Adding upstream version 1.9.15p5.upstream/1.9.15p5upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 776 insertions, 0 deletions

diff --git a/plugins/sudoers/auth/pam.c b/plugins/sudoers/auth/pam.c
new file mode 100644
index 0000000..e8d1785
--- /dev/null
+++ b/plugins/sudoers/auth/pam.c
@@ -0,0 +1,776 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 1999-2005, 2007-2020 Todd C. Miller <Todd.Miller@sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * Sponsored in part by the Defense Advanced Research Projects
+ * Agency (DARPA) and Air Force Research Laboratory, Air Force
+ * Materiel Command, USAF, under agreement number F39502-99-1-0512.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <config.h>
+
+#ifdef HAVE_PAM
+
+#include <sys/types.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <pwd.h>
+#include <errno.h>
+
+#ifdef HAVE_PAM_PAM_APPL_H
+# include <pam/pam_appl.h>
+#else
+# include <security/pam_appl.h>
+#endif
+
+#ifdef __hpux
+# include <nl_types.h>
+#endif
+
+#ifdef HAVE_LIBINTL_H
+# if defined(__LINUX_PAM__)
+#  define PAM_TEXT_DOMAIN	"Linux-PAM"
+# elif defined(__sun__)
+#  define PAM_TEXT_DOMAIN	"SUNW_OST_SYSOSPAM"
+# endif
+#endif
+
+/* We don't want to translate the strings in the calls to dgt(). */
+#ifdef PAM_TEXT_DOMAIN
+# define dgt(d, t)	dgettext(d, t)
+#endif
+
+#include <sudoers.h>
+#include "sudo_auth.h"
+
+/* Only OpenPAM and Linux PAM use const qualifiers. */
+#ifdef PAM_SUN_CODEBASE
+# define PAM_CONST
+#else
+# define PAM_CONST	const
+#endif
+
+/* Ambiguity in spec: is it an array of pointers or a pointer to an array? */
+#ifdef PAM_SUN_CODEBASE
+# define PAM_MSG_GET(msg, n) (*(msg) + (n))
+#else
+# define PAM_MSG_GET(msg, n) ((msg)[(n)])
+#endif
+
+#ifndef PAM_DATA_SILENT
+#define PAM_DATA_SILENT	0
+#endif
+
+struct sudo_pam_closure {
+    const struct sudoers_context *ctx;
+    struct sudo_conv_callback *callback;
+};
+
+struct conv_filter {
+    char *msg;
+    size_t msglen;
+};
+
+static int converse(int, PAM_CONST struct pam_message **,
+		    struct pam_response **, void *);
+static struct sudo_pam_closure pam_closure;
+static struct pam_conv pam_conv = { converse, &pam_closure };
+static const char *def_prompt = PASSPROMPT;
+static bool getpass_error;
+static bool noninteractive;
+static pam_handle_t *pamh;
+static struct conv_filter *conv_filter;
+
+static void
+conv_filter_init(const struct sudoers_context *ctx)
+{
+    debug_decl(conv_filter_init, SUDOERS_DEBUG_AUTH);
+
+#ifdef __hpux
+    /*
+     * HP-UX displays last login information as part of either account
+     * management (in trusted mode) or session management (regular mode).
+     * Filter those out in the conversation function unless running a shell.
