libc: Add sendfile and queue

10 files changed, 425 insertions, 2 deletions

diff --git a/kernel/cpu/syscall.c b/kernel/cpu/syscall.c
index 0dd2356..d31835d 100644
--- a/kernel/cpu/syscall.c
+++ b/kernel/cpu/syscall.c
@@ -567,6 +567,83 @@ int syscall_queue_wait(int fd, struct queue_entry *events, int num_events) {
   return queue_wait(fd, events, num_events);
 }
 
+u32 syscall_sendfile(int out_fd, int in_fd, off_t *offset, size_t count,
+                     int *error_rc) {
+  int is_inf = (0 == count);
+
+  if (offset) {
+    if (!mmu_is_valid_userpointer(offset, sizeof(off_t))) {
+      return -EFAULT;
+    }
+  }
+  if (error_rc) {
+    if (!mmu_is_valid_userpointer(error_rc, sizeof(int))) {
+      return -EFAULT;
+    }
+  }
+
+  vfs_fd_t *in_fd_ptr = get_vfs_fd(in_fd, NULL);
+  if (!in_fd_ptr) {
+    return -EBADF;
+  }
+
+  vfs_fd_t *out_fd_ptr = get_vfs_fd(out_fd, NULL);
+  if (!out_fd_ptr) {
+    return -EBADF;
+  }
+
+  int real_rc = 0;
+
+  off_t read_offset = (offset) ? (*offset) : in_fd_ptr->offset;
+
+  for (; count > 0 || is_inf;) {
+    u8 buffer[8192];
+    int read_amount = min(sizeof(buffer), count);
+    if (is_inf) {
+      read_amount = sizeof(buffer);
+    }
+    int rc = vfs_pread(in_fd, buffer, read_amount, read_offset);
+    if (0 > rc) {
+      if (error_rc) {
+        *error_rc = rc;
+      }
+      return real_rc;
+    }
+
+    if (0 == rc) {
+      break;
+    }
+
+    int rc2 = vfs_pwrite(out_fd, buffer, rc, out_fd_ptr->offset);
+    if (0 > rc2) {
+      if (error_rc) {
+        *error_rc = rc2;
+      }
+      return real_rc;
+    }
+    real_rc += rc2;
+    if (!is_inf) {
+      count -= rc2;
+    }
+    out_fd_ptr->offset += rc2;
+
+    read_offset += rc2;
+    if (offset) {
+      *offset = read_offset;
+    } else {
+      in_fd_ptr->offset = read_offset;
+    }
+
+    if (rc < read_amount) {
+      break;
+    }
+  }
+  if (error_rc) {
+    *error_rc = 0;
+  }
+  return real_rc;
+}
+
 int (*syscall_functions[])() = {
     (void(*))syscall_open,
     (void(*))syscall_read,
@@ -614,7 +691,7 @@ int (*syscall_functions[])() = {
     (void(*))syscall_queue_create,
     (void(*))syscall_queue_mod_entries,
     (void(*))syscall_queue_wait,
-
+    (void(*))syscall_sendfile,
 };
 
 void int_syscall(reg_t *r);
diff --git a/userland/libc/Makefile b/userland/libc/Makefile
index 34e9016..a41e8e4 100644
--- a/userland/libc/Makefile
+++ b/userland/libc/Makefile
@@ -2,7 +2,7 @@ CC="i686-sb-gcc"
 AR="i686-sb-ar"
 AS="i686-sb-as"
 CFLAGS = -ggdb -ffreestanding -nostdlib -Ofast -Wall -Wextra -pedantic -Werror -Wimplicit-fallthrough -I./include/ -static -I../../include/ -Wno-int-conversion -Wno-unused-parameter
