Fix path generation for Dhcpv4 bootloader.

Right now we always look for e.g. "\grubx64.efi", which is completely
wrong.  This makes it look for the path shim was loaded from and modify
that to end in a sanitized version of our default loader name.

Resolves: rhbz#1032583

Signed-off-by: Peter Jones <pjones@redhat.com>

2 files changed, 66 insertions, 7 deletions

diff --git a/include/str.h b/include/str.h
new file mode 100644
index 00000000..0f3e003a
--- /dev/null
+++ b/include/str.h
@@ -0,0 +1,45 @@
+#ifndef SHIM_STR_H
+#define SHIM_STR_H
+
+static inline
+__attribute__((unused))
+unsigned long strnlena(const CHAR8 *s, unsigned long n)
+{
+	unsigned long i;
+	for (i = 0; i <= n; i++)
+		if (s[i] == '\0')
+			break;
+	return i;
+}
+
+static inline
+__attribute__((unused))
+CHAR8 *
+strncpya(CHAR8 *dest, const CHAR8 *src, unsigned long n)
+{
+	unsigned long i;
+
+	for (i = 0; i < n && src[i] != '\0'; i++)
+		dest[i] = src[i];
+	for (; i < n; i++)
+		dest[i] = '\0';
+
+	return dest;
+}
+
+static inline
+__attribute__((unused))
+CHAR8 *
+strcata(CHAR8 *dest, const CHAR8 *src)
+{
+	unsigned long dest_len = strlena(dest);
+	unsigned long i;
+
+	for (i = 0; src[i] != '\0'; i++)
+		dest[dest_len + i] = src[i];
+	dest[dest_len + i] = '\0';
+
+	return dest;
+}
+
+#endif /* SHIM_STR_H */
diff --git a/netboot.c b/netboot.c
index a83c82ae..1732dc71 100644
--- a/netboot.c
+++ b/netboot.c
@@ -38,6 +38,7 @@
 #include <string.h>
 #include "shim.h"
 #include "netboot.h"
+#include "str.h"
 
 static inline unsigned short int __swap16(unsigned short int x)
 {
@@ -305,19 +306,32 @@ static EFI_STATUS parseDhcp6()
 
 static EFI_STATUS parseDhcp4()
 {
-	CHAR8 *template = (CHAR8 *)DEFAULT_LOADER_CHAR;
-	full_path = AllocateZeroPool(strlen(template)+1);
+	CHAR8 *template = (CHAR8 *)translate_slashes(DEFAULT_LOADER_CHAR);
+	UINTN template_len = strlen(template) + 1;
+
+	UINTN dir_len = strnlena(pxe->Mode->DhcpAck.Dhcpv4.BootpBootFile, 127);
+	UINTN i;
+	UINT8 *dir = pxe->Mode->DhcpAck.Dhcpv4.BootpBootFile;
+
+	for (i = dir_len; i >= 0; i--) {
+		if (dir[i] == '/')
+			break;
+	}
+	dir_len = (i >= 0) ? i + 1 : 0;
+
+	full_path = AllocateZeroPool(dir_len + template_len);
 
 	if (!full_path)
 		return EFI_OUT_OF_RESOURCES;
 
+	if (dir_len > 0) {
+		strncpya(full_path, dir, dir_len);
+		if (full_path[dir_len-1] == '/' && template[0] == '/')
+			full_path[dir_len-1] = '\0';
+	}
+	strcata(full_path, template);
 	memcpy(&tftp_addr.v4, pxe->Mode->DhcpAck.Dhcpv4.BootpSiAddr, 4);
 
-	memcpy(full_path, template, strlen(template));
-
-	/* Note we don't capture the filename option here because we know its shim.efi
-	 * We instead assume the filename at the end of the path is going to be grubx64.efi
-	 */
 	return EFI_SUCCESS;
 }