+     */
+    if (!ISSET(ctx->mode, MODE_SHELL|MODE_LOGIN_SHELL)) {
+	int i, nfilt = 0, maxfilters = 0;
+	struct conv_filter *newfilt;
+	nl_catd catd;
+	char *msg;
+
+	/*
+	 * 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
+	 */
+	if ((catd = catopen("pam_comsec", NL_CAT_LOCALE)) != -1) {
+	    maxfilters += 4;
+	    newfilt = reallocarray(conv_filter, maxfilters + 1,
+		sizeof(*conv_filter));
+	    if (newfilt != NULL) {
+		conv_filter = newfilt;
+		for (i = 1; i < 5; i++) {
+		    if ((msg = catgets(catd, 1, i, NULL)) == NULL)
+			break;
+		    sudo_debug_printf(SUDO_DEBUG_INFO|SUDO_DEBUG_LINENO,
+			"adding \"%s\" to conversation filter", msg);
+		    if ((conv_filter[nfilt].msg = strdup(msg)) == NULL)
+			break;
+		    conv_filter[nfilt].msglen = strcspn(msg, "%");
+		    nfilt++;
+		}
+	    }
+	}
+	/*
+	 * Messages from PAM session management when trusted mode is disabled:
+	 *  3 Last successful login:       %s %s %s %s
+	 *  4 Last authentication failure: %s %s %s %s
+	 */
+	if ((catd = catopen("pam_hpsec", NL_CAT_LOCALE)) != -1) {
+	    maxfilters += 2;
+	    newfilt = reallocarray(conv_filter, maxfilters + 1,
+		sizeof(*conv_filter));
+	    if (newfilt != NULL) {
+		conv_filter = newfilt;
+		for (i = 3; i < 5; i++) {
+		    if ((msg = catgets(catd, 1, i, NULL)) == NULL)
+			break;
+		    sudo_debug_printf(SUDO_DEBUG_INFO|SUDO_DEBUG_LINENO,
+			"adding \"%s\" to conversation filter", msg);
+		    if ((conv_filter[nfilt].msg = strdup(msg)) == NULL)
+			break;
+		    conv_filter[nfilt].msglen = strcspn(msg, "%");
+		    nfilt++;
+		}
+	    }
+	}
+	if (conv_filter != NULL) {
+	    conv_filter[nfilt].msg = NULL;
+	    conv_filter[nfilt].msglen = 0;
+	}
+    }
+#endif /* __hpux */
+    debug_return;
+}
+
+/*
+ * Like pam_strerror() but never returns NULL and uses strerror(errno)
+ * for PAM_SYSTEM_ERR.
+ */
+static const char *
+sudo_pam_strerror(pam_handle_t *handle, int errnum)
+{
+    const char *errstr;
+    static char errbuf[32];
+
+    if (errnum == PAM_SYSTEM_ERR)
+	return strerror(errno);
+    if ((errstr = pam_strerror(handle, errnum)) == NULL)
+	(void)snprintf(errbuf, sizeof(errbuf), "PAM error %d", errnum);
+    return errstr;
+}
+
+static int
+sudo_pam_init2(const struct sudoers_context *ctx, struct passwd *pw,
+    sudo_auth *auth, bool quiet)
+{
+    static int pam_status = PAM_SUCCESS;
+    const char *ttypath = ctx->user.ttypath;
+    const char *errstr, *pam_service;
+    int rc;
+    debug_decl(sudo_pam_init, SUDOERS_DEBUG_AUTH);
+
+    /* Stash pointer to last pam status. */
+    auth->data = &pam_status;
+
+    if (pamh != NULL) {
+	/* Already initialized (may happen with AIX or with sub-commands). */
+	debug_return_int(AUTH_SUCCESS);
+    }
+
+    /* Stash value of noninteractive flag for conversation function. */
+    noninteractive = IS_NONINTERACTIVE(auth);
+
+    /* Store context in closure so converse() has access to it. */
+    pam_closure.ctx = ctx;
+
+    /* Initialize PAM. */
+    if (ISSET(ctx->mode, MODE_ASKPASS) && def_pam_askpass_service != NULL) {
+	pam_service = def_pam_askpass_service;
+    } else {
+	pam_service = ISSET(ctx->mode, MODE_LOGIN_SHELL) ?
+	    def_pam_login_service : def_pam_service;
+    }
+    pam_status = pam_start(pam_service, pw->pw_name, &pam_conv, &pamh);
+    if (pam_status != PAM_SUCCESS) {
+	errstr = sudo_pam_strerror(NULL, pam_status);
+	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+	    "pam_start(%s, %s, %p, %p): %s", pam_service, pw->pw_name,
+	    &pam_conv, &pamh, errstr);
+	if (!quiet)
+	    log_warningx(ctx, 0, N_("unable to initialize PAM: %s"), errstr);
+	debug_return_int(AUTH_ERROR);
+    }
+
+    /* Initialize conversation function message filter. */
+    conv_filter_init(ctx);
+
+    /*
+     * Set PAM_RUSER to the invoking user (the "from" user).
