[LEDE-DEV] [PATCH ubox] getrandom: add helper for getrandom() syscall

[Etienne Champetier]

Hi,

Everything is fine except your computer clock ;)
ubox commit:
author    Etienne CHAMPETIER <champetier.etienne at gmail.com>
    Thu, 9 Jun 2016 16:03:00 +0300 (13:03 +0000)
committer    John Crispin <john at phrozen.org>
    Wed, 8 Jun 2016 01:19:24 +0300 (00:19 +0200)

staging commit:
author    John Crispin <john at phrozen.org>
    Wed, 8 Jun 2016 01:22:16 +0300 (00:22 +0200)
committer    John Crispin <john at phrozen.org>
    Wed, 8 Jun 2016 01:56:48 +0300

Thanks
Etienne

2016-06-09 17:17 GMT+03:00 John Crispin <john at phrozen.org>:
> Hi Etienne,
>
> pushed the patch to ubox.git and updated the ubox package inside my
> staging tree. should the tool be installed to /usr/bin ? if not let me
> know and i will fix the staged commit.
>
>         John
>
> On 09/06/2016 15:03, Etienne CHAMPETIER wrote:
>> getrandom() was introduced in version 3.17 of the Linux kernel.
>> By default getrandom() block until /dev/urandom pool has been initialized
>> and then read from it.
>> Read buffer is 256 bytes so getrandom() calls always succeed.
>>
>> First usage will be to save a seed for /dev/urandom.
>>
>> Signed-off-by: Etienne CHAMPETIER <champetier.etienne at gmail.com>
>> ---
>>  CMakeLists.txt |  5 +++++
>>  getrandom.c    | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 63 insertions(+)
>>  create mode 100644 getrandom.c
>>
>> diff --git a/CMakeLists.txt b/CMakeLists.txt
>> index 834b5b6..73e8753 100644
>> --- a/CMakeLists.txt
>> +++ b/CMakeLists.txt
>> @@ -16,6 +16,11 @@ IF(DEBUG)
>>    ADD_DEFINITIONS(-DDEBUG -g3)
>>  ENDIF()
>>
>> +ADD_EXECUTABLE(getrandom getrandom.c)
>> +INSTALL(TARGETS getrandom
>> +     RUNTIME DESTINATION bin
>> +)
>> +
>>  ADD_EXECUTABLE(kmodloader kmodloader.c)
>>  TARGET_LINK_LIBRARIES(kmodloader ubox)
>>
>> diff --git a/getrandom.c b/getrandom.c
>> new file mode 100644
>> index 0000000..9671202
>> --- /dev/null
>> +++ b/getrandom.c
>> @@ -0,0 +1,58 @@
>> +/*
>> + * Copyright (C) 2016 Etienne Champetier <champetier.etienne at gmail.com>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License as published by
>> + * the Free Software Foundation; either version 2 of the License, or
>> + * (at your option) any later version.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + */
>> +#define _GNU_SOURCE
>> +#include <errno.h>
>> +#include <linux/random.h>
>> +#include <stdio.h>
>> +#include <stdlib.h>
>> +#include <string.h>
>> +#include <sys/syscall.h>
>> +#include <unistd.h>
>> +
>> +#define ERROR_EXIT(fmt, ...) do { \
>> +        fprintf(stderr, fmt, ## __VA_ARGS__); \
>> +        return EXIT_FAILURE; \
>> +        } while (0)
>> +
>> +static int usage(char *name)
>> +{
>> +    fprintf(stderr, "Usage: %s <nb>\n", name);
>> +    fprintf(stderr, " => return <nb> bytes from getrandom()\n");
>> +    return EXIT_FAILURE;
>> +}
>> +
>> +int main(int argc, char *argv[])
>> +{
>> +    if (argc != 2)
>> +        return usage(argv[0]);
>> +
>> +    if (isatty(STDOUT_FILENO))
>> +        ERROR_EXIT("Not outputting random to a tty\n");
>> +
>> +    int nbtot = atoi(argv[1]);
>> +    if (nbtot < 1)
>> +        ERROR_EXIT("Invalid <nb> param (must be > 0)\n");
>> +
>> +    char buf[256];
>> +    int len = sizeof(buf);
>> +    while (nbtot > 0) {
>> +        if (nbtot <= sizeof(buf))
>> +            len = nbtot;
>> +        if (syscall(SYS_getrandom, buf, len, 0) == -1)
>> +            ERROR_EXIT("getrandom() failed: %s\n", strerror(errno));
>> +        if (write(STDOUT_FILENO, buf, len) != len)
>> +            ERROR_EXIT("write() failed: %s\n", strerror(errno));
>> +        nbtot -= sizeof(buf);
>> +    }
>> +}
>>
>
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