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util/nvmutil: Harden pledge promises

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After reading a file, remove rpath.

When removing rpath, also remove wpath if flags
are not to O_RDONLY (read-only disk operation).

When wpath is permitted, and a file was successfully
written, remove wpath.

In order to permit /dev/urandom access in rhex(),
I call it as a void just before re-calling pledge.

The rhex() function has been written in such a way
that /dev/urandom only needs to be read *once*.

Signed-off-by: Leah Rowe <leah@libreboot.org>
This commit is contained in:
Leah Rowe
2023-05-31 08:02:46 +01:00
parent c759a7a095
commit c2cd191676
1 changed files with 11 additions and 7 deletions
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util/nvmutil/nvmutil.c
+11 -7
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@@ -124,6 +124,11 @@ main(int argc, char *argv[])
skipread[part ^ 1] = (cmd == &cmd_copy) | skipread[part ^ 1] = (cmd == &cmd_copy) |
(cmd == &cmd_setchecksum) | (cmd == &cmd_brick); (cmd == &cmd_setchecksum) | (cmd == &cmd_brick);
readGbeFile(&fd, FILENAME, flags, nr); readGbeFile(&fd, FILENAME, flags, nr);
(void)rhex();
if (flags == O_RDONLY)
xpledge("stdio", NULL);
else
xpledge("stdio wpath", NULL);
if (strMac != NULL) if (strMac != NULL)
cmd_setmac(strMac); /* nvm gbe.bin setmac */ cmd_setmac(strMac); /* nvm gbe.bin setmac */
else if (cmd != NULL) else if (cmd != NULL)
@@ -219,18 +224,16 @@ hextonum(char ch)
uint8_t uint8_t
rhex(void) rhex(void)
{ {
static int rfd = -1; static int rfd = -1, n = 0;
static uint64_t rnum = 0; static uint8_t rnum[16];
if (rnum == 0) { if (!n) {
if (rfd == -1) if (rfd == -1)
if ((rfd = open("/dev/urandom", O_RDONLY)) == -1) if ((rfd = open("/dev/urandom", O_RDONLY)) == -1)
err(errno, "/dev/urandom"); err(errno, "/dev/urandom");
if (read(rfd, (uint8_t *) &rnum, 8) == -1) if (read(rfd, (uint8_t *) &rnum, (n = 15) + 1) == -1)
err(errno, "/dev/urandom"); err(errno, "/dev/urandom");
} }
uint8_t rval = (uint8_t) (rnum & 0xf); return rnum[n--] & 0xf;
rnum >>= 4;
return rval;
} }
void void
@@ -366,6 +369,7 @@ next_part:
} }
if (close((*fd))) if (close((*fd)))
err(errno, "%s", filename); err(errno, "%s", filename);
xpledge("stdio", NULL);
} }
void void