[FFmpeg-devel] [PATCH 1/2] avutil/aes_ctr: simplify and optimize av_aes_ctr_crypt()

[FFmpeg-devel] [PATCH 1/2] avutil/aes_ctr: simplify and optimize av_aes_ctr_crypt()

[James Almer]

Process data in chunks of four or eight bytes, depending on host, instead of one
at a time.

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavutil/aes_ctr.c | 47 ++++++++++++++++++++-------------------------
 1 file changed, 21 insertions(+), 26 deletions(-)

diff --git a/libavutil/aes_ctr.c b/libavutil/aes_ctr.c
index c2d6d570e7..d720aa6aaf 100644
--- a/libavutil/aes_ctr.c
+++ b/libavutil/aes_ctr.c
@@ -24,6 +24,7 @@
 #include "aes_ctr.h"
 #include "aes.h"
 #include "aes_internal.h"
+#include "intreadwrite.h"
 #include "macros.h"
 #include "mem.h"
 #include "random_seed.h"
@@ -32,8 +33,7 @@
 
 typedef struct AVAESCTR {
     uint8_t counter[AES_BLOCK_SIZE];
-    uint8_t encrypted_counter[AES_BLOCK_SIZE];
-    int block_offset;
+    DECLARE_ALIGNED(8, uint8_t, encrypted_counter)[AES_BLOCK_SIZE];
     AVAES aes;
 } AVAESCTR;
 
@@ -46,13 +46,11 @@ void av_aes_ctr_set_iv(struct AVAESCTR *a, const uint8_t* iv)
 {
     memcpy(a->counter, iv, AES_CTR_IV_SIZE);
     memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
-    a->block_offset = 0;
 }
 
 void av_aes_ctr_set_full_iv(struct AVAESCTR *a, const uint8_t* iv)
 {
     memcpy(a->counter, iv, sizeof(a->counter));
-    a->block_offset = 0;
 }
 
 const uint8_t* av_aes_ctr_get_iv(struct AVAESCTR *a)
@@ -75,7 +73,6 @@ int av_aes_ctr_init(struct AVAESCTR *a, const uint8_t *key)
     av_aes_init(&a->aes, key, 128, 0);
 
     memset(a->counter, 0, sizeof(a->counter));
-    a->block_offset = 0;
 
     return 0;
 }
@@ -101,31 +98,29 @@ void av_aes_ctr_increment_iv(struct AVAESCTR *a)
 {
     av_aes_ctr_increment_be64(a->counter);
     memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
-    a->block_offset = 0;
 }
 
 void av_aes_ctr_crypt(struct AVAESCTR *a, uint8_t *dst, const uint8_t *src, int count)
 {
-    const uint8_t* src_end = src + count;
-    const uint8_t* cur_end_pos;
-    uint8_t* encrypted_counter_pos;
-
-    while (src < src_end) {
-        if (a->block_offset == 0) {
-            av_aes_crypt(&a->aes, a->encrypted_counter, a->counter, 1, NULL, 0);
-
-            av_aes_ctr_increment_be64(a->counter + 8);
-        }
-
-        encrypted_counter_pos = a->encrypted_counter + a->block_offset;
-        cur_end_pos = src + AES_BLOCK_SIZE - a->block_offset;
-        cur_end_pos = FFMIN(cur_end_pos, src_end);
-
-        a->block_offset += cur_end_pos - src;
-        a->block_offset &= (AES_BLOCK_SIZE - 1);
+    while (count >= AES_BLOCK_SIZE) {
+        av_aes_crypt(&a->aes, a->encrypted_counter, a->counter, 1, NULL, 0);
+        av_aes_ctr_increment_be64(a->counter + 8);
+#if HAVE_FAST_64BIT
+        for (int len = 0; len < AES_BLOCK_SIZE; len += 8)
+            AV_WN64(&dst[len], AV_RN64(&src[len]) ^ AV_RN64A(&a->encrypted_counter[len]));
+#else
+        for (int len = 0; len < AES_BLOCK_SIZE; len += 4)
+            AV_WN32(&dst[len], AV_RN32(&src[len]) ^ AV_RN32A(&a->encrypted_counter[len]));
+#endif
+        dst += AES_BLOCK_SIZE;
+        src += AES_BLOCK_SIZE;
+        count -= AES_BLOCK_SIZE;
+    }
 
