From 84b94010a7b08003cc3fb93635582849398e7ae2 Mon Sep 17 00:00:00 2001
From: Neil Bickford <nbickford@nvidia.com>
Date: Tue, 22 Feb 2022 23:48:42 -0800
Subject: [PATCH 1/4] Add checks for PNM integer read overflows, add a 1GB
limit on IDAT chunk sizes to fix an OOM issue, and check for a situation
where a sequence of bad Huffman code reads could result in a left shift by a
negative number.
---
pxr/imaging/hio/stb/stb_image.h | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/pxr/imaging/hio/stb/stb_image.h b/pxr/imaging/hio/stb/stb_image.h
index d60371b95f..6321f5e02c 100644
--- a/pxr/imaging/hio/stb/stb_image.h
+++ b/pxr/imaging/hio/stb/stb_image.h
@@ -2283,6 +2283,7 @@ static int stbi__jpeg_decode_block_prog_ac(stbi__jpeg *j, short data[64], stbi__
k += (r >> 4) & 15; // run
s = r & 15; // combined length
j->code_buffer <<= s;
+ if (s > j->code_bits) return stbi__err("bad huffman code","Combined length longer than code bits available");
j->code_bits -= s;
zig = stbi__jpeg_dezigzag[k++];
data[zig] = (short) ((r >> 8) * (1 << shift));
@@ -5116,6 +5117,7 @@ static int stbi__parse_png_file(stbi__png *z, int scan, int req_comp)
if (first) return stbi__err("first not IHDR", "Corrupt PNG");
if (pal_img_n && !pal_len) return stbi__err("no PLTE","Corrupt PNG");
if (scan == STBI__SCAN_header) { s->img_n = pal_img_n; return 1; }
+ if (c.length > (1u << 30)) return stbi__err("IDAT size limit", "IDAT section larger than 2^30 bytes");
if ((int)(ioff + c.length) < (int)ioff) return 0;
if (ioff + c.length > idata_limit) {
stbi__uint32 idata_limit_old = idata_limit;
@@ -7486,6 +7488,8 @@ static int stbi__pnm_getinteger(stbi__context *s, char *c)
while (!stbi__at_eof(s) && stbi__pnm_isdigit(*c)) {
value = value*10 + (*c - '0');
*c = (char) stbi__get8(s);
+ if((value > 214748364) || (value == 214748364 && *c > '7'))
+ return stbi__err("integer parse overflow", "Parsing an integer in the PPM header overflowed a 32-bit int");
}
return value;
@@ -7516,9 +7520,13 @@ static int stbi__pnm_info(stbi__context *s, int *x, int *y, int *comp)
stbi__pnm_skip_whitespace(s, &c);
*x = stbi__pnm_getinteger(s, &c); // read width
+ if(*x == 0)
+ return stbi__err("invalid width", "PPM image header had zero or overflowing width");
stbi__pnm_skip_whitespace(s, &c);
*y = stbi__pnm_getinteger(s, &c); // read height
+ if (*y == 0)
+ return stbi__err("invalid width", "PPM image header had zero or overflowing width");
stbi__pnm_skip_whitespace(s, &c);
maxv = stbi__pnm_getinteger(s, &c); // read max value
From 96fe76c21308653d22672e986dd39506f6871421 Mon Sep 17 00:00:00 2001
From: Neil Bickford <nbickford@nvidia.com>
Date: Wed, 23 Feb 2022 00:53:34 -0800
Subject: [PATCH 2/4] Add range checks to fix a few crash issues in stb_image
issues 1289 and 1291
---
pxr/imaging/hio/stb/stb_image.h | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/pxr/imaging/hio/stb/stb_image.h b/pxr/imaging/hio/stb/stb_image.h
index 6321f5e02c..800c83db32 100644
--- a/pxr/imaging/hio/stb/stb_image.h
+++ b/pxr/imaging/hio/stb/stb_image.h
@@ -1985,9 +1985,12 @@ static int stbi__build_huffman(stbi__huffman *h, int *count)
int i,j,k=0;
unsigned int code;
// build size list for each symbol (from JPEG spec)
- for (i=0; i < 16; ++i)
- for (j=0; j < count[i]; ++j)
+ for (i=0; i < 16; ++i) {
+ for (j=0; j < count[i]; ++j) {
h->size[k++] = (stbi_uc) (i+1);
+ if(k >= 257) return stbi__err("bad size list","Corrupt JPEG");
+ }
+ }
h->size[k] = 0;
// compute actual symbols (from jpeg spec)
@@ -2112,6 +2115,8 @@ stbi_inline static int stbi__jpeg_huff_decode(stbi__jpeg *j, stbi__huffman *h)
// convert the huffman code to the symbol id
c = ((j->code_buffer >> (32 - k)) & stbi__bmask[k]) + h->delta[k];
+ if(c < 0 || c >= 256) // symbol id out of bounds!
