This is a relatively old diff that eliminates some gratuitous
differences in the various parser functions. The cert parsing is
still a bit special and let's not mention mfts... That can't really
be helped. All the others can be brought to essentially the same form.

There's of course lots of bikeshedding potential here. I just chose one
option that I happen to like.

Index: parser.c
===================================================================
RCS file: /cvs/src/usr.sbin/rpki-client/parser.c,v
diff -u -p -r1.142 parser.c
--- parser.c	20 Aug 2024 13:31:49 -0000	1.142
+++ parser.c	29 Aug 2024 10:26:41 -0000
@@ -165,36 +165,38 @@ static struct roa *
 proc_parser_roa(char *file, const unsigned char *der, size_t len,
     const struct entity *entp)
 {
-	struct roa		*roa;
+	struct roa		*roa = NULL;
+	X509			*x509 = NULL;
 	struct auth		*a;
 	struct crl		*crl;
-	X509			*x509;
 	const char		*errstr;
 
 	if ((roa = roa_parse(&x509, file, entp->talid, der, len)) == NULL)
-		return NULL;
+		goto out;
 
 	a = find_issuer(file, entp->certid, roa->aki, entp->mftaki);
-	if (a == NULL) {
-		X509_free(x509);
-		roa_free(roa);
-		return NULL;
-	}
+	if (a == NULL)
+		goto out;
 	crl = crl_get(&crlt, a);
 
 	if (!valid_x509(file, ctx, x509, a, crl, &errstr)) {
 		warnx("%s: %s", file, errstr);
-		X509_free(x509);
-		roa_free(roa);
-		return NULL;
+		goto out;
 	}
 	X509_free(x509);
+	x509 = NULL;
 
 	roa->talid = a->cert->talid;
 
 	roa->expires = x509_find_expires(roa->notafter, a, &crlt);
 
 	return roa;
+
+ out:
+	roa_free(roa);
+	X509_free(x509);
+
+	return NULL;
 }
 
 /*
@@ -205,36 +207,38 @@ static struct spl *
 proc_parser_spl(char *file, const unsigned char *der, size_t len,
     const struct entity *entp)
 {
-	struct spl		*spl;
+	struct spl		*spl = NULL;
+	X509			*x509 = NULL;
 	struct auth		*a;
 	struct crl		*crl;
-	X509			*x509;
 	const char		*errstr;
 
 	if ((spl = spl_parse(&x509, file, entp->talid, der, len)) == NULL)
-		return NULL;
+		goto out;
 
 	a = find_issuer(file, entp->certid, spl->aki, entp->mftaki);
-	if (a == NULL) {
-		X509_free(x509);
-		spl_free(spl);
-		return NULL;
-	}
+	if (a == NULL)
+		goto out;
 	crl = crl_get(&crlt, a);
 
 	if (!valid_x509(file, ctx, x509, a, crl, &errstr)) {
 		warnx("%s: %s", file, errstr);
-		X509_free(x509);
-		spl_free(spl);
-		return NULL;
+		goto out;
 	}
 	X509_free(x509);
+	x509 = NULL;
 
 	spl->talid = a->cert->talid;
 
 	spl->expires = x509_find_expires(spl->notafter, a, &crlt);
 
 	return spl;
+
+ out:
+	spl_free(spl);
+	X509_free(x509);
+
+	return NULL;
 }
 
 /*
@@ -546,7 +550,7 @@ static struct cert *
 proc_parser_cert(char *file, const unsigned char *der, size_t len,
     const struct entity *entp)
 {
-	struct cert	*cert;
+	struct cert	*cert = NULL;
 	struct crl	*crl;
 	struct auth	*a;
 	const char	*errstr = NULL;
@@ -556,30 +560,25 @@ proc_parser_cert(char *file, const unsig
 	cert = cert_parse_pre(file, der, len);
 	cert = cert_parse(file, cert);
 	if (cert == NULL)
-		return NULL;
+		goto out;
 
 	a = find_issuer(file, entp->certid, cert->aki, entp->mftaki);
-	if (a == NULL) {
-		cert_free(cert);
-		return NULL;
-	}
+	if (a == NULL)
+		goto out;
 	crl = crl_get(&crlt, a);
 
 	if (!valid_x509(file, ctx, cert->x509, a, crl, &errstr) ||
 	    !valid_cert(file, a, cert)) {
 		if (errstr != NULL)
 			warnx("%s: %s", file, errstr);
-		cert_free(cert);
-		return NULL;
+		goto out;
 	}
 
 	cert->talid = a->cert->talid;
 
 	if (cert->purpose == CERT_PURPOSE_BGPSEC_ROUTER) {
-		if (!constraints_validate(file, cert)) {
-			cert_free(cert);
-			return NULL;
-		}
+		if (!constraints_validate(file, cert))
+			goto out;
 	}
 