-        while (src < cur_end_pos) {
-            *dst++ = *src++ ^ *encrypted_counter_pos++;
-        }
+    if (count > 0) {
+        av_aes_crypt(&a->aes, a->encrypted_counter, a->counter, 1, NULL, 0);
+        av_aes_ctr_increment_be64(a->counter + 8);
+        for (int len = 0; len < count; len++)
+            dst[len] = src[len] ^ a->encrypted_counter[len];
     }
 }
-- 
2.49.0

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[FFmpeg-devel] [PATCH 2/2] avutil/aes_ctr: simplify incrementing the counter

[James Almer]

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavutil/aes_ctr.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/libavutil/aes_ctr.c b/libavutil/aes_ctr.c
index d720aa6aaf..63dcb20d3a 100644
--- a/libavutil/aes_ctr.c
+++ b/libavutil/aes_ctr.c
@@ -32,7 +32,7 @@
 #define AES_BLOCK_SIZE (16)
 
 typedef struct AVAESCTR {
-    uint8_t counter[AES_BLOCK_SIZE];
+    DECLARE_ALIGNED(8, uint8_t, counter)[AES_BLOCK_SIZE];
     DECLARE_ALIGNED(8, uint8_t, encrypted_counter)[AES_BLOCK_SIZE];
     AVAES aes;
 } AVAESCTR;
@@ -82,16 +82,10 @@ void av_aes_ctr_free(struct AVAESCTR *a)
     av_free(a);
 }
 
-static void av_aes_ctr_increment_be64(uint8_t* counter)
+static inline void av_aes_ctr_increment_be64(uint8_t* counter)
 {
-    uint8_t* cur_pos;
-
-    for (cur_pos = counter + 7; cur_pos >= counter; cur_pos--) {
-        (*cur_pos)++;
-        if (*cur_pos != 0) {
-            break;
-        }
-    }
+    uint64_t c = AV_RB64A(counter) + 1;
+    AV_WB64A(counter, c);
 }
 
 void av_aes_ctr_increment_iv(struct AVAESCTR *a)
-- 
2.49.0

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Re: [FFmpeg-devel] [PATCH 1/2] avutil/aes_ctr: simplify and optimize av_aes_ctr_crypt()

[Nicolas George]

James Almer (HE12025-04-01):
> Process data in chunks of four or eight bytes, depending on host, instead of one
> at a time.
> 
> Signed-off-by: James Almer <jamrial@gmail.com>
> ---
>  libavutil/aes_ctr.c | 47 ++++++++++++++++++++-------------------------
>  1 file changed, 21 insertions(+), 26 deletions(-)

A commit message where the word “optimize” appears should include a
benchmark.

Regards,

-- 
  Nicolas George
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[FFmpeg-devel] [PATCH v2 1/2] avutil/aes_ctr: simplify and optimize av_aes_ctr_crypt()

[James Almer]

Process data in chunks of four or eight bytes, depending on host, instead of
one at a time.

before:
55561 decicycles in av_aes_ctr_crypt

after:
52204 decicycles in av_aes_ctr_crypt

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavutil/aes_ctr.c | 47 ++++++++++++++++++++-------------------------
 1 file changed, 21 insertions(+), 26 deletions(-)

diff --git a/libavutil/aes_ctr.c b/libavutil/aes_ctr.c
index c2d6d570e7..d720aa6aaf 100644
--- a/libavutil/aes_ctr.c
+++ b/libavutil/aes_ctr.c
@@ -24,6 +24,7 @@
 #include "aes_ctr.h"
 #include "aes.h"
 #include "aes_internal.h"
+#include "intreadwrite.h"
 #include "macros.h"
 #include "mem.h"
 #include "random_seed.h"
@@ -32,8 +33,7 @@
 
 typedef struct AVAESCTR {
     uint8_t counter[AES_BLOCK_SIZE];
-    uint8_t encrypted_counter[AES_BLOCK_SIZE];
-    int block_offset;
+    DECLARE_ALIGNED(8, uint8_t, encrypted_counter)[AES_BLOCK_SIZE];
     AVAES aes;
 } AVAESCTR;
 