+ return -1;
STBI_ASSERT((((j->code_buffer) >> (32 - h->size[c])) & stbi__bmask[h->size[c]]) == h->code[c]);
// convert the id to a symbol
@@ -3103,6 +3108,7 @@ static int stbi__process_marker(stbi__jpeg *z, int m)
sizes[i] = stbi__get8(z->s);
n += sizes[i];
}
+ if(n > 256) return stbi__err("bad DHT header","Corrupt JPEG"); // Loop over i < n would write past end of values!
L -= 17;
if (tc == 0) {
if (!stbi__build_huffman(z->huff_dc+th, sizes)) return 0;
From 47164e4086c1349ef3042fb04e0f7f7ceaf1fcee Mon Sep 17 00:00:00 2001
From: Neil Bickford <nbickford@nvidia.com>
Date: Wed, 23 Feb 2022 23:48:49 -0800
Subject: [PATCH 3/4] Add checks for signed integer overflow; further guard
against cases where stbi__grow_buffer_unsafe doesn't read all bits required.
---
pxr/imaging/hio/stb/stb_image.h | 27 ++++++++++++++++++++++++++-
1 file changed, 26 insertions(+), 1 deletion(-)
diff --git a/pxr/imaging/hio/stb/stb_image.h b/pxr/imaging/hio/stb/stb_image.h
index 800c83db32..9d10099bbe 100644
--- a/pxr/imaging/hio/stb/stb_image.h
+++ b/pxr/imaging/hio/stb/stb_image.h
@@ -1063,6 +1063,23 @@ static void *stbi__malloc_mad4(int a, int b, int c, int d, int add)
}
#endif
+// returns 1 if the sum of two signed ints is valid (between -2^31 and 2^31-1 inclusive), 0 on overflow.
+static int stbi__addints_valid(int a, int b)
+{
+ if ((a >= 0) != (b >= 0)) return 1; // a and b have different signs, so no overflow
+ if (a < 0 && b < 0) return a >= INT_MIN - b; // same as a + b >= INT_MIN; INT_MIN - b cannot overflow since b < 0.
+ return a <= INT_MAX - b;
+}
+
+// returns 1 if the product of two signed shorts is valid, 0 on overflow.
+static int stbi__mul2shorts_valid(short a, short b)
+{
+ if (b == 0 || b == -1) return 1; // multiplication by 0 is always 0; check for -1 so SHRT_MIN/b doesn't overflow
+ if ((a >= 0) == (b >= 0)) return a <= SHRT_MAX/b; // product is positive, so similar to mul2sizes_valid
+ if (b < 0) return a <= SHRT_MIN / b; // same as a * b >= SHRT_MIN
+ return a >= SHRT_MIN / b;
+}
+
// stbi__err - error
// stbi__errpf - error returning pointer to float
// stbi__errpuc - error returning pointer to unsigned char
@@ -2135,6 +2152,7 @@ stbi_inline static int stbi__extend_receive(stbi__jpeg *j, int n)
unsigned int k;
int sgn;
if (j->code_bits < n) stbi__grow_buffer_unsafe(j);
+ if (j->code_bits < n) return 0; // ran out of bits from stream, return 0s intead of continuing
sgn = j->code_buffer >> 31; // sign bit always in MSB; 0 if MSB clear (positive), 1 if MSB set (negative)
k = stbi_lrot(j->code_buffer, n);
@@ -2149,6 +2167,7 @@ stbi_inline static int stbi__jpeg_get_bits(stbi__jpeg *j, int n)
{
unsigned int k;
if (j->code_bits < n) stbi__grow_buffer_unsafe(j);
+ if (j->code_bits < n) return 0; // ran out of bits from stream, return 0s intead of continuing
k = stbi_lrot(j->code_buffer, n);
j->code_buffer = k & ~stbi__bmask[n];
k &= stbi__bmask[n];
@@ -2160,6 +2179,7 @@ stbi_inline static int stbi__jpeg_get_bit(stbi__jpeg *j)
{
unsigned int k;
if (j->code_bits < 1) stbi__grow_buffer_unsafe(j);
+ if (j->code_bits < 1) return 0; // ran out of bits from stream, return 0s intead of continuing
k = j->code_buffer;
j->code_buffer <<= 1;
--j->code_bits;
@@ -2197,8 +2217,10 @@ static int stbi__jpeg_decode_block(stbi__jpeg *j, short data[64], stbi__huffman
memset(data,0,64*sizeof(data[0]));
diff = t ? stbi__extend_receive(j, t) : 0;