+     * Solaris 7 and below require PAM_RHOST to be set if PAM_RUSER is.
+     * Note: PAM_RHOST may cause a DNS lookup on Linux in libaudit.
+     */
+    if (def_pam_ruser) {
+	rc = pam_set_item(pamh, PAM_RUSER, ctx->user.name);
+	if (rc != PAM_SUCCESS) {
+	    errstr = sudo_pam_strerror(pamh, rc);
+	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+		"pam_set_item(pamh, PAM_RUSER, %s): %s", ctx->user.name, errstr);
+	}
+    }
+    if (def_pam_rhost) {
+	rc = pam_set_item(pamh, PAM_RHOST, ctx->user.host);
+	if (rc != PAM_SUCCESS) {
+	    errstr = sudo_pam_strerror(pamh, rc);
+	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+		"pam_set_item(pamh, PAM_RHOST, %s): %s", ctx->user.host, errstr);
+	}
+    }
+    if (ttypath != NULL) {
+	rc = pam_set_item(pamh, PAM_TTY, ttypath);
+	if (rc != PAM_SUCCESS) {
+	    errstr = sudo_pam_strerror(pamh, rc);
+	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+		"pam_set_item(pamh, PAM_TTY, %s): %s", ttypath, errstr);
+	}
+    }
+
+    /*
+     * If PAM session and setcred support is disabled we don't
+     * need to keep a sudo process around to close the session.
+     */
+    if (!def_pam_session && !def_pam_setcred)
+	auth->end_session = NULL;
+
+    debug_return_int(AUTH_SUCCESS);
+}
+
+int
+sudo_pam_init(const struct sudoers_context *ctx, struct passwd *pw,
+    sudo_auth *auth)
+{
+    return sudo_pam_init2(ctx, pw, auth, false);
+}
+
+#ifdef _AIX
+int
+sudo_pam_init_quiet(const struct sudoers_context *ctx, struct passwd *pw,
+    sudo_auth *auth)
+{
+    return sudo_pam_init2(ctx, pw, auth, true);
+}
+#endif /* _AIX */
+
+int
+sudo_pam_verify(const struct sudoers_context *ctx, struct passwd *pw,
+    const 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);
+
+    def_prompt = prompt;		/* for converse */
+    getpass_error = false;		/* set by converse if user presses ^C */
+    pam_closure.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 && ctx->user.ccname != NULL) {
+		if (sudo_setenv("KRB5CCNAME", ctx->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 def_prompt, the passed-in prompt may be freed later. */
+    def_prompt = PASSPROMPT;
+
+	/* 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() or running non-interactive */
+	debug_return_int(noninteractive ? AUTH_NONINTERACTIVE : AUTH_INTR);
+    }
+    switch (*pam_status) {
+	case PAM_SUCCESS:
+	    debug_return_int(AUTH_SUCCESS);
+	case PAM_AUTH_ERR:
+	case PAM_AUTHINFO_UNAVAIL:
+	case PAM_MAXTRIES:
+	case PAM_PERM_DENIED:
+	    sudo_debug_printf(SUDO_DEBUG_WARN|SUDO_DEBUG_LINENO,
+		"pam_authenticate: %d", *pam_status);
+	    debug_return_int(AUTH_FAILURE);
+	default:
+	    s = sudo_pam_strerror(pamh, *pam_status);
+	    log_warningx(ctx, 0, N_("PAM authentication error: %s"), s);
+	    debug_return_int(AUTH_ERROR);
+    }
+}
+
+int
+sudo_pam_approval(const struct sudoers_context *ctx, struct passwd *pw,
+    sudo_auth *auth, bool exempt)
+{
+    const char *s;
+    int rc, status = AUTH_SUCCESS;