@@ -46,13 +46,11 @@ void av_aes_ctr_set_iv(struct AVAESCTR *a, const uint8_t* iv)
 {
     memcpy(a->counter, iv, AES_CTR_IV_SIZE);
     memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
-    a->block_offset = 0;
 }
 
 void av_aes_ctr_set_full_iv(struct AVAESCTR *a, const uint8_t* iv)
 {
     memcpy(a->counter, iv, sizeof(a->counter));
-    a->block_offset = 0;
 }
 
 const uint8_t* av_aes_ctr_get_iv(struct AVAESCTR *a)
@@ -75,7 +73,6 @@ int av_aes_ctr_init(struct AVAESCTR *a, const uint8_t *key)
     av_aes_init(&a->aes, key, 128, 0);
 
     memset(a->counter, 0, sizeof(a->counter));
-    a->block_offset = 0;
 
     return 0;
 }
@@ -101,31 +98,29 @@ void av_aes_ctr_increment_iv(struct AVAESCTR *a)
 {
     av_aes_ctr_increment_be64(a->counter);
     memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
-    a->block_offset = 0;
 }
 
 void av_aes_ctr_crypt(struct AVAESCTR *a, uint8_t *dst, const uint8_t *src, int count)
 {
-    const uint8_t* src_end = src + count;
-    const uint8_t* cur_end_pos;
-    uint8_t* encrypted_counter_pos;
-
-    while (src < src_end) {
-        if (a->block_offset == 0) {
-            av_aes_crypt(&a->aes, a->encrypted_counter, a->counter, 1, NULL, 0);
-
-            av_aes_ctr_increment_be64(a->counter + 8);
-        }
-
-        encrypted_counter_pos = a->encrypted_counter + a->block_offset;
-        cur_end_pos = src + AES_BLOCK_SIZE - a->block_offset;
-        cur_end_pos = FFMIN(cur_end_pos, src_end);
-
-        a->block_offset += cur_end_pos - src;
-        a->block_offset &= (AES_BLOCK_SIZE - 1);
+    while (count >= AES_BLOCK_SIZE) {
+        av_aes_crypt(&a->aes, a->encrypted_counter, a->counter, 1, NULL, 0);
+        av_aes_ctr_increment_be64(a->counter + 8);
+#if HAVE_FAST_64BIT
+        for (int len = 0; len < AES_BLOCK_SIZE; len += 8)
+            AV_WN64(&dst[len], AV_RN64(&src[len]) ^ AV_RN64A(&a->encrypted_counter[len]));
+#else
+        for (int len = 0; len < AES_BLOCK_SIZE; len += 4)
+            AV_WN32(&dst[len], AV_RN32(&src[len]) ^ AV_RN32A(&a->encrypted_counter[len]));
+#endif
+        dst += AES_BLOCK_SIZE;
+        src += AES_BLOCK_SIZE;
+        count -= AES_BLOCK_SIZE;
+    }
 
-        while (src < cur_end_pos) {
-            *dst++ = *src++ ^ *encrypted_counter_pos++;
-        }
+    if (count > 0) {
+        av_aes_crypt(&a->aes, a->encrypted_counter, a->counter, 1, NULL, 0);
+        av_aes_ctr_increment_be64(a->counter + 8);
+        for (int len = 0; len < count; len++)
+            dst[len] = src[len] ^ a->encrypted_counter[len];
     }
 }
-- 
2.49.0

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[FFmpeg-devel] [PATCH 3/3] avutil/tests/aes_ctr: test more than a single block worth of data

[James Almer]

This should exercise the implementation more thoroughly after the previous
change.

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavutil/tests/aes_ctr.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/libavutil/tests/aes_ctr.c b/libavutil/tests/aes_ctr.c
index 486dae3348..65b49ee7fe 100644
--- a/libavutil/tests/aes_ctr.c
+++ b/libavutil/tests/aes_ctr.c
@@ -23,9 +23,10 @@
 #include "libavutil/aes_ctr.h"
 
 static const DECLARE_ALIGNED(8, uint8_t, plain)[] = {
-    0x6d, 0x6f, 0x73, 0x74, 0x20, 0x72, 0x61, 0x6e, 0x64, 0x6f, 0x6d
+    0x6d, 0x6f, 0x73, 0x74, 0x20, 0x72, 0x61, 0x6e, 0x64, 0x6f,
+    0x6d, 0x6f, 0x73, 0x74, 0x20, 0x72, 0x61, 0x6e, 0x64, 0x6f
 };
-static DECLARE_ALIGNED(8, uint8_t, tmp)[11];
+static DECLARE_ALIGNED(8, uint8_t, tmp)[20];
 
 int main (void)
 {
-- 
2.49.0

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[FFmpeg-devel] [PATCH 4/6] avutil/test/aes_ctr: also check the encrypted buffer

[James Almer]

The test in its current form is just ensuring the plain text output is the same
as the plain text input, not bothering to check if anything was done with the
latter. av_aes_ctr_crypt() could be a simple memcpy under the hood and this
test would still succeed.

