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random: Reduce variable scopes in CSPRNG #10426

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Merged
merged 4 commits into from
Jan 25, 2023
Merged

random: Reduce variable scopes in CSPRNG #10426

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ff255e0
random: Convert the urandom loop into a while() loop
TimWolla Jan 23, 2023
80e0680
random: Move the errno reset immediately above the getrandom(2) call
TimWolla Jan 23, 2023
5b2529c
random: Reduce the scope of `n` in the CSPRNG
TimWolla Jan 23, 2023
bd2de6d
random: Declare `n` outside of preprocessor branch
TimWolla Jan 23, 2023
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13 changes: 8 additions & 5 deletions ext/random/random.c
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Original file line number Diff line number Diff line change
Expand Up @@ -517,16 +517,13 @@ PHPAPI int php_random_bytes(void *bytes, size_t size, bool should_throw)
arc4random_buf(bytes, size);
#else
size_t read_bytes = 0;
ssize_t n;
# if (defined(__linux__) && defined(SYS_getrandom)) || (defined(__FreeBSD__) && __FreeBSD_version >= 1200000) || (defined(__DragonFly__) && __DragonFly_version >= 500700) || \
defined(__sun) || (defined(__NetBSD__) && __NetBSD_Version__ >= 1000000000)
/* Linux getrandom(2) syscall or FreeBSD/DragonFlyBSD/NetBSD getrandom(2) function
* Being a syscall, implemented in the kernel, getrandom offers higher quality output
* compared to the arc4random api albeit a fallback to /dev/urandom is considered.
*/
while (read_bytes < size) {
errno = 0;

/* Below, (bytes + read_bytes) is pointer arithmetic.

bytes read_bytes size
Expand All @@ -536,6 +533,9 @@ PHPAPI int php_random_bytes(void *bytes, size_t size, bool should_throw)
amount_to_read
*/
size_t amount_to_read = size - read_bytes;
ssize_t n;

errno = 0;
# if defined(__linux__)
n = syscall(SYS_getrandom, bytes + read_bytes, amount_to_read, 0);
# else
Expand Down Expand Up @@ -605,9 +605,10 @@ PHPAPI int php_random_bytes(void *bytes, size_t size, bool should_throw)
RANDOM_G(random_fd) = fd;
}

for (read_bytes = 0; read_bytes < size; read_bytes += (size_t) n) {
read_bytes = 0;
while (read_bytes < size) {
errno = 0;
n = read(fd, bytes + read_bytes, size - read_bytes);
ssize_t n = read(fd, bytes + read_bytes, size - read_bytes);

if (n <= 0) {
if (should_throw) {
Expand All @@ -619,6 +620,8 @@ PHPAPI int php_random_bytes(void *bytes, size_t size, bool should_throw)
}
return FAILURE;
}

read_bytes += (size_t) n;
}
}
#endif
Expand Down