 	/*
@@ -589,6 +588,11 @@ proc_parser_cert(char *file, const unsig
 		auth_insert(file, &auths, cert, a);
 
 	return cert;
+
+ out:
+	cert_free(cert);
+
+	return NULL;
 }
 
 static int
@@ -695,34 +699,36 @@ static struct gbr *
 proc_parser_gbr(char *file, const unsigned char *der, size_t len,
     const struct entity *entp)
 {
-	struct gbr	*gbr;
-	X509		*x509;
+	struct gbr	*gbr = NULL;
+	X509		*x509 = NULL;
 	struct crl	*crl;
 	struct auth	*a;
 	const char	*errstr;
 
 	if ((gbr = gbr_parse(&x509, file, entp->talid, der, len)) == NULL)
-		return NULL;
+		goto out;
 
 	a = find_issuer(file, entp->certid, gbr->aki, entp->mftaki);
-	if (a == NULL) {
-		X509_free(x509);
-		gbr_free(gbr);
-		return NULL;
-	}
+	if (a == NULL)
+		goto out;
 	crl = crl_get(&crlt, a);
 
 	if (!valid_x509(file, ctx, x509, a, crl, &errstr)) {
 		warnx("%s: %s", file, errstr);
-		X509_free(x509);
-		gbr_free(gbr);
-		return NULL;
+		goto out;
 	}
 	X509_free(x509);
+	x509 = NULL;
 
 	gbr->talid = a->cert->talid;
 
 	return gbr;
+
+ out:
+	gbr_free(gbr);
+	X509_free(x509);
+
+	return NULL;
 }
 
 /*
@@ -732,36 +738,38 @@ static struct aspa *
 proc_parser_aspa(char *file, const unsigned char *der, size_t len,
     const struct entity *entp)
 {
-	struct aspa	*aspa;
+	struct aspa	*aspa = NULL;
+	X509		*x509 = NULL;
 	struct auth	*a;
 	struct crl	*crl;
-	X509		*x509;
 	const char	*errstr;
 
 	if ((aspa = aspa_parse(&x509, file, entp->talid, der, len)) == NULL)
-		return NULL;
+		goto out;
 
 	a = find_issuer(file, entp->certid, aspa->aki, entp->mftaki);
-	if (a == NULL) {
-		X509_free(x509);
-		aspa_free(aspa);
-		return NULL;
-	}
+	if (a == NULL)
+		goto out;
 	crl = crl_get(&crlt, a);
 
 	if (!valid_x509(file, ctx, x509, a, crl, &errstr)) {
 		warnx("%s: %s", file, errstr);
-		X509_free(x509);
-		aspa_free(aspa);
-		return NULL;
+		goto out;
 	}
 	X509_free(x509);
+	x509 = NULL;
 
 	aspa->talid = a->cert->talid;
 
 	aspa->expires = x509_find_expires(aspa->notafter, a, &crlt);
 
 	return aspa;
+
+ out:
+	aspa_free(aspa);
+	X509_free(x509);
+
+	return NULL;
 }
 
 /*
@@ -771,15 +779,14 @@ static struct tak *
 proc_parser_tak(char *file, const unsigned char *der, size_t len,
     const struct entity *entp)
 {
-	struct tak	*tak;
-	X509		*x509;
+	struct tak	*tak = NULL;
+	X509		*x509 = NULL;
 	struct crl	*crl;
 	struct auth	*a;
 	const char	*errstr;
-	int		 rc = 0;
 
 	if ((tak = tak_parse(&x509, file, entp->talid, der, len)) == NULL)
-		return NULL;
+		goto out;
 
 	a = find_issuer(file, entp->certid, tak->aki, entp->mftaki);
 	if (a == NULL)
@@ -790,20 +797,22 @@ proc_parser_tak(char *file, const unsign
 		warnx("%s: %s", file, errstr);
 		goto out;
 	}
+	X509_free(x509);
+	x509 = NULL;
 
 	/* TAK EE must be signed by self-signed CA */
 	if (a->issuer != NULL)
 		goto out;
 
 	tak->talid = a->cert->talid;
-	rc = 1;
+
+	return tak;
+
  out:
-	if (rc == 0) {
-		tak_free(tak);
-		tak = NULL;
-	}
+	tak_free(tak);
 	X509_free(x509);
-	return tak;
+
+	return NULL;
 }
 
 /*