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crypto/rand/randfile.c: avoid signed integer overflow in RAND_load_file 

If a file supplied to RAND_load_file is too big (more than INT_MAX bytes),
it is possible to trigger a signer integer overflow during ret calculation.
Avoid it by returning early when we are about to hit it on the next
iteration.

Reported-by: Liu-Ermeng <liuermeng2@huawei.com>
Resolves: https://github.com/openssl/openssl/issues/28375
Signed-off-by: Eugene Syromiatnikov <esyr@openssl.org>

Reviewed-by: Paul Dale <ppzgs1@gmail.com>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/28379)
This commit is contained in:
Eugene Syromiatnikov 2025-08-29 10:02:39 +02:00 committed by Tomas Mraz
parent 876188d8a3
commit 35db6a15d4
2 changed files with 6 additions and 0 deletions
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4
crypto/rand/randfile.c
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@ -167,6 +167,10 @@ int RAND_load_file(const char *file, long bytes)
/* If given a bytecount, and we did it, break. */ /* If given a bytecount, and we did it, break. */
if (bytes > 0 && (bytes -= i) <= 0) if (bytes > 0 && (bytes -= i) <= 0)
break; break;
/* We can hit a signed integer overflow on the next iteration */
if (ret > INT_MAX - RAND_LOAD_BUF_SIZE)
break;
} }
OPENSSL_cleanse(buf, sizeof(buf)); OPENSSL_cleanse(buf, sizeof(buf));

2
doc/man3/RAND_load_file.pod
View File

@ -20,6 +20,8 @@ RAND_load_file() reads a number of bytes from file B<filename> and
adds them to the PRNG. If B<max_bytes> is nonnegative, adds them to the PRNG. If B<max_bytes> is nonnegative,
up to B<max_bytes> are read; up to B<max_bytes> are read;
if B<max_bytes> is -1, the complete file is read. if B<max_bytes> is -1, the complete file is read.
RAND_load_file() can read less than the complete file or the requested number
of bytes if it doesn't fit in the return value type.
Do not load the same file multiple times unless its contents have Do not load the same file multiple times unless its contents have
been updated by RAND_write_file() between reads. been updated by RAND_write_file() between reads.
Also, note that B<filename> should be adequately protected so that an Also, note that B<filename> should be adequately protected so that an