Add an example program to verify that a file has specific capabilities.

This program is not installed by default. Its more of a code sample
to help folk trying to put such checks into other programs (package
managers for example).

Signed-off-by: Andrew G. Morgan <morgan@kernel.org>

4 files changed, 81 insertions, 4 deletions

diff --git a/doc/cap_clear.3 b/doc/cap_clear.3
index 3fb5178..48f5cc0 100644
--- a/doc/cap_clear.3
+++ b/doc/cap_clear.3
@@ -98,7 +98,7 @@ returned value carries further information about which of three sets,
 differ. Specifically, the macro
 .B CAP_DIFFERS
 .RI ( status ", " flag )
-evaluates to 0 if the returned status differs in its
+evaluates to non-zero if the returned status differs in its
 .I flag
 components.
 .SH "RETURN VALUE"
diff --git a/progs/.gitignore b/progs/.gitignore
index 280c19e..f42095f 100644
--- a/progs/.gitignore
+++ b/progs/.gitignore
@@ -2,3 +2,4 @@ capsh
 getcap
 getpcaps
 setcap
+verify-caps
diff --git a/progs/Makefile b/progs/Makefile
index a8e0e53..3f66a38 100644
--- a/progs/Makefile
+++ b/progs/Makefile
@@ -5,13 +5,14 @@ include $(topdir)/Make.Rules
 # Programs: all of the examples that we will compile
 #
 PROGS=getpcaps getcap setcap capsh
+BUILD=$(PROGS) verify-caps
 
 LDFLAGS += --static 
 LDLIBS += -lcap
 
-all: $(PROGS)
+all: $(BUILD)
 
-$(PROGS): %: %.o
+$(BUILD): %: %.o
 	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $< $(LDLIBS)
 
 %.o: %.c $(INCS)
@@ -25,4 +26,4 @@ install: all
 
 clean:
 	$(LOCALCLEAN)
-	rm -f *.o $(PROGS) tcapsh ping
+	rm -f *.o $(BUILD) tcapsh ping
diff --git a/progs/verify-caps.c b/progs/verify-caps.c
new file mode 100644
index 0000000..2efef17
--- /dev/null
+++ b/progs/verify-caps.c
@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2008 Andrew G. Morgan <morgan@kernel.org>
+ *
+ * This is a simple script that attempts to verify a file has
+ * a specific set of capabilities associated with it. This
+ * code is intended to be a simple prototype for inclusion
+ * in package manager applications.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/capability.h>
+
+static int caps_differ(const char *filename, const char *file_caps)
+{
+    int cmp;
+    cap_t in_effect, reference;
+    
+    in_effect = cap_get_file(filename);
+    reference = cap_from_text(file_caps);
+
+    if ((in_effect == NULL) || (reference == NULL)) {
+	char *text;
+
+	if (in_effect == reference) {
+	    return 0;
+	} else if (in_effect != NULL) {
+	    text = cap_to_text(in_effect, NULL);
+	    printf("reference caps (empty) vs. current (%s)\n", text);
+	} else {
+	    text = cap_to_text(reference, NULL);
+	    printf("reference caps (%s) vs. current (empty)\n", text);
+	}
+	cap_free(text);
+	return 1;
+    }
+
+    cmp = cap_compare(in_effect, reference);
+    if (cmp == 0) {
+	return 0;
+    } else {
+	char *text_ref, *text_current;
+
+	text_current = cap_to_text(in_effect, NULL);
+	text_ref = cap_to_text(reference, NULL);
+
+	printf("reference caps (%s) vs. current (%s) [differ:%s%s%s]\n",
+	       text_ref, text_current,
+	       CAP_DIFFERS(cmp, CAP_PERMITTED) ? "p" : "",
+	       CAP_DIFFERS(cmp, CAP_INHERITABLE) ? "i" : "",
+	       CAP_DIFFERS(cmp, CAP_EFFECTIVE) ? "e" : "");
+
+	cap_free(text_ref);
+	cap_free(text_current);
+
+	return cmp;
+    }
+}
+
+int main(int argc, char *argv[])
+{
+    if (argc != 3) {
+	fprintf(stderr, "usage: %s <filename> <expected-caps>\n", argv[0]);
+	exit(1);
+    }
+
+    if (caps_differ(argv[1], argv[2])) {
+	printf("capabilities differ\n");
+	exit(1);
+    } else {
+	printf("capabibilities are as expected\n");
+    }
+
+    exit(0);
+}