-OBJ=crt0.o libc.o malloc/malloc.o pty.o sys/mman/mmap.o sys/mman/munmap.o memset.o assert.o stdio/snprintf.o stdio/vfprintf.o string/memcpy.o string/memcmp.o string/strcmp.o ubsan.o string/strcpy.o isspace.o stdio/puts.o stdio/putchar.o dirent/opendir.o dirent/readdir.o dirent/closedir.o unistd/getopt.o dirent/scandir.o dirent/alphasort.o stdio/printf.o stdio/vdprintf.o stdio/vprintf.o stdio/dprintf.o stdio/vprintf.o string/strlen.o string/strnlen.o stdio/stdin.o stdio/getchar.o stdio/fgetc.o arpa/inet/htons.o arpa/inet/htonl.o stdio/fread.o stdio/fwrite.o stdio/fopen.o stdio/fclose.o stdio/fseek.o ctype/isascii.o stdio/fprintf.o stdlib/atoi.o stdlib/strtol.o ctype/toupper.o ctype/tolower.o string/strcat.o string/strchr.o string/sscanf.o sys/stat/stat.o stdlib/getenv.o string/strrchr.o stdio/ftell.o stdio/tmpfile.o stdio/fgets.o stdio/feof.o stdio/fscanf.o stdio/ungetc.o string/strncmp.o stdio/fputc.o string/strncpy.o stdio/remove.o stdio/ferror.o stdio/fputs.o stdlib/rand.o stdlib/srand.o unistd/getpid.o stdlib/strtoul.o stdio/fflush.o stdlib/abort.o string/strcspn.o time/localtime.o time/time.o time/clock_gettime.o time/gmtime.o time/strftime.o string/strpbrk.o ctype/isdigit.o ctype/isalpha.o ctype/isxdigit.o ctype/ispunct.o stdio/setvbuf.o stdio/fileno.o stdio/putc.o stdio/sprintf.o stdlib/abs.o string/strspn.o stdlib/qsort.o string/memmove.o setjmp/longjmp.o setjmp/setjmp.o libgen/basename.o string/strdup.o string/strndup.o string/strlcpy.o stdlib/atexit.o stdio/open_memstream.o libgen/dirname.o unistd/unlink.o string/strstr.o string/strcasecmp.o string/strncasecmp.o stdlib/mkstemp.o string/strtok.o unistd/execvp.o unistd/_exit.o ctype/isalnum.o time/ctime_r.o stdlib/strtold.o sys/time/gettimeofday.o stdio/fgetpos.o stdio/fsetpos.o ctype/isprint.o stdlib/system.o stdio/tmpnam.o unistd/msleep.o stdlib/atof.o stdlib/strtod.o stdio/rename.o sys/stat/mkdir.o unistd/uptime.o unistd/ftruncate.o sys/socket/recvfrom.o sys/socket/sendto.o signal/kill.o signal/sigaction.o unistd/chdir.o unistd/getcwd.o stdio/getdelim.o stdio/getline.o unistd/isatty.o sys/socket/listen.o stdlib/realpath.o systemcall.o sys/random/randomfill.o fcntl/open.o unistd/write.o unistd/pwrite.o fcntl/open_process.o tb/sb.o tb/sv.o string/memchr.o stdlib/atol.o stdlib/atoll.o stdlib/strtoll.o sys/stat/fstat.o unistd/lseek.o ctype/isupper.o ctype/islower.o ctype/isblank.o ctype/isgraph.o ctype/iscntrl.o math/ldexp.o sys/socket/connect.o sys/socket/setsockopt.o arpa/inet/ntohl.o arpa/inet/ntohs.o netdb/getaddrinfo.o tb/sha1.o sys/socket/getpeername.o fcntl/fcntl.o queue.o
