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plugins/auth/pam: expose sudo prompt to PAM via SUDO_PROMPT env #539

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plugins/auth/pam: expose sudo prompt to PAM via SUDO_PROMPT env #539

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41 changes: 41 additions & 0 deletions plugins/sudoers/auth/pam.c
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,7 @@
#endif

#include <sudoers.h>
#include <sudo_compat.h>
#include "sudo_auth.h"

/* Only OpenPAM and Linux PAM use const qualifiers. */
Expand Down Expand Up @@ -313,12 +314,52 @@ sudo_pam_verify(const struct sudoers_context *ctx, struct passwd *pw,
}
}

/*
* Clear SUDO_PROMPT before authentication to avoid stale values
* from previous PAM transactions.
*/
rc = pam_putenv(pamh, "SUDO_PROMPT");
if (rc != PAM_SUCCESS && rc != PAM_BAD_ITEM) {
const char *errstr = sudo_pam_strerror(pamh, rc);
sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
"pam_putenv(pamh, SUDO_PROMPT): %s", errstr);
debug_return_int(AUTH_ERROR);
}

if (def_prompt && ctx->user.prompt) {
char *sudo_prompt = NULL;

if (asprintf(&sudo_prompt, "SUDO_PROMPT=%s", def_prompt) != -1) {
rc = pam_putenv(pamh, sudo_prompt);
free(sudo_prompt);

if (rc != PAM_SUCCESS) {
const char *errstr = sudo_pam_strerror(pamh, rc);
sudo_debug_printf(SUDO_DEBUG_WARN|SUDO_DEBUG_LINENO,
"pam_putenv(pamh, SUDO_PROMPT, %s): %s",
def_prompt, errstr);
}
} else {
const char *errstr = strerror(errno);
sudo_debug_printf(SUDO_DEBUG_WARN|SUDO_DEBUG_LINENO,
"unable to set SUDO_PROMPT: %s", errstr);
}
}

/* PAM_SILENT prevents the authentication service from generating output. */
*pam_status = pam_authenticate(pamh, def_pam_silent ? PAM_SILENT : 0);

/* Restore def_prompt, the passed-in prompt may be freed later. */
def_prompt = PASSPROMPT;

/* Clear the SUDO_PROMPT PAM environment variable. */
rc = pam_putenv(pamh, "SUDO_PROMPT");
if (rc != PAM_SUCCESS) {
const char *errstr = sudo_pam_strerror(pamh, rc);
sudo_debug_printf(SUDO_DEBUG_WARN|SUDO_DEBUG_LINENO,
"pam_putenv(pamh, SUDO_PROMPT): %s", errstr);
}

/* Restore KRB5CCNAME to its original value. */
if (envccname == NULL && sudo_unsetenv("KRB5CCNAME") != 0) {
sudo_debug_printf(SUDO_DEBUG_WARN|SUDO_DEBUG_LINENO,
Expand Down
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