| Message ID | 20240408153006.69840-1-cgoettsche@seltendoof.de (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Petr Lautrbach |
| Headers | show |
| Series | [RFC,1/3] newrole: constant time password comparison | expand |
On Mon, Apr 8, 2024 at 11:31 AM Christian Göttsche <cgoettsche@seltendoof.de> wrote: > > From: Christian Göttsche <cgzones@googlemail.com> > > Perform the password hash comparison in a time constant way to avoid > leaking the length of the identical prefix via a side-channel. > Since only hashes are compared leaking the total length is non critical. > > Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Should we just require PAM for newrole and be done with it? > --- > policycoreutils/newrole/newrole.c | 20 +++++++++++++++++++- > 1 file changed, 19 insertions(+), 1 deletion(-) > > diff --git a/policycoreutils/newrole/newrole.c b/policycoreutils/newrole/newrole.c > index 5a1a1129..1e01d2ef 100644 > --- a/policycoreutils/newrole/newrole.c > +++ b/policycoreutils/newrole/newrole.c > @@ -338,6 +338,24 @@ static void memzero(void *ptr, size_t size) > } > } > > +static int streq_constant(const char *userinput, const char *secret) > +{ > + const volatile char *x = userinput, *y = secret; > + size_t i, u_len, s_len; > + int ret = 0; > + > + u_len = strlen(userinput); > + s_len = strlen(secret); > + > + if (u_len != s_len) > + return 0; > + > + for (i = 0; i < u_len; i++) > + ret |= x[i] ^ y[i]; > + > + return ret == 0; > +} > + > /* authenticate_via_shadow_passwd() > * > * in: uname - the calling user's user name > @@ -383,7 +401,7 @@ static int authenticate_via_shadow_passwd(const char *uname) > return 0; > } > > - ret = !strcmp(encrypted_password_s, p_shadow_line->sp_pwdp); > + ret = streq_constant(encrypted_password_s, p_shadow_line->sp_pwdp); > memzero(encrypted_password_s, strlen(encrypted_password_s)); > return ret; > } > -- > 2.43.0 > >
diff --git a/policycoreutils/newrole/newrole.c b/policycoreutils/newrole/newrole.c index 5a1a1129..1e01d2ef 100644 --- a/policycoreutils/newrole/newrole.c +++ b/policycoreutils/newrole/newrole.c @@ -338,6 +338,24 @@ static void memzero(void *ptr, size_t size) } } +static int streq_constant(const char *userinput, const char *secret) +{ + const volatile char *x = userinput, *y = secret; + size_t i, u_len, s_len; + int ret = 0; + + u_len = strlen(userinput); + s_len = strlen(secret); + + if (u_len != s_len) + return 0; + + for (i = 0; i < u_len; i++) + ret |= x[i] ^ y[i]; + + return ret == 0; +} + /* authenticate_via_shadow_passwd() * * in: uname - the calling user's user name @@ -383,7 +401,7 @@ static int authenticate_via_shadow_passwd(const char *uname) return 0; } - ret = !strcmp(encrypted_password_s, p_shadow_line->sp_pwdp); + ret = streq_constant(encrypted_password_s, p_shadow_line->sp_pwdp); memzero(encrypted_password_s, strlen(encrypted_password_s)); return ret; }