+OBJ=crt0.o libc.o malloc/malloc.o pty.o sys/mman/mmap.o sys/mman/munmap.o memset.o assert.o stdio/snprintf.o stdio/vfprintf.o string/memcpy.o string/memcmp.o string/strcmp.o ubsan.o string/strcpy.o isspace.o stdio/puts.o stdio/putchar.o dirent/opendir.o dirent/readdir.o dirent/closedir.o unistd/getopt.o dirent/scandir.o dirent/alphasort.o stdio/printf.o stdio/vdprintf.o stdio/vprintf.o stdio/dprintf.o stdio/vprintf.o string/strlen.o string/strnlen.o stdio/stdin.o stdio/getchar.o stdio/fgetc.o arpa/inet/htons.o arpa/inet/htonl.o stdio/fread.o stdio/fwrite.o stdio/fopen.o stdio/fclose.o stdio/fseek.o ctype/isascii.o stdio/fprintf.o stdlib/atoi.o stdlib/strtol.o ctype/toupper.o ctype/tolower.o string/strcat.o string/strchr.o string/sscanf.o sys/stat/stat.o stdlib/getenv.o string/strrchr.o stdio/ftell.o stdio/tmpfile.o stdio/fgets.o stdio/feof.o stdio/fscanf.o stdio/ungetc.o string/strncmp.o stdio/fputc.o string/strncpy.o stdio/remove.o stdio/ferror.o stdio/fputs.o stdlib/rand.o stdlib/srand.o unistd/getpid.o stdlib/strtoul.o stdio/fflush.o stdlib/abort.o string/strcspn.o time/localtime.o time/time.o time/clock_gettime.o time/gmtime.o time/strftime.o string/strpbrk.o ctype/isdigit.o ctype/isalpha.o ctype/isxdigit.o ctype/ispunct.o stdio/setvbuf.o stdio/fileno.o stdio/putc.o stdio/sprintf.o stdlib/abs.o string/strspn.o stdlib/qsort.o string/memmove.o setjmp/longjmp.o setjmp/setjmp.o libgen/basename.o string/strdup.o string/strndup.o string/strlcpy.o stdlib/atexit.o stdio/open_memstream.o libgen/dirname.o unistd/unlink.o string/strstr.o string/strcasecmp.o string/strncasecmp.o stdlib/mkstemp.o string/strtok.o unistd/execvp.o unistd/_exit.o ctype/isalnum.o time/ctime_r.o stdlib/strtold.o sys/time/gettimeofday.o stdio/fgetpos.o stdio/fsetpos.o ctype/isprint.o stdlib/system.o stdio/tmpnam.o unistd/msleep.o stdlib/atof.o stdlib/strtod.o stdio/rename.o sys/stat/mkdir.o unistd/uptime.o unistd/ftruncate.o sys/socket/recvfrom.o sys/socket/sendto.o signal/kill.o signal/sigaction.o unistd/chdir.o unistd/getcwd.o stdio/getdelim.o stdio/getline.o unistd/isatty.o sys/socket/listen.o stdlib/realpath.o systemcall.o sys/random/randomfill.o fcntl/open.o unistd/write.o unistd/pwrite.o fcntl/open_process.o tb/sb.o tb/sv.o string/memchr.o stdlib/atol.o stdlib/atoll.o stdlib/strtoll.o sys/stat/fstat.o unistd/lseek.o ctype/isupper.o ctype/islower.o ctype/isblank.o ctype/isgraph.o ctype/iscntrl.o math/ldexp.o sys/socket/connect.o sys/socket/setsockopt.o arpa/inet/ntohl.o arpa/inet/ntohs.o netdb/getaddrinfo.o tb/sha1.o sys/socket/getpeername.o fcntl/fcntl.o queue.o sys/sendfile.o
 all: libc.a
 
 %.o: %.c
diff --git a/userland/libc/fcntl/fcntl.c b/userland/libc/fcntl/fcntl.c
new file mode 100644
index 0000000..0a4be9e
--- /dev/null
+++ b/userland/libc/fcntl/fcntl.c
@@ -0,0 +1,15 @@
+#include <fcntl.h>
+#include <stdarg.h>
+#include <syscall.h>
+
+int fcntl(int fd, int cmd, ...) {
+  int arg = 0;
+
+  if ((F_GETFL == cmd) || (F_SETFL == cmd)) {
+    va_list ap;