+    int *pam_status = (int *) auth->data;
+    debug_decl(sudo_pam_approval, SUDOERS_DEBUG_AUTH);
+
+    if (def_pam_acct_mgmt) {
+	rc = pam_acct_mgmt(pamh, PAM_SILENT);
+	switch (rc) {
+	    case PAM_SUCCESS:
+		break;
+	    case PAM_AUTH_ERR:
+		log_warningx(ctx, 0, N_("account validation failure, "
+		    "is your account locked?"));
+		status = AUTH_ERROR;
+		break;
+	    case PAM_NEW_AUTHTOK_REQD:
+		/* Ignore if user is exempt from password restrictions. */
+		if (exempt) {
+		    rc = *pam_status;
+		    break;
+		}
+		/* New password required, try to change it. */
+		log_warningx(ctx, 0, N_("Account or password is "
+		    "expired, reset your password and try again"));
+		rc = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
+		if (rc == PAM_SUCCESS)
+		    break;
+		s = pam_strerror(pamh, rc);
+		log_warningx(ctx, 0,
+		    N_("unable to change expired password: %s"), s);
+		status = AUTH_FAILURE;
+		break;
+	    case PAM_AUTHTOK_EXPIRED:
+		/* Ignore if user is exempt from password restrictions. */
+		if (exempt) {
+		    rc = *pam_status;
+		    break;
+		}
+		/* Password expired, cannot be updated by user. */
+		log_warningx(ctx, 0,
+		    N_("Password expired, contact your system administrator"));
+		status = AUTH_ERROR;
+		break;
+	    case PAM_ACCT_EXPIRED:
+		log_warningx(ctx, 0,
+		    N_("Account expired or PAM config lacks an \"account\" "
+		    "section for sudo, contact your system administrator"));
+		status = AUTH_ERROR;
+		break;
+	    case PAM_AUTHINFO_UNAVAIL:
+	    case PAM_MAXTRIES:
+	    case PAM_PERM_DENIED:
+		s = sudo_pam_strerror(pamh, rc);
+		log_warningx(ctx, 0, N_("PAM account management error: %s"), s);
+		status = AUTH_FAILURE;
+		break;
+	    default:
+		s = sudo_pam_strerror(pamh, rc);
+		log_warningx(ctx, 0, N_("PAM account management error: %s"), s);
+		status = AUTH_ERROR;
+		break;
+	}
+	*pam_status = rc;
+    }
+    debug_return_int(status);
+}
+
+int
+sudo_pam_cleanup(const struct sudoers_context *ctx, struct passwd *pw,
+    sudo_auth *auth, bool force)
+{
+    int *pam_status = (int *) auth->data;
+    debug_decl(sudo_pam_cleanup, SUDOERS_DEBUG_AUTH);
+
+    /* If successful, we can't close the session until sudo_pam_end_session() */
+    if (force || *pam_status != PAM_SUCCESS || auth->end_session == NULL) {
+	*pam_status = pam_end(pamh, *pam_status | PAM_DATA_SILENT);
+	pamh = NULL;
+    }
+    debug_return_int(*pam_status == PAM_SUCCESS ? AUTH_SUCCESS : AUTH_FAILURE);
+}
+
+int
+sudo_pam_begin_session(const struct sudoers_context *ctx, struct passwd *pw,
+    char **user_envp[], sudo_auth *auth)
+{
+    int rc, status = AUTH_SUCCESS;
+    int *pam_status = (int *) auth->data;
+    const char *errstr;
+    debug_decl(sudo_pam_begin_session, SUDOERS_DEBUG_AUTH);
+
+    /*
+     * If there is no valid user we cannot open a PAM session.
+     * This is not an error as sudo can run commands with arbitrary
+     * uids, it just means we are done from a session management standpoint.
