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pam: pass KRB5CCNAME to pam_authenticate environment if available

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If a PAM module wants to authenticate user using GSSAPI, the authentication
is broken if non-default ccache name is used in KRB5CCNAME environment
variable.

One way to mitigate this would be to add this to env_keep, but this also
makes the variable available in the executed command which may not
be always desirable.

This patch sets KRB5CCNAME for pam_authenticate only, if it is available
and not yet set.
This commit is contained in:
Pavel Březina
2021-01-18 12:30:52 +01:00
committed by Todd C. Miller
parent c05fe93669
commit 3b7977a42c
1 changed files with 24 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

28
plugins/sudoers/auth/pam.c
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@@ -114,10 +114,10 @@ conv_filter_init(void)
/*
* Messages from PAM account management when trusted mode is enabled:
* 1 Last successful login for %s: %s
* 2 Last successful login for %s: %s on %s
* 3 Last unsuccessful login for %s: %s
* 4 Last unsuccessful login for %s: %s on %s
* 1 Last successful login for %s: %s
* 2 Last successful login for %s: %s on %s
* 3 Last unsuccessful login for %s: %s
* 4 Last unsuccessful login for %s: %s on %s
*/
if ((catd = catopen("pam_comsec", NL_CAT_LOCALE)) != -1) {
maxfilters += 4;
@@ -288,6 +288,7 @@ sudo_pam_init_quiet(struct passwd *pw, sudo_auth *auth)
int
sudo_pam_verify(struct passwd *pw, char *prompt, sudo_auth *auth, struct sudo_conv_callback *callback)
{
const char *envccname;
const char *s;
int *pam_status = (int *) auth->data;
debug_decl(sudo_pam_verify, SUDOERS_DEBUG_AUTH);
@@ -296,8 +297,27 @@ sudo_pam_verify(struct passwd *pw, char *prompt, sudo_auth *auth, struct sudo_co
getpass_error = false; /* set by converse if user presses ^C */
conv_callback = callback; /* passed to conversation function */
/* Set KRB5CCNAME from the user environment if not set to propagate this
* information to PAM modules that may use it to authentication. */
envccname = sudo_getenv("KRB5CCNAME");
if (envccname == NULL && user_ccname != NULL) {
if (sudo_setenv("KRB5CCNAME", user_ccname, true) != 0) {
sudo_debug_printf(SUDO_DEBUG_WARN|SUDO_DEBUG_LINENO,
"unable to set KRB5CCNAME");
debug_return_int(AUTH_FAILURE);
}
}
/* PAM_SILENT prevents the authentication service from generating output. */
*pam_status = pam_authenticate(pamh, PAM_SILENT);
/* Restore KRB5CCNAME to its original value. */
if (envccname == NULL && sudo_unsetenv("KRB5CCNAME") != 0) {
sudo_debug_printf(SUDO_DEBUG_WARN|SUDO_DEBUG_LINENO,
"unable to restore KRB5CCNAME");
debug_return_int(AUTH_FAILURE);
}
if (getpass_error) {
/* error or ^C from tgetpass() */
debug_return_int(AUTH_INTR);