+    va_start(ap, cmd);
+    arg = va_arg(ap, int);
+    va_end(ap);
+  }
+  RC_ERRNO(syscall(SYS_FCNTL, fd, cmd, arg, 0, 0));
+}
diff --git a/userland/libc/include/queue.h b/userland/libc/include/queue.h
new file mode 100644
index 0000000..4883871
--- /dev/null
+++ b/userland/libc/include/queue.h
@@ -0,0 +1,21 @@
+#include <stdint.h>
+
+#define QUEUE_MOD_ADD 0
+#define QUEUE_MOD_CHANGE 1
+#define QUEUE_MOD_DELETE 2
+
+#define QUEUE_WAIT_READ (1 << 0)
+#define QUEUE_WAIT_WRITE (1 << 1)
+#define QUEUE_WAIT_CLOSE (1 << 2)
+
+struct queue_entry {
+  int fd;
+  uint8_t listen;
+  int data_type;
+  void *data;
+};
+
+int queue_create(void);
+int queue_mod_entries(int fd, int flag, struct queue_entry *entries,
+                      int num_entries);
+int queue_wait(int fd, struct queue_entry *events, int num_events);
diff --git a/userland/libc/include/sys/sendfile.h b/userland/libc/include/sys/sendfile.h
new file mode 100644
index 0000000..5e83999
--- /dev/null
+++ b/userland/libc/include/sys/sendfile.h
@@ -0,0 +1,7 @@
+#include <stdint.h>
+#include <typedefs.h>
+#include <stddef.h>
+#include <sys/types.h>
+
+u32 sendfile(int out_fd, int in_fd, off_t *offset, size_t count,
+             int *error_rc);
diff --git a/userland/libc/include/syscall.h b/userland/libc/include/syscall.h
index 87622c5..dda4b82 100644
--- a/userland/libc/include/syscall.h
+++ b/userland/libc/include/syscall.h
@@ -51,6 +51,7 @@
 #define SYS_QUEUE_CREATE 43
 #define SYS_QUEUE_MOD_ENTRIES 44
 #define SYS_QUEUE_WAIT 45
+#define SYS_SENDFILE 46
 
 int syscall(uint32_t eax, uint32_t ebx, uint32_t ecx, uint32_t edx,
             uint32_t esi, uint32_t edi);
diff --git a/userland/libc/include/tb/sha1.h b/userland/libc/include/tb/sha1.h
new file mode 100644
index 0000000..fe84196
--- /dev/null
+++ b/userland/libc/include/tb/sha1.h
@@ -0,0 +1,26 @@
+//
+// Copyright (C) 2022-2023 by Anton Kling <anton@kling.gg>
+//
+// SPDX-License-Identifier: 0BSD
+//
+#ifndef SHA1
+#define SHA1
+#include <stddef.h>
+#include <stdint.h>
+
+#define BLOCK_BYTES (64) /* 512/8 */
+#define SHA1_LEN (20)
+
+typedef struct SHA1_CTX {
+  uint32_t h[5];
+  uint8_t block[BLOCK_BYTES];
+  uint64_t active_len;
+  uint64_t len;
+} SHA1_CTX;
+
+void SHA1_Init(SHA1_CTX *ctx);
+void SHA1_Update(SHA1_CTX *ctx, const void *data, uint64_t len);
+void SHA1_Final(SHA1_CTX *ctx, unsigned char *message_digest);
+void SHA1_HMAC(unsigned char *message, uint64_t message_len, unsigned char *key,
+               uint64_t key_len, uint8_t output[SHA1_LEN]);
+#endif
diff --git a/userland/libc/queue.c b/userland/libc/queue.c
new file mode 100644
index 0000000..6d4d380
--- /dev/null
+++ b/userland/libc/queue.c
@@ -0,0 +1,15 @@
+#include <queue.h>
+#include <syscall.h>
+
+int queue_create(void) {