+     */
+    if (pw == NULL) {
+	if (pamh != NULL) {
+	    rc = pam_end(pamh, PAM_SUCCESS | PAM_DATA_SILENT);
+	    if (rc != PAM_SUCCESS) {
+		errstr = sudo_pam_strerror(pamh, rc);
+		sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+		    "pam_end: %s", errstr);
+	    }
+	    pamh = NULL;
+	}
+	goto done;
+    }
+
+    /*
+     * Update PAM_USER to reference the user we are running the command
+     * as, as opposed to the user we authenticated as.
+     */
+    rc = pam_set_item(pamh, PAM_USER, pw->pw_name);
+    if (rc != PAM_SUCCESS) {
+	errstr = sudo_pam_strerror(pamh, rc);
+	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+	    "pam_set_item(pamh, PAM_USER, %s): %s", pw->pw_name, errstr);
+    }
+
+    /*
+     * Reinitialize credentials when changing the user.
+     * We don't worry about a failure from pam_setcred() since with
+     * stacked PAM auth modules a failure from one module may override
+     * PAM_SUCCESS from another.  For example, given a non-local user,
+     * pam_unix will fail but pam_ldap or pam_sss may succeed, but if
+     * pam_unix is first in the stack, pam_setcred() will fail.
+     */
+    if (def_pam_setcred) {
+	rc = pam_setcred(pamh, PAM_REINITIALIZE_CRED);
+	if (rc != PAM_SUCCESS) {
+	    errstr = sudo_pam_strerror(pamh, rc);
+	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+		"pam_setcred: %s", errstr);
+	    def_pam_setcred = false;
+	}
+    }
+
+    if (def_pam_session) {
+	/*
+	 * We use PAM_SILENT to prevent pam_lastlog from printing last login
+	 * information except when explicitly running a shell.
+	 */
+	const bool silent = !ISSET(ctx->mode, MODE_SHELL|MODE_LOGIN_SHELL);
+	rc = pam_open_session(pamh, silent ? PAM_SILENT : 0);
+	switch (rc) {
+	case PAM_SUCCESS:
+	    break;
+	case PAM_SESSION_ERR:
+	    /* Treat PAM_SESSION_ERR as a non-fatal error. */
+	    errstr = sudo_pam_strerror(pamh, rc);
+	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+		"pam_open_session: %s", errstr);
+	    /* Avoid closing session that was not opened. */
+	    def_pam_session = false;
+	    break;
+	default:
+	    /* Unexpected session failure, treat as fatal error. */
+	    *pam_status = rc;
+	    errstr = sudo_pam_strerror(pamh, rc);
+	    log_warningx(ctx, 0, N_("%s: %s"), "pam_open_session", errstr);
+	    rc = pam_end(pamh, *pam_status | PAM_DATA_SILENT);
+	    if (rc != PAM_SUCCESS) {
+		errstr = sudo_pam_strerror(pamh, rc);
+		sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+		    "pam_end: %s", errstr);
+	    }
+	    pamh = NULL;
+	    status = AUTH_ERROR;
+	    goto done;
+	}
+    }
+
+#ifdef HAVE_PAM_GETENVLIST
+    /*
+     * Update environment based on what is stored in pamh.
+     * If no authentication is done we will only have environment
+     * variables if pam_env is called via session.
