diff options
Diffstat (limited to 'crypto')
| -rw-r--r-- | crypto/rand/rand_unix.c | 107 |
1 files changed, 101 insertions, 6 deletions
diff --git a/crypto/rand/rand_unix.c b/crypto/rand/rand_unix.c index ada42f8b80..0d449d235a 100644 --- a/crypto/rand/rand_unix.c +++ b/crypto/rand/rand_unix.c @@ -14,12 +14,16 @@ #include <stdio.h> #include "internal/cryptlib.h" #include <openssl/rand.h> +#include <openssl/crypto.h> #include "rand_lcl.h" #include "internal/rand_int.h" #include <stdio.h> #include "internal/dso.h" #if defined(__linux) # include <asm/unistd.h> +# include <sys/ipc.h> +# include <sys/shm.h> +# include <sys/utsname.h> #endif #if defined(__FreeBSD__) && !defined(OPENSSL_SYS_UEFI) # include <sys/types.h> @@ -357,6 +361,96 @@ static struct random_device { } random_devices[OSSL_NELEM(random_device_paths)]; static int keep_random_devices_open = 1; +# if defined(__linux) && defined(DEVRANDOM_WAIT) +static void *shm_addr; + +# if !defined(FIPS_MODE) +static void cleanup_shm(void) +{ + shmdt(shm_addr); +} +# endif + +/* + * Ensure that the system randomness source has been adequately seeded. + * This is done by having the first start of libcrypto, wait until the device + * /dev/random becomes able to supply a byte of entropy. Subsequent starts + * of the library and later reseedings do not need to do this. + */ +static int wait_random_seeded(void) +{ + static int seeded = OPENSSL_RAND_SEED_DEVRANDOM_SHM_ID < 0; + static const int kernel_version[] = { DEVRANDOM_SAFE_KERNEL }; + int kernel[2]; + int shm_id, fd, r; + char c, *p; + struct utsname un; + fd_set fds; + + if (!seeded) { + /* See if anthing has created the global seeded indication */ + if ((shm_id = shmget(OPENSSL_RAND_SEED_DEVRANDOM_SHM_ID, 1, 0)) == -1) { + /* + * Check the kernel's version and fail if it is too recent. + * + * Linux kernels from 4.8 onwards do not guarantee that + * /dev/urandom is properly seeded when /dev/random becomes + * readable. However, such kernels support the getentropy(2) + * system call and this should always succeed which renders + * this alternative but essentially identical source moot. + */ + if (uname(&un) == 0) { + kernel[0] = atoi(un.release); + p = strchr(un.release, '.'); + kernel[1] = p == NULL ? 0 : atoi(p + 1); + if (kernel[0] > kernel_version[0] + || (kernel[0] == kernel_version[0] + && kernel[1] >= kernel_version[1])) { + return 0; + } + } + /* Open /dev/random and wait for it to be readable */ + if ((fd = open(DEVRANDOM_WAIT, O_RDONLY)) != -1) { + if (DEVRANDM_WAIT_USE_SELECT) { + FD_ZERO(&fds); + FD_SET(fd, &fds); + while ((r = select(fd + 1, &fds, NULL, NULL, NULL)) < 0 + && errno == EINTR); + } else { + while ((r = read(fd, &c, 1)) < 0 && errno == EINTR); + } + close(fd); + if (r == 1) { + seeded = 1; + /* Craete the shared memory indicator */ + shm_id = shmget(OPENSSL_RAND_SEED_DEVRANDOM_SHM_ID, 1, + IPC_CREAT | S_IRUSR | S_IRGRP | S_IROTH); + } + } + } + if (shm_id != -1) { + seeded = 1; + /* + * Map the shared memory to prevent its premature destruction. + * If this call fails, it isn't a big problem. + */ + shm_addr = shmat(shm_id, NULL, SHM_RDONLY); +# ifndef FIPS_MODE + /* TODO 3.0: The FIPS provider doesn't have OPENSSL_atexit */ + if (shm_addr != (void *)-1) + OPENSSL_atexit(&cleanup_shm); +# endif + } + } + return seeded; +} +# else /* defined __linux */ +static int wait_random_seeded(void) +{ + return 1; +} +# endif + /* * Verify that the file descriptor associated with the random source is * still valid. The rationale for doing this is the fact that it is not @@ -518,13 +612,14 @@ size_t rand_pool_acquire_entropy(RAND_POOL *pool) # endif # if defined(OPENSSL_RAND_SEED_DEVRANDOM) - bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/); - { + if (wait_random_seeded()) { size_t i; - for (i = 0; bytes_needed > 0 && i < OSSL_NELEM(random_device_paths); i++) { + bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/); + for (i = 0; bytes_needed > 0 && i < OSSL_NELEM(random_device_paths); + i++) { ssize_t bytes = 0; - /* Maximum allowed number of consecutive unsuccessful attempts */ + /* Maximum number of consecutive unsuccessful attempts */ int attempts = 3; const int fd = get_random_device(i); @@ -538,7 +633,7 @@ size_t rand_pool_acquire_entropy(RAND_POOL *pool) if (bytes > 0) { rand_pool_add_end(pool, bytes, 8 * bytes); bytes_needed -= bytes; - attempts = 3; /* reset counter after successful attempt */ + attempts = 3; /* reset counter on successful attempt */ } else if (bytes < 0 && errno != EINTR) { break; } @@ -546,7 +641,7 @@ size_t rand_pool_acquire_entropy(RAND_POOL *pool) if (bytes < 0 || !keep_random_devices_open) close_random_device(i); - bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/); + bytes_needed = rand_pool_bytes_needed(pool, 1); } entropy_available = rand_pool_entropy_available(pool); if (entropy_available > 0) |