pkg: refactor out a pkg_read_fd()

We already have to do this for reading the pubkey, just pull it out for
other uses.  The ECC signer will use this to verify the bootstrap if
the PUBKEY mechanism is used.

Reviewed by:	bapt, emaste

(cherry picked from commit 2ecfc040a0)

usr.sbin/pkg/pkg.c

@@ -386,32 +386,46 @@ load_fingerprints(const char *path, int *count)
 	return (fingerprints);
 }
 
+char *
+pkg_read_fd(int fd, size_t *osz)
+{
+	char *obuf;
+	char buf[4096];
+	FILE *fp;
+	ssize_t r;
+
+	obuf = NULL;
+	*osz = 0;
+	fp = open_memstream(&obuf, osz);
+	if (fp == NULL)
+		err(EXIT_FAILURE, "open_memstream()");
+
+	while ((r = read(fd, buf, sizeof(buf))) >0) {
+		fwrite(buf, 1, r, fp);
+	}
+
+	if (ferror(fp))
+		errx(EXIT_FAILURE, "reading file");
+
+	fclose(fp);
+
+	return (obuf);
+}
+
 static struct pubkey *
 read_pubkey(int fd)
 {
 	struct pubkey *pk;
 	char *sigb;
 	size_t sigsz;
-	FILE *sig;
-	char buf[4096];
-	int r;
 
 	if (lseek(fd, 0, 0) == -1) {
 		warn("lseek");
 		return (NULL);
 	}
 
-	sigsz = 0;
-	sigb = NULL;
-	sig = open_memstream(&sigb, &sigsz);
-	if (sig == NULL)
-		err(EXIT_FAILURE, "open_memstream()");
+	sigb = pkg_read_fd(fd, &sigsz);
 
-	while ((r = read(fd, buf, sizeof(buf))) >0) {
-		fwrite(buf, 1, r, sig);
-	}
-
-	fclose(sig);
 	pk = calloc(1, sizeof(struct pubkey));
 	pk->siglen = sigsz;
 	pk->sig = calloc(1, pk->siglen);

usr.sbin/pkg/pkg.h

@@ -47,4 +47,6 @@ struct pubkey {
 bool rsa_verify_cert(int, const char *, const unsigned char *, int,
     unsigned char *, int);
 
+char *pkg_read_fd(int fd, size_t *osz);
+
 #endif /* _PKG_H */