utils: Implement find_program() to try BINDIR path before PATH

To support install paths that are not covered by $PATH, and still allow
swtpm_setup and swtpm_localca to find swtpm and swtpm_cert executables,
implement find_program() to prepend the install path if only the program
name is given and otherwise fall back to g_find_program_in_path().

Update the man page stating that swtpm from the installation directory
(BINDIR) is tried to be used before one is attempted to be found in
the PATH.

Resolves: #795
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>

man/man8/swtpm_setup.pod

@@ -39,8 +39,9 @@ Prefix with dir:// to use directory backend, or file:// to use linear file.
 
 =item B<--tpm <path to executable>>
 
-Path to the TPM executable; this is an optional argument and
-by default the swtpm executable found in the PATH will be used.
+Path to the TPM executable; this is an optional argument and by default the
+swtpm executable found in the installation directory (BINDIR) will be used
+before swtpm is tried to be found in the PATH.
 
 =item B<--tpm2>
 

src/swtpm_localca/swtpm_localca.c

@@ -361,7 +361,7 @@ static int create_cert(unsigned long flags, const gchar *typ, const gchar *direc
     int ret = 1;
     size_t i, j;
 
-    swtpm_cert_path = g_find_program_in_path("swtpm_cert");
+    swtpm_cert_path = find_program("swtpm_cert");
     if (swtpm_cert_path == NULL) {
         logerr(gl_LOGFILE, "Could not find swtpm_cert in PATH.\n");
         return 1;

src/swtpm_setup/swtpm_setup.c

@@ -1233,7 +1233,7 @@ int main(int argc, char *argv[])
     if (init(&config_file) < 0)
         goto error;
 
-    swtpm_prg = g_find_program_in_path("swtpm");
+    swtpm_prg = find_program("swtpm");
     if (swtpm_prg) {
         tmp = g_strconcat(swtpm_prg, " socket", NULL);
         g_free(swtpm_prg);

src/utils/swtpm_utils.c

@@ -22,6 +22,7 @@
 
 #include <glib.h>
 
+#include "swtpm_conf.h"
 #include "swtpm_utils.h"
 
 void append_to_file(const char *pathname, const char *str)
@@ -440,3 +441,22 @@ int check_directory_access(const gchar *directory, int mode, const struct passwd
     }
     return 0;
 }
+
+/* A program that is only described by the name of the executable is searched
+ * for in the BINDIR path and only then in $PATH
+ */
+gchar *find_program(const gchar *program)
+{
+    g_autofree gchar *dirname = g_path_get_dirname(program);
+    gchar *path;
+
+    if (g_strcmp0(".", dirname) == 0) {
+        path = g_strdup_printf(BINDIR "/%s", program);
+        if (g_file_test(path, G_FILE_TEST_IS_EXECUTABLE))
+            return path;
+
+        g_free(path);
+    }
+
+    return g_find_program_in_path(program);
+}

src/utils/swtpm_utils.h

@@ -43,4 +43,6 @@ gchar *str_replace(const char *in, const char *torep, const char *rep);
 
 int check_directory_access(const gchar *directory, int mode, const struct passwd *curr_user);
 
+gchar *find_program(const gchar *program);
+
 #endif /* SWTPM_UTILS_H */