+  RC_ERRNO(syscall(SYS_QUEUE_CREATE, 0, 0, 0, 0, 0));
+}
+
+int queue_mod_entries(int fd, int flag, struct queue_entry *entries,
+                      int num_entries) {
+  RC_ERRNO(syscall(SYS_QUEUE_MOD_ENTRIES, fd, flag, entries, num_entries, 0));
+}
+
+int queue_wait(int fd, struct queue_entry *events, int num_events) {
+  RC_ERRNO(syscall(SYS_QUEUE_WAIT, fd, events, num_events, 0, 0));
+}
diff --git a/userland/libc/sys/sendfile.c b/userland/libc/sys/sendfile.c
new file mode 100644
index 0000000..818883b
--- /dev/null
+++ b/userland/libc/sys/sendfile.c
@@ -0,0 +1,12 @@
+#include <sys/sendfile.h>
+#include <syscall.h>
+#include <errno.h>
+
+u32 sendfile(int out_fd, int in_fd, off_t *offset, size_t count,
+             int *error_rc) {
+  u32 r = syscall(SYS_SENDFILE, out_fd, in_fd, offset, count, error_rc);
+  if (error_rc) {
+    errno = -1 * *error_rc;
+  }
+  return r;
+}
diff --git a/userland/libc/tb/sha1.c b/userland/libc/tb/sha1.c
new file mode 100644
index 0000000..90e4e2a
--- /dev/null
+++ b/userland/libc/tb/sha1.c
@@ -0,0 +1,249 @@
+//
+// Copyright (C) 2022-2023 by Anton Kling <anton@kling.gg>
+//
+// SPDX-License-Identifier: 0BSD
+//
+#include <tb/sha1.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+
+#define SHA1_CONSTANT_H0 0x67452301
+#define SHA1_CONSTANT_H1 0xefcdab89
+#define SHA1_CONSTANT_H2 0x98badcfe
+#define SHA1_CONSTANT_H3 0x10325476
+#define SHA1_CONSTANT_H4 0xc3d2e1f0
+
+#define SHA1_CONSTANT_K1 0x5a827999
+#define SHA1_CONSTANT_K2 0x6ed9eba1
+#define SHA1_CONSTANT_K3 0x8f1bbcdc
+#define SHA1_CONSTANT_K4 0xca62c1d6
+
+void SHA1_Init(SHA1_CTX *ctx) {
+  // 6.1.1 SHA-1 Preprocessing
+
+  // 1. Set the initial hash value, H(0), as specified in Sec. 5.3.1
+  ctx->h[0] = SHA1_CONSTANT_H0;
+  ctx->h[1] = SHA1_CONSTANT_H1;
+  ctx->h[2] = SHA1_CONSTANT_H2;
+  ctx->h[3] = SHA1_CONSTANT_H3;
+  ctx->h[4] = SHA1_CONSTANT_H4;
+
+  ctx->len = ctx->active_len = 0;
+
+  memset(ctx->block, 0, BLOCK_BYTES);
+}
+
+uint32_t reverse_32(uint32_t _value) {
+  return (((_value & 0x000000FF) << 24) | ((_value & 0x0000FF00) << 8) |
+          ((_value & 0x00FF0000) >> 8) | ((_value & 0xFF000000) >> 24));
+}
+
+void pad_sha1_message(uint8_t *M, uint64_t l, uint64_t active_l,
+                      uint8_t *block) {
+  memset(block, 0, 1024 / 8);
+  memcpy(block, M, active_l / 8);
+
+#define ARRAY_NUM(_loc) (((_loc) / 8) + !(0 == ((_loc) % 8)))
+
+  // 5. PREPROCESSING
+
+  // 5.1.1 SHA-1, SHA-224 and SHA-256
+
+  // Append the bit “1” to the end of the message
+  block[ARRAY_NUM(active_l)] = 1 << 7;
+
+  // followed by k zero bits, where k is the smallest, non-negative
+  // solution to the equation 'l + 1 + k \cong 448 mod 512'
+  int k;
+  uint64_t rest = (active_l + 1) % 512;
+  if (rest < 448)
