Hi Joe,
On Tue, May 15, 2018 at 01:25:09PM -0500, Joe Hershberger wrote:
> On Tue, May 15, 2018 at 5:03 AM, Quentin Schulz
> <quentin.sch...@bootlin.com> wrote:
> > While the `env export` can take as parameters variables to be exported,
> > `env import` does not have such a mechanism of variable selection.
> >
> > Let's add a `-w` option that asks `env import` to look for the
> > `whitelisted_vars` env variable for a space-separated list of variables
> > that are whitelisted.
> >
> > Every env variable present in env at `addr` and in `whitelisted_vars`
> > env variable will override the value of the variable in the current env.
> > All the remaining variables are left untouched.
> >
> > One of its use case could be to load a secure environment from the
> > signed U-Boot binary and load only a handful of variables from an
> > other, unsecure, environment without completely losing control of
> > U-Boot.
> >
> > Signed-off-by: Quentin Schulz <quentin.sch...@bootlin.com>
> > ---
> > cmd/nvedit.c | 66
> > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
> > 1 file changed, 62 insertions(+), 4 deletions(-)
> >
> > diff --git a/cmd/nvedit.c b/cmd/nvedit.c
> > index 4e79d03856..4637ec656c 100644
> > --- a/cmd/nvedit.c
> > +++ b/cmd/nvedit.c
> > @@ -971,7 +971,7 @@ sep_err:
> >
> > #ifdef CONFIG_CMD_IMPORTENV
> > /*
> > - * env import [-d] [-t [-r] | -b | -c] addr [size]
> > + * env import [-d] [-t [-r] | -b | -c] [-w] addr [size]
> > * -d: delete existing environment before importing;
> > * otherwise overwrite / append to existing definitions
> > * -t: assume text format; either "size" must be given or the
> > @@ -982,6 +982,10 @@ sep_err:
> > * for line endings. Only effective in addition to -t.
> > * -b: assume binary format ('\0' separated, "\0\0" terminated)
> > * -c: assume checksum protected environment format
> > + * -w: specify that whitelisting of variables should be used when
> > + * importing environment. The space-separated list of variables
> > + * that should override the ones in current environment is
> > stored
> > + * in `whitelisted_vars`.
> > * addr: memory address to read from
> > * size: length of input data; if missing, proper '\0'
> > * termination is mandatory
> > @@ -991,17 +995,21 @@ static int do_env_import(cmd_tbl_t *cmdtp, int flag,
> > {
> > ulong addr;
> > char *cmd, *ptr;
> > + char **array = NULL;
> > char sep = '\n';
> > int chk = 0;
> > int fmt = 0;
> > int del = 0;
> > int crlf_is_lf = 0;
> > + int wl = 0;
> > + int wl_count = 0;
> > + unsigned int i;
> > size_t size;
> >
> > cmd = *argv;
> >
> > while (--argc > 0 && **++argv == '-') {
> > - char *arg = *argv;
> > + char *arg = *argv, *str, *token, *tmp;
> > while (*++arg) {
> > switch (*arg) {
> > case 'b': /* raw binary format */
> > @@ -1026,6 +1034,43 @@ static int do_env_import(cmd_tbl_t *cmdtp, int flag,
> > case 'd':
> > del = 1;
> > break;
> > + case 'w':
> > + wl = 1;
> > + wl_count = 1;
> > +
> > + str = env_get("whitelisted_vars");
>
> I don't like how this is grabbing the list from the env. I think a
> comma-separated list should be a parameter following the '-w'.
>
Comma are valids in the name of environment variables if I'm not
mistaken. (Did a quick setenv test,123 test and it saved test in
test,123). So that's not an option.
Using a space separated list after "-w" is also not easy as I don't see
from a quick thought how to differentiate the list of vars passed to -w
from the addr and size parameters at the end of the function (how to
know if size was passed or not?).
Is there any other character aside from a space that can be used to
separate the list of variables?
> > + if (!str) {
> > + puts("## Error: whitelisted_vars is
> > not set.\n");
> > + return CMD_RET_USAGE;
> > + }
> > +
> > + tmp = malloc(sizeof(char) * (strlen(str) +
> > 1));
> > + strcpy(tmp, str);
> > +
> > + token = strchr(tmp, ' ');
> > + while (!token) {
> > + wl_count++;
> > + token = strchr(token + 1, ' ');
> > + }
> > +
> > + strcpy(tmp, str);
> > +
> > + array = malloc(sizeof(char *) * wl_count);
> > + wl_count = 0;
> > +
> > + token = strtok(tmp, " ");
> > + while (token) {
> > + unsigned int size = strlen(token);
> > +
> > + array[wl_count] =
> > malloc(sizeof(char) *
> > + (size +
> > 1));
>
> Why malloc again for every string? Just use the buffer we already have.
>
Do an array[wl_count] = token instead?
I'm not sure this will work with this patch's code.
From what I understand from strtok[1], token is a pointer to somewhere
in the string tmp. So we're screwed once tmp is freed aren't we?
I could move the free(tmp) to the final goto I'm talking about below
though and get away with it.
> > + strcpy(array[wl_count], token);
> > + wl_count++;
> > + token = strtok(NULL, " ");
> > + }
> > +
> > + free(tmp);
> > + break;
> > default:
> > return CMD_RET_USAGE;
> > }
> > @@ -1083,12 +1128,25 @@ static int do_env_import(cmd_tbl_t *cmdtp, int flag,
> > }
> >
> > if (himport_r(&env_htab, ptr, size, sep, del ? 0 : H_NOCLEAR,
> > - crlf_is_lf, 0, NULL) == 0) {
> > + crlf_is_lf, wl ? wl_count : 0, wl ? array : NULL) ==
> > 0) {
> > pr_err("Environment import failed: errno = %d\n", errno);
> > +
> > + if (wl) {
> > + for (i = 0; i < wl_count; i++)
> > + free(array[i]);
> > + free(array);
> > + }
>
> It would be better to have a consolidated cleanup at the end of the function.
>
Sure. I'll add a goto with appropriate return value.
Thanks,
Quentin
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