140 lines
4.5 KiB
Diff
140 lines
4.5 KiB
Diff
From 9813e8bc8b3295f343809fac43298a73a93ffc97 Mon Sep 17 00:00:00 2001
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From: Laszlo Ersek <lersek@redhat.com>
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Date: Tue, 28 Jan 2020 23:33:46 +0100
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Subject: [PATCH] translate_slashes(): don't write to string literals
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Currently, all three invocations of the translate_slashes() function may
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lead to writes to the string literal that is #defined with the
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DEFAULT_LOADER_CHAR macro. According to ISO C99 6.4.5p6, this is undefined
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behavior ("If the program attempts to modify such an array, the behavior
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is undefined").
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This bug crashes shim on e.g. the 64-bit ArmVirtQemu platform ("Data
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abort: Permission fault"), where the platform firmware maps the .text
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section (which contains the string literal) read-only.
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Modify translate_slashes() so that it copies and translates characters
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from an input array of "char" to an output array of "CHAR8".
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While at it, fix another bug. Before this patch, if translate_slashes()
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ever encountered a double backslash (translating it to a single forward
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slash), then the output would end up shorter than the input. However, the
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output was not NUL-terminated in-place, therefore the original string
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length (and according trailing garbage) would be preserved. After this
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patch, the NUL-termination on contraction is automatic, as the output
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array's contents are indeterminate when entering the function, and so we
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must NUL-terminate it anyway.
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Fixes: 8e9124227d18475d3bc634c33518963fc8db7c98
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Fixes: e62b69a5b0b87c6df7a4fc23906134945309e927
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Fixes: 3d79bcb2651b9eae809b975b3e03e2f96c067072
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1795654
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Signed-off-by: Laszlo Ersek <lersek@redhat.com>
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---
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include/str.h | 14 ++++++++------
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httpboot.c | 4 ++--
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netboot.c | 16 +++++++++++-----
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3 files changed, 21 insertions(+), 13 deletions(-)
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diff --git a/include/str.h b/include/str.h
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index 9a748366bd1..f73c6212cd9 100644
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--- a/include/str.h
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+++ b/include/str.h
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@@ -45,21 +45,23 @@ strcata(CHAR8 *dest, const CHAR8 *src)
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static inline
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__attribute__((unused))
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CHAR8 *
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-translate_slashes(char *str)
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+translate_slashes(CHAR8 *out, const char *str)
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{
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int i;
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int j;
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- if (str == NULL)
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- return (CHAR8 *)str;
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+ if (str == NULL || out == NULL)
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+ return NULL;
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for (i = 0, j = 0; str[i] != '\0'; i++, j++) {
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if (str[i] == '\\') {
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- str[j] = '/';
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+ out[j] = '/';
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if (str[i+1] == '\\')
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i++;
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- }
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+ } else
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+ out[j] = str[i];
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}
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- return (CHAR8 *)str;
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+ out[j] = '\0';
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+ return out;
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}
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#endif /* SHIM_STR_H */
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diff --git a/httpboot.c b/httpboot.c
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index 3622e85867c..2d27e8ed993 100644
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--- a/httpboot.c
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+++ b/httpboot.c
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@@ -743,14 +743,14 @@ httpboot_fetch_buffer (EFI_HANDLE image, VOID **buffer, UINT64 *buf_size)
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{
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EFI_STATUS efi_status;
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EFI_HANDLE nic;
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- CHAR8 *next_loader = NULL;
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+ CHAR8 next_loader[sizeof DEFAULT_LOADER_CHAR];
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CHAR8 *next_uri = NULL;
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CHAR8 *hostname = NULL;
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if (!uri)
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return EFI_NOT_READY;
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- next_loader = translate_slashes(DEFAULT_LOADER_CHAR);
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+ translate_slashes(next_loader, DEFAULT_LOADER_CHAR);
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/* Create the URI for the next loader based on the original URI */
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efi_status = generate_next_uri(uri, next_loader, &next_uri);
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diff --git a/netboot.c b/netboot.c
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index 583fe4bee71..6d293bca9dd 100644
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--- a/netboot.c
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+++ b/netboot.c
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@@ -189,7 +189,9 @@ static BOOLEAN extract_tftp_info(CHAR8 *url)
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CHAR8 *start, *end;
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CHAR8 ip6str[40];
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CHAR8 ip6inv[16];
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- CHAR8 *template = (CHAR8 *)translate_slashes(DEFAULT_LOADER_CHAR);
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+ CHAR8 template[sizeof DEFAULT_LOADER_CHAR];
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+
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+ translate_slashes(template, DEFAULT_LOADER_CHAR);
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// to check against str2ip6() errors
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memset(ip6inv, 0, sizeof(ip6inv));
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@@ -254,10 +256,14 @@ static EFI_STATUS parseDhcp6()
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static EFI_STATUS parseDhcp4()
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{
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- CHAR8 *template = (CHAR8 *)translate_slashes(DEFAULT_LOADER_CHAR);
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- INTN template_len = strlen(template) + 1;
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+ CHAR8 template[sizeof DEFAULT_LOADER_CHAR];
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+ INTN template_len;
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+ UINTN template_ofs = 0;
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EFI_PXE_BASE_CODE_DHCPV4_PACKET* pkt_v4 = (EFI_PXE_BASE_CODE_DHCPV4_PACKET *)&pxe->Mode->DhcpAck.Dhcpv4;
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+ translate_slashes(template, DEFAULT_LOADER_CHAR);
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+ template_len = strlen(template) + 1;
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+
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if(pxe->Mode->ProxyOfferReceived) {
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/*
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* Proxy should not have precedence. Check if DhcpAck
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@@ -288,8 +294,8 @@ static EFI_STATUS parseDhcp4()
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full_path[dir_len-1] = '\0';
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}
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if (dir_len == 0 && dir[0] != '/' && template[0] == '/')
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- template++;
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- strcata(full_path, template);
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+ template_ofs++;
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+ strcata(full_path, template + template_ofs);
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memcpy(&tftp_addr.v4, pkt_v4->BootpSiAddr, 4);
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return EFI_SUCCESS;
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--
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2.26.2
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