On 7/4/2023 5:41 PM, James Almer wrote:
Uses the existing code for av_get_random_seed() to return a buffer with
cryptographically secure random data, or an error if none could be generated.
Signed-off-by: James Almer <jamr...@gmail.com>
---
libavutil/random_seed.c | 54 ++++++++++++++++++++++++++++-------------
libavutil/random_seed.h | 12 +++++++++
2 files changed, 49 insertions(+), 17 deletions(-)
diff --git a/libavutil/random_seed.c b/libavutil/random_seed.c
index 66dd504ef0..0ed8f89cc6 100644
--- a/libavutil/random_seed.c
+++ b/libavutil/random_seed.c
@@ -46,20 +46,22 @@
#define TEST 0
#endif
-static int read_random(uint32_t *dst, const char *file)
-{
#if HAVE_UNISTD_H
+static int read_random(uint8_t *dst, size_t len, const char *file)
+{
int fd = avpriv_open(file, O_RDONLY);
- int err = -1;
+ ssize_t err = -1;
+ if (len > SSIZE_MAX)
+ return -1;
if (fd == -1)
return -1;
- err = read(fd, dst, sizeof(*dst));
+ err = read(fd, dst, len);
close(fd);
+ if (err == -1)
+ return AVERROR(errno);
- return err;
-#else
- return -1;
+ return err == len;
#endif
}
@@ -118,29 +120,47 @@ static uint32_t get_generic_seed(void)
return AV_RB32(digest) + AV_RB32(digest + 16);
}
-uint32_t av_get_random_seed(void)
+int av_random(uint8_t* buf, size_t len)
{
- uint32_t seed;
+ int err = AVERROR_UNKNOWN;
Changed this locally to AVERROR(ENOSYS), which is the more correct error
value if nothing below is available.
Will send a v3 with that change after this one is reviewed anyway since
this code is delicate and i want to push exactly what was approved.
#if HAVE_BCRYPT
BCRYPT_ALG_HANDLE algo_handle;
NTSTATUS ret = BCryptOpenAlgorithmProvider(&algo_handle,
BCRYPT_RNG_ALGORITHM,
MS_PRIMITIVE_PROVIDER, 0);
if (BCRYPT_SUCCESS(ret)) {
- NTSTATUS ret = BCryptGenRandom(algo_handle, (UCHAR*)&seed,
sizeof(seed), 0);
+ NTSTATUS ret = BCryptGenRandom(algo_handle, (PUCHAR)buf, len, 0);
BCryptCloseAlgorithmProvider(algo_handle, 0);
if (BCRYPT_SUCCESS(ret))
- return seed;
+ return 0;
}
#endif
#if HAVE_ARC4RANDOM
- return arc4random();
+ arc4random_buf(buf, len);
+ return 0;
+#endif
+
+#if HAVE_UNISTD_H
+ err = read_random(buf, len, "/dev/urandom");
+ if (err == 1)
+ return 0;
+ err = read_random(buf, len, "/dev/random");
+ if (err == 1)
+ return 0;
+ if (err == 0)
+ err = AVERROR_UNKNOWN;
#endif
- if (read_random(&seed, "/dev/urandom") == sizeof(seed))
- return seed;
- if (read_random(&seed, "/dev/random") == sizeof(seed))
- return seed;
- return get_generic_seed();
+ return err;
+}
+
+uint32_t av_get_random_seed(void)
+{
+ uint32_t seed;
+
+ if (av_random((uint8_t *)&seed, sizeof(seed)) < 0)
+ return get_generic_seed();
+
+ return seed;
}
diff --git a/libavutil/random_seed.h b/libavutil/random_seed.h
index 0462a048e0..ce982bb82f 100644
--- a/libavutil/random_seed.h
+++ b/libavutil/random_seed.h
@@ -36,6 +36,18 @@
*/
uint32_t av_get_random_seed(void);
+/**
+ * Generate cryptographically secure random data, i.e. suitable for use as
+ * encryption keys and similar.
+ *
+ * @param buf buffer into which the random data will be written
+ * @param len size of buf in bytes
+ *
+ * @retval 0 success, and len bytes of random data was written into buf, or
+ * a negative AVERROR code if random data could not be generated.
+ */
+int av_random(uint8_t* buf, size_t len);
+
/**
* @}
*/
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