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util/nvmutil: generalised checksum verification

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the existing verification is retained, an a few commands.

this is an additional security mechanism. redundancy is
best.

Signed-off-by: Leah Rowe <leah@libreboot.org>
This commit is contained in:
Leah Rowe
2026-03-08 20:22:31 +00:00
parent 3330f005fd
commit 1400508400
1 changed files with 104 additions and 15 deletions
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util/nvmutil/nvmutil.c
+104 -15
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@@ -43,6 +43,7 @@ static void open_dev_urandom(void);
static void xopen(int *fd, const char *path, int flags, struct stat *st);
static void read_gbe_file(void);
static void read_gbe_file_part(size_t part);
static void read_checksums(void);
static void cmd_setmac(void);
static void parse_mac_string(void);
static void set_mac_byte(size_t mac_byte_pos);
@@ -206,6 +207,16 @@ enum {
ARG_PART
};
enum {
SKIP_CHECKSUM_READ,
CHECKSUM_READ
};
enum {
SKIP_CHECKSUM_WRITE,
CHECKSUM_WRITE
};
struct commands {
size_t chk; /* use by in later check on run_cmd,
against cmd index, to verify correct enum order */
@@ -217,44 +228,62 @@ struct commands {
/* affected by invert */
uint8_t arg_part; /* 0: no part given. 1: part given */
/* if set, only the user-specified part is read */
uint8_t chksum_read;
/* if set: validate checksum before operation */
/* affected by invert */
uint8_t chksum_write;
/* if set: update checksum before write */
/* affected by invert */
};
/*
* Pointers used for running nvmutil commands
*/
static const struct commands command[] = {
{ CMD_DUMP, "dump", cmd_dump, ARGC_3, NO_INVERT,
SET_MOD_OFF, ARG_NOPART },
{ CMD_DUMP, "dump", cmd_dump, ARGC_3,
NO_INVERT, SET_MOD_OFF,
ARG_NOPART,
SKIP_CHECKSUM_READ, SKIP_CHECKSUM_WRITE },
{ CMD_SETMAC, "setmac", cmd_setmac, ARGC_3, NO_INVERT,
SET_MOD_OFF, ARG_NOPART },
{ CMD_SETMAC, "setmac", cmd_setmac, ARGC_3,
NO_INVERT, SET_MOD_OFF,
ARG_NOPART,
CHECKSUM_READ, CHECKSUM_WRITE },
/*
* Invert read and set both parts modified.
* No actual copying in memory is performed.
*/
{ CMD_SWAP, "swap", cmd_swap, ARGC_3, PART_INVERT,
SET_MOD_BOTH, ARG_NOPART },
{ CMD_SWAP, "swap", cmd_swap, ARGC_3,
PART_INVERT, SET_MOD_BOTH,
ARG_NOPART,
CHECKSUM_READ, SKIP_CHECKSUM_WRITE },
/*
* Invert read and set the copied part modified.
* No actual copying in memory is performed.
* arg_part set: we only need to read the specified part.
*/
{ CMD_COPY, "copy", cmd_copy, ARGC_4, PART_INVERT,
SET_MOD_N, ARG_PART },
{ CMD_COPY, "copy", cmd_copy, ARGC_4,
PART_INVERT, SET_MOD_N,
ARG_PART,
CHECKSUM_READ, SKIP_CHECKSUM_WRITE },
/*
* arg_part set: we need only read the specified part.
*/
{ CMD_BRICK, "brick", cmd_brick, ARGC_4, NO_INVERT,
SET_MOD_OFF, ARG_PART },
{ CMD_BRICK, "brick", cmd_brick, ARGC_4,
NO_INVERT, SET_MOD_OFF,
ARG_PART,
CHECKSUM_READ, SKIP_CHECKSUM_WRITE },
/*
* arg_part set: we need only read the specified part.
*/
{ CMD_SETCHECKSUM, "setchecksum", cmd_setchecksum,
ARGC_4, NO_INVERT, SET_MOD_OFF, ARG_PART },
{ CMD_SETCHECKSUM, "setchecksum", cmd_setchecksum, ARGC_4,
NO_INVERT, SET_MOD_OFF,
ARG_PART,
SKIP_CHECKSUM_READ, CHECKSUM_WRITE },
};
#define MAX_CMD_LEN 50
@@ -334,6 +363,8 @@ main(int argc, char *argv[])
#endif
read_gbe_file();
read_checksums();
run_cmd(cmd_index);
if (errno)
@@ -414,12 +445,24 @@ sanitize_command_index(size_t c)
if (command[c].arg_part > 1)
err(ECANCELED, "cmd index %zu: arg_part above 1", c);
if (ARG_NOPART)
err(ECANCELED, "ARG_NOPART is non-zero");
if (ARG_PART != 1)
err(ECANCELED, "ARG_PART is a value other than one");
err(ECANCELED, "ARG_PART is a value other than 1");
if (command[c].chksum_read > 1)
err(ECANCELED, "cmd index %zu: chksum_read above 1", c);
if (SKIP_CHECKSUM_READ)
err(ECANCELED, "SKIP_CHECKSUM_READ is non-zero");
if (CHECKSUM_READ != 1)
err(ECANCELED, "CHECKSUM_READ is a value other than 1");
if (command[c].chksum_write > 1)
err(ECANCELED, "cmd index %zu: chksum_write above 1", c);
if (SKIP_CHECKSUM_WRITE)
err(ECANCELED, "SKIP_CHECKSUM_WRITE is non-zero");
if (CHECKSUM_WRITE != 1)
err(ECANCELED, "CHECKSUM_WRITE is a value other than 1");
}
static void
@@ -651,6 +694,52 @@ read_gbe_file_part(size_t p)
GBE_PART_SIZE, gbe_file_offset(p, "pread"), fname, "pread");
}
static void
read_checksums(void)
{
size_t p;
uint8_t invert;
uint8_t arg_part;
uint8_t num_invalid;
uint8_t max_invalid;
if (!command[cmd_index].chksum_read)
return;
num_invalid = 0;
max_invalid = 2;
invert = command[cmd_index].invert;
arg_part = command[cmd_index].arg_part;
if (arg_part)
max_invalid = 1;
for (p = 0; p < 2; p++) {
check_part_num(p);
/*
* Only verify a part if it was *read*
*/
if (arg_part && (p == (part ^ 1 ^ invert)))
continue;
if (!good_checksum(p))
++num_invalid;
}
/*
* If at least one checksum is valid,
* we can reset errno. This matters,
* because good_checksum() sets it.
*/
if (num_invalid < max_invalid)
errno = 0;
if (num_invalid >= max_invalid)
err(ECANCELED, "No valid checksum found in file: %s",
fname);
}
static void
cmd_setmac(void)
{