Update TE policy and MAC text conversion routines to support partial

label updates.  Biba and MLS already supported this.  This permits the
userland library to submit relative updates on MAC labels, rather
than submitting an entire label to replace the current label.  This
also requires changes to the MAC modules, which are forthcoming.

Obtained from:	TrustedBSD Project
Sponsored by:	DARPA, NAI Labs

2 files changed, 71 insertions, 10 deletions

diff --git a/lib/libc/posix1e/mac_te.c b/lib/libc/posix1e/mac_te.c
index c74dbfb..c3e3f5e 100644
--- a/lib/libc/posix1e/mac_te.c
+++ b/lib/libc/posix1e/mac_te.c
@@ -45,8 +45,9 @@
 #include <string.h>
 
 /*
- * TE labels simply consist of the typename.  The typename must not be
- * the empty string, and must not exceed the length limit in the label.
+ * TE labels simply consist of the typename.  The type length may
+ * be zero indicating that the text form did not include a type,
+ * but the string length must not exceed the length limit in the label.
  */
 
 int
@@ -54,8 +55,6 @@ mac_te_label_from_string(char *string, struct mac *label)
 {
 
 	bzero(&label->m_te, sizeof(label->m_te));
-	if (strlen(string) == 0)
-		return (EINVAL);
 	if (strlcpy(label->m_te.mt_type, string,
 	    sizeof(label->m_te.mt_type)) >= sizeof(label->m_te.mt_type))
 		return (EINVAL);
diff --git a/lib/libc/posix1e/mac_text.c b/lib/libc/posix1e/mac_text.c
index 3ab6484d..c244fdc 100644
--- a/lib/libc/posix1e/mac_text.c
+++ b/lib/libc/posix1e/mac_text.c
@@ -68,7 +68,7 @@ char *
 mac_to_text(struct mac *mac_p, size_t *len_p)
 {
 	char *biba = NULL, *mls = NULL, *string = NULL, *te = NULL;
-	int len = -1;
+	int len = -1, before;
 
 	biba = mac_biba_string_from_label(mac_p);
 	if (biba == NULL)
@@ -82,10 +82,50 @@ mac_to_text(struct mac *mac_p, size_t *len_p)
 	if (te == NULL)
 		goto out;
 
-	len = asprintf(&string, "%s%s%s%s%s%s%s%s%s%s%s",
-	    STRING_BIBA, STRING_ELEMENTSEP, biba, STRING_LISTSEP,
-	    STRING_MLS, STRING_ELEMENTSEP, mls, STRING_LISTSEP,
-	    STRING_TE, STRING_ELEMENTSEP, te);
+	len = 0;
+	if (strlen(biba) != 0)
+		len += strlen(STRING_LISTSEP) + strlen(STRING_BIBA) +
+		    strlen(STRING_ELEMENTSEP) + strlen(biba);
+	if (strlen(mls) != 0)
+		len += strlen(STRING_LISTSEP) + strlen(STRING_MLS) +
+		    strlen(STRING_ELEMENTSEP) + strlen(mls);
+	if (strlen(te) != 0)
+		len += strlen(STRING_LISTSEP) + strlen(STRING_TE) +
+		    strlen(STRING_ELEMENTSEP) + strlen(te);
+
+	if (len == 0) {
+		string = strdup("");
+		goto out;
+	}
+
+	string = (char *) malloc(len+1);
+	if (string == NULL)
+		return (NULL);
+
+	len = 0;
+	before = 0;
+
+	if (strlen(biba) != 0) {
+		if (before)
+			len += sprintf(string + len, "%s", STRING_LISTSEP);
+		len += sprintf(string + len, "%s%s%s", STRING_BIBA,
+		    STRING_ELEMENTSEP, biba);
+		before = 1;
+	}
+	if (strlen(mls) != 0) {
+		if (before)
+			len += sprintf(string + len, "%s", STRING_LISTSEP);
+		len += sprintf(string + len, "%s%s%s", STRING_MLS,
+		    STRING_ELEMENTSEP, mls);
+		before = 1;
+	}
+	if (strlen(te) != 0) {
+		if (before)
+			len += sprintf(string + len, "%s", STRING_LISTSEP);
+		len += sprintf(string + len, "%s%s%s", STRING_TE,
+		    STRING_ELEMENTSEP, te);
+		before = 1;
+	}
 
 out:
 	if (biba != NULL)
@@ -165,7 +205,29 @@ mac_from_text(const char *text_p)
 		}
 	}
 
-	if (biba_seen != 1 || mls_seen != 1 || te_seen != 1) {
+	if (biba_seen == 0) {
+		error = mac_biba_label_from_string("", label);
+		if (error) {
+			errno = error;
+			goto exit2;
+		}
+	}
+	if (mls_seen == 0) {
+		error = mac_mls_label_from_string("", label);
+		if (error) {
+			errno = error;
+			goto exit2;
+		}
+	}
+	if (te_seen == 0) {
+		error = mac_te_label_from_string("", label);
+		if (error) {
+			errno = error;
+			goto exit2;
+		}
+	}
+
+	if (biba_seen > 1 || mls_seen > 1 || te_seen > 1) {
 		errno = EINVAL;
 		goto exit2;
 	}