+/*
+ * The code in this file was taken from openssh-5.2p1, Copyright (c) 1996 by
+ * Internet Software Consortium. Portions Copyright (c) 1995 by International
+ * Business Machines, Inc.
+ */
+
+/** \file base64.c Uudecode and base64decode implementation. */
+
+#include <regex.h>
+
+#include "para.h"
+#include "error.h"
+#include "base64.h"
+#include "string.h"
+
+static const char Base64[] =
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+static const char Pad64 = '=';
+
+/**
+ * base64-decode a buffer.
+ *
+ * \param src The buffer to decode.
+ * \param target Result is stored here.
+ * \param targsize Number of bytes of \a target.
+ *
+ * Skips all whitespace anywhere. Converts characters, four at a time, starting
+ * at (or after) src from base - 64 numbers into three 8 bit bytes in the
+ * target area.
+ *
+ * \return The number of data bytes stored at the target, -E_BASE64 on errors.
+ */
+int base64_decode(char const *src, unsigned char *target, size_t targsize)
+{
+ unsigned int tarindex, state;
+ int ch;
+ char *pos;
+
+ state = 0;
+ tarindex = 0;
+
+ while ((ch = *src++) != '\0') {
+ if (para_isspace(ch)) /* Skip whitespace anywhere. */
+ continue;
+
+ if (ch == Pad64)
+ break;
+
+ pos = strchr(Base64, ch);
+ if (pos == NULL) /* A non-base64 character. */
+ return -E_BASE64;
+
+ switch (state) {
+ case 0:
+ if (tarindex >= targsize)
+ return -E_BASE64;
+ target[tarindex] = (pos - Base64) << 2;
+ state = 1;
+ break;
+ case 1:
+ if (tarindex + 1 >= targsize)
+ return -E_BASE64;
+ target[tarindex] |= (pos - Base64) >> 4;
+ target[tarindex + 1] = ((pos - Base64) & 0x0f) << 4;
+ tarindex++;
+ state = 2;
+ break;
+ case 2:
+ if (tarindex + 1 >= targsize)
+ return -E_BASE64;
+ target[tarindex] |= (pos - Base64) >> 2;
+ target[tarindex + 1] = ((pos - Base64) & 0x03) << 6;
+ tarindex++;
+ state = 3;
+ break;
+ case 3:
+ if (tarindex >= targsize)
+ return -E_BASE64;
+ target[tarindex] |= pos - Base64;
+ tarindex++;
+ state = 0;
+ break;
+ }
+ }
+
+ /*
+ * We are done decoding Base-64 chars. Let's see if we ended
+ * on a byte boundary, and/or with erroneous trailing characters.
+ */
+
+ if (ch == Pad64) { /* We got a pad char. */
+ ch = *src++; /* Skip it, get next. */
+ switch (state) {
+ case 0: /* Invalid = in first position */
+ case 1: /* Invalid = in second position */
+ return -E_BASE64;
+
+ case 2: /* Valid, means one byte of info */
+ /* Skip any number of spaces. */
+ for (; ch != '\0'; ch = *src++)
+ if (!isspace(ch))
+ break;
+ /* Make sure there is another trailing = sign. */
+ if (ch != Pad64)
+ return -E_BASE64;
+ ch = *src++; /* Skip the = */
+ /* Fall through to "single trailing =" case. */
+ /* FALLTHROUGH */
+
+ case 3: /* Valid, means two bytes of info */
+ /*
+ * We know this char is an =. Is there anything but
+ * whitespace after it?
+ */
+ for (; ch != '\0'; ch = *src++)
+ if (!isspace(ch))
+ return -E_BASE64;
+
+ /*
+ * Now make sure for cases 2 and 3 that the "extra"
+ * bits that slopped past the last full byte were
+ * zeros. If we don't check them, they become a
+ * subliminal channel.
+ */
+ if (target[tarindex] != 0)
+ return -E_BASE64;
+ }
+ } else {
+ /*
+ * We ended by seeing the end of the string. Make sure we
+ * have no partial bytes lying around.
+ */
+ if (state != 0)
+ return -E_BASE64;
+ }
+ return tarindex;
+}
+
+/**
+ * uudecode a buffer.
+ *
+ * \param src The buffer to decode.
+ * \param target Result buffer.
+ * \param targsize The length of \a target in bytes.
+ *
+ * This is just a simple wrapper for base64_decode() which strips whitespace.
+ *
+ * \return The return value of the underlying call to base64_decode().
+ */
+int uudecode(const char *src, unsigned char *target, size_t targsize)
+{
+ int len;
+ char *encoded, *p;
+
+ /* copy the 'readonly' source */
+ encoded = para_strdup(src);
+ /* skip whitespace and data */
+ for (p = encoded; *p == ' ' || *p == '\t'; p++)
+ ;
+ for (; *p != '\0' && *p != ' ' && *p != '\t'; p++)
+ ;
+ /* and remove trailing whitespace because base64_decode needs this */
+ *p = '\0';
+ len = base64_decode(encoded, target, targsize);
+ free(encoded);
+ return len;
+}
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