From d615cb6c39d401a569941be2a615176191afa7ac Mon Sep 17 00:00:00 2001
From: Chrostoper Ertl <chertl@microsoft.com>
Date: Thu, 28 Nov 2019 16:33:59 +0000
Subject: [PATCH] fru: Fix buffer overflow vulnerabilities

Partial fix for CVE-2020-5208, see
https://github.com/ipmitool/ipmitool/security/advisories/GHSA-g659-9qxw-p7cp

The `read_fru_area_section` function only performs size validation of
requested read size, and falsely assumes that the IPMI message will not
respond with more than the requested amount of data; it uses the
unvalidated response size to copy into `frubuf`. If the response is
larger than the request, this can result in overflowing the buffer.

The same issue affects the `read_fru_area` function.

[Retrieve from
https://github.com/ipmitool/ipmitool/commit/e824c23316ae50beb7f7488f2055ac65e8b341f2]
Signed-off-by: Heiko Thiery <heiko.thiery@gmail.com>
---
 lib/ipmi_fru.c | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/lib/ipmi_fru.c b/lib/ipmi_fru.c
index cf00eff..af99aa9 100644
--- a/lib/ipmi_fru.c
+++ b/lib/ipmi_fru.c
@@ -615,7 +615,10 @@ int
 read_fru_area(struct ipmi_intf * intf, struct fru_info *fru, uint8_t id,
 			uint32_t offset, uint32_t length, uint8_t *frubuf)
 {
-	uint32_t off = offset, tmp, finish;
+	uint32_t off = offset;
+	uint32_t tmp;
+	uint32_t finish;
+	uint32_t size_left_in_buffer;
 	struct ipmi_rs * rsp;
 	struct ipmi_rq req;
 	uint8_t msg_data[4];
@@ -628,10 +631,12 @@ read_fru_area(struct ipmi_intf * intf, struct fru_info *fru, uint8_t id,
 
 	finish = offset + length;
 	if (finish > fru->size) {
+		memset(frubuf + fru->size, 0, length - fru->size);
 		finish = fru->size;
 		lprintf(LOG_NOTICE, "Read FRU Area length %d too large, "
 			"Adjusting to %d",
 			offset + length, finish - offset);
+		length = finish - offset;
 	}
 
 	memset(&req, 0, sizeof(req));
@@ -667,6 +672,7 @@ read_fru_area(struct ipmi_intf * intf, struct fru_info *fru, uint8_t id,
 		}
 	}
 
+	size_left_in_buffer = length;
 	do {
 		tmp = fru->access ? off >> 1 : off;
 		msg_data[0] = id;
@@ -707,9 +713,18 @@ read_fru_area(struct ipmi_intf * intf, struct fru_info *fru, uint8_t id,
 		}
 
 		tmp = fru->access ? rsp->data[0] << 1 : rsp->data[0];
+		if(rsp->data_len < 1
+		   || tmp > rsp->data_len - 1
+		   || tmp > size_left_in_buffer)
+		{
+			printf(" Not enough buffer size");
+			return -1;
+		}
+
 		memcpy(frubuf, rsp->data + 1, tmp);
 		off += tmp;
 		frubuf += tmp;
+		size_left_in_buffer -= tmp;
 		/* sometimes the size returned in the Info command
 		* is too large.  return 0 so higher level function
 		* still attempts to parse what was returned */
@@ -742,7 +757,9 @@ read_fru_area_section(struct ipmi_intf * intf, struct fru_info *fru, uint8_t id,
 			uint32_t offset, uint32_t length, uint8_t *frubuf)
 {
 	static uint32_t fru_data_rqst_size = 20;
-	uint32_t off = offset, tmp, finish;
+	uint32_t off = offset;
+	uint32_t tmp, finish;
+	uint32_t size_left_in_buffer;
 	struct ipmi_rs * rsp;
 	struct ipmi_rq req;
 	uint8_t msg_data[4];
@@ -755,10 +772,12 @@ read_fru_area_section(struct ipmi_intf * intf, struct fru_info *fru, uint8_t id,
 
 	finish = offset + length;
 	if (finish > fru->size) {
+		memset(frubuf + fru->size, 0, length - fru->size);
 		finish = fru->size;
 		lprintf(LOG_NOTICE, "Read FRU Area length %d too large, "
 			"Adjusting to %d",
 			offset + length, finish - offset);
+		length = finish - offset;
 	}
 
 	memset(&req, 0, sizeof(req));
@@ -773,6 +792,8 @@ read_fru_area_section(struct ipmi_intf * intf, struct fru_info *fru, uint8_t id,
 	if (fru->access && fru_data_rqst_size > 16)
 #endif
 		fru_data_rqst_size = 16;
+
+	size_left_in_buffer = length;
 	do {
 		tmp = fru->access ? off >> 1 : off;
 		msg_data[0] = id;
@@ -804,8 +825,16 @@ read_fru_area_section(struct ipmi_intf * intf, struct fru_info *fru, uint8_t id,
 		}
 
 		tmp = fru->access ? rsp->data[0] << 1 : rsp->data[0];
+		if(rsp->data_len < 1
+		   || tmp > rsp->data_len - 1
+		   || tmp > size_left_in_buffer)
+		{
+			printf(" Not enough buffer size");
+			return -1;
+		}
 		memcpy((frubuf + off)-offset, rsp->data + 1, tmp);
 		off += tmp;
+		size_left_in_buffer -= tmp;
 
 		/* sometimes the size returned in the Info command
 		* is too large.  return 0 so higher level function
-- 
2.20.1