+    k = 448 - rest;
+  else
+    k = 512 - rest + 448;
+
+  memset(block + ARRAY_NUM(active_l) + 2, 0x0, k / 8);
+
+  // Then append the 64-bit block that is equal to the number 'l' expressed
+  // using a binary representatio
+  uint32_t *final_32bit_block;
+  final_32bit_block = (uint32_t *)(block + active_l / 8 + k / 8 + 1);
+
+  *(final_32bit_block) = reverse_32(l >> 32);
+  *(final_32bit_block + 1) = reverse_32(l & 0xFFFFFFFF);
+}
+
+uint32_t sha1_f(uint8_t t, uint32_t x, uint32_t y, uint32_t z) {
+  if (t <= 19) {
+    // Ch(x,y,z)
+    return (x & y) ^ ((~x) & z);
+  }
+  if (t <= 39 || t >= 60) {
+    // Parity(x,y,z)
+    return x ^ y ^ z;
+  }
+  if (t <= 59) {
+    // Maj(x,y,z)
+    return (x & y) ^ (x & z) ^ (y & z);
+  }
+  return 0;
+}
+
+uint32_t sha1_get_k(uint8_t t) {
+  if (t <= 19)
+    return SHA1_CONSTANT_K1;
+  if (t <= 39)
+    return SHA1_CONSTANT_K2;
+  if (t <= 59)
+    return SHA1_CONSTANT_K3;
+  if (t <= 79)
+    return SHA1_CONSTANT_K4;
+  return 0;
+}
+
+uint32_t ROTL(uint32_t value, uint8_t shift) {
+  uint32_t rotated = value << shift;
+  uint32_t did_overflow = value >> (32 - shift);
+  return (rotated | did_overflow);
+}
+
+void add_block(SHA1_CTX *ctx, uint8_t *_block) {
+  uint32_t *block = (uint32_t *)_block;
+  for (size_t i = 0; i < 16; i++)
+    block[i] = reverse_32(block[i]);
+
+  uint32_t W[80];
+  uint32_t a, b, c, d, e;
+  uint32_t *M = block;
+
+  // 1. Prepare the message schedule, {Wt}:
+  for (size_t t = 0; t < 16; t++)
+    W[t] = M[t];
+
+  for (size_t t = 16; t < 80; t++) {
+    // ROTL(1)(W(t-3) ^ W(t-8) ^ W(t-16))
+    W[t] = ROTL((W[t - 3] ^ W[t - 8] ^ W[t - 14] ^ W[t - 16]), 1);
+  }
+
+  // 2. Initialize the five working variables, a, b, c, d, and e, with the
+  // (i-1)^(st) hash value:
+  a = ctx->h[0];
+  b = ctx->h[1];
+  c = ctx->h[2];
+  d = ctx->h[3];
+  e = ctx->h[4];
+
+  // 3. For t=0 to 79:
+  for (size_t t = 0; t < 80; t++) {
+    uint32_t T = ROTL(a, 5) + sha1_f(t, b, c, d) + e + sha1_get_k(t) + W[t];
+    e = d;
+    d = c;
+    c = ROTL(b, 30);
+    b = a;
+    a = T;
+  }
+
+  // 4. Compute the ith intermediate hash value H(i):
+  ctx->h[0] = a + ctx->h[0];
+  ctx->h[1] = b + ctx->h[1];
+  ctx->h[2] = c + ctx->h[2];
+  ctx->h[3] = d + ctx->h[3];
+  ctx->h[4] = e + ctx->h[4];
+}
+
+void SHA1_Final(SHA1_CTX *ctx, unsigned char *message_digest) {
+  uint8_t block[BLOCK_BYTES * 2] = {0};
+  pad_sha1_message(ctx->block, ctx->len * 8, ctx->active_len * 8, block);
+
+  add_block(ctx, block);
+
+  if (((ctx->active_len * 8 + 1) % 512) >= 448)
+    add_block(ctx, block + BLOCK_BYTES);
+
+  for (size_t i = 0; i < 5; i++)
+    ctx->h[i] = reverse_32(ctx->h[i]);
+
+  for (size_t i = 0; i < 5; i++)
