From 7a590a370a199f5fb5e3835e9473baab0f7539c4 Mon Sep 17 00:00:00 2001 From: Conrad Meyer Date: Thu, 11 Apr 2019 05:08:49 +0000 Subject: [PATCH] sort(1): Simplify and bound random seeding Bound input file processing length to avoid the issue reported in [1]. For simplicity, only allow regular file and character device inputs. For character devices, only allow /dev/random (and /dev/urandom symblink). 32 bytes of random is perfectly sufficient to seed MD5; we don't need any more. Users that want to use large files as seeds are encouraged to truncate those files down to an appropriate input file via tools like sha256(1). (This does not change the sort algorithm of sort -R.) [1]: https://lists.freebsd.org/pipermail/freebsd-hackers/2018-August/053152.html PR: 230792 Reported by: Ali Abdallah Relnotes: yes --- usr.bin/sort/sort.c | 115 +++++++++++++++++++++++++------------------- 1 file changed, 66 insertions(+), 49 deletions(-) diff --git a/usr.bin/sort/sort.c b/usr.bin/sort/sort.c index eb034c4ae887..844841c50458 100644 --- a/usr.bin/sort/sort.c +++ b/usr.bin/sort/sort.c @@ -36,6 +36,7 @@ __FBSDID("$FreeBSD$"); #include #include +#include #include #include #include @@ -61,13 +62,7 @@ nl_catd catalog; #define OPTIONS "bcCdfghik:Mmno:RrsS:t:T:uVz" -#define DEFAULT_RANDOM_SORT_SEED_FILE ("/dev/random") -#define MAX_DEFAULT_RANDOM_SEED_DATA_SIZE (1024) - static bool need_random; -static const char *random_source = DEFAULT_RANDOM_SORT_SEED_FILE; -static const void *random_seed; -static size_t random_seed_size; MD5_CTX md5_ctx; @@ -907,55 +902,76 @@ fix_obsolete_keys(int *argc, char **argv) } /* - * Set random seed + * Seed random sort */ static void -set_random_seed(void) +get_random_seed(const char *random_source) { - if (strcmp(random_source, DEFAULT_RANDOM_SORT_SEED_FILE) == 0) { - FILE* fseed; - MD5_CTX ctx; - char rsd[MAX_DEFAULT_RANDOM_SEED_DATA_SIZE]; - size_t sz = 0; + char randseed[32]; + struct stat fsb, rsb; + ssize_t rd; + int rsfd; - fseed = openfile(random_source, "r"); - while (!feof(fseed)) { - int cr; + rsfd = -1; + rd = sizeof(randseed); - cr = fgetc(fseed); - if (cr == EOF) - break; - - rsd[sz++] = (char) cr; - - if (sz >= MAX_DEFAULT_RANDOM_SEED_DATA_SIZE) - break; - } - - closefile(fseed, random_source); - - MD5Init(&ctx); - MD5Update(&ctx, rsd, sz); - - random_seed = MD5End(&ctx, NULL); - random_seed_size = strlen(random_seed); - - } else { - MD5_CTX ctx; - char *b; - - MD5Init(&ctx); - b = MD5File(random_source, NULL); - if (b == NULL) - err(2, NULL); - - random_seed = b; - random_seed_size = strlen(b); + if (random_source == NULL) { + if (getentropy(randseed, sizeof(randseed)) < 0) + err(EX_SOFTWARE, "getentropy"); + goto out; } + + rsfd = open(random_source, O_RDONLY | O_CLOEXEC); + if (rsfd < 0) + err(EX_NOINPUT, "open: %s", random_source); + + if (fstat(rsfd, &fsb) != 0) + err(EX_SOFTWARE, "fstat"); + + if (!S_ISREG(fsb.st_mode) && !S_ISCHR(fsb.st_mode)) + err(EX_USAGE, + "random seed isn't a regular file or /dev/random"); + + /* + * Regular files: read up to maximum seed size and explicitly + * reject longer files. + */ + if (S_ISREG(fsb.st_mode)) { + if (fsb.st_size > (off_t)sizeof(randseed)) + errx(EX_USAGE, "random seed is too large (%jd >" + " %zu)!", (intmax_t)fsb.st_size, + sizeof(randseed)); + else if (fsb.st_size < 1) + errx(EX_USAGE, "random seed is too small (" + "0 bytes)"); + + memset(randseed, 0, sizeof(randseed)); + + rd = read(rsfd, randseed, fsb.st_size); + if (rd < 0) + err(EX_SOFTWARE, "reading random seed file %s", + random_source); + if (rd < (ssize_t)fsb.st_size) + errx(EX_SOFTWARE, "short read from %s", random_source); + } else if (S_ISCHR(fsb.st_mode)) { + if (stat("/dev/random", &rsb) < 0) + err(EX_SOFTWARE, "stat"); + + if (fsb.st_dev != rsb.st_dev || + fsb.st_ino != rsb.st_ino) + errx(EX_USAGE, "random seed is a character " + "device other than /dev/random"); + + if (getentropy(randseed, sizeof(randseed)) < 0) + err(EX_SOFTWARE, "getentropy"); + } + +out: + if (rsfd >= 0) + close(rsfd); + MD5Init(&md5_ctx); - if(random_seed_size>0) { - MD5Update(&md5_ctx, random_seed, random_seed_size); - } + MD5Update(&md5_ctx, randseed, rd); } /* @@ -965,6 +981,7 @@ int main(int argc, char **argv) { char *outfile, *real_outfile; + char *random_source = NULL; int c, result; bool mef_flags[NUMBER_OF_MUTUALLY_EXCLUSIVE_FLAGS] = { false, false, false, false, false, false }; @@ -1225,7 +1242,7 @@ main(int argc, char **argv) } if (need_random) - set_random_seed(); + get_random_seed(random_source); /* Case when the outfile equals one of the input files: */ if (strcmp(outfile, "-")) {