+     */
+    if (user_envp != NULL) {
+	char **pam_envp = pam_getenvlist(pamh);
+	if (pam_envp != NULL) {
+	    /* Merge pam env with user env. */
+	    if (!env_init(*user_envp) || !env_merge(ctx, pam_envp))
+		status = AUTH_ERROR;
+	    *user_envp = env_get();
+	    free(pam_envp);
+	    /* XXX - we leak any duplicates that were in pam_envp */
+	}
+    }
+#endif /* HAVE_PAM_GETENVLIST */
+
+done:
+    debug_return_int(status);
+}
+
+int
+sudo_pam_end_session(sudo_auth *auth)
+{
+    int rc, status = AUTH_SUCCESS;
+    const char *errstr;
+    debug_decl(sudo_pam_end_session, SUDOERS_DEBUG_AUTH);
+
+    if (pamh != NULL) {
+	if (def_pam_session) {
+	    rc = pam_close_session(pamh, PAM_SILENT);
+	    if (rc != PAM_SUCCESS) {
+		errstr = sudo_pam_strerror(pamh, rc);
+		sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+		    "pam_close_session: %s", errstr);
+	    }
+	}
+	if (def_pam_setcred) {
+	    rc = pam_setcred(pamh, PAM_DELETE_CRED | PAM_SILENT);
+	    if (rc != PAM_SUCCESS) {
+		errstr = sudo_pam_strerror(pamh, rc);
+		sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+		    "pam_setcred: %s", errstr);
+	    }
+	}
+	rc = pam_end(pamh, PAM_SUCCESS | PAM_DATA_SILENT);
+	if (rc != PAM_SUCCESS) {
+	    errstr = sudo_pam_strerror(pamh, rc);
+	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+		"pam_end: %s", errstr);
+	    status = AUTH_ERROR;
+	}
+	pamh = NULL;
+    }
+
+    debug_return_int(status);
+}
+
+#define PROMPT_IS_PASSWORD(_p) \
+    (strncmp((_p), "Password:", 9) == 0 && \
+	((_p)[9] == '\0' || ((_p)[9] == ' ' && (_p)[10] == '\0')))
+
+#ifdef PAM_TEXT_DOMAIN
+# define PAM_PROMPT_IS_PASSWORD(_p) \
+    (strcmp((_p), dgt(PAM_TEXT_DOMAIN, "Password:")) == 0 || \
+	strcmp((_p), dgt(PAM_TEXT_DOMAIN, "Password: ")) == 0 || \
+	PROMPT_IS_PASSWORD(_p))
+#else
+# define PAM_PROMPT_IS_PASSWORD(_p)	PROMPT_IS_PASSWORD(_p)
+#endif /* PAM_TEXT_DOMAIN */
+
+/*
+ * We use the PAM prompt in preference to sudo's as long
+ * as passprompt_override is not set and:
+ *  a) the (translated) sudo prompt matches /^Password: ?/
+ * or:
+ *  b) the PAM prompt itself *doesn't* match /^Password: ?/
+ *     or /^username's Password: ?/
+ *
+ * The intent is to use the PAM prompt for things like
+ * challenge-response, otherwise use sudo's prompt.
+ * There may also be cases where a localized translation
+ * of "Password: " exists for PAM but not for sudo.
+ */
+static bool
+use_pam_prompt(const char *pam_prompt)
+{
+    size_t user_len;
+    debug_decl(use_pam_prompt, SUDOERS_DEBUG_AUTH);
+
+    /* Always use sudo prompt if passprompt_override is set. */
+    if (def_passprompt_override)
+	debug_return_bool(false);
+
+    /* If sudo prompt matches "^Password: ?$", use PAM prompt. */
+    if (PROMPT_IS_PASSWORD(def_prompt))
+	debug_return_bool(true);
+
+    /* If PAM prompt matches "^Password: ?$", use sudo prompt. */
+    if (PAM_PROMPT_IS_PASSWORD(pam_prompt))
+	debug_return_bool(false);
+
+    /*
+     * Some PAM modules use "^username's Password: ?$" instead of
+     * "^Password: ?" so check for that too.
+     */
+    if (pam_closure.ctx != NULL) {
+	const char *user_name = pam_closure.ctx->user.name;
+	user_len = strlen(user_name);
+	if (strncmp(pam_prompt, user_name, user_len) == 0) {
+	    const char *cp = pam_prompt + user_len;
+	    if (strncmp(cp, "'s Password:", 12) == 0 &&
+		(cp[12] == '\0' || (cp[12] == ' ' && cp[13] == '\0')))
+		debug_return_bool(false);
+	}
+    }
+
+    /* Otherwise, use the PAM prompt. */
+    debug_return_bool(true);
+}
+
+static bool
+is_filtered(const char *msg)
+{
+    bool filtered = false;
+
+    if (conv_filter != NULL) {
+	struct conv_filter *filt = conv_filter;
+	while (filt->msg != NULL) {
+	    if (strncmp(msg, filt->msg, filt->msglen) == 0) {
+		filtered = true;
+		break;
+	    }
+	    filt++;
+	}
+    }
+    return filtered;
+}
+
+/*
+ * ``Conversation function'' for PAM <-> human interaction.