+    memcpy(message_digest + sizeof(uint32_t) * i, &ctx->h[i], sizeof(uint32_t));
+}
+
+void SHA1_Update(SHA1_CTX *ctx, const void *data, uint64_t len) {
+  for (; len > 0;) {
+    size_t write_len = ((ctx->active_len + len) > BLOCK_BYTES)
+                           ? (BLOCK_BYTES - ctx->active_len)
+                           : len;
+
+    memcpy(ctx->block + ctx->active_len, data, write_len);
+    ctx->len += write_len;
+    ctx->active_len += write_len;
+    if (BLOCK_BYTES != ctx->active_len)
+      return;
+
+    add_block(ctx, ctx->block);
+    memset(ctx->block, 0, BLOCK_BYTES);
+    ctx->active_len = 0;
+
+    len -= write_len;
+    data = (const void *)((uintptr_t)data + write_len);
+  }
+}
+
+// https://www.rfc-editor.org/rfc/rfc2104
+#define BLOCK_SIZE 64
+void SHA1_HMAC(unsigned char *message, uint64_t message_len, unsigned char *key,
+               uint64_t key_len, uint8_t output[SHA1_LEN]) {
+  // This function can be presented as follows:
+  // H(K XOR opad, H(K XOR ipad, message))
+  //
+  // H    : SHA1 hashing algorithm.
+  // K    : Key that got shrunk/padded to block size.
+  // ipad : the byte 0x36 repeated B times
+  // opad : the byte 0x5C repeated B times.
+  // message : The input.
+
+  char o_key_pad[BLOCK_SIZE];
+  char i_key_pad[BLOCK_SIZE];
+
+  // (1) append zeros to the end of K to create a B byte string
+  // (e.g., if K is of length 20 bytes and B=64, then K will be
+  // appended with 44 zero bytes 0x00)
+  unsigned char hashed_key[SHA1_LEN];
+  if (key_len > BLOCK_SIZE) {
+    SHA1_CTX ctx;
+    SHA1_Init(&ctx);
+    SHA1_Update(&ctx, key, key_len);
+    SHA1_Final(&ctx, hashed_key);
+    key = hashed_key;
+    key_len = SHA1_LEN;
+  }
+
+  // (2) XOR (bitwise exclusive-OR) the B byte string computed in step
+  // (1) with ipad
+  // (5) XOR (bitwise exclusive-OR) the B byte string computed in
+  // step (1) with opad
+  memset(i_key_pad, 0x36, BLOCK_SIZE);
+  memset(o_key_pad, 0x5C, BLOCK_SIZE);
+  for (size_t i = 0; i < key_len; i++) {
+    i_key_pad[i] ^= key[i];
+    o_key_pad[i] ^= key[i];
+  }
+
+  // (3) append the stream of data 'message' to the B byte string resulting
+  //     from step (2)
+  // (4) apply H to the stream generated in step (3)
+  SHA1_CTX first_ctx;
+  SHA1_Init(&first_ctx);
+  SHA1_Update(&first_ctx, i_key_pad, BLOCK_SIZE);
+  SHA1_Update(&first_ctx, message, message_len);
+  SHA1_Final(&first_ctx, output);
+
+  // (6) append the H result from step (4) to the B byte string
+  // resulting from step (5)
+  // (7) apply H to the stream generated in step (6) and output
+  //     the result
+  SHA1_CTX second_ctx;
+  SHA1_Init(&second_ctx);
+  SHA1_Update(&second_ctx, o_key_pad, BLOCK_SIZE);
+  SHA1_Update(&second_ctx, output, SHA1_LEN);
+  SHA1_Final(&second_ctx, output);
+}