usign-exec: change usign_f_* fingerprint argument to char[17]

This makes it more obvious that a buffer with space for 17 characters is
expected to be passed. The code still works the same (a char[17] is
equivalent to char* as an argument).

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>

usign-exec.c

@@ -94,7 +94,7 @@ int usign_s(const char *msgfile, const char *seckeyfile, const char *sigfile, bo
  * call usign -F ... and set fingerprint returned
  * return WEXITSTATUS or -1 if fork fails
  */
-static int usign_f(char *fingerprint, const char *pubkeyfile, const char *seckeyfile, const char *sigfile, bool quiet) {
+static int usign_f(char fingerprint[17], const char *pubkeyfile, const char *seckeyfile, const char *sigfile, bool quiet) {
 	int fds[2];
 	pid_t pid;
 	int status;
@@ -162,21 +162,21 @@ static int usign_f(char *fingerprint, const char *pubkeyfile, const char *seckey
 /*
  * call usign -F -p ...
  */
-int usign_f_pubkey(char *fingerprint, const char *pubkeyfile, bool quiet) {
+int usign_f_pubkey(char fingerprint[17], const char *pubkeyfile, bool quiet) {
 	return usign_f(fingerprint, pubkeyfile, NULL, NULL, quiet);
 }
 
 /*
  * call usign -F -s ...
  */
-int usign_f_seckey(char *fingerprint, const char *seckeyfile, bool quiet) {
+int usign_f_seckey(char fingerprint[17], const char *seckeyfile, bool quiet) {
 	return usign_f(fingerprint, NULL, seckeyfile, NULL, quiet);
 }
 
 /*
  * call usign -F -x ...
  */
-int usign_f_sig(char *fingerprint, const char *sigfile, bool quiet) {
+int usign_f_sig(char fingerprint[17], const char *sigfile, bool quiet) {
 	return usign_f(fingerprint, NULL, NULL, sigfile, quiet);
 }
 

usign.h

@@ -37,11 +37,11 @@ int usign_s(const char *msgfile, const char *seckeyfile, const char *sigfile, bo
  *
  * calls: usign -F ...
  */
-int usign_f_pubkey(char *fingerprint, const char *pubkeyfile, bool quiet);
+int usign_f_pubkey(char fingerprint[17], const char *pubkeyfile, bool quiet);
 
-int usign_f_seckey(char *fingerprint, const char *seckeyfile, bool quiet);
+int usign_f_seckey(char fingerprint[17], const char *seckeyfile, bool quiet);
 
-int usign_f_sig(char *fingerprint, const char *sigfile, bool quiet);
+int usign_f_sig(char fingerprint[17], const char *sigfile, bool quiet);
 
 /**
  * custom extension to check for revokers