+ */
+static int
+converse(int num_msg, PAM_CONST struct pam_message **msg,
+    struct pam_response **reply_out, void *appdata_ptr)
+{
+    struct sudo_conv_callback *callback = NULL;
+    struct sudo_pam_closure *closure = appdata_ptr;
+    struct pam_response *reply;
+    const char *prompt;
+    char *pass;
+    int n, type;
+    debug_decl(converse, SUDOERS_DEBUG_AUTH);
+
+    if (num_msg <= 0 || num_msg > PAM_MAX_NUM_MSG) {
+	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+	    "invalid number of PAM messages: %d", num_msg);
+	debug_return_int(PAM_CONV_ERR);
+    }
+    sudo_debug_printf(SUDO_DEBUG_DEBUG|SUDO_DEBUG_LINENO,
+	"number of PAM messages: %d", num_msg);
+
+    reply = calloc((size_t)num_msg, sizeof(struct pam_response));
+    if (reply == NULL) {
+	sudo_warnx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+	debug_return_int(PAM_BUF_ERR);
+    }
+
+    if (closure != NULL)
+	callback = closure->callback;
+
+    for (n = 0; n < num_msg; n++) {
+	PAM_CONST struct pam_message *pm = PAM_MSG_GET(msg, n);
+
+	type = SUDO_CONV_PROMPT_ECHO_OFF;
+	switch (pm->msg_style) {
+	    case PAM_PROMPT_ECHO_ON:
+		type = SUDO_CONV_PROMPT_ECHO_ON;
+		FALLTHROUGH;
+	    case PAM_PROMPT_ECHO_OFF:
+		/* Error out if the last password read was interrupted. */
+		if (getpass_error)
+		    goto bad;
+
+		/* Treat non-interactive mode as a getpass error. */
+		if (noninteractive) {
+		    getpass_error = true;
+		    goto bad;
+		}
+
+		/* Choose either the sudo prompt or the PAM one. */
+		prompt = use_pam_prompt(pm->msg) ? pm->msg : def_prompt;
+
+		/* Read the password unless interrupted. */
+		pass = auth_getpass(prompt, type, callback);
+		if (pass == NULL) {
+		    /* Error (or ^C) reading password, don't try again. */
+		    getpass_error = true;
+		    goto bad;
+		}
+		if (strlen(pass) >= PAM_MAX_RESP_SIZE) {
+		    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+			"password longer than %d", PAM_MAX_RESP_SIZE);
+		    freezero(pass, strlen(pass));
+		    pass = NULL;
+		    goto bad;
+		}
+		reply[n].resp = pass;	/* auth_getpass() malloc's a copy */
+		break;
+	    case PAM_TEXT_INFO:
+		if (pm->msg != NULL && !is_filtered(pm->msg))
+		    sudo_printf(SUDO_CONV_INFO_MSG|SUDO_CONV_PREFER_TTY,
+			"%s\n", pm->msg);
+		break;
+	    case PAM_ERROR_MSG:
+		if (pm->msg != NULL)
+		    sudo_printf(SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY,
+			"%s\n", pm->msg);
+		break;
+	    default:
+		sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+		    "unsupported message style: %d", pm->msg_style);
+		goto bad;
+	}
+    }
+
+    *reply_out = reply;
+    debug_return_int(PAM_SUCCESS);
+
+bad:
+    /* Zero and free allocated memory and return an error. */
+    for (n = 0; n < num_msg; n++) {
+	struct pam_response *pr = &reply[n];
+
+	if (pr->resp != NULL) {
+	    freezero(pr->resp, strlen(pr->resp));
+	    pr->resp = NULL;
+	}
+    }
+    free(reply);
+    debug_return_int(PAM_CONV_ERR);
+}
+
+#endif /* HAVE_PAM */