dma: better logic for guessing username

Apply better logic to guess the username when getlogin(3) is not
available for some reason, e.g. no login session at all, no access
to utmp/wtmp, etc.

Submitted-by: Peter Pentchev <roam@ringlet.net>

diff --git a/dma.c b/dma.c
index 6219faba0f667e624f785a8df82a4d81bcd45cf9..19cbc829e372c7523f8a91bd8506e4936e2a5184 100644 (file)
--- a/dma.c
+++ b/dma.c
@@ -73,6 +73,8 @@ struct virtusers virtusers = LIST_HEAD_INITIALIZER(virtusers);
 struct authusers authusers = LIST_HEAD_INITIALIZER(authusers);
 static int daemonize = 1;
 struct config *config;
+static const char *username;
+static uid_t uid;
 static struct strlist seenmsg[16][16];
 
 
@@ -115,6 +117,45 @@ hostname(void)
        return name;
 }
 
+static const char *
+check_username(const char *name, uid_t ckuid)
+{
+       struct passwd *pwd;
+
+       if (name == NULL)
+               return (NULL);
+       pwd = getpwnam(name);
+       if (pwd == NULL || pwd->pw_uid != ckuid)
+               return (NULL);
+       return (name);
+}
+
+static void
+set_username(void)
+{
+       struct passwd *pwd;
+       char *u;
+
+       uid = getuid();
+       username = check_username(getlogin(), uid);
+       if (username == NULL)
+               username = check_username(getenv("LOGNAME"), uid);
+       if (username == NULL)
+               username = check_username(getenv("USER"), uid);
+       if (username == NULL) {
+               pwd = getpwuid(uid);
+               if (pwd != NULL && pwd->pw_name != NULL &&
+                   pwd->pw_name[0] != '\0')
+                       username = check_username(strdup(pwd->pw_name), uid);
+       }
+       if (username == NULL) {
+               asprintf(&u, "%ld", (long)uid);
+               username = u;
+       }
+       if (username == NULL)
+               username = "unknown-or-invalid-username";
+}
+
 static char *
 set_from(const char *osender)
 {
@@ -123,7 +164,7 @@ set_from(const char *osender)
 
        if ((config->features & VIRTUAL) != 0) {
                SLIST_FOREACH(v, &virtusers, next) {
-                       if (strcmp(v->login, getlogin()) == 0) {
+                       if (strcmp(v->login, username) == 0) {
                                sender = strdup(v->address);
                                if (sender == NULL)
                                        return(NULL);
@@ -137,7 +178,7 @@ set_from(const char *osender)
                if (sender == NULL)
                        return (NULL);
        } else {
-               if (asprintf(&sender, "%s@%s", getlogin(), hostname()) <= 0)
+               if (asprintf(&sender, "%s@%s", username, hostname()) <= 0)
                        return (NULL);
        }
 
@@ -386,7 +427,7 @@ Received: from %s (uid %d)\n\
 \tid %"PRIxMAX"\n\
 \tby %s (%s)\n\
 \t%s\n",
-               getlogin(), getuid(),
+               username, uid,
                sender,
                queue->id,
                hostname(), VERSION,
@@ -1018,6 +1059,7 @@ main(int argc, char **argv)
        opterr = 1;
 
        openlog(tag, LOG_PID | LOG_PERROR, LOG_MAIL);
+       set_username();
 
        config = malloc(sizeof(struct config));
        if (config == NULL)