+ if (!stbi__addints_valid(j->img_comp[b].dc_pred, diff)) return stbi__err("bad delta","Corrupt JPEG");
dc = j->img_comp[b].dc_pred + diff;
j->img_comp[b].dc_pred = dc;
+ if (!stbi__mul2shorts_valid(dc, dequant[0])) return stbi__err("can't merge dc and ac", "Corrupt JPEG");
data[0] = (short) (dc * dequant[0]);
// decode AC components, see JPEG spec
@@ -2212,6 +2234,7 @@ static int stbi__jpeg_decode_block(stbi__jpeg *j, short data[64], stbi__huffman
if (r) { // fast-AC path
k += (r >> 4) & 15; // run
s = r & 15; // combined length
+ if (s > j->code_bits) return stbi__err("bad huffman code", "Combined length longer than code bits available");
j->code_buffer <<= s;
j->code_bits -= s;
// decode into unzigzag'd location
@@ -2251,8 +2274,10 @@ static int stbi__jpeg_decode_block_prog_dc(stbi__jpeg *j, short data[64], stbi__
if (t < 0 || t > 15) return stbi__err("can't merge dc and ac", "Corrupt JPEG");
diff = t ? stbi__extend_receive(j, t) : 0;
+ if (!stbi__addints_valid(j->img_comp[b].dc_pred, diff)) return stbi__err("bad delta", "Corrupt JPEG");
dc = j->img_comp[b].dc_pred + diff;
j->img_comp[b].dc_pred = dc;
+ if (!stbi__mul2shorts_valid(dc, 1 << j->succ_low)) return stbi__err("can't merge dc and ac", "Corrupt JPEG");
data[0] = (short) (dc * (1 << j->succ_low));
} else {
// refinement scan for DC coefficient
@@ -2287,8 +2312,8 @@ static int stbi__jpeg_decode_block_prog_ac(stbi__jpeg *j, short data[64], stbi__
if (r) { // fast-AC path
k += (r >> 4) & 15; // run
s = r & 15; // combined length
+ if (s > j->code_bits) return stbi__err("bad huffman code", "Combined length longer than code bits available");
j->code_buffer <<= s;
- if (s > j->code_bits) return stbi__err("bad huffman code","Combined length longer than code bits available");
j->code_bits -= s;
zig = stbi__jpeg_dezigzag[k++];
data[zig] = (short) ((r >> 8) * (1 << shift));
From 5cfc2a744ad7047cda2396cc67772f313a46093d Mon Sep 17 00:00:00 2001
From: Neil Bickford <nbickford@nvidia.com>
Date: Fri, 25 Feb 2022 14:27:31 -0800
Subject: [PATCH 4/4] Zero-initialize stbi__jpeg to avoid intermittent errors
found by fuzz-testing
---
pxr/imaging/hio/stb/stb_image.h | 3 +++
1 file changed, 3 insertions(+)
diff --git a/pxr/imaging/hio/stb/stb_image.h b/pxr/imaging/hio/stb/stb_image.h
index 9d10099bbe..631e4e51c0 100644
--- a/pxr/imaging/hio/stb/stb_image.h
+++ b/pxr/imaging/hio/stb/stb_image.h
@@ -4008,6 +4008,7 @@ static void *stbi__jpeg_load(stbi__context *s, int *x, int *y, int *comp, int re
unsigned char* result;
stbi__jpeg* j = (stbi__jpeg*) stbi__malloc(sizeof(stbi__jpeg));
if (!j) return stbi__errpuc("outofmem", "Out of memory");
+ memset(j, 0, sizeof(stbi__jpeg));
STBI_NOTUSED(ri);
j->s = s;
stbi__setup_jpeg(j);
@@ -4021,6 +4022,7 @@ static int stbi__jpeg_test(stbi__context *s)
int r;
stbi__jpeg* j = (stbi__jpeg*)stbi__malloc(sizeof(stbi__jpeg));
if (!j) return stbi__err("outofmem", "Out of memory");
+ memset(j, 0, sizeof(stbi__jpeg));
j->s = s;
stbi__setup_jpeg(j);
r = stbi__decode_jpeg_header(j, STBI__SCAN_type);
@@ -4046,6 +4048,7 @@ static int stbi__jpeg_info(stbi__context *s, int *x, int *y, int *comp)
int result;
stbi__jpeg* j = (stbi__jpeg*) (stbi__malloc(sizeof(stbi__jpeg)));
if (!j) return stbi__err("outofmem", "Out of memory");
+ memset(j, 0, sizeof(stbi__jpeg));
j->s = s;
result = stbi__jpeg_info_raw(j, x, y, comp);
STBI_FREE(j);