To check the integrity of the encrypted buffer, both the IV and the key need to
be fixed. As such, and in order to not remove the existing randomization of the
input IV, do two runs, one with random initialization data, and one with static
data.

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavutil/tests/aes_ctr.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/libavutil/tests/aes_ctr.c b/libavutil/tests/aes_ctr.c
index 65b49ee7fe..94b0201c7b 100644
--- a/libavutil/tests/aes_ctr.c
+++ b/libavutil/tests/aes_ctr.c
@@ -26,6 +26,16 @@ static const DECLARE_ALIGNED(8, uint8_t, plain)[] = {
     0x6d, 0x6f, 0x73, 0x74, 0x20, 0x72, 0x61, 0x6e, 0x64, 0x6f,
     0x6d, 0x6f, 0x73, 0x74, 0x20, 0x72, 0x61, 0x6e, 0x64, 0x6f
 };
+
+static const DECLARE_ALIGNED(8, uint8_t, encrypted)[] = {
+    0x95, 0xcd, 0x9a, 0x8a, 0x83, 0xa2, 0x1a, 0x84, 0x92, 0xed,
+    0xd6, 0xf2, 0x57, 0x2f, 0x61, 0x98, 0xbc, 0x20, 0x98, 0xee
+};
+
+static const DECLARE_ALIGNED(8, uint8_t, fixed_iv)[] = {
+    0xde, 0xad, 0xbe, 0xef, 0xde, 0xad, 0xbe, 0xef
+};
+
 static DECLARE_ALIGNED(8, uint8_t, tmp)[20];
 
 int main (void)
@@ -34,6 +44,7 @@ int main (void)
     struct AVAESCTR *ae, *ad;
     const uint8_t *iv;
 
+    for (int i = 0; i < 2; i++) {
     ae = av_aes_ctr_alloc();
     ad = av_aes_ctr_alloc();
 
@@ -46,11 +57,18 @@ int main (void)
     if (av_aes_ctr_init(ad, (const uint8_t*)"0123456789abcdef") < 0)
         goto ERROR;
 
+        if (i)
+            av_aes_ctr_set_iv(ae, fixed_iv);
+        else
     av_aes_ctr_set_random_iv(ae);
     iv =   av_aes_ctr_get_iv(ae);
     av_aes_ctr_set_full_iv(ad, iv);
 
     av_aes_ctr_crypt(ae, tmp, plain, sizeof(tmp));
+        if (i && memcmp(tmp, encrypted, sizeof(tmp)) != 0) {
+            av_log(NULL, AV_LOG_ERROR, "test failed\n");
+            goto ERROR;
+        }
     av_aes_ctr_crypt(ad, tmp, tmp,   sizeof(tmp));
 
     if (memcmp(tmp, plain, sizeof(tmp)) != 0){
@@ -58,6 +76,11 @@ int main (void)
         goto ERROR;
     }
 
+        av_aes_ctr_free(ae);
+        av_aes_ctr_free(ad);
+        ae = ad = NULL;
+    }
+
     av_log(NULL, AV_LOG_INFO, "test passed\n");
     ret = 0;
 
-- 
2.49.0

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[FFmpeg-devel] [PATCH 5/6] avutil/tests/aes_ctr: reindent after the previous commit

[James Almer]

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavutil/tests/aes_ctr.c | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/libavutil/tests/aes_ctr.c b/libavutil/tests/aes_ctr.c
index 94b0201c7b..6f21b8bda1 100644
--- a/libavutil/tests/aes_ctr.c
+++ b/libavutil/tests/aes_ctr.c
@@ -45,36 +45,36 @@ int main (void)
     const uint8_t *iv;
 
     for (int i = 0; i < 2; i++) {
-    ae = av_aes_ctr_alloc();
-    ad = av_aes_ctr_alloc();
+        ae = av_aes_ctr_alloc();
+        ad = av_aes_ctr_alloc();
 
-    if (!ae || !ad)
-        goto ERROR;
+        if (!ae || !ad)
+            goto ERROR;
 
