by the comfortable amount
* of 'RAND_DRBG_STRENGTH' bytes (not bits!). This is done on purpose
* to avoid calling RAND_add() with a small final chunk. Instead, such
* a small final chunk will be added together with the previous chunk
* (unless it's the only one).
*/
#define RAND_LOAD_BUF_SIZE (RAND_BUF_SIZE + RAND_DRBG_STRENGTH)
unsigned char buf[RAND_LOAD_BUF_SIZE];
#ifndef OPENSSL_NO_POSIX_IO
struct stat sb;
#endif
@ -98,8 +108,12 @@ int RAND_load_file(const char *file, long bytes)
return -1;
}
if (!S_ISREG(sb.st_mode) && bytes < 0)
bytes = 256;
if (bytes < 0) {
if (S_ISREG(sb.st_mode))
bytes = (sb.st_size <= LONG_MAX) ? sb.st_size : LONG_MAX;
else
bytes = RAND_DRBG_STRENGTH;
}
#endif
/*
* On VMS, setbuf() will only take 32-bit pointers, and a compilation
@ -124,9 +138,9 @@ int RAND_load_file(const char *file, long bytes)
for ( ; ; ) {
if (bytes > 0)
n = (bytes < RAND_FILE_SIZE) ? (int)bytes : RAND_FILE_SIZE;
n = (bytes <= RAND_LOAD_BUF_SIZE) ? (int)bytes : RAND_BUF_SIZE;
else
n = RAND_FILE_SIZE;
n = RAND_LOAD_BUF_SIZE;
i = fread(buf, 1, n, in);
#ifdef EINTR
if (ferror(in) && errno == EINTR){
@ -159,7 +173,7 @@ int RAND_load_file(const char *file, long bytes)
int RAND_write_file(const char *file)
{
unsigned char buf[RAND_FILE_SIZE];
unsigned char buf[RAND_BUF_SIZE];
int ret = -1;
FILE *out = NULL;
#ifndef OPENSSL_NO_POSIX_IO
@ -228,9 +242,9 @@ int RAND_write_file(const char *file)
chmod(file, 0600);
#endif
ret = fwrite(buf, 1, RAND_FILE_SIZE, out);
ret = fwrite(buf, 1, RAND_BUF_SIZE, out);
fclose(out);
OPENSSL_cleanse(buf, RAND_FILE_SIZE);
OPENSSL_cleanse(buf, RAND_BUF_SIZE);
return ret;
}