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-rw-r--r--payloads/libpayload/include/libpayload.h1
-rw-r--r--payloads/libpayload/libc/lar.c35
2 files changed, 36 insertions, 0 deletions
diff --git a/payloads/libpayload/include/libpayload.h b/payloads/libpayload/include/libpayload.h
index f9a67ed862..c05aafb37c 100644
--- a/payloads/libpayload/include/libpayload.h
+++ b/payloads/libpayload/include/libpayload.h
@@ -251,6 +251,7 @@ struct larent *readlar(struct LAR *lar);
void rewindlar(struct LAR *lar);
int larstat(struct LAR *lar, const char *path, struct larstat *buf);
void *larfptr(struct LAR *lar, const char *filename);
+int lfverify(struct LAR *lar, const char *filename);
struct LFILE * lfopen(struct LAR *lar, const char *filename);
int lfread(void *ptr, size_t size, size_t nmemb, struct LFILE *stream);
diff --git a/payloads/libpayload/libc/lar.c b/payloads/libpayload/libc/lar.c
index 6ae4052039..225b19001a 100644
--- a/payloads/libpayload/libc/lar.c
+++ b/payloads/libpayload/libc/lar.c
@@ -228,6 +228,41 @@ void * larfptr(struct LAR *lar, const char *filename)
return (void *) ((u8 *) header + ntohl(header->offset));
}
+/**
+ * Verify the checksum on a particular LAR entry
+ *
+ * @param lar A pointer to the LAR stream
+ * @param filename The lar entry to verify
+ * @return Return 1 if the entry is valid, 0 if it is not, or -1
+ * on error
+ */
+
+int lfverify(struct LAR *lar, const char *filename)
+{
+ struct lar_header *header = get_header_by_name(lar, filename);
+
+ u8 *ptr = (u8 *) header;
+ int len = ntohl(header->len) + ntohl(header->offset);
+ int offset;
+ u32 csum = 0;
+
+ if (header == NULL)
+ return -1;
+
+ /* The checksum needs to be calulated on entire data section,
+ * including any padding for the 16 byte alignment (which should
+ * be zeros
+ */
+
+ len = (len + 15) & 0xFFFFFFF0;
+
+ for(offset = 0; offset < len; offset += 4) {
+ csum += *((u32 *) (ptr + offset));
+ }
+
+ return (csum == 0xFFFFFFFF) ? 1 : 0;
+}
+
struct LFILE * lfopen(struct LAR *lar, const char *filename)
{
struct LFILE *file;