-    if (av_aes_ctr_init(ae, (const uint8_t*)"0123456789abcdef") < 0)
-        goto ERROR;
+        if (av_aes_ctr_init(ae, (const uint8_t*)"0123456789abcdef") < 0)
+            goto ERROR;
 
-    if (av_aes_ctr_init(ad, (const uint8_t*)"0123456789abcdef") < 0)
-        goto ERROR;
+        if (av_aes_ctr_init(ad, (const uint8_t*)"0123456789abcdef") < 0)
+            goto ERROR;
 
         if (i)
             av_aes_ctr_set_iv(ae, fixed_iv);
         else
-    av_aes_ctr_set_random_iv(ae);
-    iv =   av_aes_ctr_get_iv(ae);
-    av_aes_ctr_set_full_iv(ad, iv);
+            av_aes_ctr_set_random_iv(ae);
+        iv =   av_aes_ctr_get_iv(ae);
+        av_aes_ctr_set_full_iv(ad, iv);
 
-    av_aes_ctr_crypt(ae, tmp, plain, sizeof(tmp));
+        av_aes_ctr_crypt(ae, tmp, plain, sizeof(tmp));
         if (i && memcmp(tmp, encrypted, sizeof(tmp)) != 0) {
             av_log(NULL, AV_LOG_ERROR, "test failed\n");
             goto ERROR;
         }
-    av_aes_ctr_crypt(ad, tmp, tmp,   sizeof(tmp));
 
-    if (memcmp(tmp, plain, sizeof(tmp)) != 0){
-        av_log(NULL, AV_LOG_ERROR, "test failed\n");
-        goto ERROR;
-    }
+        av_aes_ctr_crypt(ad, tmp, tmp,   sizeof(tmp));
+        if (memcmp(tmp, plain, sizeof(tmp)) != 0){
+            av_log(NULL, AV_LOG_ERROR, "test failed\n");
+            goto ERROR;
+        }
 
         av_aes_ctr_free(ae);
         av_aes_ctr_free(ad);
-- 
2.49.0

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[FFmpeg-devel] [PATCH 6/6] avutil/tests/aes_ctr: also randomize the encryption key

[James Almer]

And not just the IV.

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavutil/tests/aes_ctr.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/libavutil/tests/aes_ctr.c b/libavutil/tests/aes_ctr.c
index 6f21b8bda1..fad24014cc 100644
--- a/libavutil/tests/aes_ctr.c
+++ b/libavutil/tests/aes_ctr.c
@@ -18,6 +18,7 @@
 
 #include <string.h>
 
+#include "libavutil/random_seed.h"
 #include "libavutil/log.h"
 #include "libavutil/mem_internal.h"
 #include "libavutil/aes_ctr.h"
@@ -36,13 +37,20 @@ static const DECLARE_ALIGNED(8, uint8_t, fixed_iv)[] = {
     0xde, 0xad, 0xbe, 0xef, 0xde, 0xad, 0xbe, 0xef
 };
 
+static const DECLARE_ALIGNED(8, uint8_t, fixed_key)[] = {
+    0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
+    0x38, 0x39, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66
+};
+
+static DECLARE_ALIGNED(8, uint32_t, key)[2];
+
 static DECLARE_ALIGNED(8, uint8_t, tmp)[20];
 
 int main (void)
 {
     int ret = 1;
     struct AVAESCTR *ae, *ad;
-    const uint8_t *iv;
+    const uint8_t *iv, *k;
 
     for (int i = 0; i < 2; i++) {
         ae = av_aes_ctr_alloc();
@@ -51,10 +59,21 @@ int main (void)
         if (!ae || !ad)
             goto ERROR;
 
-        if (av_aes_ctr_init(ae, (const uint8_t*)"0123456789abcdef") < 0)
+        if (i)
+            k = fixed_key;
+        else {
+            // Note: av_random_bytes() should be used in a real world scenario,
+            // but since that function can fail, av_get_random_seed() is used
+            // here for the purpose of this test, as its output is sufficient.
+            key[0] = av_get_random_seed();
+            key[1] = av_get_random_seed();
+            k = (uint8_t *)key;
+        }
+
+        if (av_aes_ctr_init(ae, k) < 0)
             goto ERROR;
 
-        if (av_aes_ctr_init(ad, (const uint8_t*)"0123456789abcdef") < 0)
+        if (av_aes_ctr_init(ad, k) < 0)
             goto ERROR;
 
         if (i)
-- 
2.49.0

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